Division of Agricultural Sciences ^— — — ~ UN I V E R S I T Y OF CALIFORNIA ' % 'h&f) • A TECHNICAL STUDY OF INSECTS AFFECTING THE OAK TREE IN SOUTHERN CALIFORNIA CALIFORNIA AGRICULTURAL EXPERIMENT STATION LELAND R. BROWN CLARK O. EADS BULLETIN 810 How to use this bulletin: For the person not trained as an entomologist, a few suggestions may be helpful. First: Identify the insect or its damage to the oak tree. Do this by comparing the insect at hand with the main categories in the Contents. Use the photographs to assist in this identification. Second: Read about the insect on the indicated page in the text. This should confirm the identity as well as supply interesting points about the insect's habits and necessary information on control. Third: Specific directions on combating the insect as well as precautions for personal safety, begin on page 92. (Cover photo: California oak moth) April, 1965 THE AUTHORS: Leland R. Brown is Associate Professor of Entomology and Associate Entomologist in the Experiment Station, Riverside. Clark O. Eads is Laboratory Technician IV in the Experiment Station, Riverside. CONTENTS Page Figures I. INTRODUCTION 5 H. SUCKING INSECTS 7 On the twigs: Oak treehoppers 8 1-3 Black-punctured kermes, Kermes nigropunctatus 10 4 Oak pit scales, Aster olecanium species 11 5-7 Oak wax scale, Cerococcus quercus 13 8 Ehrhorn s oak scale, Mycetococcus ehrhorni 13 9 Oak lecanium scale, Lecanium quercitronis 14 10 Oak scale, Quernaspis quercus 15 11 On the leaves: Crown whitefly, Aleuroplatus coronatus 16 12-13 Gelatinous whitefly, Aleuroplatus gelatinosus 18 14 Stanford's whitefly, Tetraleurodes stanfordi 18 15 Woolly oak aphid, Stegophylla quercicola 19 16 Coast live oak erineum mite, Aceria mackiei 19 17 HI. LEAF-CONSUMING INSECTS 21 Moth larvae: Live oak leaf cutter, Lampronia species 22 18-30 Oak ribbed case maker, Bucculatrix albertiella 29 31-34 Oak leaf blotch miner, Lithocolletis agrifoliella 31 35-39 Stenomid oak leaf tier, Setiostoma fernaldella 33 40-45 Fruit tree leaf roller, Archips argyrospilus 36 46-50 Phycitid oak leaf tier, Rhodophaea caliginella 38 51-52 Tent caterpillars, Malacosoma californicum, M. constrictum 40 53-58 Western tussock moth, Hemerocampa vetusta 41 59-64 California oak moth, Phryganidia calif ornica 44 65-71 Salt-marsh caterpillar, Estigmene acrea 47 72-76 Black oak woollybear, Hemihyalea edwardsii 49 77-79 Beetle: Live oak weevil, Deporaus glastinus 51 80-81 Wasp larva: Oak leaf sawfly, Periclista species 51 82 Fly larva: Agromyzid leaf miner 53 83-85 IV. BORING INSECTS 55 In the trunk and limbs: Dry-wood termites, Kalotermes species 56 86-88 Western sycamore borer, Ramosia resplendens 57 89-94 3 Page Figures Carpenterworm, Prionoxystus robiniae 60 95-101 Pacific flatheaded borer, Chrysobothris mail 64 102-104 Nautical borer, Xylotrechus nauticus 66 105 Oak bark beetles, Pseudopityophthorus species 67 106-107 In the twigs: Oak twig girdler, Agrilus angelicus 69 108-113 Roundheaded oak twig borer, Styloxus fulleri 74 114-115 In the acorns: Filbertworm, Melissopus latiferreanus 75 116-118 Filbert weevil, Curculio uniformis 77 119-123 V. OAK GALL INSECTS (Cynipid wasps) 79 On the twigs: California gallfly, Andricus calif ornicus 80 124-126 Irregular spindle gall wasp, Andricus chrysolepidicola . . 81 127-128 Live oak gallfly, Callirhytis pomiformis 82 129-132 Cork oak cynipid, Plagiotrochus suberi 83 133 Twig club gall wasp, Callirhytis suttoni 84 134 On the leaves and catkins: White oak cone gall wasp, Andricus kingi 85 135 Spined turban gall wasp, Antron douglasii 85 136 Two-horned oak gall wasp, Dryocosmus dubiosus 86 137-140 Jumping oak gall wasp, Neuroterus saltatorius 89 141-142 Distorted leaf gall wasp, Neuroterus varians 90 143-144 Woollybear gall wasp, Sphaeroteras trimaculosum .... 91 145 VI. CONTROL OF OAK INSECT PESTS 92 Spraying equipment 92 Formulations of insecticides 94 Precautions in the use of insecticides 96 Dosages of insecticides 97 Sucking insects 98 Leaf-consuming insects 100 Boring insects 101 Gall insects 102 Warning on use of pesticides 102 LITERATURE CITED 103 A Technical Study of Insects Affecting the Oak Tree in Southern California 1 2 by Leland R. Brown and Clark O. Eads I. INTRODUCTION JL he oak tree has long been held in one of man's favorites and that he is high esteem by man, for aesthetic often concerned about its welfare, reasons, for its shade, and for the prod- There is also evidence that man is ucts produced by and from it. The not alone in holding the oak in high ancient Romans called this tree Quer- regard, although his reasons are cus, as do the scientist and plantsman unique. Oak is the preferred food plant to this day. The tales of Robin Hood in of many insects. Despite its favored Sherwood Forest owe much of their position as an ornamental tree, on the atmosphere to the oaks present there, basis of numbers of different kinds of Certain early California Indians used insects affecting it, the oak is one of the the oak acorns as food. Such oak names least desirable choices of an orna- as "robles" and "encino," surviving as mental to plant. Often man is attracted place names, suggest that the early to the oak as a mature tree so that he Spanish-Californians appreciated this does not have a choice whether or not handsome, sturdy, shade-giving plant it should be planted. The number of in this hot, arid region. The oak thus insects on the oak, however, does not seems to be entwined in our history present a true picture of the relation- and folklore. ship between insect and oak. There are Today, land for real-estate develop- only a few of these many different ment that has naturally-occurring kinds of insects that are of importance stands of oak is valued very highly in to the well-being of the oak tree. It has southern California. The oak is con- been our experience that even the spicuous in parks and is used to a con- worst insect infestations are usually siderable extent in parkways along our secondary in importance to such seri- streets. Some homeowners think so ous problems as drought, armillaria highly of their oak tree that they build root rot, or the poor horticultural prac- their homes around the tree or will tices that promote these naturally-oc- make changes in house plans rather curring disastrous conditions. Most in- than cut a single limb. Thus there is sects or the ir injurious effects on the Considerable evidence that this tree is 2 The authors began their studies on the Los Angeles campus of the University of California in 1949, and 1 Submitted for publication February 3, 1964. from 1960 on continued them on the Riverside campus. tree can be seen, in contrast to those invisible and difficult-to-diagnose con- ditions below ground. Since insects are readily apparent, many people are interested in them. These interested persons range from the horticulturally untrained house- holder to the highly and perhaps nar- rowly trained research entomologist. Many people in state and county governments concerned with regulat- ing or advising the sale and use of plants and insecticides are concerned with insects affecting the oak. Chem- ical companies developing or selling insecticides are interested. The com- mercial pest control operator must know about oak insects and their con- trol in order to conduct his business effectively. The plant nurseryman is often besieged by customers seeking help on current oak insect problems. The primary purpose of this bulletin is to present our observations and studies of insects affecting the oak tree in southern California. In our research and the writing of this bulletin we have been quite aware of the diversity of background of the persons interested in this information. We have made an effort to supply answers to the ques- tions that anyone interested in oak insects in this area might have. Nat- urally we will be happy to answer any questions on oak insects not found in this bulletin, and any criticism or cor- rection of material here presented is welcome. We have not attempted to describe or list all the insects recorded on oak in this area, but are discussing only those which we have observed personally and with which we have had some original experience. We have been very particular to make certain that this information represents the true situation under field conditions rather than that in the laboratory, glasshouse or lathhouse. Most of the photographs were made in the labora- tory of material collected in the field. All the photographs are original and are reproductions from 35 mm Koda- chrome film. The true size of an insect in these photographs may be found by measuring and dividing by the stated magnification. * We are well aware of the many defi- ciencies and gaps of knowledge in our studies. Our studies in many cases are 4 only a beginning. For certain insects not included here, the reader may refer to Essig (1958 or 1926). We know too that presenting these insects on the basis of the part of the plant attacked is not completely satisfactory to every- one, even to us, but that on this basis 4 this rather specialized information will be useful to the greatest number of people. One of our objectives is to present these insects as dynamic, living organisms that are fascinating in their own right, and not only as pests that ^ must be eradicated without a second thought. We know that some persons, on finding how interesting the study of these insects can be, have decided to observe the insects rather than to kill them. We hope that what is written here will aid the intelligent person in deciding on a course of action regard- . ing insects affecting the oak. It is necessary for clear understand- ing to list the scientific names of the u oaks that may be found in southern California and their equivalent com- mon names. We are following Mathias and McClintock (1963) for these names. The first common name after a scientific name below is that suggested by them and the one which we attempt to use. Any other common names that through usage or from our force of habit may be found in this bulletin are listed thereafter. Of the 17 oak species, eight are native to California, indi- cated by (N). All the native oaks are white oaks, except the following three black oaks: Quercus agrifolia, Q. kel- loggii and Q. wislizenii. 6 Quercus agrifolia Nee. California live oak, coast live oak. (N) Quercus alba L. American white oak. Quercus chrysolepis Liebm. Golden cup oak. Maul oak. Canyon oak. (N) Quercus coccinea Muenchh. Scarlet oak. k Quercus douglasii Hook, and Arn. Blue oak. (N) Quercus durata Jeps. Leather oak. (N) Quercus ilex L. Holly oak. Quercus kelloggii Newb. Kellogg oak. California black oak. (N) Quercus lobata Nee. Valley oak. California white oak. (N) Quercus palustris Muenchh. Eastern pin oak. Quercus phellos L. Willow oak. Quercus robur L. English oak. Quercus rubra L. Red oak. Quercus suber L. Cork oak. Quercus turbinella Greene ( = dumosa Nutt). California scrub oak. (N) Quercus virginiana Mill. Southern live oak. Quercus wislizenii A. DC. Interior k live oak. (N) Mathias and McClintock (1963) do not list Quercus engelmannii Greene, mesa oak or Engelmann oak, as an orna- mental. Several other oaks native to other parts of California are described by Jepson (1923-1925); these oaks are used as ornamentals by some persons in southern California. It gives us pleasure to acknowledge the help of the following people in our work on oak insects: Commercial pest control operators: Mr. Harold Mit- chell, Mr. Donald Hall, Mr. Joe Mori, and Mr. Joseph Wagner; former stu- dents: Mr. Frank Sala, Mr. Armand Sarinana, Mr. William Nelson, Mr. Robert Lyon, and Mr. Noel McFar- land; Dr. Charles Hanson, formerly of the Alco Chemical Co.; the following from the Los Angeles County Agri- cultural Commissioner's Office: Mr. Emory Myers, Mr. Donald Ferrell and Mr. David Dyer; Mr. H. H. Keifer of the State Department of Agriculture; and from the University of California: the late Professor Pierre Miller, the late Dr. Ralph H. Smith, Dr. R. M. Bohart, Dr. E. G. Linsley, Mr. Andrew Deal, and Dr. R. N. Jefferson. Many others have made contributions to our study, for which we are grateful. II. SUCKING INSECTS X he sucking insects include imma- ture whiteflies, aphids, leafhoppers, treehoppers and scale insects, to men- tion but a few. We are also including the mites in this rather artificial cate- * gory, as the effects of their feeding somewhat resemble those of sucking insects. The mouthparts of sucking in- sects, both young and mature, are simi- lar in being composed of several long, thin, needlelike stylets. These stylets v are grooved and are joined to form two parallel tubes, one for the saliva com- ing out of the insect, and one — the larger — for the partially digested food being sucked into the insect. These stylets may be very thin and hairlike, and in the diaspid scales, for example, may be several times the length of the body. The stylets are inserted into a tender, succulent part of the plant, or into or near the plant's vascular tubes, which conduct sugars in solution. A rather well-muscled pump in the front part of the insect's digestive tract sucks in the watery food. In most cases this action removes the water, the mate- rials in solution, and finely divided bodies, such as the green chloroplasts, from the plant cell but leaves the cell walls. Instead of having a normal dark- green surface and crisp feel, the leaf becomes yellowed, in spots or evenly, and is limp. As the desiccated cells die, the leaf surface turns brown, and the leaf may drop. With some other suck- ing insects, such as aphids, that feed on young, tender growth and in the vas- cular system, the leaf may not lose its green color particularly, but will be- come wrinkled and distorted, perhaps partially as a result of the toxic action of the saliva on the growth-controlling mechanisms in the individual cells. The scale insects may cause weaken- ing or death of the twigs on which they are feeding. Sucking insects are often found in enormous numbers on particular parts of the plant, such as the new growth. Many of these gregarious groups, such as the aphids, move very little, or, like the scale insects after their first molt, not at all. Others, such as the leafhop- pers and treehoppers, may be quite agile and move quickly. It would seem that the sole defense of some of the sucking insects against their enemies is not escape but their great prolific- ness. Except when newly hatched, some of the sucking insects — the scales, for example — have very little resemblance to other insects. When mature, the scales may resemble a bead or a pebble, or may be covered with an "armor" that resembles the head of a pin or a minute oyster shell. Generally, sucking insects are smaller than the leaf-consuming or boring in- sects, which are discussed later. Some sucking insects, such as aphids and the coccid scales, defecate honey- dew, which drops on the leaves or on articles under the tree. Usually a black smut fungus lives on this sticky solution, which makes the plant ap- pear as if it were dusted with coal * dust and causes it to be very unsightly. The honeydew is defecated as a result of the action of the filter chamber in , the insect's digestive tract. The filter chamber concentrates the protein and fat components of the predominantly 4 carbohydrate-containing plant sap; the excess water and carbohydrates are defecated as honeydew. Ants feed on this honeydew and will even transport aphids to a more succulent part of the plant to assure the flow of honeydew. Such honeydew producers are some- 4 times popularly referred to as "ants' cows." Ants will also protect these honeydew producers from their insect enemies. In controlling these sucking insects, therefore, it is also desirable to apply control measures for ants, such as spraying around and on the trunk of the tree (see the section on Control). Discussion of the specific sucking insects that we have found feeding on oaks in southern California follows. Oak treehoppers Figs. 1-3 Occasionally small oak twigs may be found that are dead or dying. Upon close examination numerous slitlike or crescent-like punctures, as in figure 3, may be found on these twigs. These injuries are places where the adult treehopper (Homoptera: Membrac- idae) has inserted its saber-like ovi- positor into the twig and deposited one or more eggs (fig. 1). Careful cut- ting into the bark or wood may reveal these eggs. Such ovipositional punc- tures may be so numerous as to dis- rupt, apparently, the fluid flow in the vascular system of the twig, resulting in its death. There may also be some toxic effects of fluids associated with - 8 Fig. 1. Adult of an undetermined species of oak treehopper on twig of holly oak. 13. 5> the egg or with inserting the egg into the tissue. Adult and immature tree- hoppers further weaken the twig by sucking the sap. Closer examination of the twigs may reveal small colonies of the immature forms of the tree- hopper, as shown in figure 2. Adult treehoppers have the interesting habit of scurrying to the opposite side of the twig or leaf when approached, as do leafhoppers. We do not know the identity of the treehopper illustrated here. It is pos- sibly the oak treehopper, Platycotis vittata (Fabricius); see Essig (1958). But the injury and life cycle stages shown are associated with the same species of treehopper. Essig also lists the variety quadrivittata (Say) — the specimens shown are definitely not this variety — of P. vittata and P. minax Goding as affecting oaks in California and other western states. We have no- ticed membracids on Quercus agrifolia and Q. ilex in April, May, and July, but it is likely that they could be found during any of the warmer months of the year and on other spe- cies of oak. Insecticidal control of the adult and immature forms of oak tree- hoppers is not difficult with high pres- sure, thorough-coverage sprays; we do Fig. 2. Nymphs of an unidentified species of oak treehopper on holly oak twig; note that they are gregarious. 13.5x. Fig. 3. Slitlike oppositional punctures in holly oak twigs made by an unidentified species of oak treehopper. 3.5x. not know of any practical method of killing the eggs in the tissue. Sprays of malathion or DDT have given good control; see section on Control. Black-punctured kermes Fig. 4 The black-punctured kermes, Kermes nigropunctatus Ehrhorn and Cock- erell (Homoptera: Kermidae), is a rather striking gall-like scale insect, whose color is light brown or a darker brown. It is a somewhat "bumpy" scale, being almost spherical. The scale has two black spots near the forward edge, which give the appearance of a hole made by a pin; hence the common name. Although this scale is met with fairly frequently, generally in small groups, it is doubtful if it causes much damage. It may be found on the smaller twigs, the petioles (leafstalks), and the midribs of the leaves. We have seen the scale only on live oaks, but it has been noted (Essig, 1958) on all the black oaks. Although control generally is not necessary, sprays such as those used for the coccid and diaspid scales will eliminate this insect. See section on Control. Fig. 4. Adults of the black-punctured kermes, Kermes nigropunctatus, on twig of coast live oak. 3.5x. 10 Oak pit scales Figs. 5-7 Of all the sucking insects affecting oaks, the pit scales, Aster olecanium species (Homoptera: Asterolecani- idae), have the greatest potential for damage. When the scale settles on the twig and begins to feed, a swelling of the twig tissue occurs around the in- sect (fig. 7), so that the insect is in effect in a "pit"; hence the common name. In the lower right corner of figure 6, three pits can be seen where scales have been removed. Infestations by these scales on the twigs occur in enormous numbers (see again fig. 6). This has a severe debilitating effect on the twigs, resulting frequently in their death (fig. 5). Such infestations, fol- lowed by drought conditions, can re- sult in severe weakening or even death of mature trees. According to Pritchard and Beer (1950), there are three oak pit scales in California: Aster olecanium variolo- sum (Ratzeburg), called the "golden oak scale"; A. minus Lindinger, and A. quercicola (Bouche). All three species are European in origin and were first noted in California on these dates — A. variolosum: 1913; A. quercicola: 1931; and A. minus: 1944. We first saw what we think is A. minus in southern Cali- fornia (Arcadia) in late 1956, on Quer- cus engelmannii, and it is likely to have been in this location some time before that. Since then it has been found in several other locations along the south edge of the San Gabriel mountain range and on other white oaks. Pritch- ard and Beer say that although A. vari- olosum was the first species found in California, it is rarely seen and then only on the imported English oak, Quercus robur. According to them, A. minus is the most commonly found species in this state. Both black and white oaks are affected by these scales, the latter more frequently. Aster olecanium variolosum, the largest of the three species present, is Fig. 5. Note generally weakened condition of these branches of coast live oak from a severe infestation of an oak pit scale, Aster olecanium minus. 11 W' J*~ - -a * Jl. j** 4 *. '* * ' Fig. 6. Numerous adults and pits of the golden oak scale, Asterolecanium variolosum, on two twigs of Quercus robur. 5.8x. slightly over 2 mm in diameter, and is A. minus and A. quercicola in Cali- yellowish green or golden. Craighead fornia, with crawlers hatching from (1950) notes one generation per year early May to late September. Peak for A. variolosum in the eastern hatch occurs two to three weeks after United States. Pritchard and Beer first hatching. (1950) report that this is also true for A spray of 4 to 5 per cent dormant Fig. 7. Developing pit on twig of Quercus robur of the golden oak scale, Asterolecanium vario- losum. 5.8x. oil emulsion has long been recom- mended, but Pritchard and Beer showed that a spray of 2 per cent light medium oil plus F/2 pounds of actual toxaphene, in emulsifiable form per 100 gallons of water, and timed with peak hatch, gave excellent control. Since then the following spray, timed with peak hatch, has been shown to be quite effective: 1V2 gallons of light medium oil plus 1V2 pints of malathion emulsifiable concentrate (8 pounds per gallon), per 100 gallons of water. See section on Control. Oak wax scale Fig. 8 This insect, Cerococcus quercus Corn- stock (Homoptera: Asterolecaniidae), is seldom met with, but it is so unusual and striking in appearance that the in- formed person should be able to rec- ognize it. Both as a living specimen in nature and in old collections, the scale is a bright yellow. Professor Corn- stock (1916) states, and our own ob- servation confirms, that the body of the female scale is largely composed of yellow wax. Essig (1958) and Jaeger (1940) note that this wax, although ex- tremely bitter, was used by the In- dians as a kind of chewing gum. The clump pictured in figure 8 is typical. The female body is somewhat hemi- spherical, with a lateral ridge of tu- bercles corresponding to the body seg- mentation; the body is about 6 mm long by 5 mm wide. We have noticed crawlers hatching in enormous num- bers in late April. The insect infests oak in the semi-arid foothill and moun- tain regions. Several of our records note it on scrub oak, Quercus dumosa. Control would not be necessary in most cases; if it is desired, however, materials such as oil-malathion com- bination sprays, used for the coccid scales, should give good control; see section on Control. Fig. 8. Clump of adults of the oak wax scale, Cerococcus quercus, on twig of scrub oak; note emergence hole of parasite in center scale. 4.5x. Ehrhorn's oak scale Fig. 9 At one time Mycetococcus ehrhorni (Cockerell), Ehrhorn's oak scale (Ho- moptera: Asterolecaniidae), was one of the most common of oak scales, ac- cording to Mr. Emory Myers, ento- mologist for the County of Los Angeles. Herbert (1936) considers the effects of this insect more serious than those of the oak pit scale, Asteroleca- nium variolosum; this may have been true at the time of his writing and in view of the rarity of the latter. But in comparison to the oak pit scales as a group, now known to be in southern California, we would consider this My- 13 Fig. 9. Colony of Ehrhorn's oak scale, Mycetococcus ehrhorni, on twig of coast live oak in as- sociation with a grayish fungus common to this scale. 3.1x. cetococcus insignificant. Ehrhorn's oak scale is quite widespread on oaks in southern California; but unless one knows where to look and what to look for, most infestations will go unno- ticed. Nevertheless it is an interesting species. The actual body of the scale is small, pyriform (pear-shaped), about 1 mm long, and bright red. But the body of the scale is not visible un- less one digs into the large mass of white secretion and grayish fungus mycelium that usually surrounds it. The "mycelium scale," as Herbert calls it, is thus an appropriate common name also. The appearance of the mass on the twig in figure 9 is typical in a heavy infestation. Lighter infesta- tions do not have this heavy deposit of whitish material. In heavy infesta- tions the lower side of the large limbs is so encrusted with this scale and its secretions as to make the limbs appear whitewashed. Our records note infes- tations only on the coast live oak, but Essig (1958) records the valley and tan oaks as hosts also. An oil-malathion combination spray, such as is used against the pit scales, is effective for control. Because of the difficulty of contacting the insect beneath the mass of mycelium and whitish secretion, Herbert suggested a first spray of 8-8-50 Bordeaux, presumably to kill the fungus, and then a 4 per cent sum- mer oil spray later to kill the scale. This high oil concentration was evi- dently intended only for the limbs, not the leaves. Also, a Bordeaux spray closely preceding sprays of present- day synthetic insecticides would likely render these insecticides ineffective. See section on Control. Oak lecanium scale Fig. 10 This scale insect, Lecanium querci- tronis Fitch (Homoptera: Coccidae), is a very important sucking pest, sec- ond perhaps only to the oak pit scales. Copious quantities of sap are with- drawn by the frequently large scale colonies on the twigs and smaller limbs, thereby killing these and weak- ening the tree. Large amounts of hon- eydew are produced which drop to the leaves and twigs beneath. On this sticky solution lives a black smut fun- gus, sometimes to the extent of making 14 the whole tree appear as if it were dusted with coal dust. Not only does this detract from the ornamental value of the tree, but this sticky solution is a nuisance to persons having posses- sions under the oak tree, such as auto- mobiles and lawn furniture. All our records note that this scale infests only coast live oak in southern California. As can be seen in figure 10, the female scale is very convex, being almost hemispherical, is slightly longer than broad, varying from 4 to 7 mm in length. It is brown, has a smooth, shiny surface that shows a very slight white powderiness. The larger, imma- ture forms usually show a longitudinal median yellow stripe on the dorsum. The eggs, many coming from a single female, are oval and yellowish pink. Hatching occurs in April, and there is evidently a single generation per year. Control by thorough-coverage spray- ing is not difficult if application of the spray is timed for the crawler hatch or shortly thereafter. Control at other times of the year seems to be more difficult. One and one-half to two per cent light medium oil emulsions have been used in the past. However, con- siderable experience has shown that potency of the oil can be increased by the addition of l 1 /^ pounds of actual malathion, in an emulsifiable concen- trate formulation. Dimethoate and Sevin are promising materials for con- trol of this category of insect. See sec- tion on Control. Fig. 10. Adults and crawlers of the oak lecanium, Lecanium quercitronis, on twig of coast live oak. 4.5x. Oak scale Fig. 11 Quernaspis quercus (Comstock), an armored scale (Homoptera: Diaspid- idae), was first described under Chion- aspis, and much of the readily avail- able literature (Essig, 1958; Doane et al, 1936; and Herbert, 1936) assigns it to this genus. However, we are in- clined to follow Ferris (1937), who erects this monotypic genus, Quernas- pis, to hold quercus. This is described as a common scale (Essig; Doane et al.), although we would say it is a rather uncommon scale in our expe- rience. It is, however, much more com- mon than other diaspid scales on oak. We have noticed it only on coast live oak and scrub oak; it was first de- scribed from valley oak and subse- quently has been found on maul and tan oaks (Essig). It is known from the 15 ■£', * % Fig. 11. Males and females (with two female scales inverted to show red bodies) of the oak scale, Quernaspis quercus, on twig of coast live oak. 15.7x. tip of Baja California to the San Fran- cisco Bay region, and in Texas and Florida locations (Ferris, 1937). The female scale or armor is like Chionas- pis, that is, spatulate or oystershell- like, white, but with natural soiling appears gray, and may be elongate or curved, like the center specimen in figure 11; it is about 2 mm long. The female body beneath the armor is red- dish brown or could be called port- wine colored. The females seem to pre- fer the twigs, while the males heavily infest the leaves. According to Ferns, the genus and species are distin- guished from all other scales, when the female body is cleared and exam- ined microscopically, by the fused me- dian pygidial lobes and the scleroses around the marginal pores on the pygi- dium (posterior end of body). The scale of the male is similar to that of many diaspid genera: that is, white, tricarinate (three-ridged), elongate, and about 1.3 mm long. Control is not difficult; malathion alone, or — better — in combination with fight medium oil, offers good control. See section on Control. Crown whitefly Figs. 12-13 Aleuroplatus coronatus (Quaintance), the crown whitefly (Homoptera: Aley- rodidae), is perhaps the most common of the insects affecting oaks throughout this area. Our records show coast live oak as the most frequent host, but list interior live and scrub oak, too. Essig (1958) and Herbert (1936) include valley and tan oaks also. Frequently one finds live oak leaves whose lower surface is covered with the immature forms (fig. 12). The tree bears such huge infestations without apparent damage. One often finds many heavily infested leaves that have fallen to the ground. A heavy infestation on a leaf may shorten its effective life, causing it to fall before it normally would. The overall effect on the tree might be similar to a fight pruning. Perhaps the crown whitefly is most noticeable to persons near oaks when the adults (fig. 13) are emerging from their "pu- pal" cases on the leaves during the warm days of February, March, and April. These small, fragile, harmless 16 Fig. 12. Immature forms of the crown whitefly, Aleuroplatus coronatus, on the lower leaf surface of coast live oak. 22.7x. (to human beings) white, flying in- sects can then be present in such enor- mous numbers as to resemble the swirling of snowflakes in a storm. Under such conditions the insect is a nuisance, bothering persons, even being in their homes. The most common and distinctive stage of the crown whitefly found dur- ing the greater part of the year is the immature (or "larval" and "pupal") stage, during which the insect is found attached to the lower leaf surface, as in figure 12. This stage is oval, 1 mm long, black, surrounded by a fre- quently unapparent sloping rim of gelatinous material, and covered with rather straight, broad, white waxy plates radiating from the dorsum, these latter somewhat resembling a minute crown; hence the common name. The adult stage, present only for a short period any time from mid- February through April, is much less distinctive; the adult resembles many other whiteflies in having a pale-yellow body with wings covered with dust- like white wax; the body measures about 1.1 mm in length. The eggs (fig. 13) are elongate, fusiform (cigar- shaped), attached by a small stylus at one end to the undersurface of the leaf, and are pinkish white near hatch- ing. After hatching, the crawler finds a suitable place and settles on the lower leaf surface; very seldom will it settle on the upper leaf surface. A ring of white wax is secreted, and gradually the vertical wax plates are secreted. There is only one brood annually. Control of the crown whitefly is not difficult. Oftentimes this whitefly is heavily parasitized, but this condition does not appear to be effective as far as a control method is concerned. Thorough spraying is necessary, with particular effort to cover the lower sur- face of the leaves. Spraying at almost any time of the year will effect some control. Treatment at a time shortly before expected adult emergence or after egg-laying gives optimum con- trol. Sprays of malathion alone or ma- lathion-oil combinations are very effective. Dimethoate is a promising material. See section on Control. 17 Fig. 13. Eggs and adult of the crown white- fly, Aleuroplatus coronatus, on the lower leaf surface of coast live oak; star-shaped bodies are stellate leaf hairs. 13.5x. Gelatinous whitefly Fig. 14 Aleuroplatus gelatinosus (Cocker ell), the gelatinous whitefly (Homoptera: Aleyrodidae), is quite rare compared to the crown whitefly, but is found often enough to be included. Our records indicate only the black oaks as the hosts. The immature stage of this whitefly is found on the lower surface of the leaf. The immature body (fig. 14) rests upon a rather thick, wide, trans- parent layer of what appears to be a gelatinous material; hence the common name. We suspect that this layer is transparent wax. The body is black, oval and about 1 mm long. No white wax plates protrude from the dorsum in this species. Control would hardly be necessary; but if it is considered needed, measures suggested for the crown whitefly would suffice. See sec- tion on Control. Stanford's whitefly Fig. 15 Like the gelatinous whitefly above, Tetraleurodes stanfordi (Bemis), Stan- ford's whitefly (Homoptera: Aleyrod- idae), is not nearly as common as the crown whitefly, but is met with often enough to be included. Whereas crown whitefly is almost never found on the top of the leaf, Stanford's whitefly is almost never found on the bottom. Our records note only the black oaks as the hosts, but Essig ( 1958) states that this insect is also found on the tan oak. The immature case is quite black and shin- ing, and the only waxy secretion is a marginal white fringe all around the body. Control is generally not neces- sary; but if it is, measures suggested for the crown whitefly will suffice. See section on Control. Fig. 14. Immature forms, one inverted, of the gelatinous whitefly, Aleuroplatus gelatinosus, on the lower leaf surface of coast live oak. 21x. T:3?&~\ Woolly oak aphid Fig. 16 Stegophylla quercicola (Baker), the woolly oak aphid (Homoptera: Aphid- idae), lives free on the leaves, or causes the leaves to roll up, or down, and lives inside the marginal pseudogall thus formed (fig. 16). This injury is distinc- tive for this insect. It apparently does not do any appreciable damage, but occasionally may be quite common and people inquire about it. We have found it only on coast live oak in our area. The wingless forms, which cause the pseudogalls, are green, with a de- cided bluish cast. Adults are covered by a mass of loose, cottony wax fibers. Control usually is not necessary; if it is desired, however, see section on Con- trol. Coast live oak erineum mite Fig. 17 The unusual injury inflicted by Aceria mackiei (Keifer), the coast live oak erineum mite (Acarina: Eriophyidae), is met with occasionally (fig. 17). The lower sides of the leaves have concave areas which are filled with reddish hairlike material; such an area is called an "erineum." Among these hairs one may find these minute, elongate, 4- legged eriophyid mites. They are ap- proximately 0.2 mm long. The erineum is represented on the upper leaf sur- face as a convexity. Evidently the feed- ing of these mites induces the oak leaf to produce this typical growth. Unless one has a compound microscope, the morphological details of the mite can- not be seen nor the mite identified. The typical injury, however, will identify the mite with sufficient accuracy for most purposes. Not only have we noted infestations on coast live oak, but also on maul oak and scrub oak. Keifer (1938, 1952) notes these oaks, as well as the interior live oak and the huckle- berry oak, as hosts. We have never had to suggest a control measure for this mite, but it is likely that diazinon, which is effective for other eriophyid mites, would give adequate control; see section on Control. Fig. 15. Immature forms of Stanford's whitefly, Tetraleurodes stanfordi, on the upper leaf surface of coast live oak. 22.7x. few A*J ,...;.■■■■■'* Fig. 16. Upper leaf surface of coast live oak with edges rolled to protect a woolly oak aphid, Stegophylla quercicola. 2.7x. Fig. 17. Gall-like injury, or erineum pockets, of the coast live oak erineum mite, Aceria mackiei, to leaves of scrub oak; (left) lower leaf surface; (right) upper leaf surface. 5.4x. 20 III. LEAF-CONSUMING INSECTS In contrast to the foregoing sucking tively strong muscles so that they are insects, those consuming the leaves are well adapted for crushing plant tissue, members of the higher orders of in- There is no remnant of the plant cell sects — that is, the Lepidoptera (moths structure left, as there is when sucking and butterflies), Coleoptera (beetles insects feed. The cell walls, cell par- and weevils), Hymenoptera (ants, bees tides, and fluid are ground and swal- and wasps), and Diptera (flies). These lowed by the insect. The only time orders have four stages in their life some of these plant parts may be seen cycle: egg, larva, pupa and adult, each again is after they have passed through stage being much different in appear- the insect's digestive tract. The drop- ance from the others. The larva is ping of the grainlike fecal pellets from always a feeding, wormlike stage, the an oak heavily infested with leaf- pupa is a resting stage; the usually chewing larvae — for instance, oak winged adult feeds also, although it worm larvae — may be in such numbers may not consume the same type of as to sound like a light rain. In the case food nor in such quantities as the larva, of young larvae, or some of the smaller Larvae of moths and butterflies have leaf -feeding species, such as the Lamp- chewing mouthparts, and the adults ronia or the live oak weevil, the feed- have long, tubelike siphoning mouth- ing may remove only the upper or parts, thus being well adapted for lower leaf surface, leaving the other feeding on nectar and other liquid surface and the veins intact. This is foods. Larvae and adults of the moths sometimes spoken of as "skeletonizing," and butterflies may feed on different although this term usually refers to the plants, and if on the same plant, cer- removal of both upper and lower leaf tainly on different parts. Both larvae surfaces and spongy and palisade cells, and adults of the beetles have chewing with the veins remaining intact. In the mouthparts and usually feed on the case of larger larvae, the edges of the same plant and often on the same plant leaf may be removed so that the leaf part. Larvae and adults of the may appear scalloped, or holes may ap- tenthredinid wasps have chewing pear in it, or the leaf blade may be re- mouthparts, but they do not neces- moved, with only the midrib remain- sarily feed on the same part of the ing; or the complete leaf, including the plant; or the feeding of the adult may petiole, may be consumed. In the case be rather inconspicuous compared to of the leaf miners the two surfaces of that of the larva. The fly larva included the leaf are left intact and all or certain here (agromyzid) has mouth hooks for parts of the leaf tissue between the gouging a mine into the leaf tissue, surfaces may be removed. The exact whereas the adult fly probably feeds nature of the feeding damage often on nectar. assists in identifying the insect causing The mouthparts that do the chewing the damage, even though the insect is are, for the most part, the two man- absent. dibles, or jaws. These are quite hard A discussion follows of the specific and opposable in the vertical plane as leaf-consuming insects that we have contrasted to mans in the horizontal found associated with the oak. In the plane. They are supplied with rela- case of the moth larvae, the largest 21 category, the succession of species is from the more primitive to the more highly developed. Only the moth larvae have small hooks (crochets) on their abdominal legs, but crochets may not be present on the primitive Lepi- doptera. Live oak leaf cutter Figs. 18-30 This small insect of interesting habits was identified in 1940 by Dr. Annette F. Braun for Dr. R. M. Bohart, then at the University of California in Los Angeles. She identified it as an unde- scribed species near the genus Lam- pronia, of the Incurvariidae, a family of case-bearing micro-Lepidoptera. We •have continued to assign this generic name to our observations and notes. (Top) Fig. 18. Mines, holes, "houses," and injury of two larvae of the live oak leaf cut- ter, Lampronia sp., on coast live oak leaf. 2.2x. (Bottom) Fig. 19. Holes and "house" roofs being cut — one almost complete and one about half done — by larvae of the live oak leaf cutter, Lampronia sp. 1.7x. The larva of this insect cuts oval holes in the oak leaf (figs. 18, 19, 24, 25), covers itself with the piece cut out (figs. 27, 28), and proceeds to skeleton- ize oval areas, usually on the lower leaf surface. We have noted some trees with most of the leaves so affected (as in Tapia Park, Los Angeles County). The overall effect on the tree is prob- ably similar to a defoliation, that is, a reduction of the amount of chloro- phyll-containing tissue. Otherwise, we have not observed any drastic effects of heavy infestations on the tree. We have noticed this Lampronia through most of southern California where live oaks are found. Although not a com- mon insect, it can be present in large populations as noted above. 22 Fig. 20. Mining injury and frass of first-instar larvae of the live oak leaf cutter, Lampronia sp., on lower leaf surface. 6.7x. (Mine on left here is enlarged in figures 21-23.) Fig. 21. First-instar larval mine of the live oak leaf cutter, Lampronia sp., before the frass is expelled from the mine. 25x. mm - 1 % Fig. 22. Mine in figure 21 with most of the frass expelled to the outside of the leaf mine by the larva of the live oak leaf cutter, Lampronia sp. 2(X A near relative of this interesting in- sect is the fairly well-known maple leaf cutter, Paraclemensia acerifoliella, of the eastern states. Comstock and Herrick's account of the activities of the maple leaf cutter, in Needham et al. (1928), makes fascinating reading. The egg presumably is similar to that of the maple leaf cutter (Need- ham et al.): soft, white, elliptical, and deposited singly in pear-shaped pockets beneath the leaf epidermis. The last-instar larva (figs. 26-28) is almost 5 mm long, pale pink; the head and the pronotal, small mesonotal, and anal shields are dark brown. The larva is somewhat flattened, with thoracic legs present (in later instars at least), and has five instars. The pupa (fig. 29) is a pale brownish-yellow color which darkens before maturity. The adult (fig. 30) has a wing expanse of 9 to 10 mm, the fore wing being of uni- form iridescent grayish brown and having an almost obscure light spot on the dorsal, or hind, margin; the head scales are yellowish brown, with the antennae annulated yellow-brown and gray-brown alternately. There are probably two generations per year, although much overlapping of generations has been noted. The adults (spring or summer brood) are present in July, with egg-laying, larval leaf -mining and leaf-cutting occurring throughout the latter half of the year. The affected leaf falls normally in the early spring. Pupation occurs in the in- sect "house" or case either before or after the leaf falls. Many cases can be found separate from the leaf and ad- hering to the underside of nearby ob- jects, such as stumps, logs, fences, patio tables, and so forth, where the larvae have crawled to pupate. New mines can be found on the new leaves from January into March, indicating that adults (fall or winter brood) have emerged and that ovipositing has oc- curred. Considerable leaf-cutting and 24 Fig. 23. Lower leaf epidermis of the mine shown in figures 21 and 22 has been removed to expose the first-instar larva of the live oak leaf cutter, Lampronia sp. 20x. skeletonizing occur on the new leaves in March, April, and early May. Pupae are found late in May, and adult emer- gence occurs again throughout July. After hatching, the larva begins min- ing, making first a linear mine; this is gradually absorbed into a blotch mine, in which all the tissue is removed be- tween the upper and lower leaf epi- dermis (figs. 20-23). At first the frass is kept in the mine, but as the larva gets older it expels the frass out- side the mine, as in figures 20 and 22. After the second instar the larva cuts the silk-tied upper and lower mine epidermis into a small, oval envelope or purse (which becomes the inner "house"). With only the head and thorax protruding, the larva drags its purse to an unaffected part of the leaf and begins to cut out an oval about 8 mm long (figs. 24-26). It then inverts this oval leaf bit over itself and the original mine forming the purse (the inner "house"), so that the oval be- comes the roof of the outer "house." The larva attaches the complete edge of the oval to the leaf with silk and pro- ceeds to feed (i.e., skeletonize) on all the enclosed surfaces of the leaf and cut oval (fig. 27). Since this usually is not enough food, the larva cuts the silk and moves its inner and outer houses to a clean portion of the leaf — some- times even to the opposite side of the leaf — and repeats the skeletonizing process; this happened with the two larvae in figure 18. Pupation occurs within the inner house (fig. 29). The pupa protrudes about half way out of the outer house before the adult emerges. As to control measures, we have usually suggested DDT sprays up to the middle of May for the larvae or into July for the adults. It is likely that Sevin would be a satisfactory control agent, as it has been recommended for closely related pest insects; see section on Control. 25 Fig. 24. While remaining in a "house" of the upper and lower leaf mine epidermis, the live oak leaf cutter larva, Lampronia sp., cuts an oval for a new "roof." llx. Fig. 25. Same larva and "house" as in figure 24, but larva has rotated house, illustrating method of cutting oval hole. llx. 26 Fig. 26. Larva of the live oak leaf cutter, Lampronia species, in figures 24 and 25 is here exposed; also note some surface feeding, llx. Fig. 27. A "roof" of the live oak leaf cutter, Lampronia species, has been lifted to expose larva in its "house-within-a-house"; note feeding on enclosed surfaces. 6.5x. 27 Fig. 28. Exposed larva of the live oak leaf cutter, Lampronia species, as it nears pupation; "roof" is normally attached to leaf by white silken threads at its edge. 13. 5x. Fig. 29. Ventral aspect of pupa of the live oak leaf cutter, Lampronia species, in its "house- within-a-house." 13.5x. 28 ill! s. Fig. 30. Living adult of the live oak leaf cutter, Lampronia species, in characteristic attitude at rest. 12. 8*. Oak ribbed case maker Figs. 31-34 The oak ribbed case maker, Buccula- trix albertiella Busck (Lepidoptera: Lyonetiidae), is one of the more com- mon insects affecting oak, and at times it can cause serious leaf damage. The larva first mines the leaf and then comes out of the mine to skeletonize the undersides of the leaves in the later ins tars. In heavy infestations the larvae may consume most of the chlorophyll, giving the leaf a brownish appearance (fig. 31); the overall appearance of the tree is of a decided brownish hue in such heavy infestations. So far as we know, having observed damaging in- festations on both coast live oak and valley oak, both black and white oaks are affected. We have not observed the egg, but presumably it is similar to that of other Bucculatrix species which, as noted by Needham et al. (1928), is minute, pale green, elliptical, iridescent and rough- ened. The larva is more or less cylindri- cal, even when just hatched, in contrast to Lithocolletis species, whose early in- stars are flattened. It tapers slightly toward both ends, with moderate inter- segmental incisions. Thoracic legs are present. Also present are well-de- veloped prolegs, which have a double row of uniordinal crochets on all ex- cept the anal pair; the latter have only one row. The larva is smooth-skinned while mining, but has hair-bearing tubercles later. The pupa is shining, rich brown, with a relatively short pro- jection on the head for piercing the cocoon. The cocoon is commonly found and is rather distinctive for the genus (fig. 32). It is white, 6 mm long, bluntly rounded at the ends, with con- spicuous ribs or ridges running longi- tudinally. Snodgrass (1930) gives an ex- cellent illustration of how this beauti- fully intricate, basket-like cocoon is woven by figure-eight head move- ments of the larva. When newly made, the cocoon may be surrounded by a palisade of erect silken hairs, the pur- pose of which is unknown, but perhaps is to distract possible insect enemies. The adult (see fig. 33 — these are Busck's types) has a wing expanse of about 8 mm. The fore wing has four poorly defined brown ocherous areas, 29 Fig. 31. Larval injury of the oak ribbed case maker, Bucculatrix albertiella, to leaves of valley oak. l.lx. a basal spot, two central oblique areas, and an apical area. These areas are separated by white scale borders. There is a mid-dorsal area with a black spot of raised scales and a few black scales at the apex. The posterior fringe is as wide as the wing. The hind wing is silvery white, lanceolate (lance- or dagger-shaped), and has a surround- ing fringe wider than the wing. The head and thorax are brown-ocherous. The abdomen is silvery white. We suspect that there are two broods a year, or more likely, one spring brood and a partial summer brood. New cocoons can be found in the spring and again in late summer. The spring brood adults emerge in late April and May. It is probable that there is a long pupal diapause for some of the spring brood and all of the sum- mer brood. Although we have not ob- served it, if Bucculatrix albertiella is like the rest of the genus, the larva Fig. 32. Cocoons of the oak ribbed case maker, Bucculatrix albertiella; note few palisade hairs on right. 13.5x. 30 *-'f Fig. 33. Adults, cocoon, and emergent pupal "skin" of the oak ribbed case maker, Buc- culatrix albertiella; these were labeled "Type No. 12693" at the U. S. National Museum. 5.1x. hatches by boring immediately into the leaf tissue. There the first instar is spent mining in a more or less linear mine. Then it comes out of the mine and spins a flat, circular cocoon (fig. 34). In this cocoon it sheds its skin and soon emerges to feed externally on the lower surface of the leaf, removing all the leaf tissue up to the upper epider- mis but leaving the veins. For the next and succeeding molts it spins addi- tional cocoons and molts therein. There are probably five larval instars. The fifth-instar larva spins the typical co- coon and pupates therein. The cocoons are spun frequently on the leaves, but may also be on the twigs or limbs of the oak, or other plants near the oak. Thorough-coverage sprays of DDT wettable powder applied during April will readily control this insect. It is probable that sprays of Sevin would also be quite effective; see section on Control. Oak leaf blotch miner Figs. 35-39 Leaf mines of the oak leaf blotch miner, Lithocolletis agrifoliella Braun (Lepidoptera: Gracilariidae), are seen Fig. 34. Molting cocoon of the oak ribbed case maker, Bucculatrix albertiella, on lower surface of coast live oak leaf. 3.6x. occasionally. We have never observed the insect in any situation where it could be called a pest. However, the mines are quite obvious, and requests for information concerning the insect continue to arrive. The blotch mines are white and are only on the upper surface of the leaf (fig. 36). The mines begin as a linear or serpentine type (fig. 35); as the larva gets older, it ex- pands the mine into the blotch type shown in figure 36, the larva feeding outwardly. We have noticed these blotch mines only on the black oaks throughout this area. The egg (fig. 37) is nearly flat, almost transparent, and is quite smooth-sur- faced; it is laid singly. The larvae of Lithocolletis species are unusual in being of two types. According to Braun (1923), the larvae of this species be- longs to the second type (the "flat" or Carrier aria group), which is "very much depressed, almost flat, with the sides of the segments projecting, thus giving the entire larva a beaded appearance." The earliest instars are like the right- hand specimen in figure 38; the larva then develops like the specimen in figure 39, with dark segmental macula- 31 Fig. 35. Initial injury of the oak leaf blotch miner, Lithocolletis agrifoliella, to leaves of coast live oak. l.lx. tions and a beaded appearance, the head still being definitely spadelike (prognathous). The larva on the left in figure 38 is likely the eighth instar; this large number, according to Dr. Braun, is distinctive for this group; also typi- cal is the fact that this instar is more cylindrical, with better-developed legs and the head tending toward being hypognathous. Near pupation, the larva lines the mine with silk, and pupation occurs in the mine. Emer- gence occurs after the pupa, by vigor- ous wriggling, pushes through the wall of the mine. The adult has a wing expanse of 7.5 to 9 mm. The fore wing Fig. 36. Injury of the oak leaf blotch miner, Lithocolletis agrifoliella, to leaves of the coast live oak. l.lx. is orange-red with these markings from the base: two small dark spots, two larger white spots, black-margined dis- tally; a V-shaped white mark with apex toward the wing apex, black-margined distally; and near the wing apex, a slight sigmoid white mark heavily black-margined distally. According to Dr. Braun, the moths of this second Lithocolletis group are easily recog- nized by the white markings of the fore wings being always externally dark-margined. The hind wing of this species is a metallic bluish gray, and the abdomen has the same coloration. Fig. 37. Glistening and somewhat translucent egg of the oak leaf blotch miner, Lithocolletis agrifoliella, on upper leaf surface near vein. 31x. Fig. 38. Two larvae of Lithocolletis agrifoli- ella; younger, on the right, is legless and has flattened spadelike head, while older has true legs and hypognathous head. 19x. ?'•''■' v V ■ : ' Fig. 39. Larva of Lithocolletis agrifoliella in an exposed mine; note form of mine, disposition of frass, and area of recent feeding. 5.4x. Apparently the oak leaf blotch miner spends the winter months as a larva in the mine. Pupation occurs in March through May. Small mines may be noted again in June. There are quite possibly two generations annually. We have never been asked for con- trol measures for this insect, but it is probable that a thorough-coverage DDT spray, applied in March or into April — i.e., before or as adults are flying — would achieve adequate con- trol; see section on Control. Stenomid oak leaf tier Figs. 40-45 The interesting moth called the steno- mid oak leaf tier, Setiostoma fernal- della Riley (Lepidoptera : Stenomidae), is "nowhere common," as Keifer (1936) states, but we have found the larval damage common enough in southern California to be included here. Con- spicuous whitish spots are first noticed on the leaves, as in figure 40; on closer examination these are seen to be two leaves tied together. Sometimes a third or fourth leaf may overlap, as in figure 40 and be tied in, although usually only the two leaves are worked on. If one pulls the leaves apart, the skeleton- izing injury, frass (consisting of par- tially chewed leaf bits and fecal pel- lets), and surrounding silk and frass wall can be seen; and sometimes the larva (figs. 41, 42) or pupa (fig. 43) may be found. An infestation on a single tree may be fairly heavy, but other oaks in the area may be unaffected. We have found the insect and its damage in Santa Barbara County (Buellton, Solvang and Santa Barbara), Los Angeles County (Tapia Park, Hol- lywood, Malibu, Sherman Oaks), Orange County (Yorba Linda), and Riverside County (Oak Glen). We found the insect only on black oaks, as did Keifer in other parts of the state. Fig. 40. Several pairs of coast live oak leaves tied together and injured by the stenomid oak leaf tier, Setiostoma fernaldella. 0.5x. «$r» M (Top) Fig. 41. A pair of coast live oak leaves has been pulled apart to expose the enclosed larva, frass, injury, and silk of the stenomid oak leaf tier, Setiostoma fernaldella. 2.3x. (Center) Fig. 42. An exposed larva and injury of the stenomid oak leaf tier, Setiostoma fernaldella. 5.1x. (Bottom) Fig. 43. A pair of tied coast live oak leaves pulled apart to expose three pupae and cocoons of the stenomid oak leaf tier, Setio- stoma fernaldella. 3.7x. Fig. 44. A living and colorful moth of the stenomid oak leaf tier, Setiostoma fernaldella; the forward part is chartreuse in color while the wing tips are a deep chocolate-brown. 8.4x. Fig. 45. Pinned adults of Setiostoma fernal- della; female above and male below. 5.1x. This very colorful moth, in both adult and larval stages, has been diffi- cult to place in a family; at one time it was placed in the Hyponomeutidae, then in the Glyphipterygidae, and finally in the Stenomidae (Keifer, 1936; McDunnough, 1939). Forbes (1923) places the genus in the family Xyloric- tidae. In the eastern U.S.A. there is a close relative, Setiostoma xanthobasis, which has a similar relationship to oaks (Forbes). Keifer states that the western species is one of the few members, if not the only member, of this family in the western United States. We have not seen the eggs, but pre- sumably they are laid singly on the leaves. The larvae (fig. 42) at maturity measure 12 mm in length. The thorax is dark red and somewhat wider than the abdomen, which is greenish gray with two dorsal reddish spots on each segment, and with a more or less con- tinuous reddish line along each dorso- lateral junction. The prothorax and ninth abdominal segment are chiti- nized dorsally, and the head is brown- ish. The pupa (fig. 43) is 5 to 6 mm long, brown to greenish brown, with abdominal segments 5, 6, and 7 mov- able; the venter of segment 7 has a ridge with 4 to 6 recurved spines. The adult (figs. 44, 45) is strikingly colored; when the wings are folded over the abdomen, the anterior third of the body (including the head, prothorax, and base of the fore wings and meso- thorax) appears bright yellowish green, and the remainder deep coppery chocolate-brown. The wingspan is 12 to 14 mm. The costal margin of the fore wing basally is brownish black, and the darker distal portion has several patches of scales sticking up in tufts (the highlights in the photo- graphs). The apex of the fore wing is bent downwards, giving a truncate ap- pearance at rest. The hind wing is mainly black with white fringe scales; there is a lanceolate white area along the base of the subcostal vein. The female antenna is filiform (hairlike) with alternating black and white seg- mental rings; the male antenna is simi- lar but with much long hair on the posterior. The body is black-scaled, the 35 Fig. 46. Larval injury and leaf-rolling of the fruit tree leaf roller, Archips argyrospilus, to terminal leaves of coast live oak. l.lx. tarsi having alternate black and white segmental rings. At the various locations mentioned above we have noted mature larvae from mid- March into mid-May and pupae in the "nest" from early May to mid-May; all the adult emergence has occurred between late May and early June. At one location we observed half- grown larvae in mid-September. There is one generation annually. We have never had to suggest a con- trol measure for this insect, but it is likely that a thorough-coverage spray of DDT, methoxychlor or Sevin ap- plied in late May would be effective against the emerging adults. Sprays in March and April would achieve a de- gree of control of the leaf-consuming larvae. See section on Control. Fruit tree leaf roller Figs. 46-50 Archips argyrospilus (Walker), the fruit tree leaf roller (Lepidoptera: Tortricidae), is one of the most com- mon, well-known and important insect Fig. 47. Twigs of coast live oak with egg masses of fruit tree leaf roller, Archips argyro- spilus, from which the larvae have hatched. 2.5x. pests. This tortricid is known to attack a very large number of different plants, particularly the pome fruits, such as apple, pear, peach, etc., and a number of shade and ornamental trees, includ- ing the oak tree. The larvae are voracious feeders, feeding on and within "nests" or hiding places made of leaves they have rolled and tied together with silk (fig. 46). When the insect is abundant, as has been the case periodically with the oak tree in south- ern California, the trees may be entirely defoliated over relatively large geo- graphical areas. Extensive webbing may be spun over the leaves and branches of the trees and on the plants and ground beneath the tree. There were particularly heavy infestations and damage from this insect during the years 1951, 1952 and into 1953 in Pasa- dena and in the San Bernardino Moun- tains. We have observed the insect many times since, but not in such num- bers; its typical population "explosions" are of a somewhat sporadic nature. We have noticed this insect on coast live oak, interior live oak, and California 36 Fig. 48. Mature larva of the fruit tree leaf roller, Archips argyrospilus, on leaves of coast live oak. 4 Ax. black oak. It is known throughout the United States and in many other parts of the world. Like other tortricid moths, this in- sect lays irregular flat masses of 50 to 100 eggs (fig. 47), the eggs somewhat overlapping each other, shingle-like, and the mass being entirely covered with a whitish cement. When the Fig. 49. Pupa of the fruit tree leaf roller, Archips argyrospilus, from the rolled leaf nest of coast live oak. 5.1x. larvae hatch, they gnaw their way out of the egg, leaving many fine holes in the mass. The larva (fig. 48) at maturity may be from 20 to 25 mm long, of vari- ous shades of green, with a shining black or brown head and prothoracic shield; there are pale tubercles at the base of the hairs. This leaf roller is typical of the family in that it wriggles Fig. 50. Adults of the fruit tree leaf roller, Archips argyrospilus. 5.3x. 37 violently when disturbed and may drop, hanging by a silken thread. It may be found in the rolled leaf nest, usually in the terminal leaves, crawl- ing exposed over the leaves and twigs of the oak, or hanging, abdomen down, by a silken thread from the tree. The pupa (fig. 49) is about 11 mm long, light to dark brown, and is formed usually within the rolled leaf nest; some silk webbing lines the nest during the pupal stage. The adult (fig. 50) has a wing expanse of 20 to 25 mm; the prevailing color is fawn or rusty brown, with a prominent light spot just beyond the mid-costa of the fore wing, and with other spots irregularly placed. The tips of the wings may be more or less rectangular or may curve out slightly at the apex, the outline of the resting moth presenting a kind of bell shape — the term "bell-moths" is ap- plied to many members of this family for this reason. There apparently is only one genera- tion annually throughout the United States, including Califorina (Essig, 1958; Woglum and Lewis, 1947; Met- calf et ah, 1951). In general the adults Fig. 51. Two leaves of coast live oak were pulled apart to expose the pupa, cocoon, and injury of an oak leaf tier, Rhodophaea calig- inella. 5.1x. appear from May to August, although we have noticed them as early as mid- March. Eggs are laid shortly after the adult emerges; the winter is spent in the egg stage; there is apparently a long egg diapause (period of rest or low metabolic activity). In general the larvae hatch in March, April and May, but we have noticed them as early as the first part of January. A number of insecticides, such as DDD, Sevin, and DDT, are effective against this insect and are currently being recommended for use against this and other leaf rollers; see the sec- tion on Control. Spray in the spring at the first sign of larval injury, and with enough spray pressure and volume to penetrate the "nests." If, on the basis of a large number of egg masses, a heavy infestation or epidemic can be predicted, watch development of the egg masses, and spray at the first sign of hatching. Phycitid oak leaf tier Figs. 51-52 Although Rhodophaea caliginella (Hulst), the phycitid oak leaf tier Fig. 52. Adult of an oak leaf tier, Rhodophaea caliginella, resting on an injured leaf of coast live oak. 5.1x. (Lepidoptera: Phycitidae), is not a common insect, compared, for ex- ample, with the California oak moth, it is one of the leaf tiers affecting oak that the informed person should recog- nize. It is found throughout this area and, according to Dyar (1902), it is also found in Arizona and New Mexico. The larva ties several leaves together with silk and feeds on the enclosed surfaces. There is much frass of rather large particles in the nest, as well as a considerable amount of silk and pieces of dead leaf in the walls of the nest, and there are some rather definite silken tunnels in which the larva usually stays. We have noticed this insect on coast live oak, but it is very likely also to be found on the in- terior live oak. Damage appears as a group or clump of dead leaves. We have not observed the eggs, but presumably they are similar to those of other members of the family: very small, ovoid (egg-shaped), whitish, and laid singly on the oak leaf. The larva is 10 to 12 mm long at maturity, with a translucent gray area on the dorsum of each segment (like 2 gray lines Fig. 53. Egg mass of a tent caterpillar, Mala- cosoma species (probably either calif ornicum or constrictum) , on twig of Quercus vaccini- folia. 5.9x. down the back); the rest of the seg- ment is of translucent brown. There is a large, white-centered black tubercle on the metathorax. The head and pro- thoracic shield are light brown. Gen- erally the larvae are in open-ended silken tunnels surrounded by frass be- tween the tied, skeletonized leaves. The pupa is about 9 to 10 mm long, of a dark, shining mahogany brown, with the abdomen finely punctate dorsally. It is found in a flimsy silken cocoon in the leaf nest (fig. 51). The adult (fig. 52) is about 12 mm long at rest; its wingspan is about 22 mm. It is gray generally. The fore wing is as follows: the first third from the base has a light- brown line curving from the costal to the anal region; this line is bordered basally with black scales, forming an elongated black area, and white scales. A broad diagonal area of white scales extends from two-thirds out on the costa back to the anal region, the fore- going white area being bordered dis- tally with a broad brown line; there are several indistinct dark spots on the outer border of the fore wing. The hind wing is uniformly off-white. Palpi (mouth feelers) are prominent, curved up immediately in front of the head. Antennal socket is separated from the eye by a row of scales. When the adult is seen, which is but rarely, it is typi- cally resting on the leaf, as in figure 52. There is probably a single genera- tion annually, or more likely one and a partial second brood. The larval stage has been found from mid-January to early April, and a few young larvae were noted in mid-October to mid-No- vember. Pupae may be found in their cocoons in the nest from about mid- April through May, with empty pupal cases noted in early July. Emergence of the adult occurs from mid-May into early July. Some of our observations indicate that a fair degree of parasit- ism affects tliis moth. 39 We have not had to suggest a con- trol means for this leaf tier, but have noticed an absence of this species on trees sprayed with DDT for oak moth or twig girdler. It is likely that insecti- cides such as Sevin and malathion, used on other phycitid species, would be effective on this one, too; see section on Control. As with other leaf tiers and leaf rollers, a thorough-coverage spray should be used on the oak tree, with sufficient volume and pressure of spray liquid to penetrate the leaf nests. March into early April would be an appropriate time to spray. California tent caterpillar and oak tent caterpillar Figs. 53-58 Malacosoma californicum (Packard), the California tent caterpillar, and Malacosoma constrictum (Stretch), the oak tent caterpillar (Lepidoptera: Lasiocampidae), may be found attack- ing live or deciduous oaks in this area. Occasionally they may be found in epidemic numbers (Burke, 1932), feed- ing voraciously on the foliage. A num- ber of other host plants are recorded for these caterpillar species (Essig, 1926; Langston, 1957). Burke and Langston report tents made by Mala- cosoma californicum, but M. constric- tum is said not to make tents; we have not observed tents made by either species. The eggs (fig. 53) are laid around the smaller twigs in a dark, frothy glisten- ing mass, with the surface hardening shortly after laying; apparently weath- ering during the winter may dissipate this dark shellac-like material sur- rounding the yellowish-white eggs, as has occurred in the specimen shown. The larva is the stage most likely to be observed during the year; the species are similar except as indicated: Mala- cosoma californicum (fig. 55) is quite black overall, with a very slight amount of blue on each segment near the dorsal midline; there is an orange line between the most dense hair tufts along the side; all hairs are orange. M. constrictum (fig. 54) has much more blue showing on the dark background, especially along the dorso-lateral in- tersegmental line. The dorsal hair tufts are orange, but the lateral hair tufts are white. Instead of a line between the lateral tufts, there is a small orange spot, and there is considerable gray below the lateral tufts. The head is quite blue, sprinkled with black spots. The larva of each species is about 35 Fig. 54. Mature oak tent caterpillar, Mala- cosoma constrictum. 2.2x. Fig. 55. Mature California tent caterpillar, Malacosoma californicum; compare with figure 54. 2.2x. i # /'-' * Fig. 56. Cocoon of the California tent cater- pillar, Malacosoma calif ornicum, on the leaf of interior live oak. 2.5x. mm long at maturity. The cocoon (fig. 56) is of tough whitish silk and incor- porates larval hairs; it may be found in almost any location, including the leaf as shown. The pupa (fig. 57) is about 19 mm long. The head, wing pads, and all of the dorsum are dark brown to black near emergence; the abdomen is covered with sparse brownish hair. The wing pads reach to the middle of the fourth abdominal segment. The adult (fig. 58) has a 24 to 27 mm wing- span, with the body thickly covered with long, light-brown to reddish- brown, furlike hair. Apparently there ifcw \ f t v:,/ w ' ^ f Fig. 57. Cocoon in figure 56 opened to show the pupa of the California tent caterpillar, Malacosoma calif ornicum. 2.6x. can be considerable variation in the fore-wing coloration: there may be light lines on a darker brown, or dark- brown lines on a light-brownish-white background. The hind wing is uni- formly light brown to reddish brown, and is in general darker than the fore wing. There is but a single generation per year, with overwintering occurring in the egg stage. The caterpillars hatch in the early spring and begin feeding. The adults are flying during April, May, June and July, with a peak oc- curring perhaps in June. Control of these tent caterpillars is not difficult with a thorough-coverage spray of DDT. Spray in the spring for the larvae or when the larval damage is noticed. Other materials, such as Sevin and methoxychlor, are equally effective; see section on Control. Western tussock moth Figs. 59-64 The distinctive larvae of Hemero- campa vetusta (Boisduval), the west- ern tussock moth (Lepidoptera: Ly- mantriidae), feed on the leaves and can cause a serious defoliation in a large geographical area. Although Fig. 58. Adults of the California tent cater- pillar, Malacosoma californicum, showing typical color variation. 2.2x. 41 Fig. 59. Eggs of the western tussock moth, Hemerocampa vetusta, on oak leaf; note hairs of female clinging to eggs. 3.6x. oaks are fairly seriously affected, they are not as favored as host plants as are members of the rosaceous family — for example, the commercial pome fruits, pyracantha, etc. The insect may be found on any of the oak species in southern California. The egg (fig. 59) is 1.2 mm in diame- ter, spherical, and opaquely white. The eggs are laid in clumps in closely matted gray, felty masses upon the old cocoons or bark of the larger limbs. One often finds the female atop the egg mass as though she were attempting Fig. 61. Male pupa, cocoon, and cast larval skin of the western tussock moth, Hemero- campa vetusta; from oak. 3.6x. Fig. 60. Mature larva of the western tussock moth, Hemerocampa vetusta, on oak leaf. 3x. to brood it or protect it as a hen would her eggs. The larva (fig. 60) is quite distinctive and is readily identified among the many insects affecting oak. It is 13 to 22 mm long, black with nu- merous brightly colored tubercular red and yellow spots; each red spot is the source of long, radiating gray- white hairs. There are four median white dorsal tufts and one posterior gray dorsal tuft of hairs, or tussocks, and two long anterior tufts and one posterior black hornlike tuft. Accord- ing to Volck (1907), there are five in- Fig. 62. Female pupa, cocoon, and cast larval skin of the western tussock moth, Hemero- campa vetusta; from coast live oak. 3.3x. Jt 42 stars. The cocoon (figs. 61, 62) is loosely composed of grayish-white silk and incorporates many of the larval hairs. The male pupa (fig. 61) is 12 mm long, glossy, translucent brownish black, with the wing pads coming down to the abdominal segments, and the conspicuous pectinate (comb- or feather-like antennae curving down from the head like a ram's horns. The female pupa (fig. 62) is about 16 mm. long, glossy, translucent light yellow- ish brown, without wing pads or con- spicuous antennae; the short filiform (hairlike) antennae curve down and parallel the palpi. The distinctive adult female (fig. 63) is 12 to 15 mm long, with wings apparent only as pads; the integument is glossy black and is al- most completely covered with long, wavy pinkish-gray hair. The antennae are short and filiform. The adult male (fig. 64) is winged, with an expanse of 20 to 27 mm, is generally brownish with grayish-white and dark-brown markings; the density of color is some- what variable. Volck states that a single generation occurs per year, this being for the Pa- jaro Valley near Watsonville, Califor- nia. Atkins (1958) agrees that there is a single generation; his observations were made in southern California. From our observations, however, we feel reasonably certain that there are two generations annually, or at least one and a partial second brood, in southern California. The generally warmer temperatures in this area, as compared to Watsonville, may account for this; we have noticed this effect with other insects also. In southern California larvae are commonly found feeding in March, April, and May and again from late August into late Octo- ber. Adults may be seen from May into July; again in September and Octo- ber some may be found. Like certain other insects, this one apparently is subject to sporadic outbreaks; popula- tions in some years are very high; in other years the insect is difficult to find. Insecticidal control of the larvae of this insect is not difficult. A thorough- Fig. 63. Female of the western tussock moth, Hemerocampa vetusta; note aborted wings. 5.1x. Fig. 64. Pinned male specimens of the west- ern tussock moth, Hemerocampa vetusta. 2.2x. 43 coverage spray of DDT, applied when the larvae are first noticed in the spring, affords excellent control. DDD and Sevin are also very effective when used against this insect; see section on Control. California oak moth Figs. 65-71 During years of normal rainfall the California oak moth or oak worm, Phryganidia calif ornica Packard (Lepi- doptera: Dioptidae), is perhaps the most important insect affecting oak in southern California. (We feel that dur- ing drought years the oak twig girdler, Agrilus angelicus, is perhaps more im- portant.) The larvae are voracious feeders on the foliage of all species of oak throughout this area; they almost never attack any other genera of plants. All our observations concern the coast live oak. As noted by Burke and Herbert (1920), winter populations of eggs and larvae are eliminated on the white, or deciduous, oaks when the leaves fall. Attacks are sporadic; some years the oak moth is difficult to find, and other years large geographic areas of oaks are completely defoliated by it. Although the oak tree may be com- pletely defoliated by oak-moth attack, this will not kill the tree, except possi- bly when there are repeated attacks or Fig. 65. Injured leaves of coast live oak as compared to healthy leaves caused by larvae of the California oak moth, Phryganidia cali- f arnica. 0.6x. when other limiting factors are pres- ent, such as drought. Even so, the com- plete elimination of the food-making tissue of the oak tree curtails growth during the leafless period, and de- stroys the oak's value as an orna- mental plant and shade tree. Figures 65, 66 and 68 illustrate the oak worms' feeding on individual leaves. Interest- ingly enough, the oak moth is the only member of this family found in the United States — it is present only in California, according to McDunnough (1938); other members of this family are usually neotropical in distribution (Bruesetal, 1954). The egg (fig. 66) is about 1 mm in diameter, nearly spherical, slightly flattened on top. It is white when first laid, changes to white with a red spot (see center of photograph) and then to brownish gray and, later, pinkish gray as the embryo nears hatching. After hatching (fig. 67), the larva is whitish with black tuber culate spots, a few hairs, and a relatively large, shiny dark head. The larva at maturity (fig. 68) is 25 mm long, naked (without con- spicuous hairs), black, with prominent yellow and indistinct red longitudinal stripes on the dorsum and lower part of the side. It has a large brown head that is as wide or wider than the body, and the thoracic legs are black and Fig. 66. Eggs, unhatched, hatching and hatched, of the California oak moth, Phryga- nidia californica; note newly hatched larval feeding injury also. 12x. * I *. Mw$m* Fig. 67. Newly hatched larvae of the Cali- fornia oak moth, Phryganidia calif ornica. 16.5x. the prolegs brownish pink. The pupa ( fig. 69) is 12 to 14 mm long, and with- out a cocoon; the surface is shining, smooth, whitish or yellowish, with black, yellow, and red markings. It is suspended by its posterior end (the cremaster, which has tiny hooks that attach to a small pad of silk spun on the leaf or other support). The adult (figs. 70, 71) has a wingspan of 25 to 35 mm, is uniformly pale brown, the an- tennae and wing veins being dark brown. The male (fig. 70) has pectinate antennae and faint yellowish patches near the middle of each fore wing. The female (fig. 71) has filiform antennae, and generally a shining black, scaleless thoracic dorsum. Various authors (Burke and Herbert, 1920; Essig, 1958; Herbert, 1936; Doane et at., 1936) state that there are Fig. 69. Pupa of the California oak moth, Phryganidia calif ornica, on the lower leaf sur- face of coast live oak. 4.4x. Fig. 68. Fourth-instar larvae of the California oak moth, Phryganidia calif ornica, on injured leaves of coast live oak. 2.3x. two broods annually; the three latter evidently base their statements on in- vestigations of the first-named authors, whose area of study was probably in the San Francisco Bay region. The de- velopment of the California oak moth in southern California is somewhat more difficult to understand than indi- cated by Burke and Herbert. The table on page 46 is perhaps an oversimpli- fication, but it attempts to show our concept of the development of this in- sect in this area. For ease of understanding, only two categories of development are consid- ered: early and late, and only two stages of development: mature larvae and adult moths. One would expect that, since there is evidence of five moth flights, there would be five broods, but this is prob- Fig. 70. Adult male of the California oak moth, Phryganidia calif ornica; note light wing spots and pectinate antennae. 4.4x. m*?- :,- DEVELOPMENT OF CALIFORNIA OAK MOTH IN SOUTHERN CALIFORNIA Stage of development Month and Week of Year Jan. Mar. , M °y , July j*2b. Nov. 16 24 _L_ 32 _L_ 40 48 Incidence of Broods Early-developing mature larvae 1st 2nd 3rd Early-developing adults 1st 2nd Late-developing mature larvae* 2nd Late-developing adults* 1st 2nd Adult moth flights Incidence of Moth Flights lst 2nd 3rd 4th 5th * Somewhat comparable to San Francisco Bay Region, according to Burke and Herbert (1920). /^"*** = peak and range of incidence. ably not so. Because of the longer growing season in this area, com- pared to the San Francisco Bay region, mature larvae can be found on the leaves as early as early March and as late as early June. These early-develop- ing larvae permit three broods to de- velop during the year, accounting for the first, third, and fifth moth flights, with peaks in late April, late July, and early December, respectively. The late- developing larvae permit two broods to develop, accounting for the second and fourth moth flights, with peaks in mid-June and early October, respec- tively. The first-generation larvae of both early- and late-developing groups come from eggs laid the previous year by second- and third-generation moths. It is quite likely that the early-develop- ing larvae of one season are the ances- tors of the late-developing larvae of the next season; and, conversely, the late- developing larvae of one season are the ancestors of the early-developing larvae of the next season. Although we indicate the early- and late-developing larvae as definite group entities, this is for ease of understanding our con- cept of the development of this insect; in actuality, there is continuous devel- opment among early and late groups, resulting in the appearance of almost any stage during any part of the year. However, we do have definite evi- dence, as stated above, of five peak moth flights in a season; this was par- ticularly evident in 1952. In view of this evidence we believe that when oak moth is present, there are at least two or three broods annually, with the pos- Fig. 71. Adult female of the California oak moth, Phryganidia calif ornica; note filiform antennae. 3.2x. 46 sibility of more or less in some years. Some years there is no evidence of in- festation. A complete generation will take about 15 weeks to be completed in the summer months to as long as 29 weeks during the so-called winter months in southern California. The egg stage will occupy anywhere from 10 days in the summer to 17 weeks during the winter. The pupal stage will occupy a mini- mum of two weeks. Although a number of parasites and predators of the California oak moth are known, from our observations we cannot come to any conclusion con- cerning the effects of these agents in controlling oak moth or their relation- ship to its sporadic appearance in cer- tain years. The reader is referred to Harville (1955) for a discussion of these factors. For over a decade, DDT has been a standard insecticide for control of both adults and larvae of the oak moth in this area. It is usually suggested as a thorough-coverage spray at 1 pound of the active ingredient per 100 gallons of water (i.e., 2 pounds of the 50 per cent wettable powder). Several other synthetic chlorinated hydrocarbon in- secticides are effective against larval and adult stages of this insect: for in- stance, toxaphene, lindane, methoxy- chlor, aldrin and dieldrin. It is likely also that insecticides such as Sevin and Zectran will find a place in control pro- grams of the future; see section on Control. Timing of sprays should be based on first notice of larvae and/or their injury; this means that in heavy infestations a spray in late March or in April will generally be necessary, and quite possibly a second spray in late May or early June, particularly in situations in which the oak twig gird- ler, Agrilus angelicus, is also a prob- lem. In years of light infestation, or if twig girdler is more serious than oak moth, then the one spray in late May or early June would probably be ade- quate. Salt-marsh caterpillar Figs. 72-76 Estigmene acrea (Drury), the salt- marsh caterpillar (Lepidoptera: Arc- tiidae), is one of the most common of moths. It is widely distributed throughout the United States, and its larvae attack a wide variety of host plants; only occasionally is it found on oaks in sufficient numbers to cause Fig. 72. Eggs and hatching larvae of the salt marsh caterpillar, Estigmene acrea. 4.8x. Fig. 73. An enlarged view of the eggs of salt-marsh caterpillar, Estigmene acrea. 9. 4 '"^"V ^PBfl ■r w> M k*^**i' *■ lEIf Mm£ h ' ' l^n V^^tB sa^$r* ■C^ %§!» *$*^WfcJk\ $V£ Wti&i- ?* ^wS *■ j h' si % ! ~^~ 4k l^te l *^$*J &■&££&■& *^H > j&L 'V\ if^l40Sr !!W W*a^ ^S^H 3&k m ImSki, •■• ^~m Fr/ wfati tilk ^^vlS ^Mw -¥s» <-*fPS w*£*J & ?' m Fig. 95. Pinned adults — female (above), male (below) — of the carpenterworm, Prionoxystus robiniae. l.lx. 60 Fig. 96. Posterior view of the female carpen- terworm, Prionoxystus robiniae, laying eggs in the bark crevices. 3x. discoloration of the trunk from the bleeding of a saplike substance, are indications of the presence of carpen- terworm (fig. 100). The additional evi- dence of large protruding pupal skins in the late spring is an almost certain indication that carpenterworm injury has occurred. Under attacks of several years' duration, the trunk also becomes irregular and gnarled from the tree's attempt to heal over the holes (Childs, 1914). According to Essig (1958), re- peated attacks may cause the death of the tree. Herbert (1936) states that this insect probably causes the death of more oaks than any other insect. Craig- head (1950) notes that the tunnels may permit the entrance of moisture and destructive fungi to the heartwood of the tree. Much tunneling can reduce the structural strength of a limb, mak- ing it a hazard in winds. Upon cutting into the tree, one can find tunnels up to Vz inch in diameter meandering through the heartwood and cambium areas. Many trees in addition to oak may be found infested with this insect. The insect is distributed throughout the United States. The egg (figs. 96, 97) is 2.5 to 3.0 mm long, ovoid, with a distinctly reticu- lated surface; and the color varies from greenish, when first laid, to greenish brown to dark brown just be- fore hatching. The larva (fig. 98) when first hatched has dark pink markings with brownish tubercles at the base of the rather prominent hairs, and a dark reddish-brown head and prothoracic shield. Later the pinkish areas are less prominent and the integument be- comes greenish gray. At maturity (fig. 99) the larva may be 12 mm thick and 65 mm long. The pupa (fig. 101) is up to 50 mm long, dark brown, shin- ing, and with rows of spines on the abdominal segments — a double row on all but the last three segments in the female and all but the last two in the male (Felt, 1905). The adult (figs. 95, 96) is mottled gray nearly throughout; the lighter areas of the fore wings are Fig. 97. Eggs of the carpenter- worm, Prionoxystus robiniae. 8.9x. 61 jgfca if j :r* - Fig. 98. Newly hatched larva of the carpen- terworm, Prionoxystus robiniae. 11. 7x. slightly translucent. The female is larger than the male, with a wingspan up to 90 mm and with gray hind wings. The males have a wing expanse up to 60 mm; the anterior parts of its hind wings are orange-red, and the an- tennae are more pectinate than in the female. This insect has a three-year life cycle (Childs, for the Pacific coast) to four years (Craighead, Felt, for the eastern U. S.). The adults will be found flying from March into July in southern California, with the largest numbers being noted during the middle of this period. Mating and oviposition occur soon after emergence. The eggs are deposited in small clumps in the roughened areas of the bark (fig. 98), and the females may lay a total of 200 to 400 eggs (Craighead, 1950). We have noticed newly hatched first- instar larvae beginning in early June. The young larva feeds first in the cambium region, then gradually bur- rows into the heartwood, where most of the larval stage is spent (Childs, 1914). There are probably at least 62 five instars in the larval stage. In its almost three or four years of bur- rowing, the larva occasionally comes to the surface of the trunk or limb; it is through these openings it makes that the tunnel is cleaned of frass, the latter being spilled on the trunk surface or ground, indicating the presence of a larva. Near the end of the third or fourth year, the burrows are cleaned, lined with silk, and the openings capped with a silken web. Then the larva transforms to the pupal stage in the burrow near a capped opening. About two weeks later, according to Childs, the pupa, by vigorous wrig- gling and with the aid of the spines on the abdominal segments, propels itself through the tunnel and through the silk cap on the tunnel opening (this ac- tion is similar to that of aegeriid pupae in their tunnels). When the pupa pro- trudes about two-thirds of the way out of the tunnel opening, the whole front of the pupal skin splits through the dorsum and venter of the thorax and the head; the adult then emerges. This occurs during the March through July period three or four years after life begins in the egg. {Opposite page) Fig. 100. Sawdust-like mate- rial and bleeding from the roughened trunk bark is often indicative of carpenterworm in- festation. 0.5x. (Below) Fig. 99. The mature carpenterworm, Prionoxystus robiniae. 1.5x. In attempting to control this insect there has been a degree of success in measures aimed at the larval and pupal stages in the tunnels. The poking of a fairly stiff wire down into the burrow is a rather direct method, to be used on a single tree or a few trees, and would probably be most successful near or during the pupal period. A fu- migant such as carbon bisulfide, in- jected by means of an oil can into the burrow openings and plugging the openings with clay or putty, is said to be very effective, according to Childs. He writes that the plug should be re- moved after 24 hours. If more frass is subsequently expelled from the open- ing or a pupal skin protrudes, the fumigation was probably not effective. Measures applied against the adults when they emerge will be most satis- '•** •*'♦' '-$& 1 h m % Ml I - 4 * : '•JkS Fig. 101. Empty pupal skin of the carpenter- worm, Prionoxystus robiniae, protruding from the bark. 2x. factory if some means can be used to predict when the adults will most likely be present. Cages around the in- fested trunk have been built (Burke, 1921) to catch the adults when they emerge. Much frass-expelling activity gives a clue that pupation is about to occur and that adults will soon follow. With daily inspection, the presence of the first protruding pupal skin indi- cates that emergence of the adult pop- ulation is about to occur. When such evidence is found, an insecticide of long residual activity, such as DDT, may be sprayed or brushed on the in- fested area only. This will probably serve to kill the adults at emergence or during egg-laying activities. The insecticide may be sprayed on infested trunk and limb areas at a con- centration equivalent to 1 to 3 pounds of active ingredient per 100 gallons of water. For application with a paint brush to the infested trunk or limb area, a slurry of the wettable powder formulation of this material mav be made by mixing the insecticide with water to the consistency of thin paint. See section on Control. 63 Pacific flatheaded borer Figs. 102-104 Much of the following is adapted from an excellent account of this insect by Burke (1929). He writes that this flat- headed borer, Chrysobothris mali Horn (Coleoptera: Buprestidae), is one of the worst enemies of newly planted deciduous trees and shrubs on the Pacific slope. Including the oak tree, he lists 70 plant species in 21 families that are attacked. Apparently any of these plants, whether young or well-established, that have been dis- turbed from any cause are subject to attack. Some of the disturbance factors may be drought, weakened condition from transplanting, pruning or other injuries that are left exposed, loss of vigor in nursery stock that is pot- bound, sunburned areas on the trunk or limbs, etc. The larva is the stage causing the damage; it mines in the cambium, in the fluid-conducting tis- sues (phloem), and the heartwood areas of the plant. This may cause large areas of the living tissue to die; and if these mined areas girdle the trunk, the whole plant may die; or large limbs may die if they are girdled. The mine is frequently meandering, but it may girdle spirally around a limb. The first external evidence of mining is often a wet spot on the bark. Later the bark over the mined area cracks and peels, making a roughened area (fig. 102). The mines are oval in cross section, and the larva packs them with its frass; the frass is not pushed to the outside of the plant, as is the case with the earlier-described carpenter- worm and sycamore borer larvae. The insect is distributed throughout the western United States and from sea level into the higher mountains. The egg is about 1 mm in diameter, disklike, yellowish white, and may be somewhat wrinkled from being placed in bark crevices by the ovipositor. The larva (fig. 103) varies from 15 to 18 mm in length near maturity; it becomes shorter near pupation. It varies from yellowish white generally to yellow near pupation. In form the larva some- what resembles a horseshoe nail; that is, the anterior end is rather expanded and flattened, and it tapers to a point at the tail end. The head is almost invisible, being sunken into the pro- thorax, so that the prothorax — and not the head, as the common name im- plies — is the wide, flat part. The trans- verse width of the prothorax is about 5 mm, the mesothorax 4 mm, and the metathorax 3 mm. The diameter of the almost beadlike abdominal segments is slightly less than that of the area from the metathorax back to the pointed posterior end. The ratio of the trans- verse width of the prothorax to its lon- gitudinal length is about nine to three. The transverse width of the prothorax is almost half again as wide as the dor- sal plate (not so for the closely related Chrysobothris jemorata, which is also present in this area). Also, C. mali has an ocellus near the antenna which is lacking in C. jemorata. When exposed in the mine, the larva usually has its abdomen bent back upon itself, giving Fig. 102. The bark of this oak limb has been removed to expose the oval tunnels of the Pacific flatheaded borer, Chrysobothris mali. 0.6x. 64 the larva the appearance of a hook. Buprestid larvae have neither thoracic legs nor prolegs. The pupa is 6 to 11 mm long and is translucent white when first formed, to dark bronze-colored near adult emergence. Late in its development the pupa may be seen to have a slight lobe on the anterior margin of the prosternum. The adult (fig. 104) may be from 6 to 11 mm long; it is a dark- bronze to reddish-copper color with rather distinct copper-colored spots on the elytra. The pro thorax and elytra are densely punctate ( as though punc- tured by a pin). The prosternum has a distinct, although short lobe on the an- terior margin (absent in C. femorata). Another difference between C. mali and C. femorata is that in C. mali the large tooth on the anterior femur is smooth on the basal half and dentate on the distal edge. According to Burke (1929), there is but one generation per year; however, in some of the higher elevations it may take three years for two generations to be completed. Adults can be found flying from April through August, but most emergence occurs in June and into July. The adults are particularly Fig. 103. This piece of oak wood has been split to expose the larva of the Pacific flat- headed borer, Chrysobothris mali, and its characteristic tunneling and frass. 4x. active during the warm weather and seem to prefer the warm, sunny loca- tions on the plant. Mating and egg- laying occur soon after emergence. When the larva hatches, it bores through the bottom of the eggshell directly into the bark, thus not being exposed to the atmosphere; such a remarkable adaptation must result from a lack of legs, which would pre- clude crawling about on the bark surface. Not only does the larva pack its frass in arclike waves in the tunnel, but the newly hatched larva even packs the attached eggshell full of frass. Most of the larvae reach maturity by September and October, and hol- low out the pupal chamber in the heartwood and then molt into the last larval or prepupal instar. This pre- pupal larva overwinters. From the middle of March into June, pupation occurs, with the majority pupating be- tween mid-April and mid-May. The adults emerge in the pupal cells and chew their way to the outside, leaving an oval hole (fig. 102) — the majority emerge in June and into July, thus completing the cycle. Burke notes that although this flat- headed borer has a number of natural enemies, they are not particularly effective in keeping it in check. Since, as noted above, a tree that has been disturbed for any cause is much more likely to be attacked, Burke has these suggestions for very young and older trees: (1) Wrap the trunk of the young rooted nursery stock with several thicknesses of newspapers the first year it is set out in the landscape; (2) cut out the larva with a sharp knife from the trunk or limb when the ex- ternal symptoms are first noticed; (3) plant only young, vigorous healthv nursery stock; (4) paint pruning wounds promptly with an asphalt-con- taining pruning compound; and (5) keep nursery stock and mature trees as healthy as possible, with judicious cul- 65 Fig. 104. Pinned specimens of Pacific flat- headed borer, Chrysobothris mail. 5.1x. tivation, watering, fertilizing, and pruning. It is also possible to kill the adults with insecticidal residues when they emerge. The insecticide should be ap- plied as a spray to the injured areas from mid-May into June. Lindane is very effective against buprestid bee- tles, as also is DDT. Use either at a dosage equivalent to 1 pound of active ingredient per 100 gallons of water. However, insecticidal control should not be considered a substitute for the measures suggested in the preceding paragraph, as these are of primary im- portance. See section on Control. Nautical borer Fig. 105 Occasionally adults of Xylotrechus nauticus (Mannerheim), the nautical borer (Coleoptera: Cerambycidae), may be found emerging in large num- bers from the trunk and limbs of oak. Usually this is indicative of some other difficulty affecting the tree, such as drought or dying roots caused by some disease. This insect does not ordinarily attack healthy trees. The larvae bore in the area between the sapwood and the bark; the pattern of the resulting en- graving when the infestation is not large somewhat resembles that of scolytid beetles. The tunnels are con- siderably longer and bigger than those made by scolytids, however. The tunnels are oval in cross section, and there is no nuptial tunnel as with the scolytids. Also, when the infestation is large, the tunnels may be joined to such an extent that the bark is almost completely separated from the wood. The larva of this cerambycid beetle will also tunnel deeply into the heart- wood. Much of the tunnel is hard- packed with dry, powder-like frass. This insect commonly attacks live oaks under stress throughout southern Cali- fornia and occasionally a few other plant species (Essig, 1958). The eggs of this species are laid singly or in small groups in the bark crevices, are fusiform (cigar-shaped), and grayish white. The larva is about 18 mm long, white or yellowish white, and in outline it tapers somewhat pos- teriorly from the enlarged prothorax, although not as much as do larvae of flatheaded borers. The prothorax is more rounded and not as flattened as that of the flatheaded borers; it is without the dorsal and ventral pro- thoracic plates, but the head is simi- larly sunken deeply into the thorax. Larvae of this group are sometimes called "roundheaded wood borers." The center of each abdominal segment is considerably expanded compared to the edges, making the segments appear quite prominent. The larva is legless. The pupa is slightly shorter than the larva and of a similar color when newly formed but darkens consider- ably near adult emergence. Pupation occurs in a cell hollowed out in the bark, and the adult gnaws its way to the outside. The adult (fig. 105) varies from 8 to 15 mm in length, is tan to dark brown, and has variable undu- lating whitish lines across the elytra. The posterior part of the pronotum (top of thorax nearest the head) is 66 Fig. 105. Living adults of the nautical borer, Xylo- trechus nauticus. 3x. black with a pair of ovoid white spots. The pronotum and elytra are punctate and lightly covered with light-brown hairs. The antennae are relatively short compared to those in many ceramby- cids. Sometimes the adults can be seen in considerable numbers running about on the bark, especially on the warmer days, fighting with each other and mating. The adults exhibit excel- lent protective coloration, being very nearly the color of the bark. Chemsak (1963) gives an interesting account of their mating behavior. Adults have been noted from March through September, although Linsley (1961) has found this species to be ac- tive even in December in the San Francisco Bay area. We do not know the number of generations per year; it is likely there is only one per year. Craighead (1950) notes that two Xylotrechus species in the eastern United States produce only a single generation annually. The main control of this insect should be aimed at prevention of its attack. Efforts should be made to keep the tree in as healthy a condition as possible — for example, by judicious fertilizing, pruning, and irrigation. It is possible in some situations that by the time this cerambycid beetle attacks, the tree may be beyond help. It some- times appears that sudden changes in horticultural practices, such as flood- ing irrigations after years of drought, or the installation of storm drains re- sulting in a lowered water table even during years of normal rainfall, or the cessation of irrigation in an orange grove bordered by oaks, may predis- pose the oak to decline. Therefore, it seems wise to make such changes slowly or at least moderately. DDT or lindane sprays, at the rate of 1 pound of active ingredient per 100 gallons of water, will be effective in killing the adult beetle when it is on the oak bark. See section on Control. Oak bark beetles Figs. 106-107 Occasionally one finds pinhole-sized punctures in the bark of the trunk or larger limbs of oak. By cutting out a chip with a hammer and chisel (fig. 107), one can see that the hole goes perpendicularly through the bark to the junction of the bark and sap wood. Along this junction small tunnels branch out horizontally, one on each side of the hole and perpendicular to the grain of the wood. Branching per- pendicularly from each of these lateral tunnels will be many V2 -inch-long tun- nels running parallel to the grain of the wood. Usually these short tunnels are filled with brown dustlike frass. whereas the lateral tunnels are free of frass. Both the inside of the bark and the sapwood will have these engrav- 67 »#*!#g WiJlr< yr/tf-h Fig. 106. Surface of oak sapwood showing extensive tunneling of Pseudopityophthorus species; the few large tunnels were made by adults, while at right angles many larval progeny have tunneled. 2.2x. ings (fig. 106). The hole in the bark and the two lateral tunnels are made by the adults of one of the oak bark beetles, and the many short tunnels running with the grain are made by the next generation of their larvae. When these larvae become adults and gnaw their way to the outside, the bark will be covered with many more of these "shot holes." When infestations of the oak bark beetles, Pseudopityophthorus species (Coleoptera: Scolytidae), are heavy, it is as though a thickly woven cloth had been impressed on the bark's inner surface and on the sapwood, so thoroughly does the tunneling cover these surfaces. In this woven cloth analogy the adult tunnels are the loose horizontal strands and the larval tun- nels are the tightly woven vertical strands. Sometimes considerable bleeding of sap may occur, and fre- quently the holes may appear to be the source of the bleeding. The bleeding sap may ferment and attract other in- sects, and there may be some discolor- ation at the junction of the bark and sapwood, as in figure 107. We have not been able to discover a cause and effect relationship between the pres- ence of the beetles and the bleeding. Several authors (Craighead, 1950; Doane et al, 1936; Essig, 1926; Keen, 1952) note that Pseudopityophthorus species attack only weakened, dying or dead trees. Sometimes these bark beetle pests may be found in great numbers on oak firewood piles. Also, these bark beetles are often found where there is no bleeding. Therefore, it is likely that such bleeding has some cause other than the bark beetles. However, there is little doubt that the death of the oak tree is hastened by the extensive tunneling of these beetles. Two Pseudopityophthorus species are noted as occurring in California: P. puhipennis (Leconte) and P. agri- foliae Blackman (Doane et al.). These very small beetles range from slightly over 1.0 mm to 2.5 mm in length. They are cylindrical, dark reddish brown to black, with the pronotum and elytra finely and densely punctate and with a fine, dense pubescence. The pronotal roughenings do not ex- tend behind the middle at the sides. 68 mm A PI asfis! Fig. 107. On inner surface of this oak chip are four dark, fermenting spots; seen within spots are thread-size, adult egg-laying tunnels of Pseudopityophthorus species going across the grain. 0.45x. The males have a greater development of hairs on the front (Blackman, 1928). Eggs are deposited along the tunnel on each side of the entrance hole. Upon hatching, the larvae begin bur- rowing perpendicularly to this tunnel, and near pupation they tunnel up into the bark, hollow out a chamber, and pupate there. The adult gnaws its way to the outside, flies to another tree, bores in, mates, and begins to lay its eggs, thus completing the cycle. Ac- cording to Doane et at. (1936), Pseudo- pityophthorus pubipennis appears to have two or more generations per year, with the broods overwintering under the bark in the larval and adult stages. As with the previously described boring insects, the most important measure against these oak bark beetles is to prevent their attacks. This can be accomplished by keeping the oak tree in a good state of vigor by judicious watering, fertilizing and pruning. As a secondary measure insecticidal sprays may be used to protect oaks adjacent to infested oaks. DDT, lindane and dieldrin are generally very effective against scolytid beetles, usually at the rate of V2 to 1 pound of active ingredi- ent per 100 gallons of water. See sec- tion on Control. Oak twig girdler Figs. 108-113 If one notices an oak tree in which there are numerous patches of dead leaves throughout the top, the chances are that it is infested with the oak twig girdler, Agrilus angelicus Horn (Coleoptera: Buprestidae). Examining one of these patches closely, one sees that the leaves are intact but are whit- ish brown, much in contrast to the normal dark-green leaves. By tracing back from the dead leaves to the smaller twigs, to the larger twigs, and to the point where the first green leaves are attached, one can cut into the larger twig at the junction of the living and dead tissue. If in peeling the bark at this junction, one notices flattened spiral tunnels, as in figure 108, then an infestation of oak twig girdler is fairly well confirmed. Some 69 Fig. 108. Exposed tunnels of the oak twig girdler, Agrikis angelicus, in twigs of coast live oak. l.lx. part of the tunnels may be filled with a darker brown, coarse, powder-like frass, and if one peels carefully, the delicate whitish larva may be exposed, as in figure 111. If this chain of evi- dence is found on an oak in southern California, then there is no question as to the identity of the insect causing the damage. Occasionally in some loca- tions a patch of dead leaves may have resulted from attack by Styloxus ful- leri, sl roundheaded borer (see page 74). Many different kinds of boring in- sects are attracted to trees that are weakened by drought, and this has been particularly evident in the case of the oak twig girdler during the last 10 to 15 years of subnormal rainfall in most southern California locations. This has been quite noticeable in the undeveloped areas; but even in the highly developed residential areas, despite the seemingly large amounts of water applied, twig girdler attacks have been common. Frequently, in the residential areas, lawn irrigation is in- adequate for supplying water to deep- rooted oaks that were in the neighbor- hood before the homes were built. Furthermore, paved streets, gutters, and storm drains, although neat and necessary in the modern community, conduct away much of the skimpy rain that does fall, thus not adding to the lowering underground water table. In these conditions the oak twig girdler has consistently been a most trouble- some insect, and we would classify it as the number one oak pest in southern California. We have not observed a dying oak whose condition we could say for cer- tain was caused solely by the oak twig girdler. The importance of the insect is due primarily to its deleterious effects on the ornamental value of the oak tree; that is, it affects the relation of the tree to man. Indeed, as far as the physiology of the tree is concerned, an 70 infestation of twig girdler could even have beneficial effects. The amount of leaf surface is reduced, thereby reduc- ing the amount of water loss by trans- piration; such a saving conceivably could be quite important to a tree under drought conditions. A loss of leaf surface would reduce the ratio of leaf surface to available absorbent root surface, so that the effect might be similar to a good pruning, stimu- lating new growth in a subsequent year of possibly better rainfall. But, conversely, the loss of leaves reduces the food-making capabilities of the tree so that it grows less during the period of fewer leaves. On the live oaks the patches of dead leaves and twigs persist on the tree for two years or more, so that for best appearance these must be pruned out. We have observed this twig girdler on coast live oak and interior live oak. Essig (1958) lists it also as occurring on Engelmann oak, tanbark oak, and certain oak species that have been introduced, that is, brought into the area by man. The egg (fig. 109) is 1.2 mm in diam- eter, rather flat, almost black near hatching, and is usually covered with dust which adheres to the somewhat Fig. 111. Mature larva of the oak twig girdler, Agrilus angelicus, next to its mine in the twig; the bark has been removed. 6.9x. Fig. 109. At the right is the egg of the oak twig girdler, Agrilus angelicus, on a twig of coast live oak. 33x. Fig. 110. Mature larva of the oak twig girdler, Agrilus angelicus, removed from its tunnel. 5.3x. Fig. 112. Pupa of the oak twig girdler, Agrilus angelicus, removed from its chamber in the twig; cast larval skin is at posterior end of pupa. 7.8x. 71 V *■ .s^t* ■■■' Fig. 113. Mounted adults of the oak twig girdler, Agrilus angelicus. llx. sticky surface, making it very difficult to see the egg on the twig; it is whitish when first laid. The legless larva (figs. 110, 111) at maturity is 18 to 25 mm long, glistening white. Since this is a "flatheaded borer," the prothorax is the widest part of the body, being 1.9 mm in width, with the head deeply sunken into it. The mesothorax and meta- thorax are the narrowest parts of the body, being 1.4 mm wide. The ab- domen is typical of the Agrilus genus, with the edges of each flattened seg- ment extended so that they are almost as wide as the prothorax. Forceps are at the end of the body for the purpose of grasping each fecal pellet and pack- ing it back into the tunnel. The pupa (fig. 112) is about 7.5 mm long, a deli- cate glistening white when first formed, to blackish bronze near adult emergence, with the legs, antennae and elytra adhering to the body. The adult (fig. 113) is 5 to 7 mm long and slightly less than 2 mm wide through the widest part — the abdomen. The head and pronotum are a dark brown- ish-copper color, and the elytra are somewhat darker. The pronotum is finely rugose (wrinkled), and the elytra arc finely punctate. The males have dark-green faces, while the females have brownish-bronze faces. It requires two years to complete each generation. This means that those eggs that were laid in an even-num- bered year will produce adults in the next even-numbered year; so likewise for eggs laid in odd-numbered years. There is no contact between the even- and odd-numbered year generations. The adults emerge from May into September, but the majority come out of the twigs during the early half of this period. In cooler coastal areas the majority of the adults will be emerging in late June and early July, while in the warmer inland areas they will emerge earlier — that is, from late May to late June. After emergence, the adults fly about the tree, being particularly ac- tive on warm, sunny days; they spend considerable time crawling about on the leaves or just resting on the leaves or twigs. They feed only slightly on the leaves; this damage is insignificant. Mating occurs, and shortly thereafter the female begins searching about on the twigs for suitable egg-laying sites. Usually she deposits a single egg adjacent to some irregularity in the surface of the twig, for instance, at the junction of the current and the pre- vious season's growth, or at a leaf scar or a leaf petiole. She deposits her other eggs singly in similar locations. These egg sites are nearly always on the youngest or smallest twig growth. After two or three weeks the egg hatches by the larva's boring directly through the bottom of the eggshell into the twig. Some frass may be packed in the empty eggshell. The larva bores in the sapwood of the twig, just beneath the bark or in- cluding a very slight amount of the bark. It makes a linear mine which goes toward the older twig growth. The boring of this linear mine con- tinues for three to six months; the mine 72 extends only a few inches down the twig. To this point there is practically no external indication that the twig girdler larva is in the twig. Shortly after this, the larva begins to girdle, or mine spirally around the twig; and as the weather gets warmer in the spring, the few leaves beyond the mine begin to die and turn brown, thus signalizing the presence of the larva. The girdling very effectively cuts off water and nutrients to the outer leaves. During the next season the larva continues its spiral girdling for a foot or more down the twig toward the main stem or trunk; this results in the death of many more leaves and twigs, thus enlarging the patch of dead leaves on the tree. The larva continues to girdle spirally up to the age of ap- proximately 22 months, always toward the living tissue. By this time it may be in twigs as large as V2 inch in diam- eter. At this age the larva turns in toward the center of the twig and be- gins to mine back into the wood it has caused to die; it may mine as much as 6 inches back into this dead, dry wood. Then it hollows out an ovoid pupal cell with one end somewhat nearer the twig surface — the head end. There pupation occurs. The pupal stage occupies approxi- mately two to three weeks, after which the adult emerges in the pupal cell. Soon it gnaws the short distance through the wood to the outside of the twig. This is slightly less than 24 months after its life began as an egg. Furthermore, when it was about half through its larval stage another gen- eration was started in the alternate year. This brief summary of its life cycle indicates that most of the gird- ler 's life is spent inside the twig, only a few weeks of the egg and adult stages being spent outside the twig. It is very important from the viewpoint of in- secticidal control to understand this fact. From this discussion of the oak twig girdler's injury to the tree and its life history, several aspects of its control become obvious. Most important, and as suggested for other boring insects, the tree should be kept in a good state of vigor. This is done by judicious watering, fertilizing, and pruning. Es- pecially is watering important in southern California. Watering should be deep and infrequent. An irrigation should permit water to reach a soil depth of 5 to 6 feet, as can be done with a soaker hose running for two or three days. During the warmer part of the year such soakings need not be re- peated oftener than once every two or three months. Although a number of parasites of the oak twig girdler are reported, they do not seem to be particularly effective in controlling injury from twig girdler attacks. Since the period when the adult girdler will be outside the twig can be predicted with some accuracy, it is desirable as a secondary measure to have a residually effective insecticide on the leaves and twigs when adult emergence occurs. Insecticidal control of girdler adults has been a standard practice for over a decade now. Thorough-coverage sprays of DDT, at the rate of 1 pound of active ingredient (wettable powder formulation) per 100 gallons of water, has been very effec- tive when applied in early June in coastal areas and in early May to mid- May in inland areas. Lindane is also an excellent insecticide against adults of this insect but has not been used much, compared to DDT. Insecticidal control measures should be applied for at least two consecutive years. Thev may then possibly be omitted for one or more years on oaks isolated from other oak stands. An oak near un- sprayed and heavily infested oaks likely will need sprays each year. See section on Control. 73 Fig. 114. Immature larva of the roundheaded oak twig borer, Styloxus fulleri, in twig burro> of coast live oak. 6.5x. Roundheaded oak twig borer Figs. 114-115 While examining patches of dead leaves for the oak twig girdler, Agrilus angelicus (see page 69), one occasion- ally finds, not the spiral girdling as in figure 108, but a rather large, broadly oval, frass-filled tunnel going down the center of the twig, as in figure 114. Sometimes one can also find Styloxus fulleri (Horn), the roundheaded oak twig borer (Coleoptera: Cerambyc- idae), making the tunnel as in this fig- ure. We have found this borer in only a few southern California locations, but in one of these places it was respon- sible for over 30 per cent of the patches of dead leaves on the oaks; the oak twig girdler was responsible for the remainder. Linsley (1962) notes that ". . . much of the damage attributed in early reports to Agrilus angelicus was probably caused by Styloxus/' He also notes that the cerambycid girdles branches Vi to % inch in diameter. We have not observed girdling by this beetle, at least not in the sense that the twig girdler performs; only the mining in the heartwood is known to us. But it is difficult to explain why the twig should die if only the non-living center is removed by tunneling. Keen (1952) also calls this insect a girdler. We have noticed it on both coast live oak and interior live oak. Little has been pub- lished on this insect, and prior to Linsley 's paper it was referred to as Styloxus californicus (Fall). Linsley (1962) showed that S. californicus (Fall) was the same as the earlier-de- scribed S. fulleri (Horn), and he made californicus a subspecies of S. fulleri. The larva (fig. 114) tapers to the posterior, with the prothorax enlarged and the head sunken deeply therein; it is legless and a glistening deep y el- Fig. 115. Pinned adult of the roundheaded oak twig borer, Styloxus fulleri. 3.2x. 74 low. The adult (fig. 115) varies from 10 to 18 mm in length and averages about 13 mm. It is a quite slender beetle, the elytra being about four to five times longer than their width at the base. The head is deeply impressed between the antennal tubercles, and the male antennae are about twice as long as the body, whereas the female antennae equal the body length. The prothorax is somewhat hairy, and the elytra rather glabrous (hairless) and rugose. The elytra do not cover all of the hind wings or the abdomen. Color is olive-brown throughout. Linsley (1962) suspects that this in- sect may require two years to complete its life cycle, and he suggests (1961) that the egg takes about two weeks to hatch and that the pupal stage oc- cupies about 10 days to two weeks. We have noticed emergence of adults from the twig from April into Septem- ber, with slightly more insects emerg- ing in June and July. We have not had to suggest a control measure for this insect. It may be of significance that we have never noticed it or its injury on trees sprayed for the oak twig girdler. See section on Control. Filbertworm Figs. 116-118 A large percentage of oak acorns may be wormy. The larvae which bore into them are usually one of two kinds: Melissopus latiferreanus (Walsing- ham), the filbertworm (Lepidoptera: Olethreutidae) (fig. 117), which has true legs and crochets (minute hooks) on the abdominal prolegs; or the larva of the filbert weevil, which is legless (fig. 119 and page 77). Keen (1958) gives an excellent account of each of these insects. He notes that as many as 80 per cent of the acorns on an oak may be infested by the filbertworm. The damage done to the acorn by this moth larva is shown in figure 116; the kernel is hollowed out, leaving a mass of webbing and frass. The reproduc- tive capacity of the acorn is lost by this damage. Reproduction of oaks in the tree nursery or in the wilds may be enormously reduced by such infesta- tions. According to Keen, all the oaks are affected, but to date we have noticed this insect only on black oaks in this area. The filbertworm is dis- tributed throughout the United States. Fig. 116. Three acorns cut open to show the extensive larval tunneling of the filbert- worm, Melissopus latiferrea- nus. 1.9*. -"^i i %, /;#ste*:lt ;Jlk ft sicl | r 1 jf fit- m k ^j^'v " l^frji At 1 m *JS i ' V r %. V ML mm ■Jf^-M'. I m w IP*-- p* ^Ji > "' «L ^^#r;Z %^ ■/Saw ■ pF 75 Fig. 117. Three mature larvae of the filbert- worm, Melissopus latiferreanus; middle larva is ventral side up to show the ovals of cro- chets on the abdominal prolegs. 5.2x. Oak galls also may be infested with this moth. (See page 81.) The larvae of the filbertworm (fig. 117) may be grayish white or pinkish white, with a light-brown head cap- sule and a lighter-brown prothoracic and anal shield. It may be 12 to 15 mm long. Crochets on the prolegs are uni- ordinal and in a complete oval. The pupa is mahogany brown, with quite conspicuous spiracles on the second through the sixth abdominal segment, and a double row of stout spines on the dorsum of the abdominal seg- ments. The anterior row of these spines has fewer and larger spines than the posterior. The posterior spines also have a minute ridge ex- tending forward from each spine, these corrugations appearing on the second through the sixth segment. The adult (fig. 118) is approximately 10 mm long at rest, and may have a wing expanse of 11 to 20 mm. The adult is quite variable, with as many as seven varieties known, according to Keen; but it is generally brown or reddish brown with a broad, shining, copper- colored band across the center of the fore wing and several coppery areas toward the apex (the lightest areas on the hind edge of the fore wing in figure 118 are specular reflections from these metal-like areas). The hind wing is a darker brown. According to Keen, there appears to be one generation and a partial or full second generation annually in south- ern California. Adults appear in late May, June, and July and lay their eggs singly on the acorn. During the next two months the egg hatches, the larva bores into and throughout the acorn, and usually comes to the outside to pupate in the plant debris. Adults are found again in September and Octo- ber, and larvae into December. The larvae overwinter, and pupation occurs the next spring in the cocoons. We have never had to suggest a con- trol measure for this insect, but almost certainly a DDT or Sevin spray ap- plied at the time the adults are flying would achieve control. See section on Control. I *%^ Fig. 118. Living adult of the filbertworm, Melissopus latiferreanus. 6.2x. 76 Filbert weevil Figs. 119-123 Usually one finds that the majority of an oak's acorns contain dark-brown frass or are infested with short, fat, legless worms (figs. 119 and 120). There may be as many as three or four worms in a single infested acorn, al- though usually there will be only one. Sometimes a considerable quantity of very sticky sugary sap may be bleed- ing from these infested acorns (fig. 121), which may have a rather sour odor because of sap fermentation. Enough of this fermented sap may drip to make a fairly large wet spot beneath the tree. On close examination one may find also pinhole-sized punc- tures in the acorn as in figure 123, sur- rounded by a darkened area. Some- what larger holes may be found in the acorn, too, and these lead into the dark, meandering tunnel in the acorn; generally the acorn will have fallen to the ground by the time these larger holes are found. All of these bits of evi- dence taken together indicate the presence of Curculio uniformis (Le- Fig. 119. Three mature larvae of the filbert weevil, Curculio uniformis; note absence of legs on venter of middle larva. 4.3x. Fig. 120. Young larva of the filbert weevil, Curculio uniformis, and its damage to the acorn of interior live oak; leathery shell of acorn has been removed for picture. 8.5*. conte), the filbert weevil (Coleoptera: Curculionidae), which, according to Keen (1958), may destroy 20 to 75 per cent of the acorns. The presence of larvae in the acorns may also indicate the presence of filbertworm (see page 75). In the wilds this will have a con- siderable effect on the reproduction of oak stands, and in the home yard the bleeding from infested acorns can be a nuisance. This weevil is found throughout the western United States (Essig, 1958). We have found it on most species of oaks in southern Cali- fornia. We have noticed the bleeding mentioned above only in drier areas, away from the coast. The adult female (figs. 121, 122) with her long beaklike mouthparts chews a small pinhole-sized opening in the tough covering of the acorn (fig. 123). Then she turns around, inserts her ovipositor into the hole, and lays one to several eggs in the nutmeat. These hatch into short, fat, legless, 77 Fig. 121. Adult female of the filbert weevil, Curculio uniformis, feeding at the oozing sap from an ovipositional puncture on canyon live oak acorn. 3.6x. " Fig. 122. Side view of the adult female filbert weevil, Curculio uniformis, walking on the acorn cup of canyon live oak. 5.2x. ■lllllli glistening white grubs (fig. 120), which chew meandering tunnels that darken, throughout the acorn nutmeat. The head of the larva is light brown, with the mouthparts somewhat darker. The mature larva (fig. 119) is nearly 10 mm long. Usually after the acorn drops in the fall, the larva chews its way out, leaving a much bigger hole than the oviposition hole, and digs down into the earth. Some larvae may stay in the acorn throughout the winter and enter the soil in the spring. The larva pu- pates in the spring in a pupal cell in the ground, and the adult emerges any time from July through September. The adult female (figs. 121, 122), not including the beak, is 5 to 6.5 mm long and is a typical weevil with a long, curved snout, which is about one-half the length of the body. According to Craighead (1950), the mandibles of this genus are unusual in moving ver- tically in contrast to the usual hori- zontal movement. The adult body is robust and clothed with yellowish- brown scales; there are several darker irregular transverse marks on the elytra. The adult body is thickest (2.8 mm) near the base of the elytra. There is a single generation per year. We have not had to make an insec- ticidal control recommendation for this insect. However, for a closely re- lated nut weevil of this genus (Cur- culio caryae) DDT sprays against the adults are very effective (Craighead, 1950). We have noticed considerable control of the acorn weevil on trees that were sprayed with DDT for oak twig girdler and for the California oak moth. Keen (1958) notes that for har- vested acorns vacuum fumigation with methyl bromide, at 4 pounds per 1000 cubic feet for two hours at 70° F, is effective. See section on Control. Fig. 123. Ovipositional hole made by the beak mouthparts of the filbert weevil, Curculio uniformis, in acorn of interior live oak. 19x. 78 V. OAK GALL INSECTS vJf the approximately 140 cynipid wasp gall-makers known in the wes- tern United States, only a few of the more obvious and important ones in southern California can be discussed here. The interesting and varied growths that these wasps induce the oak to produce never cease to excite the curiosity and wonder of man. Even though these as a whole are among the least economically important insects affecting oak, they are the subject of many requests for information. These are all in a single family of the Hymenoptera — the Cynipidae — most of which affect only the oak tree. Dif- ferent parts of the oak tree (leaves, twigs, etc.) have their particular com- plement of cynipid wasp species at- tacking them. It is a curious fact that the gall made by each wasp species is typical of the species — that is, it ap- pears different from other cynipid galls. In fact, there are more obvious differences between the galls than there are between the adult gall wasps causing them. This presents an enor- mous advantage to most of us in trying to identify galls (and by inference, the gall wasp causing the gall), since fre- quently the gall is present whereas the gall wasp may be absent or in an im- mature stage; and also a specialized knowledge of cynipid wasp taxonomy is less necessary. The black oaks have their particular cynipid fauna, while the white oaks have theirs; and Quercus chrysolepis, a white oak, is unique in having a cynipid fauna all its own. It is remark- able that these minute wasps recog- nize that these groups of oaks differ from each other just as man assumes that they differ. A cynipid wasp is gen- erally coextensive with its host, ac- cording to Weld (1957). Galls of various species may have typically only a single larva in the gall (monothalamous) or several (poly- thalamous). Not all wasps emerging from a gall are necessarily those re- sponsible for the formation of the gall; some may be uninvited cynipid guests (inquilines) or chalcid and other para- sites. With the exception of most of the adult stage, the complete life of cyni- pid gall wasps is spent within the host plant tissue, that is, the gall. This fact has considerable significance as far as insecticidal control is concerned. An interesting phenomenon occurs in a number of cynipid wasp species. This is the "alternation of generations" (variously termed heterogamy, heter- ogeny, or heterogony). This means that males and females of the gamic, sexual, or, most accurately, the bi- sexual generation produce only female offspring (the agamic, asexual or uni- sexual generation), which in turn may produce a male and female generation, etc. The galls produced by these re- spective generations are quite different in appearance and are usually pro- duced on a different part of the oak. The gall produced by (i.e., containing) the bisexual generation is frequently on a part of the plant that lasts only briefly, such as the catkins, whereas the unisexual generation gall is longer- lasting and on a more permanent plant part, such as the leaves; or on the leaves in contrast to the twigs, etc. To complicate matters further, the females of one generation may differ morphologically from those of the next generation. Furthermore, in some cynipid species no males have ever been found — that is, the species re- produce parthenogenetically. Already it is known that the effects of the al- ternation of generations in c\nipid 79 wasps have contributed to consider- able synonymy of wasp and gall names. Future research on the gall wasps will undoubtedly uncover more cases of alternation of generations and synonomy. Although approximately 140 cynipid wasp species and their galls are known from the western United States, there are at least 75 additional oak galls which are known but which have not been associated with a gall wasp, known or unknown to science. Future research in this area of biology offers some fascinating op- portunities for study, even though the group as a whole economically is not very important. However, biochemical studies on the mechanism of gall for- mation could have very important implications — for instance, in relation to cancer or to the growth phenomena of living things in general. The adult cynipid wasps have cer- tain obvious morphological character- istics in common, as can be seen by a rapid perusal of figures 126, 128, 132, 142 and 144. They generally are dark or somber-colored. The thorax pre- sents a humped appearance, so that the head is oriented somewhat down- ward. The posterior abdominal seg- ments appear as though they have been pushed forward into the enlarged second abdominal segment, and the abdomen appears bilaterally com- pressed. Two pairs of wings are present (these insects are not Ries des- pite certain common names). The wing venation is very much reduced, lack- ing a costal vein and a stigma, with the combined radial and subcostal veins and combined radial sector and medial veins usually remaining; frequently the apex of the fore wing includes a large triangular cell, the third cubital cell. Some conception of the translu- cent white, legless, cynipid larva may be had by examination of figure 1397 For further information on the cyni- pid gall insects, the reader is referred to Felt (1940) and, for the western United States, to McCracken and Eg- bert (1922) and particularly to Weld (1957). Weld (1959) also has much in- formation on cynipids of the eastern U. S. Weld (in Muesebeck et al, 1951) lists a very useful synoptic catalog for the Cynipoidea of North America. California gallfly Figs. 124-126 The gall of the California gallfly, Andricus calif ornicus Ashmead (Hy- menoptera: Cynipidae), is perhaps the largest and most conspicuous of the cynipid galls affecting California oaks. It is a twig gall and is frequently called an "oak apple," since it is green when young and, as it matures, the side toward the sun becomes reddish, thus causing it to look very much like an apple. The gall becomes brown later in the season before the cynipid adults chew their way out. The gall is sessile; that is, it can be removed without harming the twig. Apparently the in- festation does not harm the leaves be- i- yond the gall. It may be spherical but frequently is kidney-shaped as in figure 124, and may vary from 1 to 4 Fig. 124. The oak apple gall of the California gallfly, Andricus californicus, on twig of valley oak. 0.75x. 80 Fig. 125. Cross section of the gall of the Cali- fornia gallfly, Andricus calif ornicus; note sev- eral larval cells in center of gall. 0.8x. Fig. 126. Mounted adults of the California gallfly, Andricus calif ornicus; note few wing veins and ovipositor of specimen on right. 4.6x. inches in diameter or length. The gall is polythalamous, containing from 2 to 12 cynipids per gall (fig. 125). The galls first appear in early winter, breaking through a slit in the twig bark in early spring, and ripen in July. Old galls may persist for several years on the tree after the cynipids have gone, and may become infested with other insects — such as the filbertworm, Melissopus latiferreanus (see page 75) — which feed on the nutrients left in the gall. This oak apple may be found on all the white oaks, except canyon live oak, and is often very abundant on valley oak. Only females of this species are known. They are dark brown or dark reddish brown and from 3 to 5 mm long (fig. 126). The cynipid wasps emerge in October through December and even into February of the next year. See section on Control. Fig. 127. Gall of the irregular spindle gall wasp, Andricus chrijsolepidicola, on Quercus chrysolepis. 1.6x. Irregular spindle gall wasp Figs. 127-128 The gall of Andricus chrysolepidicola (Ashmead), the irregular spindle gall wasp (Hymenoptera: Cynipidae), is an irregular, lumpy enlargement or swel- ling of the twig that cannot be sepa- rated from the twig (fig. 127). It has roughly a spindle shape (and is not an abrupt twig swelling, as is the gall caused by Callirhytis suttoni, p. 84). At its widest part the twig may be en- larged from two to five times, or the gall may be from 10 to 20 mm in diam- eter and from 20 to 40 mm or even up to 90 mm in length. It is a polythala- 81 Fig. 128. The female irregular spindle gall wasp, Andricus chrysolepidicola; this is la- beled Paratype No. 3075 at the U. S. National Museum. 10. lx. mous gall, and frequently the larval cells are so numerous in the twig as to restrict the movement of fluid within the twig, causing the terminal leaves to die. Up to the time of adult emer- gence the gall can be cut with relative ease with a knife, but after the adults have left it becomes very hard and difficult to cut. It is found only on the white oaks, but among these is not found on the canyon oak. This species is known only from fe- males (fig. 128). The adult is a reddish- brown wasp, shaded darker in some parts, and it varies from 1.5 to 3.5 mm in length. Adults may emerge from the gall as early as January, but apparently the majority leave the gall from mid- April to mid-May. See section on Con- trol. Live oak gallfly Figs. 129-132 e The gall of Callirhytis pomiformis (Ashmead), the live oak gallfly (Hy- menoptera: Cynipidae), is another very common oak apple, but this one is restricted to the black oaks. So far as we know, little damage is done to the oak. The gall is at first green, then has reddish areas similar to those on an apple, and finally is light to dark brown. It is a sessile gall, is usually spherical, and varies from 20 to 65 mm in diameter. The galls on coast live oak (fig. 129, right, and 131) are relatively smooth-surfaced, although some slight wrinkling may occur, whereas those on the interior live oak are rather rough- ened, with short, stout spines on the surface (fig. 129, left). There may be as many as 50 radiately arranged larval Fig. 129. Galls of the live oak gallfly, Calli- rhytis pomiformis; caused by (contain) the unisexual (female only) generation. 0.8x. Fig. 130. These galls are caused by (contain) the bisexual (male and female) generation of the live oak gallfly, Callirhytis pomiformis; thev are on interior live oak. 3.2x. 82 cells in the gall (polythalamous); see figure 131. Lyon (1959) has shown that alternation of generations occurs in this species and that this very common oak apple contains the unisexual gen- eration. He describes the gall con- taining the bisexual generation (fig. 130) as a monothalamous toadstool- shaped gall, arising singly or occasion- ally in groups of two or three from the undersurface of the leaf blade of the black oaks. A curling of the leaf blade, as shown in figure 130, frequently is associated with the gall. These bi- sexual generation galls are light green Fig. 131. Cross section of the oak apple gall of the live oak gallfly, Callirhytis pomiformis; note the adults boring out of the many-celled interior containing both larvae and pupae, l.lx. Fig. 132. Several aspects of the female live oak gallfly, Callirhytis pomiformis, unisexual generation. 6x. with a tinge of pink, and at maturity are 8 to 9 mm high. They may appear as early as February or March, but most appear during late March and April. They grow quickly, appearing 10 days to two weeks after the eggs are laid in the bud, according to Lyon. A photograph of the bisexual generation gall is in Weld (1957, fig. 121, page 75); it is listed as "unknown"; that is, the identity of the wasp that caused it was unknown to Weld. The males and females of the uni- sexual generation chew out of the toadstool-shaped galls from mid-May to early June (Lyon). The partheno- genetic females from the much more common oak apples appear from late February to mid-April, with the majority appearing during the latter part of this period. The females from the oak apples (fig. 132) are black for the most part, with the abdomen of some being a reddish black. The head and thorax are coarsely punctured, while the abdomen is smooth and shin- ing. They are 3 to 4 mm long. See sec- tion on Control. Cork oak cynipid Fig. 133 The cork oak, Quercus suber, has been imported into California from southern Europe, primarily for use as an orna- mental plant. In Spain and Portugal the bark is harvested for use in making cork products. In many locations in southern California which we and others have examined, an important pest of this tree is the cork oak cynipid, Plagiotrochus suberi Weld (Hymenop- tera: Cynipidae). From figure 133 one can see that prior to some emergence from the twig the presence of the cyni- pid can hardly be noticed, so little dis- torted is the twig. However, there is a slight "bumpiness" of the twig that can be detected upon close examination. Frequently, so many of the insects are 83 Fig. 133. These cork oak twigs are heavily infested with the cork oak cynipid, Plagio- trochus suberi; Weld reared his types from these twigs, l.lx. in the bark and vascular tissue of the twig that the fluid transport of the twig is seriously disrupted and many twigs and leaves die as a result. This, of course, affects the ornamental value of the cork oak. Also, in the 1930's serious consideration was given to the estab- lishment of a cork industry in Califor- nia because of the reduced supply from Spain during the revolution there; the cork oak cynipid was an important eco- nomic factor considered (Essig, 1943). The cork oak cynipid is present only in the United States and only on the cork oak. As it is not known in Europe, there is some question where it came from and how it developed. Apparently younger trees are immune to attacks by this cynipid. Only females of the cork oak cynipid are known. They emerge from the twigs in May and June. See section on Control. Twig club gall wasp Fig. 134 The galls caused by Callirhytis suttoni (Ashmead), the twig club gall wasp (Hymenoptera: Cynipidae), are rather abrupt, irregular twig swellings (fig. 134), and may be globular or elon- gated. The twig may be enlarged from four to seven times its normal diame- ter; the galls may range from 15 to 56 mm in diameter and 20 to 80 mm in length. The bark of the gall is relatively smooth and thin. It is a polythalamous gall, with the larval cells at the base of thin-walled tubes which lead from the center to the bark. In some cases the disruption of twig functions is so complete as to cause the death of the Fig. 134. These are the galls caused probably by the twig club gall wasp, Callirhytis suttoni; they are sometimes common and debilitating to live oaks. 0.6x. 84 leaves beyond the gall. Only black oaks are affected. We have little information on the emergence of the adults from the gall, but it is likely that they emerge in the spring of the year. Weld (1957) notes that the galls contained dark pupae and adults on November 27. See sec- tion on Control. White oak cone gall wasp Fig. 135 The unusual-appearing, common, and abundant leaf gall which Andricus kingi Bassett (Hymenoptera: Cyni- pidae) causes to form (fig. 135) is more of a curiosity than something of eco- nomic importance. It is found on either side of the leaf blade of the white oaks. The gall is conical, with the sides slightly concave; the base is curved convexly with a slight stalk at- tachment to the leaf, apparently avoid- ing the veins. It is approximately 6 mm high by 5 mm in diameter, and is red- dish or reddish yellow with a slight pubescence. It is monothalamous, and adult emergence occurs through the open apex of the gall. The attachment to the leaf is weak, and the galls may drop from the leaf or with the leaf in the fall. There is a slight depression on the leaf where the gall was attached, and the leaf dies around this attach- ment. The adults emerge from the galls from February through April. Only females are known. See section on Control. Spined turban gall wasp Fig. 136 Antron douglasii (Ashmead), the spined turban gall wasp (Hymenop- tera: Cynipidae), which occurs on white oaks, is unusual in that it ex- hibits alternation of generations and the gall of the unisexual generation is very striking. This monothalamous gall (fig. 136) is rather star-shaped, is a pinkish lilac-gray and is covered with a slight waxen bloom. At maturity the gall is 8 mm high and 10 mm in diam- eter, with the points of the "star" radi- ating from the top. It is found on the undersides of the leaves, sometimes in clusters of several galls. In the fall the Fig. 135. Galls caused by the white oak cone gall wasp, Andricus kingi, on leaves of valley oak. 4.6x. 85 Fig. 136. Immature galls caused by the spined turban gall wasp, Antron douglasii, on leaves of valley oak. 1.9x. gall drops with the leaves, and by that time it has turned brown. From this gall come only females, the unisexual generation, during the months of November through February, with the majority appearing during the latter part of this period. These females "sting" or oviposit in the leaf buds, which rather rapidly expand into a "football" shape about 4 to 7 mm in length. The apex of this monothala- mous gall is drawn to a point and is somewhat ridged longitudinally, each ridge ending in a small point, probably corresponding to a leaf in the develop- ing bud. Weld (1957) has illustrated the gall in figure 76, page 70, of his 1957 work. Males and females emerge from these bisexual galls about the time the normal leaves are halfway ex- panded from the bud, that is, from April to mid-May. Oviposition occurs in these expanding leaves, and the uni- sexual gall, shown in figure 136, de- velops. See section on Control. Two-horned oak gall wasp Figs. 137-140 The two-horned oak gall which Dry- ocosmus dubiosus (Fullaway) (Hy- menoptera: Cynipidae) causes to form, is a very common leaf gall of the black oaks, and it also demonstrates alterna- tion of generations. The bisexual gen- eration galls affect the catkins. The two-horned oak gall on the leaf (fig. 137) forms on the midrib and lateral veins of the lower leaf surface, being stimulated by the growth of the uni- sexual generation larva in the vein. The injury to the leaf vein frequently results in the death of the part of the leaf served by the vein. Oftentimes two or three two-horned galls may be responsible for the death of most or all of a leaf. As many as 40 to 50 galls have been observed on a single leaf (McCracken and Egbert, 1922). We 86 Fig. 137. Lower side of coast live oak leaf with two veins infested with the two-horned oak gall caused by Dryocosmus duhiosus; several other veins show slit marks where galls have fallen off. 3.8x. have observed many trees on which practically all the foliage was killed in this manner. Foliage thus killed drops long before it normally would, so that the ornamental and shade values of the tree are diminished. McCracken and Egbert note that of all the types of galls and their effects on oaks in Santa Clara County, the two-horned gall in- festation is the most disfiguring. Thus this cynipid can be fairly important economically in some areas, and con- trol measures may be necessary. The two-horned oak gall (fig. 138) is a monothalamous gall about the size of a grain of wheat, from 2 to 4 mm long, ovoid, and usually has a small projection ( the "horns") at one or both ends. The whitish, relatively trans- lucent, naked, legless, single larva is shown in figure 139. The gall is a Fig. 138. The two-horned oak gall showing adult emergence hole; only females of Dryo- cosmus dubiosus (unisexual generation) emerge from these single-celled, long-lasting leaf galls. 17.5x. lighter green than the leaf — sometimes being almost white — when it is form- ing and for a while after it attains its maximum size; then it turns light or dark brown, as it is seen during most of the year. Many of these galls fall from the leaf, and emergence occurs on the ground. Weld (1957) notes that these galls may be collected by the quart on a sheet spread under a 87 Fig. 139. The two-horned oak gall opened to show the single female larva of Dryocosmus dubiosus. 25. 5x. heavily infested tree. This two-horned gall is particularly noticeable during the fall and winter months. New ones are often observed forming from January into April. The females emerge from the leaf gall from January through March. Some of this unisexual generation sting the leaves, while others oviposit in the oak flowers (the catkins or aments), during the rela- tively brief period these are available; this may be as early as the first part of February or as late as late April, de- pending on the temperatures of the location. After being stung, the individual flower on the catkin grows rapidly into an elongated, club-shaped gall (fig. 140), which is whitish green on the narrow basal part and shining, reddish black at the wider end. This thin- shelled monothalamous catkin gall is 4.5 to 5 mm long. A catkin that is Fig. 140. Three catkins of the coast live oak, showing the elongated club-shaped galls of Dryocosmus dubiosus; from these short-lived galls comes the bisexual generation (males and females). 2.5x. normal with the exception of the two galls on it, is shown at the right in figure 140; the catkins on the left are almost completely galled. Once in a great while a somewhat similar gall (Weld illustrates this gall in figure 132, page 75, of his 1957 work) may form on a stung leaf blade and will contain a member of the bisexual generation. The males and females of the bisexual generation emerge soon after the catkins ripen, which may be from early March to early May, according to Doutt (1959). Our observations in southern California note most emer- gence of the bisexual generation oc- curring during the early part of this period. Herbert (1936) believed that the two-horned oak gall and the catkin gall were caused by the same species of cynipid wasp, but it remained for Doutt to prove this by breeding ex- periments. Doutt graciously acknow- ledges the independent, but then un- published, discovery of the same thing by Lyon. Doutt indicates that the well- known Dryocosmus bicornis (Mc- Cracken and Egbert) — Callirhytis and Andricus are generic synonyms of Dry- ocosmus in the case of this species — must be considered by the Law of Pri- ority a synonym of Dryocosmus dubio- sus (Fullaway). 88 Emerging females of the two- horned oak gall may be controlled by thorough-coverage sprays of DDT ap- plied from January into March in southern California. An inspection of the two-horned galls, with attention given to the development of the adults still in the gall, will indicate a more precise timing of the spray. See section on Control. Jumping oak gall wasp Figs. 141-142 Neuroterus saltatorius (Edwards), the jumping oak gall wasp (Hymenoptera: Cynipidae), causes interesting and fairly common galls to form on the lower surfaces of the leaves of the white oaks (fig. 141). These galls fall to the ground from the leaves and have the curious habit of occasionally springing a short distance into the air, somewhat like the Mexican jumping bean. Essig (1958) suggests that this action is caused by the larva throwing or flipping itself against the walls of its cell. He further suggests that this may be an effort of the larva to locate the gall in a protected crack or crevice. Although the galls may be found in large numbers, we have not noticed that the white oaks are harmed par- ■ : ; i Fig. 142. Mounted adults of Neuroterus sal- tatorius next to the single-celled galls from which they emerged. 6.8x. ticularly by their presence, despite the fact that a slight amount of leaf necro- sis (death of tissue) may occur. This monothalamous gall is quite small, being 1.0 to 1.3 mm in length, ovoid, and with a small, blunt, top projection, which is slightly hairy. It is attached to the leaf blade by a very fragile pedicel. Large numbers of galls drop from the leaves in the late sum- mer and early fall. Weld (1957) says that the adults emerge from the galls in April, even though they may be present in the galls in early December. The adult (fig. 142) is quite small, varying from 0.6 to 1.0 mm in length Fig. 141. Jumping oak galls on the lower leaf surface of a white oak caused by the jumping oak gall wasp, Neu- roterus saltatorius; "jumping" occurs after the galls have fallen to the ground. 11. 7x. and is black with yellowish or brown- ish legs and antennae. One method of control suggested for heavily infested white oaks is to sweep up the leaves and galls and burn them. Spraying at the time of adult emergence from the gall (April) with a residually effective insecticide should be a much more efficient method. See section on Control. Distorted leaf gall wasp Figs. 143-144 The twig, leaf petiole and leaf (and even the acorn, according to Felt, 1940) may be involved in this very ir- regular, roughened, polythalamous gall (fig. 143) affecting the white oak. Infestation by the cynipid wasp, Neuroterus varians Kinsey (Hymenop- tera: Cynipidae), results in enormous distortion and thickening of the petioles and leaves and almost com- plete elimination of their functions. The effects on the ornamental and shade-producing values of the valley oak, for example, have been quite drastic in some areas, such as the San Fernando Valley. The female in figure 144 is black throughout, the head and thorax being rugose and the abdomen smooth. It is approximately 1.4 mm long. Mr. R. J. Lyon (personal communi- cation) has reared males as well as females from the galls, such evidence suggesting that this gall is caused by the bisexual generation. The associa- tion with the appropriate unisexual gall on the white oak has not yet been made. As shown in figure 144, the female (probably of the partheno- genetic generation) oviposits in the leaf bud of the white oak, which prob- ably offers an explanation for the rather indiscriminate location of the galls. The adult in figure 144 was ovi- positing in early March; from the control point of view, this suggests that a residually effective insecticide should be applied to the oaks before the leaf buds begin to open, say in late February. This proved to be the case, as a DDT spray applied at that time allowed the tree to develop its leaves normally and thus to fulfill its orna- mental function. Trees sprayed in early March were less free of the cynipid damage than those sprayed in late February, and those unsprayed were severely damaged. The literature notes these adult emergence dates — (a) McCracken and Egbert (1922): March to May; (b) Weld (1957): March 21 (museum types), Contra Costa Co.; April 24, Newhall; and May 3, Santa Margarita. No mention is Fig. 143. Severely distorted leaves and stems of valley oak resulting from galls of the distorted leaf gall wasp, Neuroterus varians. 1.8x. 90 made of males in the literature, only females. So these cited emergence dates may refer to emergence by a uni- sexual generation at those locations. It is obvious that much more study of this insect and its ecological relation- ships is needed. See section on Con- trol. Woollybear gall wasp Fig. 145 The gall of Sphaeroteras trimaculosum (McCracken and Egbert), the woolly- bear gall wasp (Hymenoptera: Cynip- idae), is very common on the white oaks (fig. 145), especially so on Engel- mann oak in our experience. Except on very close examination, the group of galls on the leaf has the appearance of a woollybear caterpillar. We and spray operators have had calls from the public asking seriously how to rid their oaks of caterpillars, when in reality these galls were the only evi- dence of insects on the leaves. We do not know of any particular damage these galls do to the leaf. The indi- vidual gall is rather ovoid, about 3 mm long, and densely covered with long, hairlike spikes or spines. These spicules may be light brown, reddish brown, or light red. The galls may appear singly, attached to the midvein of the lower leaf surface, but usually Fig. 145. The aggregation of galls of the woollybear gall wasp, Sphaeroteras trima- culosum, along the midrib of Engelmann oak leaves has sometimes been mistaken for woolly caterpillar larvae. 1.3x. are in a group along the midvein or main lateral veins; this contributes to the illusion of a reddish-brown woolly- bear caterpillar. The spicules may be worn down, as in the specimen on the right in figure 145. Only female wasps are known; these are 1.5 mm long, and are black with brownish-yellow an- tennae and legs. We have noted adult emergence from the galls from late December through February. Mc- Cracken and Egbert (1922) note adult emergence from the gall in early sum- mer, while Weld (1957) mentions late summer emergence. We cannot ex- plain these discrepancies. See section on Control. Fig. 144. Injury to leaves in figure 143 was initiated early, as indicated by Neuroterus varians ovipositing in the leaf bud of valley oak. 11. 2x. 91 VI. CONTROL OF OAK INSECT PESTS X he essence of efficient pest control can be summarized as the right ma- terial in the right place at the right time. As far as oak insect pests are con- cerned, much in the foregoing sections is devoted to a presentation of the right time for specific insects, such as the time of year when the most sus- ceptible, or the only susceptible, stage is present. Also, considerable informa- tion is given as to the right place, whether it be on the trunk, or on the leaves, or wherever the insect may be. Also, under each insect pest, some in- dication is given of the one or more insecticides that are effective against that insect species or group. This sec- tion will be devoted to a more detailed consideration of the appropriate insec- ticides, their formulations and dos- ages, the means of applying the insec- ticides, and precautions to be ob- served. SPRAYING EQUIPMENT Knowing the right place (where the susceptible insect stage is present) is one thing, but getting the insecticide to that place is quite another problem. After many years of experience it is obvious to those persons concerned with treating trees of all sorts that the method known as "high-pressure spraying" has much to recommend it. It is a method which after considerable trial has well-standardized, depend- able equipment, and spare parts are usually available. On the whole it is the most effective means of getting the insecticide to the required area of the plant despite slight wind conditions, or other weather factors, which would prevent the use of other means of ap- plication. It is also one of the best methods for confining the insecticide to the plant being treated, whereas with some other methods — all air- blast applicators, for example — it is very difficult to keep the insecticide from drifting to places where it is not wanted, the neighbor's fish pond or to food crops, for example. This is an im- portant consideration today, particu- larly where a single large tree is the only plant to be treated in a home yard. Drift may occur with high-pres- sure spraying, but it is generally less than would be expected with air-blast application under the same conditions. In spraying, the insecticide is diluted in water and is further diluted in space after leaving the spray nozzle. This means of homogeneous dilution of the toxic material (utilizing water) is one of the most reliable methods available. It ensures that enough toxicant gets to a particular part of the plant to kill the insect but not so much as to endanger the plant or the person spraying (this statement does not mean that protec- tive clothing need never be worn when spraying; always follow precautions listed on the insecticide package label). With most sprays, in contrast to some other treatment methods, it is not pos- 92 sible to build up insecticide deposit on the plant beyond a certain point — the point of run-off. This is a favorable safety factor. The spray tank, usually of several hundred gallons capacity, should have mechanical agitation of the spray liquid by means of rotating paddles to aid in keeping the toxicant thoroughly dispersed in the water. The pump is most frequently a type with recipro- cating pistons. Pumps of this type for spraying mature oak trees should be capable of delivering from 15 to 40 or 50 gallons per minute at liquid pres- sures of 400 to 800 or 1000 pounds per square inch. Such pumps are equipped with regulators permitting the adjust- ment of pressure and allowing the pump to maintain the pressure, but at a reduced load, when the spray gun is not spraying. The spray gun is of a type that permits fogging of the spray stream, so as not to injure, by excessive physical impact, nearby parts of the plant, and the use of a solid stream to reach the topmost part of the mature tree. Shade tree tips may be used on some spray guns to further increase efficiency in reaching distant parts of the plant. The maximum-size disc used in the spray gun should not permit de- livery that would exceed the capacity of the pump as indicated by a pressure drop when the spray gun is turned on. The aperture in spray discs may en- large with use so that the capacity of the pump is exceeded. Special hard- ened discs have a longer useful life. If considerable length of spray hose is to be used, the pressure drop should be considered and a pump of adequate capacity used to maintain pressure at the spray gun. The objective in spraying is to wet thoroughly the surface to be treated — only to the point of run-off; more than this is wasteful. The sprayer can check his spray coverage for a leaf- or twig- infesting insect — for example, by cutting down a small, remote bunch of leaves with a pole pruner immediately after spraying and examining these surfaces for the distribution of the spray droplets. It should be obvious from the pre- ceding paragraphs that a spraying machine to treat adequately large trees like the oak is a highly developed, ex- pensive, and heavy piece of mechani- cal equipment, requiring a certain de- gree of skill to operate. It is unusual for the homeowner to have or to oper- ate such equipment. We are aware of other less complex, less expensive, and less effective pieces of spray equip- ment available for the individual homeowner to use. Before selecting a particular treatment method, the homeowner, or others concerned with oak tree management, should consider all aspects of the problem: the ade- quacy of insecticidal coverage and the resulting insect control, the possibility of falling out of the tree if he must climb it to achieve adequate coverage, the question of liability insurance, the question of guaranteeing control of the pest insect, etc. When all factors are considered, many owners of oak trees consider the hiring of a highly recommended, insured and licensed commercial spray operator as the most efficient and least expensive means of pest insect control. For important warning on the use of pesticides, see page 102. 93 FORMULATIONS OF INSECTICIDES Practically all insecticides used today, including the ones suggested here, are synthetic organic compounds, usually of three well-known types: organo- chlorine (such as DDT, lindane, diel- drin, etc.), organophosphorus (such as malathion, diazinon, dimethoate, etc.) and carbamate (such as Sevin and Zec- tran). One exception is petroleum oil, which is from naturally-occurring sources. All of these materials for the most part are quite insoluble in water, the one diluent commonly available and the diluent that gives the spray method its efficiency and safety. Be- cause of this insolubility in water and to aid dispersion and ease of handling, these insecticides are formulated in two general ways to permit their use with water: wettable powders and emulsifiable concentrates. In the case of wettable powders, if the technical grade insecticide is a rel- atively dry crystalline powder at ordi- nary temperatures, it is mixed directly with an inert, powdered diluent, such as talc (the same material as used in face powder) or one of the clays. If the technical grade insecticide is a liquid, it may be sprayed as evenly as possible on the powdered diluent, or a part of the diluent, and this further mixed with the same or other pow- dered diluent to obtain a relatively homogeneous mixture. All wettable powder formulations can be wetted by water and are made so by the in- clusion at the time of manufacture of a small amount of wetting or surface- active agent in the dry powdered mix- ture. Examples of wetting agents (types of surface-active agents) are the detergents used in the home. Some of these home detergents, such as Tide, are at times used when additional wet- ting is needed in the spray tank mix- ture. Others, such as Colloidal X-77, Gresselli Spreader-Sticker, Triton B- 1956, etc., are designed specifically for spraying. The amount of insecticide in a wettable powder is indicated by a percentage, on a weight basis, such as 25 per cent, which means that in every 4 pounds of wettable powder 1 pound will be the active ingredient or techni- cal grade insecticide. Such a formula- tion is frequently abbreviated as "25WP," "WP25," or "25W." In the case of emulsifiable concen- trates, whether the technical grade in- secticide is dry crystals or a liquid, it is dissolved in a liquid organic solvent, frequently some type of light oil. To this solution is added an emulsifying agent (a type of surface-active agent), which may or may not be similar to those used in wettable powders. The emulsifier permits the oil containing the dissolved insecticide to be divided into minute droplets when it is mixed vigorously with water for spraying; this is called an emulsion and it looks like milk (which is an emulsion). The emulsifier also aids in keeping the minute insecticide-containing oil drop- lets separated in the water so that they will not combine to form a layer of oil on the water. Some emulsifiable concentrate formulations, such as those designed for the "small package trade" (the homeowner, for spraying his shrubs and flowers with a small hand sprayer), contain more emulsifier than those designed for use in power sprayers with mechanical agitation in the spray tank. This partially over- comes some of the disadvantages of lack of mechanical agitation in small hand-operated sprayers. These "small package" emulsifiable concentrate for- mulations are more expensive than those designed for power equipment, 94 primarily because of increased pack- aging costs per unit volume and for the additional emulsifier. Also, the ex- tra emulsifier in "small package" for- mulations tends to prevent adequate deposit with power sprayers. The amount of insecticide in emul- sifiable concentrates is frequently in- dicated only (or at least most promi- nently) as a percentage. This denotes the weight of the insecticide in rela- tion to the weight of a given volume of the solvent used. Since the user gen- erally has no way of knowing the weight per volume, or specific gravity, of the liquid solvent used, it is difficult to know the quantity of insecticide by this means of expression. A more readily understood expression of con- centration, and one which most insec- ticide formulators indicate somewhere on their package label, is the weight of technical grade insecticide per unit volume of finished concentrate. For example, an emulsifiable concentrate referred to as a "4-pounds-per-gallon concentrate" is easily understood to mean that every quart of it contains 1 pound of active ingredient, or each pint contains V2 pound of active ingre- dient, etc. Such a formulation is fre- quently abbreviated as "4EC," "EC4" or "4E." This permits maximum utility of this very convenient type of formu- lation. Usually, emulsifiable concen- trates indicated by the percentage method contain the following amounts of insecticide: 20-25% 2 lbs. per gallon 40-45% 4 lbs. per gallon 50-57% 5 lbs. per gallon 58-67% 6 lbs. per gallon 72-78% 8 lbs. per gallon The emulsifiable concentrate formula- tions are generally more expensive than the wettable powders per unit of insecticide. Petroleum oil used for spraying plants is available in three types of for- mulations: (a) oil alone, to which emulsifier must be added in the spray tank (tank-mix oils); (b) oil and emul- sifier — called an emulsifiable oil or emulsive oil — which is added directly to the spray tank; and (c) oil, emulsi- fier and a small amount of water — called an emulsion, flowable or "may- onnaise" type of formulation, which is added directly to the spray tank. These oils are generally competitive as to cost, but perhaps the emulsifiable oil formulation is the most convenient to use. Some may consider oil sprays old-fashioned, meaning that their ini- tial use antedates the modern syn- thetic organic insecticides. Oils are still effective, and it is well to remem- ber that oil kills the insect by a physi- cal means (by blocking the insect's tracheae or breathing tubes), whereas the others kill by a chemical means (by blocking an enzyme system, such as the acetylcholine esterase at the nerve synapse). Many cases of insect resistance to chemical means have de- veloped, whereas resistance to physi- cal means is unknown. Therefore, the insecticide killing by a physical means should not be rejected per se. Also, synthetic oils are being developed which have very interesting proper- ties, such as being highly penetrating in bark for treatment of bark beetles. 95 PRECAUTIONS IN THE USE OF INSECTICIDES With the wettable powder formula- tions the spray operator must open the insecticide container, usually a paper sack, and dump the contents into the spray tank, usually as the tank is being filled with water. This applies if the complete package of insecticide in re- lation to the amount of water being put into the tank corresponds to a recommended insecticide dosage; otherwise, he must have some weigh- ing device to measure out the required amount of insecticide. Any time be- tween the opening of the insecticide container and the wetting of the pow- der in the tank, including the weigh- ing operations, the spray operator is subject to possible contact with the poisonous powder. Getting the pow- der in the eyes or inhaling it through the nose or mouth or getting it on the hands and then in the mouth, are easy avenues of entry to the body that must be guarded against. With emulsifiable concentrate formulations, the likeli- hood of inhaling wind-blown particles is considerably reduced, since usually a bottle or can is opened and the liquid contents poured into the tank; or the liquid is measured out in a graduated container and then poured into the tank. However, most synthetic organic insecticides dissolved in an or- ganic solvent (such as the emulsifiable concentrate formulations) are ab- sorbed very readily through the skin. Thus if the liquid formulation is splashed on the hands or face, particu- larly the eyes, it should be removed immediately by washing with soap and water, or by flushing the eyes with a considerable quantity of clean water. The spray operator should know of a nearby medical doctor who is familiar with the diagnosis and treatment of in- secticide poisoning. From these examples it is apparent that the time of transfer of the insecti- cide from its package to the sprayer tank is the period of greatest hazard to the spray operator, since the insec- ticide is then in its most concentrated form. The insecticide that gets on his body after it has left the spray gun or that drips on him from the tree is less of a hazard but still is a hazard. Opening the insecticide container at the tank opening is better than doing so at any greater distance. If some of the wettable powder or emulsifiable concentrate spills on the ground or pavement, it should be diluted and flushed away with water. If insecti- cides are purchased in bulk in cartons and drums, any measuring operations may be performed more safely at the spray operator's place of business. The person spraying should always read and follow the protective directions on the insecticide package label. If coveralls, a hat, goggles, respirator and rubber gloves are suggested, then they should be worn. Insecticides should be stored out of reach of chil- dren, irresponsible persons, pets and livestock, and kept under lock and key, in a place where they cannot be con- fused with food. Since man is attracted to shade trees and is frequently unaware of in- secticide hazards, a greater than nor- mal responsibility falls on the home- lot spray operator to properly dispose of empty insecticide containers. This usually means taking them from the client's premises, rinsing, crushing and burying them at the city dump. If the containers were truly empty, then no problem would exist; however, a slight amount of concentrated insecticide al- ways remains in these containers. Un- fortunately, in the case of deaths due 96 directly to insecticides, the majority of victims are children, and often their death has resulted from discarded and presumably empty insecticide con- tainers. The writers feel that because of the close association between orna- mental plants such as oaks, and hu- man beings, special mention should be made here of these precautionary measures. The insecticides suggested in this bulletin are the safest available to human beings, consistent with a reasonable insecticidal efficiency and low phototoxicity. None of them in the suggested formulations, and when ap- plied to oaks on city lots, parkways and public parks, require a permit for their use from the County Agricultural Commissioner. If they are used ac- cording to the suggestions here and on the insecticide package label, little dif- ficulty should be experienced. As to preventing possible phytotox- icity of insecticides, it is generally de- sirable that plants be well irrigated a few days before being sprayed. It is usually advisable not to spray on very hot days or on days when smog con- centration is likely to be high. Most modern insecticides are very efficient in killing fish as well as in- sects. Thus fish ponds in the vicinity of oaks and other ornamental plants present a special problem when spray- ing is necessary. The fish can be pro- tected by one or more of the following actions: (a) as much as possible avoid spraying toward or above the pond; (b) cover the pond with a plastic sheet; (c) remove the fish to a safe place and drain the water; and (d) use cryolite (on oak worm). Children and pets (and feeding dishes of the latter) should be ex- cluded from the sprayed area during spraying operations and until the spray residue has dried on the plant. No responsible person uses or ad- vocates using insecticides indiscrimi- nately or without caution. Inspection of bulletins of this sort reveals a real effort on the part of authors to suggest a high degree of discrimination in the use of insecticides; for example, dis- cussion whether insecticides should be used at all, where, when, how and which insecticides should be applied, and precautions to be observed. We suggest here insecticide treatments only for insect infestations which are heavy, or which are developing or likely to develop. There is no point in spraying for insects not present and unlikely to be present during the pe- riod the insecticide residue is effec- tive. Any person observing what he thinks is the irresponsible use of an insecticide in California can be as- sured of a prompt response and appro- priate action simply by calling the County Agricultural Commissioner. DOSAGES OF INSECTICIDES Never before in history has man had the possible freedom from pest insects on his plants that he can enjoy today. As with other freedoms, this carries with it a responsibility, as we have em- phasized in the preceding section. Never before has the pest insect faced such a devastating factor in its envi- ronment. Most modern insecticides re- quire only contact with the insect to kill it, either direct contact with the spray or the insect crawling over a 97 sprayed surface. The array of highly effective materials available is little short of amazing. For example, in a recent publication (U. S. Dept. of Agric., 1962) over 24 acaracides were recommended for the control of spider mites. This in large part reflects the ingenuity of the chemist and the en- tomologist, but somewhat also the dogged and grim race between the de- velopment of the spider mite's resist- ance to acaracides and man's inven- tions to counter it. But, on the whole, the pest control industry has for almost every problem a choice of several highly effective insecticides unheard of as recently as two decades ago. One of the reasons for grouping the sucking insects together, the leaf-con- suming insects in another group, and the boring insects in still another is the similarity of insecticidal control meas- ures within each group. These simi- larities will be apparent in the follow- ing paragraphs. As with any gen- erality, exceptions do exist. The follow- ing recommended insecticide dosages for the control of oak insect pests are listed roughly in the order of length of experience with the material, and also taking into account its insecticidal ef- fectiveness, phytotoxicity, and mam- malian toxicity. No doubt some mate- rials lower on the list will replace ma- terials higher on the list when more is learned of their use. Consult the sec- tion on the specific insect for timing of sprays. All dosages are in amounts per 100 gallons of water, or more ac- curately, per 100 gallons of finished spray. Sucking insects Generally insecticides such as malath- ion or diazinon alone are effective in controlling insects of this group, es- pecially if some attempt is made to spray at the time of peak crawler hatch in the case of the scales. Better control is obtained, as well as more leeway in spray timing, if oil is added to either malathion or diazinon. Also Sevin (carbaryl) is coming into increas- ing use in California in controlling in- sects of this category, particularly coc- cid scales. Dimethoate is a promising material against insects of this group. Since this systemic phosphate insecti- cide has demonstrated some cases of phytotoxicity — relatively more than the other two phosphates, malathion and diazinon — caution is advised, par- ticularly with plants that may be under or near the oak tree. Diazinon is effective against the eriophyid mites, while kelthane is suggested for the spider mites. Thorough-coverage spraying should be done when the in- sect is noticed; see the preceding sec- tions on specific insects for spray timing. 98 INSECTICIDE DOSAGES FOR CONTROL OF SUCKING INSECTS Insecticide and formulation Dosage/100 gals, water Remarks 1. Oil, dormant 4 or 5 gals. Winter treatment of scales on deciduous oaks 2. Oil, light medium, plus Malathion, emuls. cone. (8 lbs. /gal.), or (5 lbs./gal.), or wett. powd. (25%) Vh gals. lV 2 pts. l%pts. 4 lbs. 3. Oil, light medium, plus Diazinon, emuls. cone. (4 lbs./gal.), or wett. powd. (50%) IV2 gals. Ipt. lib. 4. Malathion, wett. powd. (25%), or emuls. cone. (8 lbs./gal.), or (5 lbs./gal.) 4 lbs. 1V 2 pts. 1% pts. For scales, best when timed for crawler hatch; a second application 3 weeks later may be necessary 5. Diazinon, wett. powd. (50%), or emuls. cone. (4 lbs./gal.) lib. Ipt. For eriophyid mites 6. Sevin, wett. powd. (50%) 2 lbs. For coccid scales 7. Dimethoate, emuls. cone. (2.67 lbs./gal.) iy 2 pts. Watch for plant damage 8. Dieldrin, wett. powd. (50%), or emuls. cone. (I 1 /* lbs./gal.) 2 lbs. 2V 2 qts. (=5 tsp./l gal. water) For ants feeding on honey- dew; spray on tree trunk 9. Kelthane, wett. powd. (18.5%), or emuls. cone. (IV2 lbs./gal.) 2 lbs. lqt. For spider mites only Leaf-consuming insects The chlorinated hydrocarbon insecti- cides have been very useful in control- ling insects of this category. DDT is the oldest, best-known and most widely used material of the organo- chlorine group; but lindane, DDD, toxaphene and methoxychlor have been very effective against certain in- sects. The carbamate insecticide Sevin (carbaryl) is quite effective against in- sects of this category, especially the Lepidoptera, and may one day be more widely used than DDT. A rela- tively new carbamate, Zectran, is very promising. The organophosphorus in- secticides, malathion and diazinon in particular, have been used against some of these insects, but not nearly to the extent of the organochlorine or carbamate groups. Thorough-coverage spraying usually is done when the in- sects are noticed; see the sections on the particular insect. INSECTICIDE DOSAGES FOR CONTROL OF LEAF-CONSUMING INSECTS Insecticide and formulation Dosage/100 gals, water Remarks 1. DDT, wett. powd. (50%) 2 lbs. 2. Sevin, wett. powd. (50%) 2 lbs. 3. DDD (TDE) wett. powd. (50%) 2 lbs. Preferable to DDT for leaf rollers 4. Toxaphene, wett. powd. (40%), or emuls. cone. (6 lbs. /gal.) 3-4 lbs. Iqt. 5. Methoxychlor, wett. powd. (50%), or emuls. cone. (2 lbs. /gal.) 2 lbs. 2qts. 6. Malathion, wett. powd. (25%), or emuls. cone. (8 lbs. /gal.), or (51bs./gal.) 4-6 lbs. 1-2 pts. l%-3y 5 pts. 7. Diazinon, wett. powd. (50%) lib. 8. Cryolite, wett. powd. (72%) 4 lbs. An alternate and less effec- tive insecticide for use near fish ponds 100 Boring insects For the purposes of chemical control the gall insects are being included here. The insects of the boring group are the most difficult to control of the several groups discussed in this bulle- tin. The destructive stage of each species is within the woody or bark tissue of the plant and inaccessible for the most part to contact with insecti- cides. All of the species (except the termites) have one or more stages out- side the plant tissue, and this is the stage control measures are directed against. This means that a better than ordinary knowledge of the life history of the insect is necessary, much more so than with the other groups dis- cussed. Of particular importance is a knowledge of when the susceptible stage, usually the adult, is emerging from the plant. Even though this may be known precisely, it is almost always the case that the emergence period covers a span of time from three or four weeks for some species to as much as 10 or 12 weeks for others. Even though peak emergence may cover a much shorter period, many factors, such as temperature, may influence emergence, so that a precise prediction is not al- ways possible. Generally in the warmer areas (85° to 100°F summer temperatures), insects emerge earlier than in the cooler or coastal climates (70° to 85°F). Where the problem warrants it, screen-wire cages may sometimes be built around the site on the plant where emergence will occur. Sometimes a plant part, such as the twigs in the case of twig girdler, or the galls in the case of the cynipid wasps, may be put into a separate screen-wire cage under the oak tree. Daily or other periodic inspection of the cage will reveal when emergence is occurring. In selecting an insecticide, there- fore, it is desirable to use one which has a long residual activity and which can be applied to the infested area of the plant shortly before emergence oc- curs or as it is beginning. When an emergence period extends over four or five weeks, there should be a sec- ond spraying about four weeks after the first. The chlorinated hydrocarbon insecticides, especially dieldrin and DDT, are outstanding in possessing long residual activity. Lindane is ex- cellent against the beetles (scolytids, buprestids and cerambycids). The car- bamate Sevin (carbaryl) is very effec- tive against the Lepidoptera. Conventional dilutions of insecti- cides, for example, for the twig gir- dler, may be sprayed as a thorough- coverage spray; or application may be made only to the affected area, such as the trunk or larger limbs, in the case of the western sycamore borer or Pacific flatheaded borer. Also, in the case of trunk-boring insects, more con- centrated sprays, as well as slurries, may be applied to the affected area only. A slurry is made by diluting the wettable powder in a much smaller amount of water than for spraying, to about the consistency of thin paint; it may then be applied with a paintbrush to the infested area only. It should be kept in mind that a very high concentra- tion of the insecticide is in the slurry; therefore, precautions for personal safety listed on the insecticide package label should be most rigidly followed. 101 INSECTICIDE DOSAGES FOR CONTROL OF BORING INSECTS Dosage/100 Insecticide and formulation gals, water Remarks 1. Dieldrin, wett. powd. (50%) lib. Thorough-coverage spray 2. DDT, wett. powd. (50%) 2 lbs. 6-8 lbs. (Slurry) Thorough-coverage spray Trunk or larger limbs only 4 Infested area only 3. Lindane, wett. powd. (25%) 4 lbs. Very effective for scolytid, buprestid, and cerambycid beetles 4. Sevin, wett. powd. (50%) 2 lbs. Very effective for Lepidop- tera Gall insects < For control measures, the cynipid are as adults. See the preceding section N wasps may be treated as though they on boring-insect control, which begins were boring insects, which indeed they on page 101. WARNING ON USE OF PESTICIDES These recommendations for pest con- number of applications, and precau- trol are based on the best information currently available for each pesticide listed. Treatments based upon these recommendations should give ade- quate control and not cause any seri- tions for the user as well as those for fish and other wildlife. The applicator is legally responsible for treatments on a given property as well as for problems caused by drift ous hazard if the applicator follows from original property to other prop- all directions on the insecticide pack- erties or crops, age label with respect to dosage levels, 102 Literature Cited Atkins, E. L. 1958. The western tussock moth, Hemerocampa vetusta (Bdv.), on citrus in southern Cali- fornia. Jour. Econ. Ent. 51:762-65. Beer, R. E. 1955. Biological studies in the genus Periclista. Jour. Kans. Ent. Soc. 28:19-26. Blackman, M. W. 1928. The genus Pityophthorus Eichhoff in North America. New York State Coll. Forestry Tech. Pub. 25, Syracuse, N.Y. 183 pp. Braun, A. F. 1923. Genus Lithocolletis Hiibner. In Forbes, W. T. M., Lepidoptera of New York and neighboring states, pp. 186-202. Cornell Univ. Agr. Expt. Sta. Mem. 68, Ithaca, N.Y. 729 pp., 439 figs. Brues, C. T., A. L. Melander, and F. M. Carpenter 1954. Classification of insects. Harvard Mus. Compar. Zool., Bui. 108, Cambridge, Mass. 917 pp., 1219 figs. Burke, H. E., and F. B. Herbert 1920. California oak worm. U. S. Dept. Agr. Farmers' Bui. 1076, Washington, D.C. 14 pp. Burke, H. E. 1921. Notes on the carpenter worm and a new method of control. Jour. Econ. Ent. 13: 369-72. 1929. The Pacific flathead borer. U. S. Dept. Agr. Tech. Bui. 83, Washington, D.C. 36 pp. 1932. Summary of shade-tree insect activities in California for 1931. Calif. Dept. Agr. Monthly Bui. 21:358-69. Chemsak, J. A. 1963. Observations on the adult behavior of Xylotrechus nauticus (Mannerheim). Pan- Pacific Ent. 39:213. Childs, L. 1914. Oak pests — the carpenter worm. Calif. State Commr. Hort. Monthly Bui. 3:259-64. Comstock, J. H. 1916. Reports on scale insects. Cornell Univ. Agr. Expt. Sta. Bui. 372, Ithaca, N. Y. 181 pp., 36 plates, 107 figs. Craighead, F. C. 1950. Insect enemies of eastern forests. U. S. Dept. Agr. Misc. Pub. 657, Washington, D.C. 679 pp., 197 figs. Doane, R. W., E. C. Van Dyke, W. J. Chamberlin, and H. E. Burke 1936. Forest insects. McGraw-Hill Book Co., New York, N.Y. 463 pp., 234 figs. Doutt, R. L. 1959. Heterogony in Dryocosmus (Hymenoptera, Cynipidae). Ann. Ent. Soc. Amer. 52:69- 74. Dyar, H. G. 1902. List of North American Lepidoptera. U. S. Natl. Mus. Bui. 52, Washington, D.C. 723 pp. Engelhardt, G. P. 1946. The North American clear-wing moths of the family Aegeriidae. U. S. Natl. Mus. Bui. 190, Washington, D.C. 222 pp., 32 plates. Essig, E. O. 1926. Insects of western North America. Macmillan Co., New York, N.Y. 1035 pp., 766 figs. 1943. The cork oak cynipid in California. Jour. Econ. Ent. 36:123. 1958. Insects and mites of western North America. Rev. ed. Macmillan Co., New York, N.Y. 1050 pp., 766 figs. 103 Felt, E. P. : 1905. Insects affecting park and woodland trees. New York State Mus. Mem. 8. New York State Education Dept, Albany, N.Y. Vol. I. 459 pp., 48 plates, 63 figs. 1940. Plant galls and gall makers. Comstock Pub. Co., Ithaca, N.Y. 364 pp., 344 figs., 41 plates. * Ferris, G. F. 1937. Atlas of the scale insects of North America. Series I. Stanford Univ. Press, Stanford, Calif. Pp. 1-10, and serial numbers 1-136, 104 plates. Forbes, W. T. M. 1923. The Lepidoptera of New York and neighboring states. Cornell Univ. Agr. Expt. Sta. Mem. 68, Ithaca, N.Y. 729 pp., 439 figs. Harris, T. W. a \ 1862. Insects injurious to vegetation. William White Publishers, Boston, Mass. 640 pp., 8 plates, 278 figs. Harville, J. P. 1955. Ecology and population dynamics of the California oak moth. Microentomology 20:83-166. Herbert, F. B. 1936. Insect pests of western oaks and their control. Proc. Western Shade Tree Conf. 3:32- 44. Jaeger, E. C. 1940. Desert wild flowers. Stanford Univ. Press, Stanford, Calif. 322 pp., 764 figs. Jefferson, R. N., and A. E. Pritchard ' 1956. Pest control guide for floricultural crops. Univ. Calif. Agr. Expt. Sta. Leaflet 66, Berkeley, Calif. 11 pp. Jepson, W. L. 1923-1925. Manual of the flowering plants of California. Associated Students' Store, Univ. of California, Berkeley, Calif. 1238 pp., 1023 figs. Keen, F. P. 1952. Insect enemies of western forests. U. S. Dept. Agr. Misc. Pub. 273, Washington, D.C. 210 pp. 1958. Cone and seed insects of western forest trees. U. S. Dept. Agr. Tech. Bui. 1169. Keifer, H. H. 1936. California microlepidoptera X. Calif. Dept. Agr. Monthly Bui. 25:349-59. 1938. Eriophyid studies II. Calif. Dept. Agr. Monthly Bui. 27:301-23. 1952. The eriophyid mites of California. Univ. Calif. Insect Surv. Bui. 2(1): 1-123. Langston, R. L. 1957. A synopsis of hymenopterous parasites of Malacosoma in California. Univ. Calif. Publ. in Entom. 14. 49 pp., 13 tables. » Linsley, E. G. 1961. The Cerambycidae of North America. Part I. Univ. Calif. Publ. in Entom. 18. 97 pp., 35 plates, 16 figs. 1962. The Cerambycidae of North America. Part III. Univ. Calif. Publ. in Entom. 20. 188 pp., 56 figs. Lyon, R. J. 1959. 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Hymenoptera of America north of Mexico: Synoptic Catalogue. U. S. Dept. Agr., Agr. Monograph 2, Washington, D.C. 1420 pp. Needham, J. C, S. W. Frost, and B. H. Tothell 1928. Leaf-mining insects. Williams and Wilkins Co., Baltimore, Md. 351 pp., 90 figs., 5 plates. Pritchard, A. E., and R. E. Beer 1950. Biology and control of Asterolecanium scales on oaks in California. Jour. Econ. Ent. 43:494-97. Schaffner, J. V., Jr., and W. Mdddleton 1950. The sawflies and horntails. In Craighead, F. C, Insect enemies of eastern forests, pp. 542-590. U. S. Dept. Agr. Misc. Pub. 657, Washington, D.C. 679 pp., 197 figs. Smith, G. L. 1942. California cotton insects. Univ. Calif. Agr. Expt. Sta. Bui. 660. 50 pp., 35 figs. Smith, R. H. 1944. Insects and mites injurious to sycamore trees in western North America. Arborist's News 9:9-15. Snodgrass, R. E. 1930. Insects, their ways and means of living. Smithsonian Sci. Ser. 5. Smithsonian Institu- tion Series, Inc., New York, N.Y. 362 pp., 15 plates, 186 figs. Stannard, L. J. 1951. Genus Periclista. In Muesebeck, C. F. W., Hymenoptera of America north of Mexico: Synoptic Catalogue, pp. 64-66. U. S. Dept. Agr., Agr. Monograph 2, Washington, D.C. U. S. Department of Agriculture 1962. Insecticide recommendations of the Entomology Research Division for the Control of Insects Attacking Crops and Livestock for 1962. Agriculture Handbook No. 120, Washington, D.C. 152 pp. Volck, W. H. 1907. The California tussock moth. Univ. Calif. Agr. Expt. Sta. Bui. 183:191-214. Weld, L. H. 1957. Cynipid galls of the Pacific slope. Privately printed by the author at Ann Arbor, Mich. 64 pp., 205 figs. 1959. Cynipid galls of the eastern United States. Privately printed by the author at Ann Arbor, Mich. 124 pp., 31 plates. Woglum, R. S., and H. C. Lewis 1947. Leaf roller attacks citrus trees. Calif. Citrog. 32:308-9. 105 In order that the information in our publications may be more intelligible it is sometimes necessary to use trade names of products or equipment rather than complicated descriptive or chemical identifications. In so doing it is unavoidable in some cases that similar products which are on the market under other trade names may not be cited. No endorsement of named products is intended nor is criticism implied of similar products which are not mentioned. 12m-4,'65(F352)MAS ►^ .: * BLACK BOXES... Agriculture has them too Both manned and unmanned vehicles sent into space are equipped with "black boxes" that record or transmit in- formation needed by space scientists who hope to explore other planets. Not as glamorous perhaps, but equally important to our country's welfare are the measuring devices used by agri- cultural scientists to gain knowledge that will improve conditions on our own planet. From information in such "black boxes" will come better farming methods, better foods and fibers, better living. The agricultural sciences offer rewarding careers for qualified young men and women who would have a part in making the future better. Write for the booklet AGRI- CULTURE-OPEN DOOR TO YOUR FUTURE. * f (^ Ift; Agricultural Publications University Hall University of California Berkeley 4, Calif. . A ■•■■••; * .