7 I o Circular No. 87. L. O. HOWAHI) I oited States Department •»!' Auriailiure, BUREAU Ol IMOLOGY, Bntoaiknfrikt uiu! Cl.icf of Buredli ^ — W— I I I.K. THE < oi.oitvno i'(»i no itci i 1.1 i / . ptinot a -■/ det Bj 1 II i "ii : i n mu \ BntomologUt in Cha rp< rinu n I There are feu more familiar insects to the farmer and others who lead a rural life than is the Colorado potato beetle, or " potato bug," as ii i- commonly known; and yet scarcely more than fortj years ■ the potato crop of the United States had no very important insecl enemy. Not man; years later this insecl had, by it- depredations on potato, • of our most valuable food staples, caused as great concern have the San Jose scale and cotton boll weevil in the past decade, and was also the subject of much study and experiment. Although common an insect, many are not thor- o ii g Ii 1 y acquainted with its life history and habits and with ih«' best methods of combating it. and this applies particularly t<> persons farming in districts only recently invaded by the foe. The insect is continually extending it- range southward, ami many complaint- are received from localities where the pest has not become thoroughly acclimated. The potato beetle, notwithstanding all that has been don- i. suppress it. is -till a pest of great importance. It i- interesting as the first known example of an insect native to our Western States being introduced eastward and thence practically all ovei mtry and Canada (except on the Pacific ci here potato.- aiv grown. In its early day- a- a migrant there seemed to have i n no check to its eastward spread other than natural barriers, such as rivers and lake* and the Atlantic Ocean, hut iii the course of years numbers of nat- ural en. 'mi.- birds, mammals, and predaton and-parasitic insects kn..\\!i as i ■ 87 07 Kl.. 1 ;; TO£\ have learned to attack it. and. in the case of the insects, they have multiplied until now they are recognized as important factors in the control of the beetle. The species is interesting also as having led to the first use of an arsenical insecticide. Paris green, on edible plants. Fortunately, with a knowledge of the habits of this insect, > Fig. 2. — Section of potato plant showing Colorado potato beetle al work: a. Rootle; 6,6, egg masses ; cy\ half-grown larva" : ti.il. mature larvae. Somewhat enlarged (original). the use of arsenicals, and the friendly assistance of natural enemies, the grower may hold it in practical subjection. DESCRIPTIVE. The Colorado potato beetle is so well known that a description seems hardly necessary for most persons, but that there may be no [Clr. s7] in "old-faali trior's [11 US I r of confusing it with am related 3pecies or with benel ladybirds, n fvw words of description maj be given. Thebeeth (fig. 1, a; fig. 2, i) i of robusl form, about three-eighths of mii inch in length or a little more, and two thirds as wide as long. Ii i- ochreous vellov* in color, and the wing-covers are ornamented with ifii longitudinal black lines. The Read is marked with :i triangular black spot, and the thorax is dotted with ten or more irregular spots and other markings. The lower surface is also more or If— marked with black, particularly the tarsi iintl knees. /'/,- larva (fig. !. b; fig. 2, . . d,d) are quite as well known as (lit- beetles and are very commonh called "slugs." They are dark Venetian red when firsl hatched, and as they approach maturity become paler. They are -limy, disgusting looking creatures, sofl in texture, and from their peculiar coloration and appearance would no! be readily handled by anyone withoul glovi The pupa is red like the larva and look- as shown in ' . figure 1 . The eggs i fig. •_'. I>J>) are orange colored and are deposited in masses. As this beetle is sometimes confused with one <>r another of the "old-fashioned potato bugs" (blister beetles), a species of the latter is illustrated here for comparison i fig. 3)-. ORIGIN AND DISTRIBUTION. It has always been believed and, the writer maintains, with rea- son, until the contrary can be proved beyond doubt tli.n the Colo- rack) potato beetle, having become dispersed from ( Colorado ;i- a starl ing point, originated as a species in thai region. Dr. W. L Tower, however, in a publication issued in L906," has assumed thai this insect had the same origin as its principal wild food plant. Solatium n />////, which he states is essentially tropical, and thai the inseel has followed the distribution of the plant from Mexico into Texas, New co, and part- of Arizona. He also gives reasons for the belief that Leptinotarsa decemlineata has developed from /.. " intermedia Tower" after changing it- habitat, the latter occurring in both ■o and Texas, and the former not being found in Mexico at all. rding to his experience. tUSTOBI 01 I III' I \-i '< I '- 8PR] \l>. The eastward dispersal of this potato beetle from what is generally considered in original home in the West is of peculiar interest The \ Investigation ot Evolution in Clirysomelld beetles of the Genus Leptl- Dotaraa, Carnegie institution. Washington, i>. C pp. 23 el Beq. [fir. 87] beetle appears to have been first associated with injury to potato in 1865. Forty-five years prior to that time it had been recognized as feeding on the sand bur, or beaked nightshade (Solanum rostrat Dunal.), a related solanaceous plant peculiar to the Rocky Mountain region. The beetle was described in 1824 by Thomas Say. With the advance of civilization westward and the Cultivation of potato in the vicinity of its native home, the insect acquired the habit of feed- ing upon tin- more succulent plant, and about 1859 it had spread to the east as far as Nebraska. Two years afterwards it reached Kansas, and later Iowa, which it traversed in three or four year-: so that by 1864 or lMu it had crossed the Mississippi River and invaded the western borders of Illinois. In its spread through Illinois it was de- scribed by Walsh as marching through that Stale " in many separate columns, just as Sherman inarched to the sea ; the southern columns of the grand army lagged far behind the northern columns." By 18G9 it had found its way to Ohio, appearing almost simultaneously in the northern and western portions. During all this time, beginning with the year 1861, the insect had done considerable injury, and by 1870 it had become exceedingly destructive in the North and Middle West, and was continuing its eastward inarch at an increasing rate. It had now reached the Province of Ontario. By 1872 its depreda- tions in the West had noticeably abated, owing to the effectiveness of natural enemies and to the increasing use of Paris green.. _ Its prog- ress eastward, however, continued, the northern columns becoming established in Pennsylvania and New York, the southern ones reach- ing Kentucky. The next year it made its first appearance in the Dis- trict of Columbia and West Virginia, and in 187-1 it had reached the Atlantic seaboard and was reported from Connecticut to Mary- land and Virginia. By the centennial year (1870) the Colorado potato beetle had spread over an area composing more than a third of the United States, so that it occupied at that time more or less completely the States of Colorado. Nebraska. Kansas. Minnesota. Iowa. Missouri. Wisconsin. Illinois. Michigan. Indiana. Ohio. Kentucky, the New Eng- land States. New York. New Jersey. Pennsylvania. Delaware. Mary- land. Virginia, and West Virginia, and the District of Columbia, in none of which was it native except in the State first mentioned. At that time it occupied also portions of Wyoming and southern Dakota — where it was perhaps also native — and a considerable part of the more arable portions of eastern Canada. The farther spread of this insect, particularly southward, is of less interest and has, in many instances ar least, been dependent more or less on the increased cultivation of the potato. The following addi- tional statements as to the insect's progress are taken from data [Clr. 87] collated mainly from the Records of this office, some of which are published more in detail l>\ Tower.* In 1-77 the beetle ap peared in North Carolina and Tennessee, The following year il was reported to be completely overrunning portions of Canada, being found eastward in New Brunswick. In l s ~'.> it \\a- recorded from Manitoba. In 1880 its presence was observed in Texas. Since about l sv '-' complaints of injuries have been made in Nova Scotia; in L885, at Savannah, Ga.; in L888, at Jackson, Miss.; and in Smith Count;. Tex. In 1892 the species had become abundant in Alahama. and was noticed also in South Carolina. The following year its occurrence was observed by H. G, Hubbard at Fort A--iuni boine, Mont., which is evidently the most northern limit of it- original babitat, as it was not found there on potato. In succeeding Mar- other localities were added in soi f the State- which have Ween mentioned, but little of positive interest adding to it- known dis tribution has been learned gince 1893. It should be stated, however, that the species ha-- heen found at Jacksonville, Ida.: in southern Louisiana, and at San Antonio. Tex., hut these extreme localities do not indicate permanent local ion. PRESENT DI8TRIB1 HON. The natural spread of the potato beetle southward increases from time to time, a- evidenced by reports that reach this Department yearly. Undoubtedly, however, the extreme northern and southern territories which it invades do not become permanent habitats for the insect, the species dying out. mainly because of extremes of cold in the one case and of heat in the other, to he reintroduced in later years when condition- favor it- multiplication and spread from other regions. It ha- been calculated that it increased it- range from it- original home to the Atlantic coa.-t at an average annual rate of about ^ s mile-. It- spread eastward was accomplished largely by flight, as the writer had occasion to observe when a resident of Cleveland in the early day- of it- invasion of northern Ohio. Great numbers of beetles were seen on bright day- in spring and early summer, with outspread win":-, being carried directly eastward by the wind-. It ha- al-o heen disseminated largely by railroads and by lake vessels, and ha- thu- been able, through the direct agency of man. to cross the more barren plain- bordering it- native confines and the harriers made by large bodies of water. So it will he seen that the wind- and waters and eastbound train- have all aided in it- dis- semination eastward. Riley, from whose work- the present account of the early distribution of the insect ha- been taken, observed the ' I.. <■.. pp. ::•• [Clr. -Ti beetles on Lake Erie in 1870 on various floating objects, and the writer in subsequent years saw the border- of the same lake lined for a foot and more with the hordes of these hectics thai had been blown into the water and had then been cast up on the shore. Beginning with about 1880, it will be noticed, the Colorado hoetle appeared in many potato fields of the Gulf region and elsewhere in the South. In certain localities, particularly in Alabama (where it was quite injurious for a time) and South Carolina. thi> insect seems to have disappeared, and little danger of continuous injury need be anticipated there, as invasions of extreme Lower Austral territory have thus far been merely sporadic appearances. Still, whenever atmospheric conditions favor, the species docs temporary damage in such places, only to he killed down again for a number of years, after which the beetles reappear, sometimes invading new localities. It thus will be seen that it would be a somewhat difficult task to outline definitely the permanent distribution of this insect. It is nearly limited, however, as regards severe injuries to the country east of the Rocky Mountains, extending from the Lower Austral to the Transition life zone, and is likely any year to be injurious in extreme portions of this area. Injuries by this species in the potato section of Aroostook County in northern Maine are well known, and the region there, as well as arc portions of Colorado, is credited to the Boreal life zone." From recent reports it is fair to say that the species is scarcely a pest at the pres- ent day in its original habitat nor in neighboring States, since (luring the last five years no reports of extensive injuries have been received from Colorado, Kansas.'' Nebraska, or South Dakota. It appears to be firmly established, however, in the State- just west of the Mis-;>- sippi River and from there eastward to Nova Scotia and New Bruns- wick and southward to the northern portions of the Gulf States. DISTRIBUTION LIMITED BY EXTREMES OF TEMPERATURE. Some of the conditions which prevent the too rapid multiplication and permanent establishment of the potato beetle are known. At St. Louis, Mo., is was noticed by Riley that during very hot. dry weather, as in 18G8, this insect failed to go through its transformations in the ground, the latter becoming so hot and baked that the pupae dried out, and the beetle, if it succeeded in throwing off the pupal skin, failed to make its way to the surface. It was also noticed that the larvae frequently perished under the broiling sun when the ther- o These regions may in time lie recognized as lying within the Transition zone. & Report from Mr. Warren Knaus, dated May 18, 1907, states that this insect lias appeared in great numbers in Kansas and threatens serious damage to young crops. [CIr. stj mometer ranged near 100 I'. During the intense heal thai prevailed during the summer of 1890 the writer noticed the same condition in and near the District of Columbia, the eggs and larvae being literally dried up on the potato plants, and the species temporarily disap pearing altogether. Northward the Colorado potato beetle is practically limited to the Transition zone, although it occasionally invades the B ■one, as, for example, in Colorado, when ii has been found B,000 or more feet above sea level. Severe winter weather alone probably has little effed upon the insect, since it hibernal i rule, exclu- sively in the beetle state and deep in the ground. It is, moreover, one of our most hardy species, ranking with the hard shelled snout- beetles in it- resistance t<> cold and frost. Cold snaps, however, over take the insect before it has sought < " h proper hibernating quarters, iiikI when these occur it is doubtless killed ofl in great numbers. As was predicted years ago, the Rocky Mountains have proved an impassable barrier for tin- species, and the insect has not been able to reach the Pacific coast or neighboring States weal of such barrier. INJURIES. LIFE HISTORY, AND HABITS. \ All RE OF IN.il RY. A few remarks in regard to the nature of the injury inflicted by this insect are pertinent. Beetles and larva; are destructive in nearly equal proportions. In times of it- earlj occurrence east of ii- origi- nal limit this insect not only caused the entire 1"-- of crops, but some- times destroyed the potato yield of whole counties and of large por- tion- of some State-. Indeed, at one time it materially affected the market price of potatoes, not alone by reason of it- direci depreda- tion-. l>nt in discouraging farmers from the cultivation of the potato on an extensive scale. Thus in L873 the price per bushel at whole- sale in the >t. Louis market reached the high figure of $2. At the present time, fortunately, every progressive grower recognizes the fad that the control of tin- species i- a part of the necessary routine connected with the culture of tin- tuber. It was early recognized that the depredation- of this insect ma- terially affected the quality of the tuber through the defoliation to which the vines were subjected, and it was at one time difficult to obtain potatoe- that were not watery when cooked. This raises the question whether the very marked decrease in quality of potatoes in genera] at the present day i- not due directly to the many years in which the tubers have been deprived of due nourishment by more or less defoliation of the plant it-elf: for. despite all the remedial measures that are usually practiced, such a- the libera] use of arsen- icals and "bugging" or jarring, a certain amount of injury nearly [Cli 8 always takes place, which can not fail to affect the tubers when it has occurred practically without interniittence for periods of from twenty to forty years. food PLANTS. A wild species of Solatium (rostratum, and perhaps also coraw^m) is an original food plant of this potato beetle, and the latter is proba- bly incapable of developing for any number of generations on plants other than those of the potato or nightshade family (Solanaceae). The genus Solatium is preferred, and the potato, because of its greater succulence and less acrid taste, is now chosen in preference to plants that grow wild. Still, the insect is nearly always found where it- wild food plants grow, particularly where poisons or repellents are used in near-by gardens. It feeds on practically all solanaceous plants, including eggplant, tomato, tobacco, ground cherry (Physa- lis), thorn apple, and Jamestown weed (Datura), henbane (Hyoscya- nitis), belladonna, petunia, and pepper. The last is not often at- tacked, nor are the other plants of different genera from the potato, under ordinary circumstances. Occasionally, when none of these are to be had, the insect will feed on certain weeds and garden plants, among which are cabbage, thistle, and mullein. It was long ago ascertained that the tender-leaved varieties of potato are most affected, while other kinds, with less tender foliage, such as Peach Blow and Early Rose, are comparatively immune, more particularly when growing in the same field with the preferred variety. Even eggplant seems to be preferred to certain varieties of potato, and is consequently damaged at times, and tomatoes are sub- ject to injury when the foliage of potato is not available. GENERATIONS. The normal number of generations of the Colorado potato beetle is evidently two. In fact Tower" ha> observed that this number in both temperate and tropical latitudes is a remarkably constant generic character. In the course of his investigations he has not been able to get the present species to breed more than tw-ice in a season without a period of hibernation or aestivation. Person- ally the writer has never observed more than two generations in the District of Columbia. Years ago, however, Piley made the positive statement that this species is three-brooded in Missouri.'' and Lugger has made the same statement in regard to its development in Minnesota. Dr. J. B. Smith claims two generations in New Jersey, « Loc. 'it., p. 243. '< First Annual Report state Entomologist Missouri. is<;<), p. 107. [Cir. 87] with Bometimes a third partial generation which hibernates in the pupal condition. Considering the fad thai this specie* has invaded new territory and does not live an entirely natural life, having* an abundance of food and not being restricted to its single normal plant. it certainly 9eems possible thai a third generation mighl be produced in an exceptionally warm and humid season, and especially in the in.' i southern localities where 11 has becoi stablished. Li i I in- P0K1 . Hibernation takes place in the beetle stage, under the ground, some- times ic a considerable depth, the beetles having been unearthed from a few inches to several feel beneath the surface. A- a rule, however, they not penetrate deeper than s or l" inches. Exceptionally the beetles \\ inter <>\ er in rubbish. The beetles make their initial appearance quite early in spring, at times issuing from their hibernating quarters soon after the first thaw. Ai this season they fly readily during the more heated por- tions of the warmer days, ami make aerial journeys of considerable extent. " In flight, the striped elytra air raised ami held motionless from ilu' thorax, while the gauzj wings, unfolded ami vibrating, strike pleasantly mi the eye a- the sun intensifies their rosy hues." These flights frequently take place before there an' any potato plants for the insect to l'sr-. A. A. Giraalt ami A. II. Etosenfeld at Myrtle, Ga., in May ami .June. 1!Mm;. [Or. 87] 10 deposition. A single female is said to be capable of producing from five hundred to a thousand eggs. Five hundred and twenty-five were observed by Giraull and Rosenfeld in the ease of one female, Laid in masses of from 9 to 53, from May 21 to June 5. The entire life cycle from egg to adult may be passed in about four weeks. The beetles <>f the last generation issue early in autumn, feed for another three or four weeks, and then enter the earth for hiberna- tion. NATURAL ENEMIES. Tt has already been stated that atmospheric condition-, with the exception of extreme heat in its more southerly range, are not espe- cially important factors in the repression of **"k ~ /iftr v /-** this species: hence its fluctuation in num- Xjk^Sfl&L*/ tier-, which is noticeable at least locally every season, must be accounted for by the activity of its insect enemies, the numbers of which are legion. Se\ era! groups of these enemies are known, each of which contains, a- a rule, many species. Among the most i m p o r t a n t are ladybirds." many common species of w h ich, in hot h their larval and adult stages, prey upon the potato beetle, destroying great numbers of its eggs and young larvae. One of the commonest of these ladybirds is illustrated for compari- son with the Colorado beetle by figure 4. Several ground-beetles.'' also of predaceous habits, attack and devour the larva? of this potato beetle, and of these the so-called great Lebia (Lebia grandis Hentz. fig. 5) is particularly attached to this species, following it wherever it goes and doing perhaps more effective service than any single natural enemy' of which we have knowledge. Sev- eral soldier-bugs also attack it. one of which, the spined soldier- ° The ladybird enemies of this species are: Goccinella 9-notata Hbst, 0. son- guinea r... Megilla maculata DeG., Hippodamia convergent Guer., //. tS-punc- tata I... //. glacialis Fab.. Anatis 15-punctata 01. (ocellata), and Chilocorus bivulnerus Muls. &Carabid enemies include the great Lebia (Lebia grandis Hentz), the fiery ground beetle (Calosoma calidum Fab.). Pasimachus elongatus Lee., Harpalus caliginosus Fab., Lebia atriventris Say. and Brachynus kansanus Lee. Fig. 4. — A ladybird (Hippodamia convergent) which preys on the Colorado potato beetle. En- larged (author's illustration). Fig. 5. — Libia grandis, an impor- tant potato-beetle enemy. En- larged (Marx. del.K [Cir. 87] 11 \ m , r , i. illustrated at figur. 6. Other natural enemies are robber £ spiders, and a tachina fly. This last develops within the >body of he potato beetle larva and has I n observed so ahundanl ... potato Eelds that its buz^ng resembled tto noise made by Aeswara £* of bees. Wasps of pecie attack the larva*, and the rust red social wasp- has 1 n n carrying the. ;j^>J^ Not infrequently the 1 tie i f I parti; ,v. ., dull, v . Jlo is h rounde d mites. These are external parasites « and help: what >< J^udng their hosts, k species of daddy-long-legs is also a natural "Sta predator, insects include a tiger 1 tie (Tetracha virginica I (andtworove-beetl. apteatoSq undQuedt* ■■ i«G»t.). Most of the s, ies listed above have been r >rded Riley, bul manj have also been observed independently by others, and correspondenta ,,(' this Bureau fre- quently call atten- tion to the com- moner forma Thus far only in- ged foes of the po- tato beetle b a v e been discussed, but certain mammals, bird-, amphibians or batrachians, and reptile- are well- known e n e in ies. ( )ne of the ino-t im- portant of the birds is the rose-breasted grosbeak, whose servi as an enemy of this beetie have ^ 1* ' appreciated until comparatively recent times, rhe bobwhite oi qu • The soldier-bugs Include I- acuUvent, ! ''• """, enemies, as they are naturally herbivorous. t Proctacanthus milbertii Blacq. ephorocera (Lvdelto) doryphom Riley. ,,!.,,,,,,,,,,,,,,,;,,,,,,.,.,,/.. „,//„.. I.-,, bave the same habit , mosl abundanl of tbes. poda omericana Riley. tUobunum (Phalangiu ton Say. , Thlg ,,„,, is one of the most Importanl enemies ol an equal* deatri] species, the ehlncb bug. B7] ■,_T1>. Muehenl 12 also does excellent service and destroys many. Other birds which are known to eat the potato beetle, on the authority of the Biological Survey, are the following: Ruffed grouse, nighthawk, cuckoo, scarlet tanager, the wood, hermit, and olive-backed thrushes, and robin. The crow not only picks beetles from the vines, but digs them from the earth. The cardinal is a well-known potato-beetle destroyer, and even the English sparrow has been seen to eat them. Domestic fowls are of some assistance in destroying this pest, and of these the duck early took to this insect, which is distasteful to some other fowls. For some time after the spread of the Colorado beetle to new territory chickens did not attack it. presumably because it has, in common with many other leaf-beetles, a nauseous taste. For sev- eral } 7 ears, indeed, it was believed to be actually poisonous. After a time, however, chickens became better acquainted with this insect and began devouring its eggs and afterwards the larvae, finally eating the beetles with apparent relish. Skunks and snakes are reported to eat the beetles, and toads frequently gorge on them. METHODS OF CONTROL. This species is not a difficult one to control, no other method being necessary for its destruction than the free use of an arsenical or mechanical means. Before taking up the remedies that may be most profitably employed, it may be well to preface with the statement that an arsenical liquid spray is preferred, and that dry arsenicals, hand- picking, and jarring are practicable only on a small scale where the grower has no spraying outfit, and occasionally when infestation is slight and limited to a small area. Every market gardener should be equipped with a good spraying outfit. MECHANICAL METHODS. Jarring, if employed early in the season, is of considerable value. It is a time-worn remedy and so well known as scarcely to need descrijition. It is customary in many localities to gather the beetle^ and their larvae in pans containing a little water on which a very thin scum of kerosene is floating. Large shallow milk pans are excel- lent for this purpose. At the same time the Qgg masses should be picked where seen. Numerous appliances have been invented and some patented for destroying this pest, but the arsenicals are so effective that other remedies are really not necessary. Brushing. — The susceptibility of potato-beetle larva 1 to extreme heat, as has already been recounted, indicates that a remedy much in vogue against the asparagus beetle, namely, the mere brushing of the larvae from the plants on an extremely hot and dry day. will be effect - [Cir. 87] L3 ive. So far as the writer knows, however, this has never been gi a thorough trial for the potato beetle. It should l><- tested. /•',/// and spring plowing are of value in o general way, as foi other insecta which pass the winter in the earth, bul they are bj no means perfect measures, n- the beetles are hardy and nol much affected by this treatment. \i:-i \ ii ALB. Arsenicals are the best remedies for the Colorado |><>i;it<> beetle, and on small potato patches Paris ■_■ usually applied dry. mixed with Hour: but, as previously stated, it is bes( used as :i Bpray. Where early hand methods have been employed, thorough treatment w ith an arsenical should follow . Paris green, dry. When applied dry, I'mh green is mixed with from 10 to 20 parts of cheap dry flour, sifted land pla ter, or fresh air-slaked lime. This remedy affords best results early in the sea -dii mi young plants. It should be dusted on preferably when the dew is on and by means of powder guns or bellows, or the so-called •• dust-spray '" machines, so as t<> cover the plants and leave as little surface as possible for food for the first-appearing beetles. In spite of this, however, some beetles will succeed in depositing their eggs <>n the lower surface, which is difficult to reach with ;t dry mixture, and when the larvae hutch another application must be made. In fad this remedy must be ummI for some time or until the plants obtain ;i fair growth, when spraying will be found more effective. /'/(/ Paris green spray is prepared by mixing the arsenical with water or Bordeaux mixture" at the rate of 1 pound of poison to 75 to !•_'"> gallons of the diluent. It" water alone is used, quicklime in aboul the same proportion a- the poison should be added to prevent scorching. For the proper mixing and application of thi- spray a bucket pump or knapsack sprayer of good quality i- -u tli- eient for nse in small gardens, l»ut on a larger scale a potato sprayer to be drawn by one or two horses through the rows e mixed with a small quantity of water into a thin paste before the hulk of water i- added and should then lie thoroughly blended by churning in the force pump or sprayer. The mixture, being a mechanical one, i- not constant, and the Pari- green . will sink to the bottom. To avoid this it must be stirred constantly while being applied. It i- advisable to use the Bordeaux mixture diluent, as this is a valuable insect repellent a- well a- a standard rectlons for the preparation of tlii- I and the arsenicals here >!i-- cussed are given in Fanners' Bulletin 127, t". 8. Department of Agriculture, which can lie obtained en applicatl [CIr. ^71 14 fungicide, and it operates also against different forms of blight and other diseases which may threaten the crop. Arsenate of lead serves the same purpose as Paris green, and for use against the Colorado potato beetle i< still more valuable. Com- plaints have been made that several applications of Paris green are necessary during the season, and extra doses are required after each rain. Arsenate of lead is applied in practically the same manner as Paris green, but it contains less poisonous arsenical ((>0 to 70 per cent when dry), and being sold usually in the form of a paste it is used at a considerably greater strength — i. e., about 1 pound com- bined with 15 to 2f> gallons of water or Bordeaux mixture. Being more adhesive, it adheres more firmly to the leafage and is much less likely to produce scorching." Its adhesiveness is still more enhanced by the addition of about the same amount, by weight, of resin fish-oil soap as of the arsenical used. The number of sprayings to be applied will depend somewhat upon local and seasonal conditions. Two or three will ordinarily suffice for the spring brood, especially if applied just after the eggs have hatched, and the same number should be applied for the second generation. Other arsenicals may be used if preferred. Among these are ar- senite of lime with soda, which has the merit of being as efficient as Paris green and lime and far cheaper. It is not on sale at the present time ready made, like arsenate of lead. Scheele's green, similar to Paris green, is employed in the same way as the latter. Summary. — To sum up the directions for the use of arsenicals. it should be said that arsenate of lead, because it can be purchased already combined, in paste form, which is preferable, takes first place. in the writer's opinion, as a potato-beetle insecticide. The mixture of Paris green, lime, and water is in nearly the same class, because the ingredients can be purchased anywhere. The dry Paris green mixed with air-slaked lime projierly comes hist, as it is less effective than the other mixtures and much of the material is wasted. Precautions to -pre rent poisoning. — In the use of arsenicals, as well as other poisons, care should always be taken to avoid accident. This can be best accomplished by plainly marking the contents on all receptacles, such as bottles Or packages, in which the poison is kept. In addition a " POISON " label, which can be obtained of any drug- gist, should be affixed. It is best also to keep such substances under lock and key. The utensils employed in the preparation of the mix- tures which have been discussed should be thoroughly cleaned after use. a In point of fact it can be used at the rate of 1 pound to 10 gallons without injury, but this proportion is not advisable, owing to the extra cost, and scorch- ing would be apt to follow its use on plants exposed to hot sunlight. [Clr. 87] 1.-, I I: \i«k ITION "i wiin- \\li i 00P1 RATION. It i- always wisdom on the pari i>t' the agriculturist to kf»-j > down the weeds <>n the farm, and in the treatmenl of the presen( iii— *-«-t if those weed- which air kimun to fin nidi ll Willi food, such as -.1 1 1< 1 bur and Jamestown weed, were cut j 1 1 ~ t before seeding, it would pre \ tin the overdevelopment of the pest and of other insects which feed on the weeds, as well as the weeds themselves. The fanner should familiarize himself with the wild food plants of this pest. Keeping the potato patch and, in fact, the entire farm as free as possible from solanaceous weeds should be practiced by all farmers of a neighborhood, and if the potato grower could secure the cooperation of In- neighbors in the use of an arsenical spray, and would also de- stroy the insects by spraying infested wild fund plant-, the effect would soon be noticeable, as there ran be no doubt thai the 3pecies would soon be reduced to small numbers, at l<'a-t in limited areas, it' this cooperation were thorough and persistent. This statement is based on the fact thai the beetles are seldom if ever seen migrating nowaday- in any such numbers a- in earlier years, and there is not therefore the constant danger of reinfestation from a distance a- was formerly tin- case. There may, of course, be occasional exceptions. Finally, a- a general proposition, tin- potato grower should keep bis potatoes free from diseases, such a- wilt and scab, and spray for flea-beetles and any other insects which may be found in addition to the Colorado hectic. lie should also pa\ particular attention to the method- of growing best adapted for hi- location. Information in regard to the method- of potato culture i- furnished in Farmers' Bulletin No. 35, l. S. Department of Agriculture, and potato dis- eases and their treatment are considered in Farmers 4 Bulletin No. 91. Both of these publications can he had on application to the Secretarj of Agriculture. Approved : .1 wii - Wilson, S ■ ' . of . \iirh nit a . . Washington, D.C.,April /". 1 [Cli O UNIVERSITY OF FLORIDA 3 1262 05252 3361 flfflVir*.- r-, I