SB 608 .H8 H3 Copy 1 INSECTS INJURIOUS TO THE HOP IN NEW YORK WITH SPECIAL REFERENCE TO THE HOP GRUB AND THE HOP REDBUG A THESIS PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL OF CORNELL UNIVERSITY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY BY IRA MYRON HAWLEY PUBLISHED AS CORNELL UNIVERSITY AGRICULTURAL EXPERIMENT STATION MEMIOR 15. NOVEMBER. 1918 INSECTS INJURIOUS TO THE HOP IN NEW YORK WITH SPECIAL REFERENCE TO THE HOP GRUB AND THE HOP REDBUG A THESIS PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL OF CORNELL UNIVERSITY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY BY IRA MYRON HAWLEY PUBLISHED AS CORNELL UNIVERSITY AGRICULTURAL EXPERIMENT STATION MEMIOR 15, NOVEMBER, 1918 A^^' CONTENTS EiGE Nature of the hop plant 147 The hop-vine borer, or hop grub {Gortyna immanis Guente) 148 Generic history 148 Common names 149 Distribution 149 Hosts 149 Financial loss caused 150 Nature of the injury 150 The work in the head of the hop 150 The early ( inside) work in the N'ines 153 The late (outside ) work on the v-ines 154 The work in the roots 154 The work of the young larva in grass 156 Types of yards attacked 157 Description of the species 159 Life historj' and habits ,. 161 Seasonal history 165 Relation of climatic and soil conditions to seasonal history 166 Natural enemies 166 Control 169 Experiments in 1914 171 Experiments with carbon disulfid 174 Experiments in 1915 176 Experiments with carbon disulfid 176 Experiments with poison bait 179 Experiments ^ith para-dichlorobenzene 180 Recommendations 181 The hop redbug ( Paracalocoris hawleyi Knight) 182 Nature of the injury 183 Description of the species 184 Life history and habits .- 186 Seasonal history 188 Natural enemies 188 Predacious habit of the hop redbug 188 Control 189 The hop snout-nijth {Hypena humvli Harris) , 190 Description 190 Life history and habits 192 Seasonal historj- 196 Natural enemies 196 Control 196 The filamented looper ( Nematocampa limbata Haworth) 197 Description 197 Life history and habits 198 Seasonal history 201 Control 201 The hop aphis ( Phorodon humvli Schrank) 202 Seasonal history 202 Nature of the injury 204 Natural enemies 206 Spraying and control experiments 206 Recommendation 210 143 144 Contents PAGE The red wpider, or spider mite (Tetranychus telariua Linnaeus) 212 C<.iitn)l 212 TI»o hop iiu'rchfints (Poli/gonia intrrrognlinni.s Fabricius and P. comma Harris) 212 lA'iif hopiK-rs ( Empoiuca fluwscews Fabricius and E. Jlaviscciis Inrdii Coding) 215 aintrol 21G The milhpede (Julus caerideocinclus Wood) 210 Thf It'iif minor [Agromyzn sp.) 210 Flea IxTllfS ( I'si/lliixiis imiiclutnta MeLsh., and others) 217 Lc'iif tdIIits (Archips romceana Harris and A. arffyrospila Walker) 21S M isc»-lliiin'<)us inaecte on hop 218 Hiblio^raphy • 219 Literature cited 223 INSECTS INJURIOUS TO THE HOP IN NEW YORK WITH SPECIAL REFERENCE TO THE HOP GRUB AND THE HOP REDBUG INSECTS INJURIOUS TO THE HOP IN NEW YORK ' WITH SPECIAL REFERENCE TO THE HOP GRUB AND THE HOP REDBUG I. M. Hawley The investigations herein recorded were begun in the spring of 1913 and continued in 1914 and 1915. The greater part of the time was spent in investigating the hop-virie borer (Gortyna immanis Guenee) and methods for controlling it. Two new pests, the hop redbug (Paracalocoris hawleyi Knight) and the filamented looper {Nematocam'pa limhata Haworth), were also studied, as well as an old but little-known pest, the hop snout- moth (Hypena humuli Harris). Some control experiments against the hop aphis (Phorodon humuli Schrank) under New York conditions were conducted, and notes were made on a few pests of lesser importance. NATURE OF THE HOP PLANT In order that the relation of these pests to their host plant may be clearly understood, a word should be said regarding the growth and characteristics of the hop. The growing of hops in the eastern United States is restricted to small sections of New York State, and for this reason the plant is little known. The hop is a perennial plant, the roots living over from year to year and sending up each spring a fresh supply of rapidly growing vines. There are several roots in each hop hill. The hills are from seven to eight feet apart and there are from seven to eight hundred in an acre. The vines must be twined around some sort of support, the commonest form being either poles alone or a series of poles and strings. In some cases two poles and no strings are used, but the commoner method is to have one pole to a hill, with strings running from the middle of each pole to the tops of the ones adjacent to it. In July and August the main vines send out arms, and on these the hops are borne. The flowers, or burs, are produced the latter part of • Also presented to the Faculty of the Graduate School of Cornell University, June, 1916, as a thesis in partial fultillinent of the requirements for the degree of doctor of philosophy. The work was done under the direction of Professor Glenn W. Herriclc. The drawings were made by Miss Anna C. Stryke. 147 148 I. M HWVLKY July. :uhI the fiill-nrowii hops (fij?. 9) may In' picked from August 20 to the middle of SeptemiuM-, dcptMidiiiji; on variety, weutlwr conditions, iuul inseet and fungous pests. After the hops are picked they are drjed and I»m1(m|. ;ind are then ready for market. Fig. 9. hops at ru king timk Most hops are used in fillinu; the demands of the breweries. Small oval bodies, known as lupulin p;ranules, are formed at the base of each bract, and these eontain resins whieh give the characteristic taste to the Ixjverages for which hops are used. THE HOP-VINE BORER. OR HOP GRUB (Gortyna imnuinis Ciuen(!'e) fJENERIC III.STORY 1852 — Guen^, A.. Histoiro naturclle dea insectes 5 : 128 Ig74 _GroU-. \. R., Buffal.) S«,c. Xat. Sci., Bui. 2: IS. 1883 — Conwtc.ck. J. H., .Xmcr. iitir. 12 :'J7.') 18H4 — Smith. J. B., V. S. Div. Knt.. Bii!. 4, o. 8. : 34 1885 — LinttHT, .F. .\.. New York SUiU> Knt., Hopt.2:41 1803 — Smith. J. B., V. S. Nat. Mm.. Bui. 44 : 175 1897 — Howard. L. O., l'. S. Div. Knt., Bui. 7:40. 1902 — Dyar. H. (;.. Lii«t N. /V. Ix-p.. p. 175 1900 — Howard, I.. O., The hop, p. I'JS 1910— Hamp«on. C. K., Cat. Up. Phul. «:41 1917 — BarrivM, W., and .MclJunnougli, J., List Lt-p. Boriui .\i,„t Hydroecia Ciortyiia .Xpjiniea Hydroecia ( lortyiia 1 1 ydnii'cia Hydroecia (lortyiia ( lortyna Hydroecia Clortvua Insects Injurious to the Hop in New York 149 As may be seen from the preceding list, the generic name of Gortyna immanis has been changed many times by systematic workers on this group of noctuids. The reason for the changes has been the question ot the type of the genus. common names The common names apphed to Gortyna immanis are all based on the work of the larva. Dodge (1882) - gave the insect its first common name, the hop-vine borer; Comstock (1883) retained this name and added that of hop grub; Fletcher (1893 a) applied a third name, the collar- worm of the hop; and a fourth name, the hop-plant borer, was given by Howard (1897). Among hop growers the larvae are known as hop grubs, 01- more commonly as grubs. distribution Gortyna immanis is a native North American insect and has been widely collected in the northern United States and in Canada (Howard, 1897). Smith (1884) gives for its cUstribution the northern United States from the Atlantic to the Pacific. The insect is especiall}^ abundant in the Eastern States and in Canada where hops are grown. In addition captured moths are reported from the States of Illinois, Colorado, and Washington (Howard, 1897). In spite of the fact that moths have been taken in the State of Washing- ton, no injury to the hop crop of the Pacific coast is reported in entomological literature. One popular article by Daniel Fhnt (1882) has been cjuoted as describing injury by the larva of tliis insect, but the writer of the present paper believes the work described is that of a boring beetle. The "worm" that did the damage does not conform to the char- acteristics of a lepidopterous larva. HOSTS So far as known, Gortyna immanis is able to reach maturity only on the hop. Evidence exists, however, supporting the possibiUty of other hosts. In the spring of 1914 a farmer near Waterville, New York, re- ported that he had occasionally found the young larvae at work in his corn. This report the writer was unable to verify at that time. Larvae placed on young corn plants in the spring of 1915 flourished until the 2 Dates in parenthesis refer to Bibliuyraphy, page 219, or to Literature cited, page 223. 150 I. M. Hawley plants wore killed. The work was similar to that on the hop during the early stages, when the larva bores inside the stem. In the spring of 1915 the young larvae were found very commonly breeding in gnu^s in and around hopyards. Their work on grass is very much like the early work on the hop, and is discussed at some length later (pjige I'A)). Cages were placed over five of these grass plants on June 7. On August 17 thvsv cages were examined, and no live larvae, pupae, or adults were to be found. It is assumed, therefore, that the larva cannot mature on grass. I INAN(I.\L LOSS CAUSED The lo.ss due to the work of the larva of (lortyna inimanis varies greatly in different years, and in different yards in any one year. In years when the insects are numerous there may result nearly a total loss to some growers. A hop grower in Bristol, New York, informed the writer that he had seen the ilamage so great that the hops were not picked. Dodge (1882) estimated the loss due to the insect in New York State in 1879 at $000,(XK). The writer worked in one yard where there were ninety dead vines in one hundred hills, or a computable loss of twenty per cent from the work of the insect. To this must be added the damage in weakened vines. Judging from the hills ins|M>cted, this fiekl had not more than twenty-five hills ii) an acre in which the grubs had not worked. It is probal)le that a total loss of forty per cent would be a conservative estimate for this yard. NATUKE OF THi; INJURY The injury of (iorti/na iinni(tnis to the hop plant may l)e clas.sed under four phiuscs. depending on the part of the plant attacked: (1) the work in the head of the hop; (2) the early (inside) work in the vines; (3) the late (outside; work on the vines; (1) the work in the roots. 4 The work in the head of (he hop DfKJge (1882) and later writers on hop insects supposed that the egg of (i. immani.s was laid on the tip of tlie hop vine early in the spring. It was n*ix)rted that when the egg hatched, the young larva bored at once into the head, producing a blunted condition known as a muffle Insects Injurious to the Hop in New York 151 head. As is explained later, this theory of egg laying is incorrect, but it is true that some of the young larvae do find their way into the head of the hop. Newly hatched larvae of G. immanis may crawl long distances and enter any part of the hop plant that is tender enough for their small mandibles, or jaws, to break open. Some of them in their journey reach the head Fig. 10. HEALTHY AND MUFFLE-HEADED HOP VINES. NATURAL SIZE The blunted condition of the injured heads on the right should be noted (Photograph by G. W. Herrick) of the hop and find a place for easy entrance in the budlike tip. There is no definite place or manner of entrance. Some larvae bore their way into the side of the head, leaving an easily recognizable hole; others enter the tip itself and make their way between the developing leaves; while a few enter the base of the head, or the vine just below the head, causing it to bend to one side. The vines attacked become stockier, and as the 152 I. M. Hawley larva fotnls on the tondcr iiit< rior tissues, killing the growing point, the head usually takes on a short, thick shai)e with scraggly leaves, in con- trast to the pointed tip with closely folded leaves of a healthy head (fiR. 10). The root of a hop plant sends up fresh vines for a period of several weeks. The writer ha.s noteil caries in which, due to late hatching of the FlU. 11. ML>>LE-HEAUIiD HOP VINES RESll-TING FROM THE WUKK OK THE HOP-VINE BORER. REDUCED When the main bud is injured, the leaves and buds just below begin to develop i eggs, the heads of all the young shoots were completely riddled when early vines, then four feet u|) the poles, were free from injury. In 1915 larvae were found in the hop heads when the yards were first inspected on May 0. At that time* the vines of the first lot were less than one foot high. ( )cc!i.si()nal inufTle heads could .still he found by the first of June, .\fter working in the tip of the lu)p for from one to two weeks, most of the larvae drop to the ground and join tho.se working in the vines. II Insects Injurious to the Hop in New York 153 The injury result inp; from the work of the larva in the heads is relatively small. The men who tie the hops choose the unaffected vines, and if by accident a muffle-headed vine is used it may be replaced at the next tying. When the head is killed, the two buds at the node just beneath it will grow rapidly (fig. 11), and occasionally one of the arms thus re- sulting is twined on the pole in place of the main vine. The early {inside) work in the vines In contradiction to earlier accounts, the writer has obtained evi- dence that many of the newly hatched larvae enter the hop vine at once, without first working in the hop heads. Most of the eggs hatch at a time when the vines are short and tender. The young larva enters usually near the surface of the ground — from two to four inches above the bed root. Only a small hole shows on the out- side, but at this point the vine breaks on bend- ing and the work of the young larva is found within. A discolored area running up or down the pithy center of the stem marks the course taken. The burrow is filled with wast6 material behind the little larva as it rapidly eats its way along (fig. 12). The larva grows, and sheds its skin at least twice before it is ready to eat its way from the vine, whose unyielding sides prevent further growth. Fig. 12. VINES CUT OPEN TO SHOW THE WORK OF THE HOP- VINE BORER. XU l.->4 1. M. 11 awi.p:y The newly hatched larva of (;. immaniK is loss than 2 millimotors long, but when roady to l('av(> the vinos it has roaohod a longth of from 8 to 18 niilliniotoi-s. In lUlf) most of tho larvao were outsido the vines by June 9. In tho case of one hill («xaminod on that date, one Rriih was in a hop vino, one was in a blade of ^rass on the hill, and seven were working on the outside of tho vines. W hilo tho larviu^ work oftenor in young, tender shoot.s, they are .some- times found in tho bjisos of vinos that are well up tho polos. Occasionally they (Mitor a vine of this kind halfway to the tip, or from two to three feet above the ground. Sometimes a vino is found which has a muffle head and several larvae working in it at different points. All tliis strengthens the ovidonco that a larva, after crawling for some distance, enters wherever it can most easily make an opening. When a larva leaves its burrow in tho hop vine, it does one of two things: either it oats its way into a bed root, or it feeds on the outside of tho vine Ix'twoon the bod root and tho surface of tho ground. In very rare cases larvao have boon foimd focnling on runners, or rootstocks, which were not removed by grubbing in the spring. The late {outside) work on the vines After leaving tho head of the hop or the inside of the vino, tho larva usually attacks tho outsido of the vine and feeds on the sap that flows from tho woimd. In some ca.ses tho vino is eaten completely thru, but oft^'iior it is held togi-ther by a small shred and enough nourishment pas.ses thru to keep the foliage from wilting. After feeding in one place tho larva often goes to another, above or below tho old wound, and repeats its work. Vines thus attacked often send out extra rootlets above the wounded area, and much additional nourishment is received in this way. Tho sap is able to asc(>nd in vines of this kind, but the return flow of manufactured food material to the roots is cut off. The vine swells above the injmed area, duo, no doubt, to the deposition of the material being carried downward. The roots, deprived of this food supplv, bo(;om(! weaker and succumb more readily to the winter frosts. (Fig. 13.) The irork in the roots Some of the larvae eat their way into the bed loot on hatching, but it ia conunoner to find i)artly grown larvae in this ix)sition. Larvae Insects Injurious to the Hop in New York 155 are especially abundant in the roots in unhilled yards, where the roots are close to the surface of the ground. Some gnihs make shallow grooves on the outer surface, but many work in the core of the root in all directions. The writer has found twelve larvae in a single root. As the bed root is the part of a plant that lives over the winter and furnishes the growth for the coming season, any injury to it is a serious matter. One result of Fig. 13. vines broken off from the bed root as a result of the feeding of the hop-vine borer. slightly reduced The enlargement above the place of attack is to be noted this work of larvae is that an opening is made for soil water to seep in and freeze; also, fungi may enter and start decay. In yards that have been badly infested with grubs, as feeders on either vines or roots, the number of dead hills is always much greater the following spring. Many grubs are working as external feeders or in the bed root by the end of the first week in June, and by the end of the second week nearly all have finished their work inside the vines. They mature and complete their work in the roots from the middle of July to the middle of August. IfHi I. M. livwiJ V THK WORK OF THE YOUNG LARVA IX GRASS VavW ill the spring of 191"), larvao of Gortyna immanis were found workinR in gniss plants in the hopyard.s (fig. 14). The work in grass i.«< vory siniihir to tho early work in the hop vine. The grub enters, as a rule, elose to the ground and boras upward thru the stem. Injured gnis.s may soon be distinguished by the wilting of the central blade. The grub continues its work until about the third stage, and leaves the grass about the time the larvae arc leaving the inside of the hop vines. I"Ui. 1 1. I.ARVA or IIOI'-VINE noRKR IN A ORASS STEM. X 3 Karly in the spring gra.ss is (•oininoii in many hopyards, giving the grubs a good place in whielj to start tJKMr growth ffig. 15). Many larvae are found in the gras.s .along the l)orders of yards as well as in the yards themselves. It is probable that the moths go to the grass at the sides of the yards for shelter during the day, and lay their eggs there at night. After the eggs hatch, the larvae fec^d on the gntss and later move to the hops. From this it is clear why the edg(>s of th<' yards are often more seriously in^urecl than the central parts. No huvac^ were found in grass at a distance from the yards. In order to see whether other |)lants could act as hosts, weeds of all kinds were carefully examined, but in no case were larvae found working on them. Insects Injurious to the Hop in New York 157 types of yards attacked Poorly-cared-for hopyards having a growth of grass show more injury from Gortyna immanis than do those that arc well cultivated (figs. 16 and 17). This may be due partly to the less vigorous growth in the former type of yard, but it may be attributed in large measure to the fact that the eggs of the insect are laid on grass and this grass furnishes Fig. 15. grass around a hop hill in may Many larvae of Gortyna immanis work in grass at this time food for many of the young larvae before they attack the hop. Yards newly set out, if near an infested yard, are often seriously damaged. ] One grower was compelled to reset a new yard four and five times in some places before he could get it successfully started. Old yards in which the grubs have been allowed to work and multiply for a number of years, show the cumulative effect of such work. This is one reason given for taking up old yards and setting out new ones every five to ten years. 15vS 1. M. Hawley FjG. 1G. a poorly Klil'T HOPYARD, IN WHICH HAVE BEEN FOUND MANY LARVAE OF THE HOP-VINE BORER HAVE bEEN FOl'ND AJ WORK Insects Injurious to the Hop in New York 159 description of the species The egg The egg of Gortyna immanis (fig. 18) is 0.65 millimeter in diameter and 0.43 millimeter thick, flattened above and below. The color of the egg when first laid is white or yellow-white, and turns to brownish pink in from one to three days. The egg is faintly marked on the side with about one hundred branching, radiating ridges. The micropyle end has a group of raised polygonal areas, with a rosette formation in the center. The larva The six stages thru which the larva passes may be described as follows: First stage. — Length (collected specimen) 3 mm. ; head 0.3 mm. ; ground color dirty white, with prominent markings of old-rose red; sparse -vestiture of setae. Head dark brown or black; antennae, ocelli, and mouth parts light yellow brow^l. Prothorax, anterior half dirty white, dorsal shield dark brown or black. Mesothorax with four rose-colored patches on lateral aspect of segments, forming a }>road, broken, transverse band. Metathorax with markings similar to, but heavier and more irregular than, those of mesothorax. Thoracic legs with coxa white, femur, tibia, and tarsus brown. Abdomen with segments 1 to S banded similarly to meso- thorax, but bands broader, covering nearly the entire segments; tubercles inconspicuous; spir- acles small, dark-bordered, surrounded by a light ring; segment 9 more faintly marked; five pairs of prolegs; venter lighter but with rose tint on abdomen. In grass, hop heads, and vines. (Only the prominent differences are noted in the descriptions following.) Second stage. — Tvcngth 3.4-6.4 mm.; head 0.65 mm. (average of seven specimens); ground color more prominent, rose-colored markings often less extended and tending to orientation in longitudinal axis, on all segments of thorax and abdomen; setae about one- third as long as diameter of body, and tubercles bearing them more prominent. Head pale yellow-white, clypeus and la- brum darker than other parts; ocelli in a dark patch; dark spot on dorsal shield divided by a median light line; spiracles larger, and especially prominent on pro- thorax. In grass, hop heads, and vines. Third stage. — Length 6.8-8.4 mm.; head 1 mm. (average of eight specimens); ground color more extended and rose patches more regularly arranged; four longitudinal dark lines ))roken by light spaces; the second (subdorsal) line much narrower than the first and the third; tubercles bearing setae dark brown. In grass and vines. Fig. 18. EGG OF HOP-VINE BORER. X 48 Fig. 19. LARVA OF HOP-VINE BORER, FOURTH STAGE. X 5 160 I. M. Hawley Fourth Ktagf (fiR. 19).— IxjiiRth i) 15 nun.; heiul 1.43 mm. (averaRe of eight specimens);" nxjuiid wlor still in ^r \ Fig. 22. adult female of hop-vine borer. X 2 LIFE history and HABITS The egg The eggs of Gortyna immanis were said by Dodge (1882) and later writers to be laid on the tip of the hop vine by overwintering females, but the writer has never seen an egg in this position and has no evidence that they are ever so placed. Under field conditions eggs have been found only on grass, and here they have been found in large numbers. Prior to 1915 eggs had been found deposited in various places in laboratory and field cages, but no eggs that were known to be those of G. immanis had been found under field conditions. In the spring of 1915 a search was made for eggs and young larvae, and on May 10 larvae were found working in grass stems and eggs were found on dead grass blades from the same root. In August' of that year cages were built over hop hills on which grass was growing, and full-grown grubs and pupae were placed in them. On the grass in one cage eggs were found on September 1. They were laid both singly and in small groups. Most of the eggs were attached to the outer surface of the grass. On September 6 many eggs were found in the axils of the grass stems, in all cages. Several lots of eggs were found in the field near Sangerfield 162 I. M. Hawley on St'ptoinlMM- 7. and from that time on (here wjis little trouble in locating eggs on gras-^ in any yard that had Iuh-ii infested by grubs. During 1915 eggs were found nowhere except on gra.ss plants. (Figs 23 and 24.) The egg stage lasts about eight months. Eggs are laid from the middle of August to the last of September, and hatch from Fig. 23. eggs of hop-vine borer on a grass stem. x 3 the last week in April to the last of May. A distended female opened in 1014 con- tained SCiO eggs. ( )thers examined in 1015 hatl 725, 457, and (512 eggs, respectively. No data were gathered on eggs deposited. It is apparent that the nmnber of eggs Fig. 24. • eggs of hop-vine borer laid by a sk,gh- ,„„lh nu,v l,o large. Not ^.^^^^^^rVT °"" all eggs hatch, a.s many turn black and shrivel .soon aft«'r being laid. Both shrivc'led and healthy eggs are found in the same egg mass, and as many as fifty per cent may diy up — due. no doubt, to lack of fertilization. I Insects Injurious to the Hop in New York 163 Eggs are laid soon after the moths emerge. The data for three indi- viduals arc given in table 1: TABLE 1. Length of Time between Emergence 1915 and Oviposition of Three Moths, Date of emergence First eggs laid Days intervening August 25 September 2 September 5 September G 8 August 31 5 August 26 11 The larva In order to find the number of stages thru which the larva passes in its development, a series of head measurements were taken. Since the larva breeds in vines and beneath the surface of the ground, it is impossible to find the cast skins, and so grubs were preserved in alcohol during the ^mmmer of 1914. These were later examined and the transverse measure of the head was taken, as given in table 2: TABLE 2. Head Measurements of Larvae Collected in 1914 Stage Number of specimens Diameter (in millimeters) Greatest Least Average 1st 2d 3d 1 7 8 8 8 8 0.30 0.68 1.06 1.50 2.46 4.06 0.30 0.60 0.92 1.37 2.06 3.80 0.30 0.65 1.00 4th 5th 6th 1.43 2.22 3.91 It is seen from the above data that the larva of G. immanis probably passes thru six stages with five molts. The entire length of the larval period is from nine to twelve weeks, since the young larvae hatch from the last of April to the middle of May and pupation occurs during July and the first half of August. No larvae have been successfully bred thru. Smith (1884) reports that the larva makes a rude cell in which to pupate. Comstock (1883) did not observe this to be true. In rare cases ir>4 I, M. Hawley the writer hiis found a pupal cell. Whether or not one is formed de- I^'nds on the texture and the moisture eontent of the soil at the time of pupation. If the soil is of tlie eonsisteney of elay and is easily packed, a (ill may be formed. ■ The pupa There is a wide variation in the size of pupae (fig. 21, page 100). as also in the A-£V of adult moths. The writer believed that the small pupae must Ik^ those of males and that the large ones would develop into females. Breeding shows that this is not always true, since in some cases females have iM'cn reared from pupae of the smaller size. In 11)14 full-grown larvae of (7. immanis were taken into an unheated field laboratory. The length of the pupal stage under these conditions wa.s found to Ix' as given in table '.i: T.\BLK 3. Length ok Plpal Staok kor Four Specimens under Laboratort Conditions Date of pupation Date of emergence Days intervening July 2 July 3 July 5 July 6 Average, 30 days. August 8 August 7 August 9 August 11 37 35 35 36 From the above data it is .seen that tiie pupal stage lasts a little over one month in the laboratory. Observations by the writer indicate that in the field it varies from four to six weeks. Pupation occurs in the field during July and in the first part of August, and moths emerge during August and Sei)t<'mber. In l!tl4 the first pupa wa.s found on July 2. and in llHo on July V». In 1U14 the fir.st moth emerged on August 10, and in 1915 on August 11. At Waterville the writer found newly trans- formed moths in field cages ;us late its the middle of September. In most caHes the full-grown larv;i leaves the root or the vine and comes close to the surface of the ground before pupation. The pupa is often found .some di.stance down the side of the hill — a foot from the place of larval feeding o|K'rations. In rare cases the pupa may be Insects Injurious to the Hop in New York 165 found near the root and even beneath it. The moths on emerging often leave the pupal skin projecting above the ground. Smith (1884) reported that G. im?nams usually winters in the pupal stage, but after three years of observation the writer is convinced that all pupae change to adults in the fall. Cages were ex- amined late in Septembei-, and all healthy pupae had transformed. The adult Adults of G. immanis, being col- ored much like dirt, dead leaves, and hop poles (fig. 25), are seldom seen in the field. It is not uncom- mon to search for moths in a cage for some time and then find them resting quietly a few inches away. If disturbed they usually flutter their wings and crawl a short dis- tance, but do not fly far if at all. After depositing eggs the moths die in a very short time, in most cases in about a week. In one case a moth lived for twelve days after completing oviposition. Sweetened solutions were placed in some cages, but did not greatly prolong life. These data were obtained by isolating moths the abdomens of which indicated that they had been laying eggs. seasonal history The eggs of Gortyna immanis are laid in the fall on grass in and around hopyards. The eggs hatch the following spring, in April or May, and the young larvae make their way into grass or hop plants. In grass they eat into the stem near the surface of the ground and feed upward, killing the central blade. They leave the grass at about the time other larvae leave the inside of the hop. Fig. 25. adult hop-vine borer on hop pole. slightly reduced 166 1- ^^- Hawlkv In the hop the younp: Kruhs enter the part that is the most readily avjiilahle and ejisy to penetrate. This may be the hcail or any part of the vine. If the hirva enters the head, it drops to the ground in about two wtH'ks and helps to increase the lar^e mnnber already working in the vine near the root, .\bout the first of June, when the larva is in the thiril or the fourth stage, it stops inside work and either feeds on the outside of the vine, nearly or (|uite .severing it, or makes burrows in the root. In July or the fii-st part of August the larva pupates, and the moth emerges the last of August or early in September. The moth deposits eggs, whieh rest over the winter on grass. The moth dies soon after oviposit ion. RELATION OF CLIMATIC AND SOIL CONDITIONS TO SEASONAL HISTORY Weather conditions have some influence on the life history of Gortynn immanis. \ late, cold spring retards the development of the larvae somewhat, while warm weather hastens its growth. The winter of 1913-14 wa-s attendcHJ with heavy snows which covered the ground in the hop country until late spring, while that of 1914-15 was open and the groiuul was not covered. A laiger number of grubs were present the following spring imder the former conditions, in a yanl that was under clo.se obser- vation. The snow cover may act as a blanket for the overwintering eggs. The larva works in any kind of .soil. Yards on sandy soil, however, are less afTectcd than those on gravel, clay, or loam. NATURAL ENEMIES Predatory enemies The skunk. — An im|)ortant destroyer of the larvae, and probably of the pupae, of (inrtymi intnianis, i.s the skunk. About July 1, when the grubs have reached maturity, numerous holes may be seen in hop hills where, skunks have been alK)ve the injured areas. These supply nouri-shraent to so large an extei that vin(»s nearly .severed are often kept alive by this means. Hilling i- a good practice for this reason if for no other. A hop root sends up many more vines than are needed for cultural purix)ses. When the hops are tied the second time, which is usual! about June 1, these extra vines are pulled up or cut off with a knife. Th practice is of use in grul> control if done in the right manner. At thi- time many of the grubs are working on the inside of the vines, and if tl vines are destroyed the grul)s will be killed. It is better to pull the vini out than to cut them off, for. if larvae are working in the vines near tl crown, the cut may come above them anil they are then free to cra^\l out and enter vines that have been twined on the poles. The writer h: seen many grubs in the stumps of the vines just below the place whei they were cut off, and has observed them crawling to adjacent plant-. If the vines are pulled, they break off where they join the root. All sprouted vines should l>e tak"n from the yards. As grubs work in the late shoots just coming above the ground, these also should be removed n this time. In lOlo most of the grubs were outside the vines by June ' and the practice of sprouting, to be effective, should in ordinary yeai Ik' completed before June 1. An old recommendation (Smith, 1884) is to place wood a^^hes aroun 1 vines or scatter them on top of the hills. In 1914 one grower did thi- alwut June l.'i. On examining that yard some time later, the writ( found live grubs to Im' numerous in every hill and dead vines were unu- sually plentiful. Sometimes growers resort to digging out tli(> larvae. This ha.>< Ihhmi doiH' in early June, when the work outside the vines was just beginiiini: The .soil is removed from around the hills down to the bed root with a hot and the dirt is worked away from between the vines with a pointed stick Insects Injurious to the Hop in New York 171 in order to remove any grubs that may be feeding deep down near the roots. William Durar, working for George Allen, a grower, at Sanger- I field, New York, found that it took twenty-eight hours to go over 267 hills. He averaged, therefore, between 9 and 10 hills an hour, but in addition to digging out the grubs he removed the dead vines and trimmed off the lower arms. If all the time had been spent in digging grubs, it is probable that 12 hills an hour could have been gone over, or 120 hills in a day. At this rate it would take about six days for one man to dig one acre, amounting, at S2 a day, to $12 an acre. Another grower reports that grubs can be dug at the rate of 200 hills a day — a cost of $7.50 an acre. This makes digging a rather expensive process. , In digging grubs, vines that are weakened by feeding may be broken j off, and in ordinary practice of this kind the larvae working in the roots , would not be found. Men in the hop sections are needed for other work at this season of the year, and it is difficult to get help that can be relied ; on to do this work in a proper manner. For these reasons, the writer ' undertook a series of experiments to see whether an effective method of I control could not be found at a more reasonable cost to the grower and I with less demand on greatly needed labor. The results of these experi- ments are given in the following pages. Experiments in 1914 Most of the experiments in 1914 were conducted in the Gallagher yard at Sangerfield, New York. The soil in this yard is a gravelly loam. At the time when most of the materials were applied, the soil was mellow and slightl}'- moist and phosphate had been added at the rate of a few handfuls to each hill. Experiments were conducted in several parts of the yard at once, and counts were made from several hills in each of these plots. The test of efficiency for most materials is that few live grubs are to be found in the hills when counted. The number of grubs to the hill varies greatly, and so a count of a small number of hills may not give a ' true average; it may be said, however, that in any case when three or more grubs are left alive, the material may be considered ineffective, as three grubs can destroy an entire hill. The results of the experiments conducted in 1914 are given in table 4: 172 1. M. Haui.kv poo paxi 3 Si * cJrs >~ -a ^% 1 . .3 c "si ^ cS 1 5 1 3 cr "2 a en 1 g 1* 03 oj t -a -is T U U > '-' > i« 1^ K o o - e«3 in 00 C5 C5 >o < s •^ t^ 00 lO 00 t-i ■^ t^ '^ Z o5 ^:il o 1— 1 X 00 o o o o o o K eic § \ ;! o 8 a s c a o 03^ a o sc o a o C o c c = a _2 a O c O i S5 U i'lisi 3 3 ^ 1 3 ■3 "a" (N 03 - ** ti 1 a a a a a a CT3 3 a 3 g s u i ^ ca 03 03 J3 *3 00 O 09 !!5 3 53 3 ?5 3 ?5 e 3 CO (N > IN !3 s b 5&S d eS « £ cS eS S3 as eS ^ ^ ^ S J^ S ?^ I^ ^ S S J "O U 1 J= '^ "« 3 a .6 1 S 3 E § § H -a ■o — " t> '■5 1 «< s 1 1' T3 C C9 . 8 ■8 ■o J f2 -o 1 e 1 3 1 O 2! 1 o 6' 1 X II if i« u Q u K HH •-J 'X J j< Insects Injurious to the Hop in New York 173 "o "^i- (0 " ,9 a s i g ^ o m 43 c8^ 1- 00 ■? 'H--S 1 O OS'S lO ^ lO ec o o O ^ CO 00 C5 o CO C3 06 o >* >o o lO S c^ m JD 02 CO 73 A A ;5 -C -C C a a O a a O O O O ^ CO ja J3 r-; -*^ "^ tH o o o 3 g 03 a a e 3 £ £ CO Q Q Q s CO CO CO 00 '— ' ■— ' ■—I i "3 0) 3 3 >-! >-5 1-5 i-s 1-5 Tt< cs ^ ^ ^ (N -H -H ■— < >, _>> a> 0) 0) rt 3 C fl c S 3 3 1-5 3 >-5 1 4^ fl 3 •o 03 _o s d CO S V & .2 3^ -d •S^ o 2 ■5 c^ 03 . h 1 ^z; m P > ^ xi 174 \. y\. Hawlky Experiments with carbon disulfid CixrUm disulfid wivs tried jis a control mca.'^uro against tho larvae in the ('.alla^her yard. In the first exixM-inient, on July 2, a hole wan made in the soil with a sharpened stick and the liquid was poured into it from a l)ottle. The hole wius then filled in. A pint of material was used in eipht hills. One hill wius opened in fifteen minutes and the remainder T.VHLE o. Rksults of Experiments with Carbon Disulfid in 1914 — Series I (Time between injection and examination, from 48 to oO hours. No injury to vines) Experiment Distance of appli- cation from rocjt (inches) Number of injections Quantity used in each injection (cubic centi- meters) Depth of injection (inches) Number of grubs found Depth of grubs when found (inches) Con- dition of grubs 21 3 1 4 6 2 3 Sick 22 3 1 8 6 1 3 Dead 23 :i •J 2 6 2 2 Ahve, sick 24 3 2 4 6 1 5 Dead 25 6 1 2 6 1 3 Dead 26 . ..• 6 1 4 G 2 4 Dead 27 6 1 8 6 1 4 Dead 28 6 2 2 6 1 6 Dead 29 6 2 4 6 1 5 Dead 30 6 2 8 6 2 4 Dead 32 12 1 4 6 1 3 Alive, active :i3 12 1 8 6 2 ( 5 ■ 7 Dead ■ Nearljl dearT 34 12 2 2 6 1 4 Sick 36 12 2 4 6 1 3 Alive Insects Injurious to the Hop in New York 175 TABLE 6. Results of Experiments with Carbon Disulfid in 1914 — Series II (Time between injection and examination, from 48 to 54 hours. No injury to vines) Experiment Distance of appli- cation from root (inches) Number of injections Quantity used in each injection (cubic centi- meters) Depth of injection (inches) Number of grubs found Depth of grubs when found (inches) Ck)n- dition of grubs 20 3 1 2 6 3 Dead 21 3 1 4 6 4 Dead 22 3 1 8 6 3 Dead 23 3 ,2 2 6 5 Dead 24 3 2 4 6 4 Dead 25 1 2 3 6 6 6 1 1 1 2 2 2 6 6 6 4 3 2 Dead Dead Dead 26 1 2 3 6 6 6 1 1 1 4 4 4 6 6 6 2 4 6 Alive, sick Dead Dead 27 1 2 3 G 6 6 1 1 1 8 8 8 6 6 6 3 2 5 Dead Dead Dead 28 1 2 6 6 2 2 2 2 6 6 2 7 Sick Dead 29 1 2 6 6 2 2 4 4 6 6 3 5 Sick Dead 30 6 2 8 6 1 4 Dead in from one and one-half to two hours. Two grubs in the first hill opened recovered from the effects of the vapor, but 57 in the other seven hills were all dead. Many vines were injured. On the following day one pint of the material was applied to twenty hills. From four to seven hours 170 I. M. Hawley after the treatment, 1 IS jrnil)s were found; of these, 106 were dead, 6 were dying, and 6 were alive. The live grubs were on the opposite side of the iKile from the injection, or on ruimers at some distance from th€ root. The vines in some of the hills wore killed. Conditions at this time were favorable for the effective working of tht vapor. The soil was slightly moist and was mellow, and the yard wai hilled high. In addition to the grubs, millipedes and l)ettle larvae wen killed. By this time th(^ larvae were full-grown and were becomin| scarce. \ few were found, however, and these were placed in the centei of the hills and doses of different strengths were tried against them. Th« results are shown in tables 5 and (pages 174 and 175). From thes« tables it is seen that, under ideal conditions, doses as low as two cubic' centimeters to a hill were foutid effective. Of all the materials tried in 1914, carbon disulfid alone showed signs of success, and therefore the writer decided to test the material more fully in 1915. In order to test the effect of carbon disulfid on the hops, another series of ex- periments was conducted. The moi(^ important results are given in table 7| TABLE 7. Results of Injury Experiments with Caabon Disulfid in 1914 Quantity Distance of used in each Depth of Resulting Experiment application injections injection injection injury to from root (cubic cen- (inches) plant timeters) 1 Next to root 8 6 2 dead \'ine8 2 Next to root 4 6 None 3 f) inches 16 6 None 4 ) CO 00 00 00 "n "O oo TOO 11^- CQCq C<1 C^M OaDOOOO -"IiO -lOM 1-1^2 C^ O l--CO-*<0> O •* C^ O^ — < ro oo: ■* 05C^ OJ 00 O 00 O h-O i-lO OO-HO -<0 M O-H ^ .^ -H-Hrt,-Ht^NOO«OCOMIM • — i--c<3 iot^O"S< roa> o i^-H c^i CO coot— oooo-^oooo ro CO Tj< o CO 'J" IN t- 10 'O o io c^i m in el^r-HO>M "OCOCOrl-H 3 t-~ MO oooo oo o oo o o oc^ooooooininioit3-o-.o "S^ 3 fe C Q^ '^ s 3 -^00 00000000 "Om lO mio oo oo IN IN oq IN IN c e c c c 3 3 d 3 3 1-3 >-5l-5 1-3 1-3 IN IN o o a a 3 3 IT^ 3 1-5 1-5 1-2 '^ ^ 1 0> O CO o o o H e-J (N C^l CO -^J* Ca M ■* rf -f i-HrHrtrt M(N IN (NIN ri CI (N-^(NC)(NiNdrti-iCllN(M c3 a> cc ccco cc 33 3333 33 l-3>-3 I-31-31-3I-3 ^1-3 ID O c c 3 3 to CO « 00 I— r-O'ji'HcocO'-f'-i-H 00 oo<-ioooocoojc^t— t—c^c^C') 1-1 -H N tH T(l T)( 00 CO M IN CO CO CO pj-o » rt ^ ,-HlN-HIN IM rt^ rt iM rtrt rt(N-> V •ey. . ke... ke... ke... ie. . . yer. ipbel er. . . ikler radt. radt. > cj 03 cS cJ ci rt c^ o tj o o o '-ooo3aca-5„^ H< OO OOOO^ k£ K WK ffi K ffi_!KJhJh-lHOtween injection and counting, sick ones would no doubt luive recovered. The average lunnber of live grubs per hill is given to show the comparative averages for check and for treated i)lots. Fl(.. ■_".). TWOTVl'liS OF INJKCTORb lOR I SE IN TREATING SOIL WITH CARUON PISCI-FIl) Insects Injurious to the Hop in New York 179 Taken as a whole, the results are very unsatisfactory. The writer believes, however, that in some soil and under ideal moisture conditions good results may be obtained. Since these conditions cannot be con- trolled the use of carbon disulfid is of doubtful importance. Injury to hop vines from carbon disulfid. — Carbon disulfid will kill a hop vine or root whenever it comes into actual contact with it. The writer has noticed that vines which are badly eaten by the grubs are killed oftener than those that are not. A series of experiments in moist sandy soil showed that 15 cubic centimeters of carbon disulfid placed close to the vines had no serious effect. The sandy soil, being porous, no doubt allowed a better spread of the vapor. The results of an experiment in the Gallagher yard, where the soil is a gravelly loam, are given in table 9: TABLE 9. Results of Injury Experiments with Carbon Disulfid in 1915 (Injections were made on June 16; plants were examined on July 10) Experiment Quantity used in each injection (cubic cen- timeters) Number of injections Distance of application from root (inches) Number of live vines Number of dead vines la lb 16 8 24 12 32 16 21 24 1 2 1 2 1 2 2 2 4 4 4 4 4 4 4 4 2 4 2 2 1 2 2a 2b 2 2 3a 3b 4 4 4b 5b 4 3 Experiments with poison bait In spite of poor results obtained in 1914 from the use of poison bait it seemed possible that it might be applied successfully, and on June 11, 1915, a plot in the Gallagher yard was treated with a bait composed of 2| pounds of bran, | pound of white arsenic, 1^ pint of molasses, and the juice of an orange. This is stronger in arsenic than the mixture used against the army worm. A rainfall of 0.26 inch occurred soon after this experiment was started, and therefore another plot was treated on June 12 with a mixture of the same strength. The material was placed close around the vines, the dirt ISO I. iM. Hawlky 1 iH'ing romovod to make this possible. On Juno 14 the following counts \v(Mv made: in the plot treated on June 11 there were 30 grubs in ten hills, of whic-h 28 were alive and 2 were dead; in the plot treated on June 12 there were 27 grubs in ten hills, all of whieh were alive; the check showed 29 grubs in ten hills. CJrubs placed in a jelly glass with poison bait on June 12 were sick on June 13 and died on June 14. It is prob- able, therefore, that these larvae will feed on poison bait when the pre- ferred hop vines are not present, but that they will not touch it under field conditions. A bait applied in May to catch the hatching larvae might jirove elTective. unt 1 Experiments with para-dichlorobenzene ParaHlichlorobenzene has V)een successfully used against various pei of stored grains. Duckett (191o) descrilxid its use, and from his account the following data are taken: Para-dichlorobenzene is a colorless, crystsil- line substance with a boiling j^oint of 341. G° F. It volatilizes readily as a colorless vapor with an ether-like odor. This vapor, which is five times as heavy as air and twice as heavy as carbon disulfid vapor, is harmless to human b(Mngs but is a sjx^cific poison for insects under many condi- tions, killing by action on the nervous system. The insect l)egins quiver- ing and finally turns on its l)ack and, still (luivciing, dies. The cost is 15 cents a pound in l)arrel ls were counted as dead, .since the material was still active and would doubtless have killed them if left undist»nbed. Dead Lachnosterna larvae and carabids also were found, but millipedes were usually able to escape the action of the vapor. I Insects Injurious to the Hop in New York 181 Dead grubs are soft and black, and sick grubs are often slightly dis- colored. The vapor would no doubt spread more rapidly in normal years, free from the frequent heavy rains, and it will be interesting to see the effect of the material on the grubs under ordinary conditions. No plant injury was noticed during the experiments, but 56 grams of para-dichloro- benzene placed around one hill killed the plant in eleven days. TABLE 10. Results of Experiments with Para-Dichlorobenzene (Ten hills counted in each yard) Yard Date when ex- periment was started Date when ex- periment was closed Amount of material used Larvae found Per cent of control Total number Number dead Number sick Number alive June 18 June 21 June 21 July 10 July 10 June 28 A few crys- tals A few crys- tals A few crys- tals 14 39 37 12 28 32 1 4 3 1 7 2 92.8 Hicks 82.0 94.6 The ideal insecticide for grub control would be a material with long- lasting effect, which could be easily placed in the soil when early hilling is practiced. Para-dichlorobenzene may act successfully in this way. Its insolubility in water and its activity in the soil over such long periods of time would tend to indicate this. More study should be given to this side of the work. Recommendations The following practices are recommended for control of the hop- vine borer : 1. Remove all extra vines before June 1. Pull out the extra vines and remove them some distance from the yard. 2. Hill the hops, so as to give the extra rootlets an opportunity to grow. 3. Practice clean cultivation; in other words, remove the grass from the yard. 4. Keep a plowed border several yards wide around the field. 5. For an insecticide, experiment with para-dichlorobenzene, using a few crystals in each hill and coveiing with about two inches of dirt. This should be applied about the third week of May. » 182 I. M. Ha^xey TIIK IU)I' 1{HI)BUC. (Paracalocoris hawlcyi Knight) During \\\v past few years hoj) |)lants in the yards about Waterville, Mow York, csix'cially in those in the vicinity of Sanjiorfield, have shown (•(»nsj)icu()iis injury of the fohage l)y perforations of the leaves, and also a stunting; and defor- mation of the stems. In June, 1913, the vines in several yards at 8ang(M-field were notably in- jured in this manner. Careful examination of the affected plants disclosed the presence of larp;e numbers of red nymphs witii white markings. When these yards were examined early in .hily the nymphs were feeding on the vines and sap was flowing from the wounds made by them. .\ few adults were taken at that time, which later were found to Ix'long to the family Miridae. Hecause of their striking color I he writer has called them the hop redbug. Each year since 1018 the insect has increased gicatly in numbers and has caused more and more injurJ^ It may now be found in yards ten miles from Sangerfield, but it does not apjx'ar (o have readied the C'ooperstown district thirty miles distant. The writer submitteil a large series of specimens for examination to II. II. Knight, who reported them as representing a new species which he described as Paracnioron'.s hnwlcj/i. Later the determination was confirmed l)y W. L. McAtee, who in addition described several varieties of the species. Fig. ;J0. work of the hop redbug on hop vine am) lkaves. reduced Insects Injurious to the Hop in New York 183 NATURE OF THE INJURY The injury caused by the hop redbug may be recognized by the deformed and stunted vines and the irregular holes in the leaves (figs. 30 and 31). The earhest injury is made evident by many hght spots in the still folded leaves, and on close examination it is found that the epidermis is broken on the underside. Later, as growth of the leaf continues, a dead area is Fig. 31. leaves showing results of feeding of the hop redbug produced, and when this drops out an irregular hole results. The early work is found about the middle of June, and by the middle of July the leaves may be completely riddled. In later stages the nymphs may feed on the vines, causing a flow of sap from the punctures. As the vine grows it often becomes stunted on the side attacked, and by the continuance of its growth on the opposite side a sharp bend is formed. A plant is often weakened so that its cling- ing power is lost; the main stems tend to hang down, and often all the vines 184 I. M. Hawley n of \\\v lull slip down Jiroiuid the base of the polo (fig. 32). The older nymphs may feed also on the hiiis and the hop hcatls, but scM'iotis injury to thcst' parts could not be detected by the \vi itci-. Pole yards are attacked worse than arc string yards, and in string j-ards the \incs on the poles show more injiuy than do those on the strings. The work of the hop rcdbug is similar to that described by Theobald (1895) for a related species, Calocon's fidvonmculatus I)('g.. which has caused some injury to the hop in I'^ngland. DKSCRIPTIOX OF THE SPECIES The egg rhe egg of the hop redbug (fig. 33) is 1.6 Miillimctcrs long, 0.4 millimeter wide, and 0.2 millimeter thick. The color is dirty white. The egg is curved, with two promi- nent, pure white, incurving hooks on the micropyle end; one hook is pointed and the other is blunt at the tip. The sur- face of the egg is smooth and glossy. Fig. 32. a hop hii.i. so weakened bv the work of the hoi' rkd- bl'g. that the vines h.we slipped down the pole The nymph The five nymphal stages may be described as follows: First stage (fig. .'VI). — Ixingth 1.3 mm. (average of ten specimens); (reneral rolor liph' tomato red; a median variable light line extending from near the cephalic end of the head to near the posterior end of the Hecond abdominnl wnmeiit, faint in .some sfx'cimeiiH but in others dis- tinctly whit*'. Ixjrdered laterally oti the thorax by day-colored patches. .VnUmnae »vith the basal segment .slightly dubln-d. t^nnato red, and Hparsely cloth'-d «ith hairs; the second s«'gment sparsely hairy, white (2 5) and n^d (3 .">); the thinl si'gment spanwly hairy, wliite (!) and n-d (''; the fourth s<'Kment densely hairy, clay color with a .small white spot at base. Coxa of leg white, trochanter white, femur red, tibia with thn'e red jind thre<' white bands of varying breadth, tarsus white with dark tip, claw dark. F^ach abdominal segment bearing a row of dark setae; head and thorax with irregularly arranged .setae. Beak white with dark tip. Venter clay color. In a few cu.ses the median line wanting, as well as all white bands, Fig. 33. egg of hop redbug. X 24 Insects Injurious to the Hop in New York 185 the insect being red with the exception of the fourth antennal segment. (The description is for the most typical specimens.) Second stage (fig. 35). — Length 1.9 mm.; general color slightly darker; median line broader and more distinct; clay-colored border patches indistinct; bands on antennae and legs more prominent; white spots beginning to appear around setae on abdominal segments; basal Fig. 34. FIRST-STAGE NYMPH OF HOP RED- BUG. X ABOUT 20 Fig. 35. second-stage nymph of hop redbug. x nearly 15 antennal segment a darker red and much more hairy; terminal segments lighter except at tip. Aberrant specimens showing no median line, no white bands, faint bands on antennae and legs, or faint bands on antennae and none on legs. Third stage (fig. 36). — Length 2.5 mm.; general color same as that of preceding stage; red bands on antennae and legs much darker than body; wing pads beginning to show; Fig. 3G. third-stage nymph of hop REDBUG. X nearly U Fig. 37. fourth-stage n\'mph of hop REDBUG. X 9 white spots around setae more distinct. Setae longer and coarser. Some aberrant specimens as in second stage. Fourth stage (fig. 37).— Length 3.1 mm.; general color as in third stage; wuig pads brown- ish and reaching nearly to third abdominal segment; antennal segments thicker in red areas than in white; dusky spot showing around gland between third and fourth abdominal segments. Aberrant specimens as in preceding stages. ISt) 1. M. Hawlky 4 Fifth stagr (fi^. •J*^'. — IxMiRth 4 nun.; a wide variation in Cdlor, some specimens being linht red with aIino«t transparent winn pads, others dark red with wiiiR pads anding on nymphs of their own kinil. Nymphs have been found also feeding on the pupae of Nemalommpa linibuta Haworth (Geometridae), the larvae of Lycia cognnttiria (luen^'e (Geometridae), the larvae of Hypena hitmuli Harris (Noctuidae), and the pupae of Malacosoma americana Fal). (Lasio- campidat;). I Insects Injurious to the Hop in New York 189 CONTROL In 1915 it was decided to test a tobacco extract spray as a control measure against the hop redbiig. To this end nicotine sulfate, 1 pint to 100 gallons of water with 6 pounds of soap added, was applied on July 17. The material apparently killed the bugs at once. However, as 56 live nymphs were found on six sprayed hills, another spray was applied on July 19. This time Black-leaf -40, 1 pint to 100 gallons of water with 4 pounds of soap, was used. On July 20 six hills had 16 dead and 11 Uve nymphs present, but on July 21 no dead nymphs could be found. This is due to the fact that after the spray material dries, the nymphs drop off. The following experiment shows that whenever nymphs are reached they are killed. On July 19, when the field experiments in spraying were made, 40 sprayed specimens were placed in a laboratory cage, none of which revived. Thirty specimens sprayed with an atomizer were all killed by the same solution as was used in the field. Since nicotine sulfate, f pint to 100 gallons of water with 4 pounds of soap, will control the hop aphis (Phorodon humuli Schrank), the writer tried it to ascertain its effect on the hop redbug. Leaves with redbugs from vines sprayed in the field were taken into the laboratory; of 15 specimens, 6 were alive on the following day. Of 30 redbugs sprayed in the laboratory, 7 were alive twenty-four hours later. Bugs that became attached to the glass dish by means of the solution were invariably killed; those not attached often recovered. To prevent sticking, filter paper was placed in the bottom of the dish and the bugs were sprayed with an atomizer. Of 10 treated in this way, 6 were killed. It is evident that this strength is insufficient for the control of the redbug. To be successful, spraying should be done about the third week in June, before the vines have produced lai'ge arms. Most of the nymphs will have hatched and can be reached easily at this time. Later, when the vines have become dense and many have slipped down the poles, it is impossible to reach all the bugs hidden among the mass of leaves. Poles as well as vines should be drenched, since many nymphs take refuge in the cracks and under projecting bark. Because of the agility of the bugs, it is wise to spray a hill from opposite sides at the same time when possible. Winged forms fly before they can be reached by a spray. 100 I. M. Hawley THK HOP SNOUT-MOTH (Hypena humuli Harris) The larva of the hop snout-moth was recorded in 1841 as a leaf-eating pest. It is widely distributed, occurring in most parts of the United States and southern Canada. So far as known it feeds only on the hop, and thus its distribution tends to follow that of its host (Howard, 1897). It li:i.>< not been reported as a .serious pest on the Pacific coast. As a rule the injury that it causes is not great, but at intervals the larvae of the second brood occiu- in such large numbers as to strip the hop vines of their leaves. The writer has found occasional hills in (his condition but there has not been a general out- break of the insect in the past five years. i DESCRIPTION The egg Fig. 42. egg of The egg of Hjjpenn hunnili (fig. 42) is from 0.5 Hop^sNouT-MOTH. q^ luiWimoiiiv iu' diameter. In color it is pale yellow- white. The form is circular, slightly dome-shaped, flattened below. The surface Is vertically riilged and grooved. There are apparently eight primary ribs converging at the micropyle end, with two or three secondary ribs between each pair of primaries. The micro- pyle is slightly flattened and irregularly reticulated. The larva The larva (fig. 43) is from 20 to 25 Fig- 43. full-grown larva of .... • 1 1 rr adult (figs. 49 and oO) is described as follows by Dr. ^^■. T. M. Forl^es : Male straw yellow, fe- male cream white. Fore wing with three even brown lines; t.a. line ex- curved, especially over cell; inner t.p. line ex- curved beyond cell and slightly at fold, outer t.p. incurved at pt)ints where inner is excurved and in some ca.ses meeting it at those points; outer third of wing brown on inner half in male and everywhere but at apex in female; fringes brown. Hind wing similar, without t.a. line and with brown area more extensive; veins more or less bnjwn, especially in female. Spread 1!) 2.j mm. I.MALE OK FILAMENTKD LOOI'ER. LIKE HISTORY AND HAHITS The C(J(J The eggs of the filuMieiiled looper are attached by a secretion und(>r the edge of projecting bark, or tucked in cracks of tiie hop poles, and Insects Injurious to the Hop in New York 199 arc found singly, a fow in a place, or in irregular masses (figs. 51 and 52). The writer has found fifty or more eggs on a cedar hop pole by removing Fig. 51. eggs of filam e n ted looper under projecting edge of bark of a cedar hop POLE. X 8 Fig. 52. eggs of filamentkd looper on a sliver of a cedar hop pole. x 5 the bark and inspecting the crevices. Overwintering eggs are laid in August, and hatch from the middle of May until late in June of the fol- lowing year; the egg stage is therefore about ten months. Two females under observation laid eggs as indicated in table 14: TABLE 14. Data on Egg Laying by Two Moths, 1915 Specimen Date when female emerged Date when first eggs were laid Number of eggs found on August 28 Date pre- ceding which moths died 1 August 15 August 18 August 23 August 25 25 16 September 8 September '8 2 The larva The larva moves with a looping motion (fig. 53), and when disturbed it assumes an erect attitude and projects its filaments to the Umit. It 2(X) 1. M. Hawley ina>- also drop liv a thread and hang in mid-air; sixty suspended larvae have Ix^en counted on one liill after the pole had been shaken. The hirva feeds oftener on the margin of the leaf than in the central part. The veins of a leaf are often eaten thru in such a way that the leaf dies at thatl | point and a dead crumpled area on tlie margin remains. A larva, perhaps for protec- tion, often a-ssumes a posit ioni resembling this dead part of the leaf. Full-grown larvae have been found from June 25 until August 18. Six speci- mens were bred in petri dishes in the summer of 1915, as indicated in table 15. The pupa The change to the pupal stage takes place in the cracka of hoji jioles, in leaves curled and fastened with a few strands of silk, or when the larva is l''lO. 53. LARVA OK FILAMENTED LOOPER. X 2.J attached by silk flat against an uncurled leaf. Often the pupa is attached by a few strands of silk and hangs free from a leaf or a vine (fig. 54). In TABLE 15. Dates of Transformation and Length of Stages, 1915 Specimen Date when egjt wa« taken Date of hatchiuK Dates of molts Date when cocoon was spun Date when pupal stage began Date when adult stage began Number of days from m 1 June 28 June ft Julv 1ft July 20 July 7 July 5 July ft, 9. 13 July 2.1 Julv 1ft AllKU^^t It August 13 August 2 .August 3 August 7 July 29 August 28 August 27 .Vugust 15 August 15 40 2 May ft May ft May 12 May 21 May 21 53 3 Julv 21. 25, August 1 July 24.2<.», August 4 August 11 August 11 43 4 38 5 39 41 *«in> Ai •fiiiy «i • ■ .luifUDb o /lUMuo Average — Larval staffo, 28.K dayft; pupal staice, 13 5 day»\ egg to adult, 42.3 days Insects Injurious to the Hop in New York 201 many cases small pieces of dead leaves arc curled around the pupa. Pupae have been found from June 27 until August 28. The adult The brightly colored moths are common in August in the hopyards. They rest flat on the ground and on the lower leaves, with their wings half spread. The sexes are about equal in number. SEASONAL HISTORY The Ufe history of A'^e- matocampa limhata varies greatly, depending on the time of hatching of the eggs. A typical life history is as follows: The eggs, which are laid on hop poles in the latter part of August, hatch the last of the following June. The larvae become full- grown the last of July, and enter a pupal stage which covers two weeks. Adults appear the middle of August and begin to lay eggs in about one week. There is one generation a year. CONTROL The control measure sug- gested for the hop snout- moth should hold the filamented looper in check also. On July 17, 1915, several infested hills were dusted with powdered arsenate of lead and sulfur in a ratio of 1 to 10. When the hills were examined later some Uve larvae were found. Since rain followed soon after the application, how- ever, the test was not a fair one. Fig. 54. pupa of filamented looper. X 4 202 I. M. Hawley THE HOI' APHIS {Phorodoii humuli Schrank) The hop aphis, Phorodon hunnili (figs. 55 and 56), is a pest wherever hops are grown. Il lias Ik'cmi known in New York State since 1863 at least (Parker, 1913), and in some years has caused an almost total loss of the crop. As the insect has been extensively studied on the Pacific coast, the writer has limited his work on the species to observations on its seasonal history and habits in New York State, and to the application of some control measures under New York conditions. FlO. 55. WINGLESS VIVIPAROUS FEMALE OF HOP APHIS. ENLARGED SEASONAL HISTORY In the eastern United States the hop aphis has been found to winter only in the egg stage on plum. Clarke (1904) reports that in C'aliforni the aphides winter on hop roots. In order to obtain some eviden on this point for New York, the writer removed the dirt from three hills, placed vines cov- ered with the insects around the hop roots, and then cov- ered the hills. On examination the following spring, no signs of live aphides or of their eggs could In* found in these hills. Additional evidence is furnished by the fact that migratory aphiiles have always appeared on the hop before the wingless forms. Fig. .5fi. winged vivipakol's female of hop aphis, enlarged Insects Injurious to the Hop in New York 203 Altho Riley (Riley and Alwooci, 1889) reported the third generation as the one that produces winged forms in New York, it is probable that some winged forms are produced in the second generation. On May 21, 1913, full-grown lice and recent offspring were found on a plum tree near Sangerfield. On most of the leaves there was one full-grown louse, but on one leaf there were five. Some of the young of these forms had wing pads on the 4th of June. If those first found were of the first generation, the second generation pro- duces winged forms, the same as in the Pacific hop region. Some insects of the third generation also are winged. In fact, the writer has found winged forms being pro- duced on a plum tree under observation thru July and August, but, for unknown reasons, after the June migration there have been but few winged forms on the hop The height of the return mi- gration occurs during hop picking, about the first of September. On the hop the winged insects are found on the underside of the topmost leaves (fig. 57), there being from one to twenty or more to a leaf. The wingless descendants from these also five on the underside of the tender foliage. In August, when the lice are numerous, full-grown forms are occasionally found along the veins on the upper side of the leaves. When the young hops are formed, hce migrate to them in Fig. 57. WINGED VIVIPAROUS FEMALE OF HOP APHIS ON A LEAF. ENLARGED 204 1. M. IIawlkv large iiuinbers. The writer hiis noted younp; lice in hop cones when the leaves were comparatively free from the insects. Two sjX'cies of ants have been found associated with the hop aphis — a large species, Formim fusca var. suhsericai Say; and a small form, Pre- nolepia imparis Say.* NATURE OF THE INJURY The injuiy to the hop caused by Phorodon humuli is of two kinds: (1) the woakening of the \ ines and the stunting of the hop cones due to the constant r(Muoval of sap; and (2) the coating of the hops with honey- dew in which a fungus, Clado- sporium, grows. The feeding of the aphides on the leaves and the vines so weakens the plant that it is common to find hills in which the vines have not climbed above the string. The vines are dwarfed and the hop cones are small, with sickly, scraggly bracts (fig. 58). This condition is found when the aphides attack the hill in numbers early in the sinison. When the lice become nu- merous (fig. 59) the leaves glisten with the honeydew which they excrete. The entire surface of the vines and the leaves is coated with this excretion. When the lice enter the cones the bracts also are covered., The greatest damage is caused when the lice enter the full-grown ho) just before picking time. They coat the hojis with the honeydew, causing * Both npeciea determined by W. M. Whoclcr. Fig. 58. above, hops injured by the hop aphis; below, healthy hops, about one- half NATURAL SIZE 1 Insects Injurious to the Hop in New York 205 the bracts to lose their crispness and making them stick together when pressed between the fingers. The fungus Cladosporium grows in the honeydew and gives the hop a soot-covered appearance. This greatly injures the quahty and makes the hops unsalable. Among hop growers it is spoken of as black mold. Many yards in New York were injured in this manner in 1915 and the hops were not picked, while hops from some yards that were picked are Fig. 59. wingless hop aphides on a hop lem-. X about 5 still unsold. The lice are much more numci'ous in warm, moist seasons. In 1915 the rainfall records taken showed 5.49 inches during June, 7.64 inches during July, and 9.28 inches during August. This is much above the normal for these months. A wet spring followed by a long, dry period is not so serious as continued rains near harvesting time. Under the latter condition great loss may result in a few weeks, owing to the increase of the lice, the great production of honeydew, and the growth of the black mold. 200 1. M. IIawley NATURAL KNKMIES Predatory enemies 'j^B The following predatory insects have been collected feeding on the hop aphis: Coleoptera Family Adalia hipunctata Linn Coccinellidae Ilippodnmid courer(jens Guer. (lady beetle, figs. 60 and 61) Coccinellidae Cocci ncUa (rifasciata Linn Coccinellidae Coccinella 9-noiata Herbst Coccinellidae CoccineUn mnguinea Linn Coccinellidae Hippodaniia parenthesis Say Coccinellidae Anatis 15-punciata Oliv Coccinellidae Neuroptera Chrysopa oculata Say ^ (aphis lion, fig. 62) Chrysojiiflae Hctncrobius stiyiuatcrus Fitch ^ Henicrobiidae Dipt era Syrjdnis ainericamis Wiedemann^ Syrphidac AUoijrapta obliqwi Say * Syrphidac Fig. 60. LARVA OF LADY BEETLE ON A HOP LEA!-. X ABOUT 2 Parasites One parasite has been bred from the hop aphis — Praon sp.," of the order Hymcnoptera, family Braconidae. SPKAYIXG AND CONTROL EXPERIMENTS The spiaying operations for control of the hop aphis undertaken by writer. These are here growers during 1915 were observed by the described, and some original data on spraying and dusting are given. ■ Delpmiinml by R. C. Smith. • Detonnined by O. A. JohniinHcii. • Determined by A. B. Gahan, thru the kindness of Dr. L. O. Howiinl. Insects Injurious to the Hop in New York 207 Fig. (1. KGGs OF lady beetle on a hop leaf, enlarged The first spraying of the season was done on the Louie farm, at Schuyler Lake. The material used was nicotine sulfate (Black-leaf-4G) in a solu- tion of 1 gallon to 2000 gallons of water, with whale- oil soap added, 4 pounds to 100 gallons. A Friend pony outfit (fig. 63), with three leads of hose, was used. Two men, with 6-foot poles, 30°-angle nozzles, and 15 feet of hose, covered two rows each, and the third man, going behind, covered the high arms and the tops of the poles. Calyx nozzles of the Vcrmorel type, throwing more than the usual quantity of material, were used. The tank had a capacity of 150 gallons, and with a H-horse- power engine a pressure of over 150 pounds was maintained. The cost for spraying two acres a day was as follows: four men, S8; one horse, SI; 800 gallons of spray material, $6; total, S15 for two acres, or $7.50 an acre. Hops of a fine quality were produced. Under the direction of F. M, Blodgett, about ten hopyards were sprayed. In one yard, near Waterville, a pressure of 165 pounds was maintained and 600 or more gallons of spray material were used to the acre. In all cases nicotine sulfate (1-2000) and whale-oil soap (4-100) were used. During these operations the writer picked sprayed leaves and made counts Fig. 62. aphis lion, the larva of which is predacious on the hop aphis, enlarged (Photograph by H. H. Knight) Fig. 63. sprayer lsed on the lolie farm — a common type to test the effectiveness of th(^ sjiiaA'. The results of these counts are] Riven in table 10: TABLE 16. Results of Spraying Experiments with Black-Leaf-40, 1915 Yard Date of spraying Date of count N umber of lice found Number dead Per cent of control Number of leaves used Kcniarks W Hatch July 27 July 28 830 821 98.9 20 All lice counted Hatch August 18 August 19 108 100 94.3 12 Only full-grown lice counted • Hatch August 19 August 20 356 352 98.9 12 Only full-grown licafl counted Hewett August 31 September 2 721 698 96.8 20 All lice counted Sulfur is used by throwers to control the Jiop mildew, and so the writer tried eoinbinatioiis of sulfur with nicotine sulfate, usiiifi different stickei-s, to see its effect on the lice, payiiif^ no attention to the control of the hop mildew. The results are given in tal)le 17: Insects Injurious to the Hop in New York 209 TABLE 17. Results of Experiments to Test Black-Leaf-40 with Sulfur in Various Forms, 1915 (Only full-grown lice were counted. B.L.40== BIack-leaf-40, 1-2000; L.S = lime-sulfur 1-40; Sp.= soap, 4-100; S = sulfur) Material used Date of spraying Date of first count Number of leaves used Number of lice found Number alive Per cent of control Date of second count Number of leaves used Number of lice alive B. L. 40, Sp., S July 16 July 17 12 828 11 98.7 July 24 12 4 B. L. 40, L. S. July 16 July 17 12 360 16 95.5 July 24 12 30 B. L. 40, L. S., Sp. July 16 July 17 12 574 3 99.5 July 24 12 4 B. L. 40, Sp. July 17 July 20 12 77 2 97.4 July 24 12 1 Lime-sulfur leaves a smeary coating and should not be used just before the hops are to be picked. None of the sprays tested injured the hops. There has been much demand among growers for a louse-killing material that can be applied in a dust form with the sulfur used for the hop mildew. With this in view an experiment was carried on in two parts. In one (W, table 18) the hills were sprayed with water and the material was dusted on; in the other (D) the material was apphed to the dry leav&s. Both the upper and the under sides of the leaves were well covered in each case. The results of these experiments are given in table 18: TABLE 18. Results of Dusting Experiments, 1915 (Ten leaves of each kind were examined, and only adult lice were counted) Material used Date of application Date of count Number of lice found Number dead. Number alive Per cent of control Tobacco dust (W) (D) August 6 August 6 August 10 August 10 249 125 12 4 237 121 4.8 3.2 Tobacco dust and sulfur, 1-1 (W) (D) August 6 August 6 August 10 August 10 243 86 6 237 86 2.5 0.0 Tobacco dust and flour, 1-1 (W) (D) August 6 August 6 August 10 August 10 138 116 57 5 81 111 41.3 4.3 Tobacco dust and soap, 3-1 (W) (D) August 6 August 6 August 10 August 10 128 78 80 7 48 71 62.5 9.0 Tobacco dust, sulfur, and soap, 2-3-l(W) (D) August 6 August 6 August 10 August 10 126 49 113 3 13 46 89.7 6.1 210 I- I^I Hawley It is evident that dusting was not effective. The tobacco dust, which was used as the killing; a^;eIlt, was useless even when the leaves were wet. A few aj)hides were stuck to the leaves by the flour when wet. The pow- dered soap, when wet, was efficient, but inasmuch as this soap costs 22 cents a pound it cannot be considered practicable. Only a driving rain of long duration could wet the underside of the leaves, and with such a rain there would be a tendency for the lice to be washed off and a spray applied would be of little use. If the lice on the plum are killed, the infestation will be cut down. This cannot be considered as a sure control, because scrubby plum trees along fence rows are prolific breeding centers. The writer found many winged lice in one corner of a hopyard. In searching for the source he found a small jilum tree, less than three feet high and almost concealed by grass, completely covered with the pests. Lice are apparently carried long distances by the wind. Winged forms have been found in large numbers in yards where the owner declared there weic no plum trees within half a mile. A thoro search by the writer did not (Usclo.se the source of the infestation. It is po.ssible that some other host may exist, but none has been found, even tho many kinds of trees and bushes have been examined foi- lice of this species. Recommendation The following practice is recommended for control of the hop aphis: Spray the last week of June or the first week of July with nicotine sulfate (1-2000, or ^ pint t ) 100 gallons) and soap (4-100). Use a one- horse sprayer with a l')()-gallon tank and three leads of hose. Use two G- foot poles with 30°-angle nozzles and 15 feet of hose, and one longer pol(> without the angle and with 80 feet of hose. Let each of the men with the short poles cover th;' lower vines and arms of two rows, and let the man behind, with the long pole, cover thoroly the iiigher vines and arms (hg. 04). A Vermorel-type nozzle throwing a coaise spray is elH- cient, but a nozzle pror on hops in the SacrMiin'iito N'allcy «jf Cali- fornia. U. S. Bur. lOiit. Bill. 117: 1 11. P.H.il). (Hop merchants) HowAun, L. (). Hop merchants. In Some in.sects affecting the hop plant, r. S. Div. Hut. Bill. 7:47-51. 1S97. (Ix^if hoppers) F011BE.S, S. A. Emixjasca flavescens Fal)r. In The economic entomology of the sugar Ix'ct. Illinois Agr. Exp. Sla. Bui. 00:427. 19(X). (Flea Ixictlcs) l'\i{Ki:i{. William B. The life history and control of the hop flea-beetle. In Soine in.sects injurious to truck crops. U. S. Bur. Ent. Bui. 82:33-58. 1909. .Mfinoir 13, Chlorophfll I nhrritancc in Maize, the second precedinK number iu this scries of publications, naanuu!(!(i on August 31, 10 is.