# Circular No 60 I mini States Depa rtment of Ajjri* r—~ BUREAU (>!• BNTOMOLOOV I i> HOWARD I in mi imtoim t it i uum.i u /'■■iiiin rn/,, Linn, i B J I II. t ' I I I I I I N I > I S . /./. i (ling l i i; \i. I'M \i; m i i BIS i [I 3. The worst of the raanj destructive enemiee ol cabbage und othei crucifera is the larva or caterpillar of a white butterfly km >w n to science r ni in i Pit lis) rii pit Linn. The caterpillar, called the imported cab- bage worm, ie altogether too well known by farm- en throughout this coun- try ae well as in the < >1« 1 World, and the adult in Beet, the imported cab- bage butterfly, called also the white <>r rape butter- fly, is o familiar objeel to nearly everyone. It is generally recognized that the butterfly ie the pan ni of the " worn This cabbage worm ie velvety green in color, much like the cabb mi which it feeds ; and the - of the body, if viewed through an or- dinary hand lens, is Been to be somewhal rough and finely dotted with small black Boots. There is a faint yellow Btripedown the middle of the back and a i'mu of yellow spots along each side in line with the Bpiracles or breathing pores. It measures, when full-grown, about an inch and a fourth, presenting the appearance Bhown in figure 1, c. The butterfly has a win. rly two inches, and i- white, marked with Mack near the tips ol the fore-wings, a- Bhown at figure I. a. representing the female. In tin- Bex there are two conspicuous black Boots <>n each fore-wing; the malt has only one. Both Tib i - /■■ female butterfly: '. abovi Ian .i in iiiitiinii position ■•II i i led cbrj - ' -iiu'iiii v enlarged /., mon sexes have a corresponding smaller black ^ i >< >t at the upper extremity oi the hind-wings. The body of the Female is whitish ; thai of the male is usually darker above. The male is generally a little the smaller. The under surface of the hind-wingS are uniform Satiny straw-yellow and there are generally two black spots showing through, in both sexes. 'Flu- eggs are fusiform, pale yellowish, and strongly ribbed (fig. I. &). They are large enough to be readily seen with the unaided eye, and are deposited singly, usually on the lower surface of the outer leaves of cab- bage and other food plants. When the caterpillar or "worm" becomes full grown it attaches itself to a cabbage leaf or other nearby object, fastens itself by means of a stiingdike girdle, and often within the same day transforms to a chrysa- p-'/xi \ / P-T \ i. ^ Pia. 2.— Imported cabbage butterflj male, wings expanded, :it left; wings folded in nut urn I resting position at right— somewhat enlarged [original). lis of the appearance indicated at figure 1. d. The chrysalis is of varia- ble color, seeming to be influenced in this respect by the object upon which it is placed. The color thus varies from dirty gray to yellow, green, and dark gray. The length of the chrysalis is a little less than three-fourths of an inch. NATURE OP INJURY. This cabbage worm has been rightly termed the bane of the cabbage- grower, and the dread of every careful cook and housewife. It begins work early in the season, and the principal damage i^ therefore usually to young plants. After riddling the outer leaves, which continue after- ward attached to the stalk, it attacks the more tender inner leaves as they form, frequently secreting itself in the head-, which are made most unsightly by its dark green excrement, and where it is difficult to reach with insecticides. As a result, cabbages before being sent to market must lie carefully examined and the damaged leaves plucked away ; and before cooking it is frequently necessary to tear the heads apart to see that no disgusting "worm" is lurking within. Even after the dish is cooked there is danger of an admixture of animal with the vegetable food. In cool weather the caterpillar frequently feeds in free exposure on the upper surface of the leaves in the sunshine. 8 \_ , .,, j £ 1869, when thia i abbage worm » d to limit* 'I areas in Canada, New England, and New York, ii did greal dan At Si. Albans Bay, Vt., in thai yeai it caused the total destruction ol p ,,f 3,000 cabbage plants The worms made theii appearance .it. cut the first ol September, and there were from I" to 50 on a head. TheAbbi Provancher estimated th< same year a 1< &240.0 n the vicinity of Quebec alone. One farmer near Montreal losl in a single n over 12,000 heads of cabbage. The following year, accordii Mi Vngus, the entire crop of cabbage and cauliflower in Borne places about New York City, where the insects had appeared onlj the yeai before, was destroyed. The loss was estimated at half a million dollars \n interesting feature connei ted with the establishment of this in in America is the practical extirpation, at ! illetl southern cabbage butterflj {Pontia protodici Boisd. 1 ) in many regions. This is accounted for in pari hj thi earlier ppearance of the imported Bpecies, enabling the caterpillars to obtain possession of the fee< ling plan- and crowd <>ut ill" less hardy native form. 2 ORIGIN VND DIS I'Klia in >N. imported cabbage butterflj was introdi I from Europi nape half a centurj before the dat( nl writing, 3 and was first ■ I from a capture at Quebec, Canada, in I860. It was nol . en until two years latei . in the ■ . locality. I • - after this it was observed at intervals in other portions ol ' 'anada. In 1865 it< firsl appearance in the United States was noticed in Maim i'li. following year it was seen in north Hampshire and Ver- mont. Bj 1868 it had reached New York, and a Few years latei b ; attention, as each year thereaftei it was found in Borne new locality. In 1875 it appeared in Cleveland, Ohio, and two years later m Illinois. By 1 S ^> it had penetrated southward to the Gulf region. This distribution has continued until now the spi known prac ti,.i||\ in evi and Territory of the Union, although ii is occa • ,llv , , | mii i, .1 as new to some mi ire or l< sa isolated locality. It does not appear t . . be an inhabit in! of any particular life -. . nun ; to be as mm Ii ol in the < lull I ngland. I„ the l II' misphere this butterfly rangt - from the Atlant - native Bpeciee and the imported butterflj erallj rred to in literature as Pieris protodict and res| lively. Ii i- well known thai neat introduced from tl H hardy than nativi ind survivet litione which would be unfavorable i" the latter. In the writer's experience, the southern cabbage but terfl) is more susceptible to disease than the imported specii sionalh the latter returns in moderate numbers to localities from which it has apparent 1> been absent i"< !<.n^ periods. was introduced in 1856 ■•< 1857 see Rept. Dept. ^gr. for lixs \ iojji iphi ■ ..-•-■ -iitit "i" tln> Bpecies is ui\>-n l.\ Scuddei B I terfl n I . S. and Can.. Vol. II. pp. 1171 1190, 1205 1218 . the Pacific, in most localities between the thirtieth and sixtieth degrees of latitude. In Switzerland it occurs on the level of perpetual snow, and in this country it lias been taken on the barren subalpine heights of the White Mountains. FOOD AND OTHER HABITS. The imported cabbage worm feeds on the foliage of nearly all cru- ciferous plants, is particularly fond of cabbage and cauliflower, and somewhat less destructive to turnip, radish, mustard, and horseradish. It also does considerable injury to ornamental plants, such as nastur- tium, mignonette, sweet alyssum, and spider plant (Cleome). 1 The butterflies sip \\n i nectar of (lowers of many kinds, and are to lie seen any time hovering oVer them. They are especially fond of the white blossoms of crucifers. also of such plants as white aster, lavender, and thistle. Like other butterflies, this species is diurnal, and is on the wing from early morning until near dusk. It is a comparatively slow flyer, hut capable of extended flight for long distances. The butterflies sometimes congregate in immense swarms, as has frequently occurred where the insect has emigrated from the continent of Europe to England. Its occurrence in mid-ocean has been recorded. LIFE HISTORY. The butterflies appear as early as March, even in the Northern States. and thereafter can usually be seen flying about cabbage fields and else- where, throughout the year, until after several severe frosts in October. In the Gulf States they occur throughout the season. Egg deposit commences soon after the butterflies appear; in fact. pairing and egg-laying may begin within a day or two after the adult issues from the chrysalis. The duration of the different stages varies according to temperature. The observed egg period is from four to eight days. The larva eats voraciously and grows with great rapidity, attaining full maturity in from ten days to two week after hatching. It molts four times; hence there are five distinct stages, the first molt taking place (in warm weather) in about two days from the hour of hatching, the second stage lasting two or three days; the third and fourth, one or two days each, and the fifth, four or five days'-'. The duration of the chrysalis stage is from seven days to a foil night during the summer time, but the last chrysalides formed in the more northern States remain undeveloped during the winter until the following spring. The life cycle occupies periods varying between twenty-two days and five weeks. Even in New England this species is credited with being triple-brooded, but in the District of Columbia and vicinity there Ii is a decided pest mi iliis plant in the District of Columbia. Technical descriptions of the different larval stages witli particular reference t<> wing development are given by W. F. Mercer (Jour. X. Y. Em. Boc., Vol. VIII, pp. L-20, March, L900). ,„„-. be one or more addition »ne, and then it b i ibility ,, l:l , least Bii in the extreme Booth. The fii ition develoi it ilil plants. \ \ri R \i. ENEMIE8. w,,,. ,, not for certain natural checks this would be b still peater pest than it is. The b1 important oi its inBecl enemi< Bma ll parasites, all introductions from Europe. One ol them, a Bi -«f~ lUk'llh TIKI. conid, Apanteles glomeratus Linn. (fig. 3), was purposely imported in from England. During the autumn of 1904 this Bpecies held its t IV : I under complete control at Washington, D. C, killing every ' worm " which came under the writer's observation. A larva which destroyed by this parasite is Bhown in figure I. together with thi parasite's cocoons. A secondary parasite, a minute chalcis fly, Tetras- tichus microgastri Bouche, was also present, but did not militate against the effectiveness oi the Apanteles. Of Bimilar importance to 6 this Apantelea is a chalcis fly. Pteromalus puparum Linn. (fig. 5), noticed in this country in 1869, having evidently been imported with its host. Wasps, particularly Polistes pallipes Lepeh, and related forms are also of great service in reducing the numbers of this and other cabbage worms, appearing to prefer them to other prey. A small, evil-smelling plant-bug, Phymata wolffii Stal. (fig. 6), secretes itself in flowers, such as thistle and goldenrod, and destroys numbers of the butterflies, capturing them and sucking out their vital fluids. Fig 5 Pttrnmal female at left ; male at right bigbly magnified (original). Numerous other enemies attack this Cabbage worm in addition to tin- ones that have been enumerated, 1 and it is sometimes subjeel to a con- tagious bacterial disease'-' similar to that of the cabbage looper. 3 It is. however, less susceptible to this malady, and is seldom destroyed in any numbers by it. The parasitic flies can he encouraged by collect- ing the larva' and chrysalides of ,,, , , , ,„. the cabbage butterfly and placing ! m. I. Vhymata wolffu a, dorsal view . '>. lat- >- ■ ' eral view ; c, f t leg : d, snout— a, b, enlarged them in barrels or lioxes covered , d more enlai ged • from Rilej ' •. 1 with coarse mosquito netting, which will prevent the butterflies from escaping when they develop and permit the much smaller parasites to issue ami continue their good woi k. REMEDIES. In the treatment of this species it should be kept in mind that other " worms" and other cabbage pests, are more often present than not. Arsenicals. — The best remedy i< one of the arsenicals; and Paris green and arsenate of lead are prefei red to others in common use. If the former is u^a\ it may be applied either dry or wet. preferably, however. 1 Among ether predaceous enemies observed in tins country are the wheel bug [Arilus cristatus Linn.) and the armed soldier bug {Podisus spinosus Dall.). Che cabbage worm is also parasitized by the Tachina fly Exorista vulgaris Fall, 'the writer has a list of in additional European parasites. Micrococcus pieridis Burrill. 3 Autographa [Plusia) >>* a Riley. I the rate ol about I pound "I the poison to 160 gal lot « iter, It Bhould !"■ applied when the plants are iii-i Bel oul insure the poison reaching the young larva before thej have burrowed far iui" the heads. Other applications Bhould follow ac required These can be made with absolute aafet) until the heads are aboul hall formed, and, for thai matter, even later, .1- the pois lisappears from plants almost completely within three "i four we< ks after application.' Bran mash.— A mixture of bran with Pai 1 ol the standard remedies for cutworms as well ithetesti mony of some who have used n til against 'cabbage won and Bhould !><■ tried against the present species. \n- .1 can be employed in the preparation ol this mixture. It is best to mix the bran with water and BUgar before adding the poison. The proportions are 2 or ■"> ounces ol bu ■ ir >u other sweetening, and ibout I pound of bran, d> a gallon of wati 1 . as to make, wh< n stirred, a mixture that will easily run through the fingers. In it- application it 1- merelj Bprinkled, either wet or dry, over the affected plants. I In hot-water remedy.— As long igo 1- l vv ■". water, at a tempei iture of aboul 130 !•'.. was advised :i- ;i remedy foi this cabbage "worm." It clues practically no harm to the plants and kills all insects with which it comes in contact. It i ly applicable t" large fields, bowev< r, on accounl of the difficult) of maintaining the proper temperature. Kerosem emulsion is nol as effective as tin' arsenicals, because in its application it is necessary for the epra) tocomi into direct contact with the larva 5 in order to kill them. Pyre thrum is not bo useful ;i- an arsenical. < »t it- effectiveness I h James Fletcher, who still advocates it- use in Canada, wrote in l v,, l that "diluted with four times its weight "I common Hour, and then kept tightly closed for twentj tour hours (before use), leaves nothing to be desired, and thousands of dollars are yi > discolor the leaves, has the advantage of not being poisonous to human //•'/ properly appl 1 tnical analysis has ahown that cabbage which has 1 irsenical in the wa) prescribed, and then prepared foi cooking in the usual manner .1 (reek late 1 . has nol even :i trai 1 arsenic remaining, rhe use ol .11 - jainsl cabbage worms is almost universal in the United States, although growei Bometimes loatb i" acknowledge the fact i"i feai ol the loss ol customers who are do! full) acquainted with the harmlessness ol the remedy, rhere an no authentic recorded instances known to the writei ol , from thi sumption of cabbage treated with an arsenical. According to Gillette, 28 bage heads, dusted in the ordinary way, would have 1 □ by a human being :u one meal in ordei to produce poisonous effects. Still il In order t" avoid all danger, to use othei insei ticides in the case ol vegetables thai .in- i" be eaten Boon. On tlii- head i| mjgul be well i" cite the expi 1 of a Virginia market gardenei who d listed his cabbages with Parif green and flour, omitting to inform his family ol the fact. \ dai "i two latei hi lily ni this cabbage, .1- did osiers., aid afterwards was questioned by lii> wife in regard to the peculiar powder) substance on the heads. Alii. oning was anticipated, do ill results followed. beings or domestic animals. If it is not used in liberal quantity, how- ever, a proportion of the caterpillars are merely numbed by this mixture and recover. Younger caterpillars are more susceptible. Hand-picking. — For the kitchen garden where, for obvious reasons, it is undesirable to use arsenicals, hand-picking is sometimes practiced, especially when plants are first set out. The corn-meal remedy. — According to Prof. L. Bruner, corn meal dusted on cabbage causes the "worms" to drop off. and protects the crop until the meal is washed away by rain. It is applied in the morn- ing while the dew is on and is said to act as a deterrent. Chun farming and trap crops. — If cooperation in clean methods of farming and in the use of arsenicals could by any possibility be secured, much of the loss due to the ravages of this pest might be averted. The practice of leaving cabbage stalks in the field after the main crop i~ control, but without very encouraging results. Hellebore will kill this " worm."' but is not as satisfactory a remedy as the arsenicals. Trap leaves.— A remedy suggested by one of our correspondents was tested by the writer against this and other cabbage "worms," includ- ing the looper. and found worthless. It consists in placing fresh cab- bage leaves over the heads at night, the supposition being that the "worms" will gather under these traps and can be destroyed next morning. Approved : James Wilson, Secretary of Agriculture. Washington, D. C, April 28, 1905. O DOCUMENT UNIVERSITY OF FLORIDA 3 1262 05252 3247