Property ol the United States Government ' 03. I aited States Department o lU of knto It urc, EQUIH I Bj I II I III I II Mil Entomologist in Chargi of /•'/■■ iNTRoni < pom . A moderate-sized red and black plant-bug, variously known n- calico back," "fire bug," and "terrapin bug," a- well as harlequin I M J ■-#, n liar lei] All ;;il I. cabbage bug, is the most destructive insect enemy of cabbage and related crops in the southern part of the United States. At one time it was a serious pest northward to X>n Jersey and westward to Ohio 12066 fir. 108 and, indeed, threatened t<> invade New York and New England. In recenl years, however, its progress in the northern State- has been checked by atmospheric condition-. This plant-bug accomplishes it- work of destruction by sucking the sap from leaves and reins of cabbage and other crucifers, the af- fected plant- wilting, withering, and dying as if they had been swepl by fire, whence the name " fire bug." It i- a pest which, if permitted to propagate unmolested in seasons which favor it- increase, i- certain to destroy a portion if not all of the fields which it infests. A half dozen mature insects are capable of destroying a small plan! in one or two days. Some year- ago, when this species wa- abundant in the vicinity of the District of Columbia, the writer saw many large fields in Maryland and Virginia from which not a single good cab- bage could he picked, and observed similar injury to horse-radish and some other crucifers. The harlequin bug has been compared to the boll weevil as a pest in the South and to the San Jose scale as a scourge in New Jersey. Certainly it is to the cabbage grower what the other two insects are to the cotton planter and fruit raiser respectively. If growers gen- erally, however, will undertake the method- of control, a- advised in this circular, there is no reason why it should be longer destructive. DESCRIPTIVE. The name harlequin cabbage bug scarcely requires explanation to any one familar with the appearance of the insect. It- gay red and black ornamentation is suggestive of the dress of the 1 >: 1 1 • I \ tropical and has been diffused through two additional life zones, the Lower and Upper Austral. In the latter zone, however, ii has not become pel 1 1 1 ; 1 1 1 « * 1 1 1 1 \ established much farther north than about the lower or warmer half. The region about Norfolk, Va., "the gateway of the South," i- probably the northern limit of actual establishment in the A year >>r two following its discover] .i a pest this species had in vaded Louisiana, and bj 1867 was recorded from North Carolina. [I spread wa* most noticeable along the Atlantic seaboard and up the \l vsissippi River valley. In 1870 it had appeared in Missouri and Tennessee, and bj 1876 had reached Delaware. In Maryland and Vir ginia, however, it did not attract attention until l ss n. Ii was in I recorded as injurious in Ne^ Jersey, ;ii W Ibury, in L892, 1 and in 1804 ii was seen at Jamaica and " Ne^ Lots Road,' 1 Nev i ork.' Westward we 1 1 : i \ « • office records of n~ occurrence in Colorado in l s ^-_\ at Pueblo and'Denver, but it 1 1 .• i - never been an important pest in that region, and it was not until 1 S '- M * that it was recorded in Indiana and not till 1891 m Ohio. In the Latter State it progressed steadily northward until it was checked by the same atmospheric conditions which prevailed in the Eastern States and which will be mentioned presently. In the Pacific region the species is well estab lished iii southern California, but there seems to be n<> published record of the time of its firsl appearance in that State. We received specimens from San Diego, Cal., a- early as l v 7^. The insect is also recorded from Nevada. dispersion of tin- species in the Middle States has been traced li\ Mr. I'. M. Webster, and from what has just been stated and what has been placed on record by Messrs. Webster and Howard it i- very lent that it has becoi liffused largely by what Doctor Howard terms "commercial jumps,' 1 as in the case of insects like the aspara •ru^ beetle. This is a matter quite simple of accomplishment, as fertile egg masses can be carried long distances mi the insect's food plants for example, on the outer leaves of cabbages bj railroads and \>\ boat It will be noted that after the establishment of the pest in Delaware it did not attract attention farther north until twenty years later; also, that other introductions were made in different direction-- quite independent Iv of each other. Recorded bj Gideon Llncecum, Practical Entomologist, Vol. 1, p. 110, Aug. 21, miner. !»tii Kept. \..» fork State Km. f. 1802 i 1803), pp. 316 317, Ml. - Tine, Kul. v.. New Tori kg Exp. Sta. (Geneva), Dec., 1804, p. 683. • ... Km. Soc. W.i-li.. Vol. III. pp. 288 -".hi. 1- To recapitulate: This species has obviously become diffused from a central point of dispersal, Mexico, chiefly in the following three direc- tions: (1) From Texas eastward through the Gulf States and north- ward along the Atlantic seaboard to Long Island; (2) from Texas northward through the Mississippi Valley and thence through the Ohio River region into Ohio: (3) from Mexico into the neighboring States and Territories, and from Lower California into southern Cali- fornia and Nevada. The northward migration of the harlequin bug, although not with- out interruption, was apparently quite steady until recent years. Beginning with the year 1897, at which time the insect had reached its maximum as a pest in Maryland. Virginia, Delaware, and adjoin- ing States, climatic condition- adverse to it- existence developed. These consisted of sudden changes of temperature, such as cold snaps followed by warm -pells and the reverse during the winter. As a result this bug, with several other form- of southern origin, was killed while hibernating and practically disappeared in the North until, at the date of writing (1908), it i> scarcely, if ever, reported a.- in- jurious from the District of Columbia northward. These conditions were particularly noticeable in the winter of 1898-99." Small scat- tering colonic- are. however, occasionally found in this region, chiefly on wild plants, late in the fall. LIFE HISTORY. in the warm and equable climate of the South where this species is at home it is more or less active throughout the year. Farther northward, however, after the first severe frosts of December it g into hibernation in tufts of grass or under rubbish at the bases of cabbage -talks or in any convenient place. This takes place chiefly in the adult stage, although some nymphs of the last' stages remain afield as late as November and December. Doubtless the nymphs succumb in time to cold, and hence fail to survive the winter.'' The first warm days of February or March, in the Gtdf region, or of April, farther north, see the bugs appear abroad and beginning to feed. At first wild mustard and other cruciferous weeds are attacked and soon the insects are ready to reproduce their kind. On these wild plants the eggs are deposited, on end. generally in two more, or less ' Sec r.ul. 22. n. s., Div. Ent., T'. S. Dept. Agric, pp. 54, 55. 6 A number of adults and nymphs in the last two stages obtained from Lam- bert's Point, Va., October 21. 1907, were placed in a rearing cage with growing cabbage plants, grass, and similar rubbish to provide moans of hibernation. For over a mouth or until some time in December the insects continued feeding, but when examined duriag the lirst week of March it was found that all had suc- cumbed to the severe cold weather of February. [Cir. L03] parallel rows cemented together in groups of about :i dozen, .1 shown iii figure l. The) are normal!) placed on the under ridi "I the lea and hatch, in warm weather, in three or four days after deposition and in five i" eighl days in the cooler weather of earl) spring. The young bugs or nymphs pass through their five tages of metamor phosis with considerable rapidity. It has been stated thai the life cycle could be completed in warm weather in about two weeks, but this is "l>\ iously ;in exaggerat ion, as ii requires four or five weeks for the completion of the cycle in related insects. The life periods <>f tin- species were unknown until worked out bj Mr. II. ( ). Marsh, of this office. Specimens (from Texas) were under observation from the first week "I March until the first week of May. The) were under somewhat unnatural conditions, being confined in our office room, which was maintained during this period hi :m average temperature of from 68 i" 70 F. The first or stage i«'\ civ<| 1 1 days. The time from the hatching of the eggs until tin firsi molt gave the first larval instar or nymph period 7 days; the second instar required 13 days; the third, s days; the fourth, II days, while tin- fifth or pupal instar covered 17 days a total of 70 days, or lo weeks, in all, which will be not far from the maximum active period of this species. The minimum will probably fall into much lower figures, probably half of this time, or ni most not more than I-' days in extremely hot midsummer weather. When cabbage and similar plants come up the insects migrate to them. It has been surmised that owing to the rapid development of the cabbage bug in the South there is a possibility of as man) as seven or eight generations each year, while in the Ninth three or more occur. The first supposition is doubtless overdrawn, as we know of no simi- lar insect producing so many generations annually. This is a prob- lem for future study. It seems probable that four or five generations would be a more natural limit in the South and two, or possibly three, in the North. POOD PI \ \ I S. Iii the autumn after the cabbage crop has been made and in early winter, even as far north as Washington, the bugs are -till afield, seeming loath to seek shelter for the cold months. At this time they cluster on cabbage -talk- and sprouts and the leaves of turnip and like plant-, and when the supply of crucifers has become exhausted they will attack almost any form of succulent tion which i- most available and palatable. On one farm the writer observed a field of 10,000 cabbage plants completely ruined, which at the time of his visit, the first week- in October, hail been deserted by the bugs. An adjoining field of pota- toes was then attacked, afterwards one of eggplant, and numerous bugs in various stages were observed sucking the juices of these plants. Unripe fruit of eggplant was especially relished, and ripe pods of okra and beans were also attacked. The list of useful plants which this species has been found to damage include- all form- of crucifers or cole crops — cabbage and related plants, kale, collards and cauliflower, turnips, radish, horse- radish, mustard, rape, and the like — and when these crop- have been killed out truck crops of nearly all kinds are attacked, of which egg- plant, asparagus, potatoes, tomatoes, okra. beans, and licet- arc mos( affected. Damage is sometimes done to ornamental plants such as roses, sunflowers, and chrysanthemums in flower gardens, and Mr. J. M. Rankin, while an agent of this Bureau at Chico, ('ah. in Octo- ber, 190."), reported that this species, after entirely destroying a half- acre plat of cabbage, attacked the other plant- in the vicinity, includ- ing nursery plants of citrus, loquat, cherry and plum, squash. e\ another bug, Irilm I... the wheel bug, which the writer has- frequently seen attacking the ybung harlequins. The influence of natural elements, particularly cold winfc already been mentioned as a means of decimating this pest. Ii i- well to add, however, that the writer had this pecies under close ob \;iiioii in 1899, and thai ;i- a resull of sudden cold snaps, Bo per cenl of the bugs in fields near Washington in thai year had been killed by January 15, I! \il rilODS "l fMINTROL. The experience of years has shown thai in order t" obtain the besl results In the treatment of the harlequin cabbage bug preventives are necessary, as there is great difficulty in obtaining insecticides which are effective and which do no1 ;ii the same time injure or kill the plants. These preventives are: i hand methods. With stricl observance of clean fanning few of the insects will survive the following spring and I adoption of trap crops leaves fewer still to be desl royed by mechanical measures. In some cases :ill three methods shoidd be adopted, foi they are neglected the grower will find it n mosl vexatious matter to control the pe-t iii the midsl of the growing season. Clean cultural methods. Of prime importance are clean cultural methods. The value of clean methods ol farming has 1 n recognized by nearly everyone who has had experience with this insect. The practice of leaving -talk- of cabbage and oilier cruciferous plant- in the field late in the autumn and in the early winter, or of permitting rank weeds to grow up, or, in fact, allow ing an\ sorl of debris to accu- mulate, serves as a mean- of protracting the life of this insect, as all such materia] either affords it food late in the season or quarters for protection against the elements during winter. It is even inad visable to plant crucifers in the vicinity of outhouses and barns, the hue;- are apt to enter these latter for passing the winter. Throughoul the year wild plant- of the mustard family, on which the insecl chiefly breeds, should be carefully kept down nol only in the fields but in the immediate neighborhood. A li-t of such plan; given on page 6. Tiii/i ■ rops. Some plant-, such a- cabbage, turnip, or kale, may be planted late, to be lefl at interval- throughout infested fields. These trap plants attract the insects in the fall, and here the latter may be killed with pure kerosene, or by mechanical methods. Where it is con- venient to leave piles ^i rubbish until the insects are attracted to them this may be done, and the entire material, insects and all. should then be burned. H'ir. 10S] 8 The best remedy, however, and one that should be put into opera- tion by every cabbage grower who is troubled by this pest, consists in planting an early crop, which may be either mustard, rape, or kale, as a lure for the first-appearing insects. Radish and turnip serve a similar purpose. In the Gulf State- the overwintered adults appear in February and March, and in the District of Columbia and vicinity in the latter part of April. For some reason they appear to prefer the plant:- that have been enumerated, and wild mustard and other crucifers, for the first deposition of their c^ii-. On these crops and on weeds the insect- can he killed with kerosene or by the hand torch or may he collected in nets, or they may be destroyed by burning the entire trap crop when this is of no special value. Numerous reports have been received at the Department of Agriculture, and other- have been recorded, of the value of trap crops a- a mean- of controlling this pest. Some of these are worth repeating. The first test of the trap-crop remedy wa- made by Lincecum (1. C.) in Texas-, in L866. Noticing that the buy- were numerous on mustard and radish in April, he handpicked them and thus protected his cabbage crop. The practical utility of this method, however, does not appear to have been recognized until considerably later. In 1891, Mr. II. F. Weed, when entomologist of the Mississippi Agri- cultural Experiment Station, -owed a row of mustard through the center of a 1-acre field of cabbage. In April this mustard attracted the bugs in large number- and on it they were killed with undiluted kerosene, with the result that throughout that season the field re- mained free from the pest, whereas the previous year the cixjp was almost entirely destroyed." Hand methods. — If determined effort- are made to stamp out the first generation fewer insects will remain to be dealt with and very °A correspondent, Mr. J. II. Hevey, ingomar, Miss., tested the trap-crop remedy, and wrote that when the bugs made their appearance on a bed of mus- tard ho destroyed them by " bugging," i. e., by shaking them into pans of water on which a thin film of kerosene was floating. When the mustard was removed to make room for another crop a few cabbage plants became infested, but the bugs were killed as above, and finally, after the middle of July, none was left. One of the largest mowers of cabbage in Delaware reported (Sanderson, Hill. 26, n. s.. Bur. Knt.. U. S. Dept. Agric, p. 67, 1900) that at .me time it was impossible to raise cabbage on account of this pest, hut for several years In- had used kale as a trap Crop, and as a result of this procedure and careful handpicking of the few bugs that strayed to the cabbage, he had been troubled very little, while his neighbors' cabbage had frequently been ruined. In April of one year in Maryland half an acre of kale became freely infested on one side by harlequin bugs. The insects had all congregated on this side. Under the writer's direction this portion was burned, straw being used to facilitate ignition. Two weeks later not a single bug could he found in a walk about this patch, and the cabbage which was growing in several plats in tiie vicinity was tree from injury. [Cir. 103] 9 I'i'w will ilv from other quarters for the continuation of the speci Thus injur) maj be great h curtailed if not absolutely prevented foi :in entire season. The large size and bright colors- "I' the insecl render ii easj of detection and its sluggish nature h isl in il easj capture. Mr. II. Walter McWilliams, Griffin, Ga., reports thai bj offering a liiiiini\ in school children for the destruction "I this pesl he sue ceeded, in March and April, 1902, in destroying the first general ion in thai vicinity, and estimated thai this experiment saved him $100 <>n his cabbage crop alone, not counting the benefil to the children. As instance of the ease with which this insecl may !»• hand-picked, rower m Denton, Tex., gathered, in February of one year, 17,000 bugs. In case hand-picking has nol I n thoroughly done and some bugs have escaped this process and succeeded in depositing their eggs, the masses, which maj be easily recognized l«\ comparison with fig are I, ; '. should I arefully gathered and crushed. Kerosem emulsion^ according to the testimony of many who have experimented with it. is nol effective against the adults and only par tially effective when sprayed on the younger nymphs. Quite recently Prof. A. F. Conradi ! has found thai i L0 per cenl kerosene emulsion i- effect ive in killing the nymphs, as i- also whale-oil -nap. at the rate of 2 pounds to I gallons of wain. It' the insects are sprayed j after they have molted these insecticides almost invariably kill them. It is obvious that further experimentation is desirable along this line. Of/i, r ri im 1 1 ii 8. A few words should !><• said of other remedies and may be prefaced with the remark thai since the harlequin cabbage bug feeds exclusively by suction and does nol chew? it- food, the ar senicals, hellebore, and such remedies as are useful against cabbage worms are absolutely valueless against the present species. Pyre thrum is nol effective and is, moreover, too costly. I !<>t water applied at a temperature of aboul 130 1". to the infested cabbage plants should be tested. It i- nol applicable, however, t" large fields on account of the difficulty of maintaining tin' temperature at a given point, hut may he found useful in kitchen gardens. The value of hand torches for insecticidal purposes i- extremely limited. The plumbers 1 torch i- used considerably in Texas a- a means of killing this insect, but growers an- a] t to expect too much of tlii — method, and to apply it to too many kinds of insects, to the ultimate detriment of their crops. It i- possible that some id' the natural enemies of this sp especially southern egg parasites, might he utilized in its control; i. <•.. by shipping parasitized eggs from localities where thej are abundant to northern regions in which thev do not occur. Bi 9 i • Exp. st:i.. pp. '.• 11. 1007. Kir. 103] 10 M M MARY. The genera] acccount which has been given of this insect in preced- ing pages has been brought together at this time because of the practi- cal certainty that in the natural course of events this bug- will before long endeavor to reinvade territory north of it> present range (in L908), and may again become a pest for a number of years, until climatic condition- adverse to it- development or increase check its northward spread. /// conclusion, it should be repeated that the systematic destruction of the insects by mean- of the trap-crop method described, together with a system of clean cultural practice throughout the entire season and especially in the late fall, will leave little else to he done save the gathering by hand of such insects a- escape these measure- or which may fly from infested to uninfe-ted iields. T<> prevent tin' pest from advancing farther northward thai, its present limits, careful watch should be kept for flu fist appearance of tl,c insect, and remedies should be prompt and thorough. The im- portance of killing off the lir-t or hibernated brood of bugs and their progeny can not be too strongly emphasized. Approved: James Wilson, Secretary of Agriculture. Washington, D. C, May 4, 1908. [Cir. L03] o • 3 1262 05252 3460 MARSTON SCIENCE LIBRARY Date Due Due Returned Due Returned ' UNIVERSITY OF FLORIDA 3 1262 09216 5520