LIBRARY STATE PLANT BOARD April 19U3 S~591 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine R3C0MMEEDAT I01TS EOR CONTROL CE CATERPILLARS C17 CABBAGE IF TEE SOUTH UNDER PRESENT WART BOD CQ'JL I11 IONS 1/ By W. J. He id, Jr., Division of Truck Crop Insect Investigations CONTENTS Page Introduction ------------------ l Principal insects involved ----------- 2 Use cf insecticides -------------- 3 Control during plant preheading period ----- U Soil- inhabiting cutworms ----------- U Cahbage caterpillars, corn ear worm, and dinting cutworms _-_-----___-- 5 Control during plant heading period ______ •$ Methods of using dusts and sprays ------- 9 Cultural control measures ----------- 10 Where insecticides may "be obtained -------10 Summary -------------------- 10 INTRODUCTION Cabbage is one of the important vegetable crops for which in- creased production is urged by the authorities to meet wartime needs. During the period of its growth this crop is often damaged by one or more kinds of insect pests, including several species of caterpillars, or "worms". Experiments by workers of this Bureau during the last 10 years have shown that these caterpillars can be controlled at any stage of the growth of cabbage by the application of various insect- icides. The supply of some of these insecticides, especially those 17 In cooperation with the South Carolina Agricultural Experiment •Station -2- containing rotenone or pyre thrum, has "been curtailed seriously by war conditions. Tho situation with respect to the availability of rotenone-containing materials is particularly critical "because this insecticide is obtained from the roots of several species of tropical or subtropical plants such as derris, cubo, barbasco, tuba, and timbc, imported principally from areas in the South Pacific which have been cut off as a result of warfare. In order, there- fore, to conserve supplies of rotenone-containing insecticidos for uso on certain crops and on certain animals where the need is con- sidered most urgent, the War Production Board has issued a con- servation order specifying the use of these matorials. The pro- visions of this order do not permit the uso of rotononc-containing insecticides for the control of insects on cabbage. The principal purpose of this circular, therefore, is to fur- nish her?, gardeners, commercial growers, insecticide dealers, and other int"r jsted persons with recommendations as to the use of available insecticides and other control measures for combating caterpillars on cabbago under the emergency conditions resulting from the war. While the information in this circular will bo of particular value in the South, the recommendations contained therein will also apply to other parts of the country. PRINCIPAL INSECTS HTVOLVED The principal rpecies of caterpillars that cause damage to cabbage in the South are the cabbage looper, the diamondback moth (also known as the cabbage piutclla) , the imported cabbage- worm (also known as the common cabbageworm) , the cabbage web worm (or bud worm) , the corn earworm (also known as tomato fruit worm and cotton bollworm), and several species of true cutworms. Several other species, including tho cross-striped cabbage worm, sometimes occur in injuriov.9 numbers in certain areas. All these caterpillars are the immature stages of moths or butterflies. The cabbage loopor, the imported cabbageworm, and the cater- pillar (larva) of the diamondback moth are green and feed on tho leaves, bud, or head of cabbage plants. They aro sometimes known as tho "green worms" of cabbage. The looper may be distinguished by its habit of forming a hump in its body, or "looping," as it crawls. Tho imported cabbageworm has a velvety appearanco, a slender orange-colored stripe down the middle of its back, and a broken yellowish stripo along each side of its body. The cabbago looper and the imports! cabbageworm are about 1^ inches long when full grown. Caterpillars of the diamondback moth arc only about one-third inch long when full grown, arc somewhat tapered at each end, and usually wriggle actively when disturbed, often dropping from the plant and hanging by a silken thread. This species may -3- i feed on any part of the leaves, bud, or head of the plant, hut usually prefers the buds of young plants, crevices between leaves of heading plants, and the lower surface of the older leaves. The cabbage wobworm is about one-half inch long when grown, is dull grayish-yellow, and is marked with five brownish-purple stripes that run lengthwise of its body. The head is black and boars a V- shaped marking. This species feeds under a protecting web and pre- fers the buds of young plants, but may feed on other parts of the plant. The corn earworm maj vary considerably in color but usually is dark brown, with green, yellow, and black markings. This species usually feeds on the bud and heads of the plant, tunneling into these parts as a rule. Full-groxm corn oarworm s arc about 1^ inches -on^. Cutworms vary according to species as to color and markings, but usually are stout, soft-bodied caterpillars, from gray to brown to nearly bla,ck, and sometimes spotted or marked with stripes. They arc about 1^ inches long when full grown. Cutworms either live in the ground and cut off the stalks of plants, or live on the plant and feed on the buds, heads, or leaves. USE OF HTSSCTICIDSS Unfortunately, not all species of cabbage caterpillars can be controlled with the same insecticide. Materials that kill one spe- cies may not be very toxic to others, and certain insecticides use- ful during the prchoading period of plant growth, such as those con- taining arsenic and fluorine, should not be used during the heading period, on account of the harmful rcsiduo hazard. Rotcnono—containing insecticides usually have proved most satisfactory for controlling the imported cabbageworm and the diamondback moth during the heading per- iod of ca.bbagc growth; pyrethrum insecticides usually have proved most effective against the cabbage looper during this period, and combinations of rot mono and pyrethrum have been effective against all these species. Pyrethrum insecticides, when used at the strength and rate recommended in this circular, will not leave harmful residues on tho market product. The corn oarworm and cutworms are not satis- factorily controlled by either . rotenone or pyrethrum. These species must be combated, therefore, with arsenical e.nd fluorine compounds, which also arc toxic to the other species of caterpillars mentioned herein but should not be used during the plant heading period, for the reasons previously given. The following recommendations are designed to provide for the control of caterpillars on cabbage without the use of rotcnono-con- taining insecticides during the existing wartime emorgoncy. These recommendations arc also designed to conserve pyrethrum and arsenic, -lj~ "bccausc tho supplies of those materials arc limited. The adoption of the practices given in these recommendations should give satis- factory control of caterpillars on cabbage during the preheading period'of this crop. They should also give a satisfactory control of those pests during tho heading period of the crop unless tho diamondback moth caterpillars arc unusually abundant. In the latter event, the incorporation of nicotine in a'pyrethrum dust or spray, as detailed la.tor in this circular, should rodtico infestations of this species to a worth-while extent. In general, cabbage being grown in tho extreme southern parts of the United States (the southern portions of Florida and Texas) usually requires protection against caterpillars during all or the greater part of its growth. That grown in other parts of tho South usually requires insect icidal treatment dtiring all periods except the winter months. In certain parts of tho last-mentioned areas, control measures may be necessary during mild winters (those during which weekly mean temperatures do not remain below about 60° P.) or may prove unnecessary during spring seasons following severe winters, It is recommended that control measures bo started as soon as the caterpillar population averages about one "worm" per plant or when approximately 25 percent of the plants in a field show signs of re- cent caterpillar feeding. In general, control measures are unneces- sary, when weekly mean temperatures fall below about 50° F. in the fall, and should be resumed in the spring when weekly mean tempera- tures are consistently above about 60°. . C017TR0L DUPING- PLANT P3EHSADB7G- PERIOD So il- inhab it ing cutwo rms If cutvorms are present in the soil before the crop is planted, the' following poisoned bait should be broadcast on the soil surface lato in the afternoon at the rate of about 25 pounds por acre: Wheat bran ~~-~~_-~~ -25 pounds Sodium fluo silicate - - - - - 1 pound Water to moisten The bran and poison should be thoroughly mixed while dry and enough water added to dampen, but not wet, the mixture. This bait also nay be used against cutworms after tho plants are up, but to prevent serious burning, care should bo taken to see that no bait lodges in or against the plants. Por use when plants are present, it is safer and more economical to substitute cryolite for the sodium fluosilicato in the bait and to scatter tho bait at tho base of the plants at a rate of 10 to 15 pounds per acre por application. Sev- eral bait applications may prove necessary to rcdv.ee infestations satisfactorily. -5- Caution. — The poisoned "bait should "be scattered thinly. Spec- ial precautions should he taken to avoid leaving piles of "bait on the soil surface. Experience and careful ohservation have shown that if the poisoned bait is prepared and applied properly, its use will not present a hazard to domestic animals or wildlife. Cabbage Caterpillars, Corn Earworm, and Climbing Cutworms To prevent damage to young plants in the plant bed or in the field and to reduce the possibilities of damage during the heading period, which is especially important under present conditions of insecticide scarcity, either cryolite (natural or synthetic), calcium arscnato, paria green, or barium fluosilicato should be used at least every 10 days during the proheading period of plant growth if the caterpillars are present in damaging numbers — that is, an average of more than about one caterpillar per plant. Dusts. — Cryolite should be diluted to contain not loss than Uo percent of sodium fluoalumitiato, which usually moans that the undi- luted cryolite is mixed with approximately equal parts, by weight, of any of the diluents mentioned later. Barium fluosilicato should be used at about 75~Pcrcont strength, paris green at 10- to 15-percont strength, and calcium arscnato should bo used undiluted, or at 75~ porcont strength if the brand being usod causes plant injury whon used undiluted. Talc, pyrophyllitc, sulfur, or other nonalkalino ma- terials may be usod to dilute cryolite and barium fluosilicato. Hy- drated lime should be used with paris green and calcium arsenate, but not with cryolite or barium fluosilicato. Sgrays.—- Cryolite, barium fluosilicato, and calcium arsenate should be used at the rate of 2 to 3 pounds to 50 gallons of water (l ounce to 1 gallon), and paris green should bo used at the rate of one-half pound to 50 gallons of water (2 level teaspoonfuls to 1 gallon),- Two pounds of hydratcd lime should be used in each 50 gallons (2 level tablcspoonfuls of lime to 1 gallon) of the paris green spray, and be added to the calcium arsenate spray if the brand used causes plant burning. Supplementary poisoned bait. — If applications of these arsen- ical or fluorine compounds do not provide entirely adequate con- trol of the com earworm or climbing cutworms, a bait composed of 10 percent of cryolite and 90 percent of corn meal, by weight, mixed and used dry, should be sprinkled into the buds of the plants at the rate of about 25 pounds per aero just before the plants begin heading. Precautionary prehcading treatment. — To reduce the need for in- secticides during the heading period, it is suggested that a thorough application of one of the aforementioned arsenical or fluorine com- pounds be given cabbage plantings (except those that will head and be r -lj~ "because the supplies of these materials are United. The adoption of the practices given in these recommendations should give satis- factory control of caterpillars on cabbage during the preheading period of this crop. They should also give a satisfactory control of these pests during the heading period of the crop unless the diamondback moth caterpillars arc unusually abundant. In the latter event, the incorporation of nicotine in a'pyrothrum dust or spray, as detailed later in this circular, should reduco infestations of this species to a worth-while extent. In general, cabbage being grown in the extreme southern parts of the United Sta,tos (the southern portions of Florida and Texas) usually requires protection against caterpillars during all or the greater part of its growth. That grown in other parts of the South usually requires insect icidal treatment during all periods except the winter months. In certain parts of the last-mentioned areas, control measures may be necessary during mild winters (those during which weekly mean temperatures do not remain below about 60 P.) or may prove unnecessary during spring seasons following severo winters, It is recommended that control measures bo started as soon as the caterpillar population averages about one "worm" per plant or when approximately 25 percent of the plants in a field show signs of re- cent caterpillar feeding. In general, control measures are unneces- sary, when weekly mean temperatures fall below about 50° F. in the fall, and should be resumed in the spring when weokly mean tempera- tures are consistently above about 60°. . CONTROL DURING PLAiTT P REREAD BIG- PERIOD Soil- inhab i t ing cutwo rm s If cutvorms are present in the soil before the crop is planted, the" following poisoned bait should be broadcast on the soil surface late in the afternoon at the rate of about 25 pounds per acre: Wheat bran ---------- 25 pounds Sodium fluosilicato ----- l pound Water to moisten The bran and poison should be thoroughly mixed while dry and enough water added to dampen, but not wet, the mixture. This bait also nay be used against cutworms after the plants are up, but to prevent serious burning, care should be taken to see that no bait lodges -in or against the plants. Por use when plants arc present, it is safer and more economical to substitute cryolite for the sodium fluosilicato in the ba.it and to scatter the bait at the base of the plants at a rate of 10 to 15 pounds per acre per application. Sev- eral bait applications may prove necessary to reduce infestations satisfactorily. ~5- Caution. — The poisoned bait should he scattered thinly. Spec- ial precautions should he taken to avoid leaving piles of "bait on the soil surface. Experience and careful observation have shown that if the poisoned bait is prepared and applied properly, its use will not present a hazard to domestic animals or wildlife. Cabbage Caterpillars, Corn Earworm, and Climbing Cutworms To prevent damage to young plants in the plant bod or in the field and to reduce the possibilities of damage during the heading period, which is especially important under present conditions of insecticide scarcity, either cryolite (natural or synthetic), calcium arsonato, paris green, or barium fluosilicate should be used at least every 10 days during the prrheading period of plant growth if the caterpillars are present in damaging numbers — that is, an average of more than about one caterpillar per plant. Dusts, — Cryolite should be diluted to contain not less than Uo percent of sodium fTu.oalumir.ato, which usually moans that the undi- luted cryolite is mixed with approximately equal parts, by weight, of any of the diluents mentioned later. Barium fluosilicate should be used at aboixt 75~Pcrccnt strength, paris green at 10- to 15-porcont strength, and calcium arsenate should be used undiluted, or at 75" percent strength if the brand being usod causes plant injury when used undiluted. Talc, pyrophyllite, sulfur, or other nonalkalino ma- terials may be used to dilute cryolite and barium fluosilicate. Hy- drated lime should be used with paris green and calcium arsenate, but not with cryolite or barium fluosilicate. Sprays. ~- Cryolite, barium fluosilicate, and calcium arsenate should be used at the rate of 2 to 3 pounds to 50 gallons of water (l ounce to 1 gallon), and paris green should bo used at the rate of one-half pound to 50 gallons of water (2 level teaspoonfuls to 1 gallon),- Two pounds of hydratcd lime should be used in each 50 gallons (2 level table spoonfuls of lime to 1 gallon) of the paris grecr. spray, and be added to the calcium arsenate spray if the brand used causes plant burning. Supplementary poisoned bait. — If applications of these arsen- ical or fluorine compounds do not provide entirely adequate con- trol of the corn car worn or climbing cutworms, a bait composed of 10 percent of cryolite and 90 percent of corn meal, by weight, mixed and used dry, should be sprinkled into the buds of the plants at the rate of about 25 pounds per acre just before the plants begin heading. Precautionary prehoading treatment. — To reduce the need for in- secticides during the heading period, it is suggested that a thorough application of one of the aforementioned arsenical or fluorine com- pounds be given cabbage plantings (except those that will head and be r i -6 - harvested during relatively worm-free periods) just "before the plants "begin heading, even though caterpillars nay not "bo abundant at the time. This is particularly applicable to spring planting that nor- mally would not require insecticide protection during the preheading period. It is emphasized that treatments with a.rsenicals or fluorine compounds should not "be mado during the preheading period to looso- hoaded typos of cabbage intended for marketing with more than four loose outer loaves. Warning. — Calcium arsenate, paris green, cryolite, and barium fluo silicate arc poisonous and should be handled with care and stored whore children, careless persons, and domestic animals cannot roach them. Especial care should be taken in mixing or applying those in- secticides not to inhale excessive quantities. Well-designed respi- rators affording protection to the entire fa.ee should bo used when- ever available. Ifesh the hands or other exposed parts of the body thoroughly after working with these compounds. It is repeated that these materials should; not be applied to cabbage after that portion of the plant that i_s to, b_e marketed or consumed becomes exposed to view. This means that cabbage to be marketed with four "wrapper" leaves (those at least two-thirds loose from and surrounding the firm head) should not bo treated with these materials after the head begins to form (the bud loavos begin to "fold" or "cup over"), which usually occurs about ^0 to ^0 days before harvesting normally begins. The materials should never be us ed within ab out 2 weeks of harvest and all "wrapper" leaves should be stripped from the firm head if arsenical or fluorine compounds are used as a last resort in cases of severe infestations after cabbage begins to head. It probably will be found that this stripping of the loose leaves will not be a. profitable commercial practice in most areas in the South. Cab- bage to be marketed or consumed with more than four "wrapper" loaves should not receive arsenical or fluorine applications after the nor- mal time for thinning or transplanting. CONTROL DUS ETC PLA1TT-HEAD ETC PERIOD Por the control of the green-colored caterpillars on heading cabbage under present conditions, it is recommended that pyrethrun dusts or sprays bo used at least every 10 days throughout the period, if there is an average of more than one caterpillar per plant. Pyrethrun dusts. — Pyrethrun nay be used in the fern of finely- ground pyrethrun flowers in a dust or in a spray, or as extracts of theso flowers incorporated into dusts or used directly in sprays. When used at comparable pyrethrins content (the active ingredients of pyrethrun flowers), the so-called "impregnated" or "coated" forms of dust which contain oil have proved slightly more effective than L „7~ simple dust mixtures of ground pyre thrum and a diluent. For use against caterpillar populations consisting chiefly of the cabbpge looper, or the imnortod caDbagewom, or the diamondback moth, an "impregnated" or "coated" dust containing 0.2 percent of total py- rethrins or a pyre thrum powder dust (ground pyrethrum flowers) con- taining 0.3 percent of total pyrethrins is recommended. Tho "impregnated-" or "coated" pyrcthrum dusts containing 0.2 percent of total pyrethrins may usually "do purchased from dealers in a form which is ready to apply. If those materials contain more than C2 percent of total pyrethrins, however, they may bo diluted to that strength by nixing with such nonalkalino diluents as talc, pyrophyllite, sulfur, or tobacco dust. For example, if an "impreg- nated" or "coated" dust contains 2*0 percent of total pyrethrins when purchased from the dealer, it should be diluted at the rate of 1 pound of this manorial to 9 pounds of the diluent. Tho pyrcthrum powder dust (ground pyrcthrum flowers) may be purchased from dealers in a form which is ready to apply. If the powder dust contains more than 0.3 percent cf total pyrethrins, however, it may be diluted to that strength by mixing with the sane diluents mentioned previously. For example, if tho pyre thrum powder dust contains 0.5 percent of total pyrethrins it should be diluted at the rate of 1 pound of this mater- ial to 2 pounds of the diluent. Dust mixtures prepared from finely ground pyrcthrum flowers may bo improved by the addition of 2 percent by weight of a light miner- al oil (approximately SA1 10 specification) or by the addition of 1 percent cf thiocyanate (available in commercial preparations contain- ing approximately equal parts of an oil base). If either of these materials is added, the dust may be reduced to 0.2 percent of total pyrethrins content. The use of about 20 percent of sulfur (20 pounds of sulfur to 100 pounds of nixed dust) has been found to improve the effectiveness and stability of pyrcthrum dusts, Kaolin clays reduce the effectiveness of pyrcthrum dusts and should not be used as dilu- ents; especially under present conditions. F.y r c t h run sp r ay s . — Alcoholic or acetone extracts of pyrcthrum in water or pyrcthrum powders in suspension in water nay be used as sprays. The extracts should be diluted and used according to the manufacturer's directions. Sprays consisting of pyrcthrum powder and water should contain not less than O.COo percent of total pyrethrins. For example, a high grade, fresh powder (ground pyrcthrum flowers) containing about 0.9 percent of total pyrethrins should be used at the rate of 3 pounds to 50 gallons of water (l ounce to 1 gallon)-. It usually will bo found dosirable to add a nonalkalino spreading or sticking agent such as a mild soap, a miscible or sulfonated oil, or a proprietary compound, designed especially for this purpose. Cake soap may be used at the rate of about 2 pounds to 50 gallons of spray and the liquid materials, in general, at tho rate of 1 part to U00 r parts of spray. The use of spreading agents has the disadvantage of removing some or all of the wd&y ""bloom" from cabbage leaves, there- by affecting the appearance of the plan"4* and sometimes causing them to he more susceptible to damage hy low t'gmporaturoc. . Use of nicotine against diamondback moth.' — If caterpillars of the diamondback moth arc c^pecia.'. i.y numerous, or if the history of the Ideality or crop is such that a hea,Ty infos cati:>:; .of this spe- cies is expected-, it is suggested that nicotine he added to the py- rothrum dust or spray, Nicotine, cither the "free" or the "fixed" form, has been found to reduce infestations of diamondback moth caterpillars to a worth-while extent under prc^:>nt conditions, but is of little value in the ccntrcl of the other important species of cabbage ca^eroj liars. The free form of nicotine aire will be ef- fective against aphids, or plant i..ioo, ' that may be present. About 2 percent of nicotine should be added to a pyrethrum dust. Approx- imately C.-07 to 0.1 percent of nicotine (l part of nicotine sulfate to UOO parts of water, or 2 to 3 pounds of a iU-pcrccnt "fixed" nicotine powder to 50 gallons of vatcr) should be added to a py- rethrum spray,- The nicotine may be applied separate] y from the py- rethrum if desired, but should not be depended on entirely for cat- erpillar control. Ho lime should bo invc.LvGd in the amplication of nicotine if cryolite has recent!:- been used, or if either cryolite or pyrethrum arc to be used in the near future. Caution. — Some observations indicate that materials such as nicotine, chiocyanates, and oils, which cause increased toxicity of pyrethrum-containing dust nixturcs, may also have a deteriorating effect on such mixtures in prolonged storage. It is not advisable, therefore, to buy or to prepare a greater quantity of these dust mixtures than is likely to be needed in 19^3 » regardless of the availability of the materials. Use of other insecticides and hand picking. — Thus far no en- tirely satisfactory, readily available substitute for pyrethrum and rotcnonc in the control of cabbage caterpillars has been found. The search for now insecticides rand methods of Improving known ones is continuing, Phenothiasinc, a comparatively new compound, is sufficiently toxic to cabbage caterpillars to be of value in case pyrethrum is not available. This material may be used as a dust at not loss than 20-percent strength, diluted with talc, clay, pyrophyllitc, or other nonalkalino materials. For use as a spray, phenothiazinc should be used at the rate of 2 to 3 pounds per 50 gallons of water (l ounce to 1 gallon) with a spreading and sticking agent. If used regularly once a vrock, a relatively strong soap spray (l pound of a mild laundry soap to 5 gallons of water) will give •9- fairly satisfactory results, but should not "be used near or during b e 1 o w~ f r e e z ing t emp e ratur e s . For small plantings, especially home gardens, hand removal of cateroillars is of value. METHODS 0? US BIG- DUSTS AUD SPRA.YS Dusts. — For best results, insecticidal dusts should be applied when the air is calm, or nearly so, when the atmosphere is so heavy as to hold bho dust near the ground, and when the plants arc slightly moist with dew. The period after sunset and for several hours there- after usually is a favorable time of day for dusting,. Arsenical and fluorin." compounds also may be applied to advantage during the early morning, '/re thrum, however, is more effective generally when the plants a." ■ £ry or only slightly moist. Consequently, the early morning ..our? arc not a fa/orable time for applying this insecticide because the plants are likely to bo droii-cned with dew at that time. Dust should be applied at a rate ranging from 10 to 25 pounds per aero per application (about 2 ounces to ^0 feet of row), depending on the size of plants, the spacing of the rows, and the dilution of the insecticide. Spray s. — Spray s may be applied at any time of day, but the wind should act be so high as to interfere with thorough coverage and tender plants should not be sprayed with strong soap solutions while in direct sunlight during hot weather. Sprays should be used at a rate of ^0 to 100 gallons per acre per application (about 2 auarts to 50 feet of row). Dusting and spraying equipment should be adjusted so as to give thorough coverage of the plants, and such equipment should be kept in good mechanical condition, especially now that machinery is dif- ficult to replace. lifhen applying rusts -co dry plants during slightly windy weather, especially dusts containing nicotine, the use of a cloth aprcn or trailer that extends for 10 to 20 feet back of the dust machine usually will be of value. The use of cloth bags for applying dusts and of watering cans, or similar containers, for ap- plying sprays is not advised, as those methods usually result in relatively poor caterpillar control ar.d in waste of insecticides. Insecticide materials, especially those containing pyrethrum, which deteriorates relatively rapidly, should be used as soon as practicable after being mixed. -10- CULTURAL CONTROL MEASURES To reduce caterpillar damage and the need for insecticides, cabbage should be grown whenever possible during periods when cat- erpillars usually are least abundant; the crop should not be planted near caterpillar— infested older plantings; the rows should be of uniform width in order to permit most offoctivo adjustment of spray- ing and dusting equipment; tho plants should be uniformly spaced along the row to prevent crowding and consequent poor distribution of insecticides; tho heads should bo cut as soon as ready for market or home use; and crop remains should be plowed under or otherwise disposed of as soon as harvesting is completed,, Caterpillar- infested plant beds should bo poisoned with tho insecticides discussed earlier in this circular before the plants arc pulled, and an infested field planting should not be thinned before the described control measures are used. Plants with in- jured or destroyed buds should not be transplanted or be left in the row during thinning operations. Sufficient seed should bo used to insure a good plant stand with- out a waste of seed. Cabbage should bo given good cultural care, and fungicides and fertilizers should bo applied to keep the plants in a healthy condition. WHERE INSECTICIDES MAY BE OBTAINED Information regarding the purcha.se of the materials mentioned in this circular usually may be obtained from local dealers in ag- ricultural supplies, seedsmen, general stores, and drug stores, or through the county agricultural agent, State agricultural experiment station, State department of agriculture, or the Bureau of Entomology and Plant Quarantine, Agricultural Research Administration, United States Department of Agriculture. SUMMARY ..." Recommendations arc givon for^tho uso of available insecticides and other control measures for, the control of cabbage caterpillars under emergency' conditions-resulting from the war. Rotenone-contain- ing insecticides are not available for uso on cabbage. The only sat- "i^factory substitute for rotcnone insecticides for use on cabbage after the heads begin to form arc those containing tho active prin- ciples of pyrethrum. It is recommended that dust mixtures contain at least Q.2 percent of pyrethrins. If a simple mixture of ground pyrethrum flowers and an inert diluent is used, it should contain 0.3 percent of pyrethrins. -11- To a^oic" a harmfiil residue hazard the arsenical or fluorine compounds should not "be used on any part of the cartage plant that is to be marketed. Th.1s means that cabbage intended for marketing as U. S. Grade No. 1 (v:hich allows four loose outer leaves) should not bo poisoned with those materials after the heads begin to form or the leaves start "cupping," that is, when the leaves in the center of the plant cease to spread outward. This usvially occurs _"0 to !40 days before harvesting normally begins. During the prehoading period cf cabbage growth, dusts or sprays containing cryolite, calcium arsenate, paris green, or barium fluo- silieatn shor.Xd be used. If applications of these ei'cenicals or fluorine co-pounds do rot provide adequate control for the corn ear- worm or climbing cutworm, a poisoned "bait consisting of cryolite and corn me. J should be sprinkled into the buds of the plants just be- fore they bogin heading. Applications c^ insecticides should be made at 10-day inter- vals beginning, as soon* as there is approximately one "worm11 per plant or when approximately 2^ percent of the plants in a field shew signs of caterpillar feeding. Control of cabbage caterpillars can be aided by the destruc- tion of crop remnants as soon as harvesting is completed; by grow- ing cabbage whenever possible during periods when the caterpillars are lrr s abundant; and by planting new cabbage as far as possible from older caterpillar- infested cabbage. UNIVERSITY OF FLORIDA ■■lilt 111 11,1 3 1262 09224 6932