October 19^5 E-672 United States Department of Agriculture Agricultural Research Administration EXPERLVENTS VriTH DDT AGAINST INSECTS ATTACKING GUAYULE By V. E. Romney, T. P. Cassidy, and G. T. York, Division of Forest Insect Investigations Guayule ( Par then ium argentatigm Gray) is a shrub being grovm under field conditions as a war measure for its rubber content, and under greenhouse conditions for experimental purposes. A number of pests attack guayule under field and greenhouse conditions, such as Lygus ^ugs, red spiders, whiteflles, mealybugs, ♦:hrips, and aphids. This paper reports results from tests conducted at Salinas, Calif., during the period January 19^^ to February 19^5 to determine the effect of DDT ( l-trichloro-2, 2-b is (p-chlorophenyl) ethane) on these pests. Formulations The DDT was applied both as a dust and as a spray. Dusts were made by dissolving 1 part of DDT (technical) in 2^ parts of acetone and using this solution to impregnate pyrophyllite, the amount of carrier depending upon the percentage of DDT required in the duet. The pyrophyllite wetted with the DDT-acetone solution was spread over paper and allowed to dry for 2k hours and then ground in a ball mill for 2 to 3 hours. For sprays the DDT was used in the form of an amulsion. An . / emulsion concentrate was made up according to the following formula — ' (figures in parts by weight): DDT 15, acetone 30, methylcycloheianol 15, sulfonated vegetable oil 36, and ammonia 4. Addition of ammonia was later found to decrease stability of the concentrate and add nothing to toxicity. The acetone and methylcyclohexanol were Tfarmed together over a water bath, the DDT was dissolved in the warmed mixture, and then the sulfonated vegetable oil-ammo: lia mixture was added slowly with stirring. According to the manufactiirer, the vegetable oil contained 75 percent of sulfonated cantor oil. For use the concentrate was diluted, usually at the rate of 1 part to 50 parts of water to make a 0.3-percent DDT emulsion. In some tests a wetting agent was added to the water, and in others the amo^ant of DDT varied. 1/ This is a modification of a formula given in Soap and Sanlt. Chem. 19 (7): 103 (example 1). 191^3. 21 1945 Preliminary Cage Tests For preliminary tests with DDT dusts the cylindrical cas© illus- trated in figure 1 2/ was used. The cage was made of l6-me3h screen wire and measured 3? inches in diameter by 5^ Inches tail. The 'base was a pint ice-cream carton which had "been treated with hot paraffin to enable it to retain water. Nettleleaf goosefoot ( Chenopodium murale L.) was used as a food plant in most tests. The dusts were applied with a samll plunger- type hand duster, by giving two puffs on opposite aides of each cage. Excess dust was blown by mouth from the floor of the cage after each treatment. Moat of the tests with dusts were arranged as randomized blocks and replicated 10 times with 10 insects in each cage. The insects within the screen- wire cages were treated with DDT dusts in a frame building, then moved immediately into a screened insectary during January l^^h when maximum tempera- tures ranged from 65° to 75° F. and minimum temperatures from 35° to Results from cage tests using 5-percent DDT dust against adults of Ijrg us hesperu s Knight after 2h hours showed 90 percent dead, 8 per- cent do\m, and 2 percent normal, compared with 55 percent dead, 29 percent doxm, and l6 percent normal for the 2.5-percent HUJ} dust. After 43 hours the 2.5-percent DDT dust killed 9h percent and 6 percent were down, showing that this pleuit bug is highly susceptible to DHT. Tests conducted with the western spotted cucumber beetle (Dla- brotic a undecinrpunctata Mann. ) showed that this insect is more sus- ceptible than Lygus to the DDT dusts. The 2.5-percent dust Icilled 91 percent of the beetles after 2k hours, and after kQ hours all were dead, while none were dead in the checks. Similar tests replicated seven times showed adults of the false chinch bug ( Nysius erlcae var. minutus Uhler) to be highly susceptible to 5-percent DDT dust after 2h hours, while in two replications larvae of the diamondback moth ( Plutella maculipennls Curt.) were less sus- ceptible, although all larvae were either dead or down on the bottom of the cage after 2^4- hours. Aphlds were less susceptible to DDT than the Insects mentioned above, although kill was practically complete within 5 to 7 da^ after treatment. The effect of 5- percent DDT dust on the tuniip apiiid ( Rhopalosiphum paeudobrassicae (Ifevis)) illustrates the effect of DIG? on aphids. This species was found reproducing in the tips of B."a ssi ca 2/ Designed by the senior author and Orin A, Hills in 1939« -> sp. Infested tips were dusted with ^-percent DOT ar-d then enclocod jn cheesecloth. The ti-eatmcnts were replicated five times. A""ter 3 dcjs 65.1 percent of the aphlde were dead or down, after ? da^s 97.9 Po^- cent, and after 7 days 100 percent. In the checlcB from 1.3 to 6.3 percent were dead or down. Dui'ing the ejcperiment maximijin teiiricrabiu'eo avei-aged 65.^° F, and minlmuiu temperatures ifO.3*^. Similar reculta v-Lth respect to time required to kill and general susceptibility were obtained with the green peach aphid ( Myzue persicae (Sulz.)) and the pea aphid (M acrosiphum pisi KLtb , ) , Field Experiments for Control of Iprgus Bugs Two experiments for control of Lygua hesperua on guayule vere con- ducted under field conditions beginning in June. In experiment 1 DDT was applied as dusts and sprats, each in two concentrations, "wltli i; replications of each test. A 5 by 5 Latin-square arrangement ims used with plots \Q) feet square. Ttie dusts were applied with rotary liand dusters. The sprays were applied with equipment illustrated in figure 2, which consisted of a paint gun and an air- compressor (5), '^rf.th a gasoline motor for power. An air pressure of 6^-75 pounds per square inch was ms.intained. In the sprayed plots only 8 of the I6 ro^fs in a plot were treated, but the dusts were applied to the entire plots. Six days after treatment counts were made with a sampling cage (Hills 2). The results, given in table 1, show 98 percent kill or higher from all treatments. These large reductions in Lygus numbers, effected by single applications of DDT, caused highly significant increases in tlie via- bility of guayule seed over that produced in the untreated ched: plots. Tl-je seed was harvested from six tagged plants near the center of each treated plot. These results are in agreement with those obtained by Hills (3) on sugar-beet seed. - k - Table 1. --Effect of DDT on I^gus heopergg populations under field con- ditions and the effect on the viability of guajrule seed. Salinas, Calif., June l6 to July 20, ISM Concentration ; of WS : • Doeax^e of : mixture : per : acre : Mortality of ! adults and : nyuiphs j ! Average germination : of gu^ule ; seed 1/ Percent Pounds Percent Percent Dusts: 2.5 33.9 98.0 5 33.1 99.6 32.i^ Emulsions: Gallons 0.15 lk.6 98.8 33.7 .3 Ik. 6 99.6 29.8 Difference required for significance at 5-poJ^cent level 12,4 l/ Germination in untreated checks, l6,l percent. In experiment 2 about 3 acres composed of many small plots were sprayed with a 0,13^- percent DDT emulsion at the rate of 76.5 gallons per acre. The spray was applied with a 10- nozzle power sprayer at 100 pounds pressure. Counts were made k days after treatment. Eill of adults and nymphs averaged 95.8 percent, which corroborates results from otiier tests showing the effectiveness of DDT against I^gus bugs. Two plots of lim beans (65 by IQk feet) were treated with 5-per- cant WT dust with a rotary hand duster at the rate of kG pounds per acre on August 15. Counts made 2 weeks later with a sanrpling cage showed an average of 1,7 Lygus adults and no nymphs per foot of row in the treated plots, coaipared with 6.1 adults and 10.2 nymphs per foot in two untreated checks « There had apparently been some reinfestation by adults in the plots after treatment. No plant injury was noted. - 5 - Experiments for Control of Greenhouse Peete Red eplder e . --The problem of controlling mites and Insects on gua- jrule under greenhouse conditions has been of m^or concern. The shrub is a good host of the two-spotted mite ( Tetranychue bimaculatus Harvey), as identified bv E. A, McGregor. Control of the mite has been essential to the success of experimental work where plants remain in the greenhouse throughout a normal growing season or continuously for several years. Dusting sulfur has been recommended for red spider control, and it was used on guayule with fair success, but when it was applied to marlola ( Part hen lu m Incanum H.B.K.) or crosses of marlola with g-aayule under greenhouse conditions, it burned the leaves. Weigel (7) reported poor results against Tetranychus spp. in sever- al tests with DDT in aerosol form, spray suspensions, and dusts. How- ever, in most cases he measured the effects after kQ hours, which is too soon for maximum results wl^-h red spiders. Steiner (6) reported that red spiders became more numerous on apple trees sprayed with DDT suspensions, and that the killing of certain predators allowed an in- crease of Eioropean red mites ( para tetranychus piloeue (C. and F.)) after treatr^'^nt. Baker and Porter (1) also stat that at dosages used against the codling moth (Carpocapea pomonella 'L.)) the DDT did not control orchard mi tee. Tuose workers, amorig otners, have contributed to the general impression that DDT is not very toxic to red spiders and that it has little chance of being used in their control. Data presented in this paper, however, show that red spiders are more diffi- cult to control with DDT than are many forms, but that DDT is toxic to them and that control may be a matter of formulation and proper appli- cation. In tests for red spider control the DDT emulsions we^ . -pplled with a paint gun fig. 2) with air pressure set at hO to 50 pounds per square inch. Approximately the same amount of emulsion was applied for each treatment within an experiment, which was enough to wet the upper and lower leaf surfaces to the dripping point. The sprfcylng was done outside the greenhouse, and as plants for each treatment were sprayed they wert moved Into position on a bench in the greenhouse. Teats with em.ilelona were arranged as randomized blocks vrlth 3 to 8 replicates . Five experiments were conducted during the period I-larch 19kh to February 19^5 to determine the effect of DDT emulsions and other re- comjiiended chemicals against Tetranychi ^s bimacu latijis. The results, which are given in table 2, were determined by examining both surfaces of 10 to 15 leaves taken at random from each plant, with the aid of a binocular microscope. - 6 - Table 2. — Effect of DDT and other materials on Tetranychus blmaculatus applied as sprays under greenhouse conditions on guayule : Time : Total • • :Total :Kill between • mites :live mites :of Spray treatment ! treatment : and eggs : larger than: eggs and counts In leaf : first :and samples : ins tar : mites • • Days Number Number Percent Experiment 1, three replicates Checks, water, once 5 2,065 1,3^3 4.6 12 951 678 6.3 DDT smulsion, 0.3 percent : Once 5 1,51^+ 88.1 12 9^5 14 Twice 5 1,209 5 99.3 Tartar erne t Ic -glycerol : Once 5 1,7^*1 253 66.1 12 1,228 219 57.8 Twice 5 1,856 IU9 79.3 Experiment 2, eight replicates — ' Checks, water 6 22,606 8,lU9 1.4 DDT emulsion: 0.1 percent /■ 13,072 269 89.8 0.3 percent 6 1U,069 7 98.1 Experiment 3, seven replicates Checks, water /■ 1,633 630 7.7 DDT emulsion, 0.3 percent 6 1,1^39 1 96.4 Experiro.ent five replicates Checks, water 9.5 2,5^*5 791 1^.7 DDT emulsion, 0.3 percent : Eegular formula (in water) 9.5 1,106 21 89.2 In 0.01-percent Vat sol OT 9.5 1,023 11 91.6 In I-percent Triton B-1956 9.5 1,038 6 93.6 EN-111, 5 lb. per 100 gal. 9.5 2,657 97 55.5 Triton B-1956, 2 percent 9.5 2,303 46 81.6 1/ On mariola plants. Tab le 2 . - -(Continued) : Time : Total : Total • :ICill : between : ml ':es :live iiiitoa:of Spray treatnient ; : treatment rand : larger : and :eggs in :than firs t:and : countG '.leaf rinstar :initos : sanplea « • • • • • • Days Number Number Percent Experiment 5, six replicate-3 Checks, water containing acetone 0,6 percent and Vateol or 0.01 percent DET emulsion, 0.3 percent: Regular formula Less ammonia Less DDT Less methylcyclohexanol Less sulfonated vegetable oil Sulfonated vegetable oil in 0.01-percent Vatsol OT DDT 0,3 percent with acetone in 0.01-percent Vatsol OT 8 8 8 8 8 8 8 8,299 3,693 2,828 2,500 i^,659 2,527 5,^+33 h,2k0 3 6 2,013 8 1,-573 2,6k0 2,227 2.8 97.0 95.9 13.6 96.6 30.1 17.1 16.5 In the first experiment 9 guayule plants containing these mites were sprayed with 0.3-percent EDT emulsion. Results on 3 of those plants were recorded after 5 days, and on 3 others after 12 dajrs, while 5 plants were sprayed a second time on March 26 and the results recorded 5 dao's after the second treatment. The same arrangeiaent was made for plants sprayed with tartar emetic-glycerol, which was used at the rate of 20 grams of tartar emetic and 100 ml. of glycerol per gallon of water, as suggested by Weigel and Johnson (8). Daily mxi.nnaTn temperatures averaged 89° F. and ranged from 78.50 to 950; miniinmii temperatures averaged 66.90 and ranged from 6I0 to 76°. The higii kill of mites and eggs after one application of DDT emulsion indicates a - 8 - residual effect ooa the newly hatched mites. Two applicationfl almost eliminated the mite population. ^So0t of the live mites found on these plants were nevljr hatched, and some of them were abnormally sluggish. The tartar emetic-glycerol spray was not nearly so effective as the DDT* Both sprays showed some OTlcidal effect. Slight plant lnjui7 was caused by the tartar emetic , while none was noted on plants sprayed with DDI!. Experiment 2 shows very effective results with the 0,3-percent DDT emulsion as applied to mites on marlola plants cuid significantly less kill with the O.l-porcent emulsion. Experiment 3 corroborates the results of eiperltoente 1 and 2 with respect to the effectiveness of 0.3-percent DDT emulsion. Again the nuaiber of live mites larger than first instar was remEurlcably low. Experiment k was conducted to determine the comparative effective- ness of IW-lll (a dinitro-o-oyolohexylpnenol salt), Triton B-1956 (a phthallc glyceryl aklyd raaln), as suggested by Parker (k) , and DDT emulsions, both the regular formula atnd with the addition of a wetting agent. Infested guayule plants were sprayed with approxioately 100 aln of each naterlal used. Dally maximum temperatures averaged 82. F. azui ranged from 77° to 92°; minimum tens>erattares averaged 39 and ranged tram. to 62°. There was an obvious difference in results be- tween the ohsokB and the treatments. Statistical analysis showed the combined kill of mites and eggs sprayed with m-111 to be sigaif ioant- ly less than with the other treatments, owing to em apparent lack of ovlcldal effect. When based on kill of mites, however, there was no statistical difference in effectiveness of the various treatments. Experiment 5 was conducted from February 3 to 11, 19^5 > to evalu- ate the varloiis components of the DDT emulsion used to control red spiders in 19'^. One ingredient in this formula was deleted at a time and the remaining mixture was tested, nie checks were sprayed with water containing 0.6 percent of acetone and O.OI percent of Vatsol OT, since these ingredients were oomnon to all treatments in this experi- ment. The amount of material sprayed on the six plants in each treat- ment ranged from 370 to 391 ml. After treatment the plants were main- tained in a greenhouse section at 70^ to 80^ F. The data (experiment ^, table 2) show that the DDT is the principal toxic ingredient, and that neither aomonia nor jBSthyloyclohexanol appreciably increases th^ toxicity. The sulfonated vegetable oil appears to be very Important in combination with DDT, but alone it killed only a small percentage of eggs and mi tea. An eoulsion of DDT with acetone emd Vatsol OT alone is undesirable, since the DDT readily separates out upon dilution with water. - 9 - Some Information relative to the rate of kill In experiment 5 waa obtained by placing collars around each plant, as Illustrated in figure 3. Dead mites were collected from the collars kQ, 96, and ihk hours after treatment. Around the plants sprayed with the regular DDT fonmila Q5h dead mites were collected after kQ hours, 670 after 96 ho-urs, and 562 after ikk hours. During the first kQ- hour period more than three-fourths of the dead mites on the collars were larger than first inatars, but during the second period, this condition was reversed, and during' the third pei'iod 92.5 percent were newly hatched. Samples from six lots of technical DDT from the same company were used in preparing 0.3-p9rcent emulsions to determine whether or not the DDT in the various lots varied in toxicity to the two- spotted mite. Six guayule plants were sprayed vith each emulsion, Tlie regular formula was used with the addition of 0.01-percent Vatsol OT. Results from this experiment are given in table 3, Lot 6 was found to be significantly less toxic than the other five lots. These results were similar to those obtained in greenhouse control operations with the same lots of DDT when the wetting €igent was used with the regular formula. STATE PLANT BOAK - 10 - Table 3. --Toxicity of various lots of DDT to Tetranychus btoaculatus 8.5 days after spraying with 0,3-perceiit DDT emulsion : Average number per guayule leaf :K111 of Lot : Dead mites and : : collapsed eggs : Live : mites ♦ Viable :mites and lefZfZB 1/ Percent 1 26.1 .59 .63 95.5 2 23.6 .72 95.3 3 19.8 .65 .92 92.7 k 19.5 .22 96.8 5 17.0 .67 .56 93.3 6 13.1 1.12 .78 87.3 Diff 3rence required for sigoificance —' Plants sprayed with 0.6- per cent acetone and 0.01-percent Vatsol or were used as checks, and 3.5 percent of the mites and eggs were dead on the plants. Mealybugs , - - An erperlBsnt was begun on May 5 to determine the effectiveness of 0.3-percent DDT emulsion on the Mexican mealybug ( Phenacoccus gossyp ii T. and C), Five plants were sprayed with the DDT emulsion and five plants were sprayed with water as checks. Two treatments were replicated 5 times. Seven days after the plants were sprayed €lL1 mealybugs and egg masses were counted on the 10 plants in the experiment and on paper collars around the base of these plants. The survival after 7 days varied with the form of the in- sect. The Immature stages were effectively controlled. Females with- out egg masses averaged hQ.I percent alive, and those with egg masses 77.^ percent. Males in cocoons averaged 22.1 percent alive. About half of the egg masses were at least partly destroyed by the treat- ment. Since the population consisted largely of immature stages, an - 11 - average of 87,2 percent control was effected for all stages. Seven dajs after spraying there were on the 5 treated plants 27 females without egg masses, 62 females with egg masses, 267 nvales in cocoons, and 1,135 of the immature stages; of this total 1,301 were dead and 191 were alive. The residual effect of 0.3-percent DiDT emulsion on nymphs hatching from recently deposited egg masses of Phenacoccua gosaypli was tested by treatment of two plants on May 12. Seventeen days later mealybugs were counted on the treated and check plants and on the collars around the base of the plants. Most of the mealybugs had died soon after leaving the eggs, and only a few that had managed to get onto new growth had survived. The insect was found to be very susceptible to the residual effect of the "DDI when in the first two instars, although the majority were killed while still in the first instar. The later instars showed greater resistance. Apparently two applications properly timed would eliminate an infestation of this species of mealybug. Miscellaneous greenhouse pests . — Eighteen potted guoyule plants became infested under green house conditions with Aleyrodes spiraeoides Q. and Trialeurodes vaporariorum (Westw. ) (whitef lies ) , Myzus perslcae (aphid), Tetranychus bimaculatue (mite), Franlrl 1 n1 ella occidentalls trehemei Morg,, Thrlps tabaci Lind. (thrips), Eng oasca arlda DeL., (leafhopper), and spiders. Nine plants selected from the group at random were sprayed with 0.3-P©rcent DDT emulsion on May 23. They were then covered with fine-mesh cheesecloth cages (fig. 3) and placed on a greenhouse bench. The other 9 plants were sprayed with water, also encaged with cheesecloth, and placed on another bench. Fourteen days after treatment the cages were inspected by untying the tops and coimting all forms which could be found in them, except mites. The insects were counted as they were removed from the cages. All species were taken from the check cages in various degrees of abundance, but not a single live specimen was found in the cages on the sprayed plants. Seventeen days after treatment 10 leaves col- lected at random from each of these plants were examined for insects under a binocular microscope. One whitefly pupa, which appeared to be fidive, was found on the treated leaves and all other fonas on them were dead, while many live insects and mites were found on the leaves from the check plants. Control of Miscellaneous Pests with DDT The field cricket ( Gryllus asslmllis (F.)) was found to Infest greenhouses during the fall rainy season at Salinas. Infestations were often large, and controlled by dusting lightly with either 5- or 10-percent DDT in locations frequented by them. Crawling of the - 12 - crickets over the dusted surfaces was apparently lethal, A bait made vith 1 part by weight of 10-percent DDT dust and 10 parts of commer- cially sweetened bran was also found to be effective against crlclcets. The combined treatment of dusting and baiting proved very effective. Soil in ice-cream cartons dusted lightly with 5-percent DDT dust killed 72 percent of the sowbugs confined in them within k days and 9h percent within 7 days. Under field conditions dusting the soil with 5-percent DDT gave effective control of sowbugs after 10 days. Barracks Infested with the bedbug ( Clmez lectularius L, ) were sprayed with a 5-percent DDT-kerosene solution by use of the paint gun illustrated in figure 2, with air pressure set at 90 pounds* All cracks on the inside of the building f^rtA the wooden cots were sprayed. This treatment controlled the bedbugs. The windows, ceilings, and walls of rooms sprayed lightly with a 2, 5- percent DDT-kerosene solution were found to be lethal to housef lies ( Musca domestlca (L, ) ) and mosquitoes in the vicinity of Salinas for approximately 30 days, after which the effect dwindled until practically no effect was apparent after 60 days. Frame houses in the vicinity of Salinas became heavily infested on the outside with several species of webbing spiders. One test showed a 2.5-percent DDT-kerosene solution to be very effective against them when applied with a paint gun at 90 pounds air pressure, SummEiry Preliminary cage tests showed that adults of l ^yguB heopenis Knight, the western spotted cucumber beetle ( Dlabrotlca unde cliipunctata Mann, ) , and the false chinch bug ( Hyaius erlcae var, mlnutus ifliler), and larvae of the dlamondback moth" ( Piutella macul. pennls Curt, ) were highly susceptible to DDT dusts, Aphlds were suscoptible to DDT dusts, but maximum kill did not occur until 5 to 7 days after treat- ment. Those tested included the turnip aphid ( Rho]^aloBiphum pseudobras s 1 cae (Davis)), the green peach aphid (ht; J2us peroicae XSulz. ) ), and the pea aphid ( hiacrosiph um pi si ELtb. ), Field teste showed Ip^gus hes peino to be very susceptible to dusts and emulsions containing DDI', and since dusts are more con- venient to apply, they are recotnLiended for control of this Insect, Experiments conducted 'onder greenhouse conditions for conti'ol of the two- spotted mite ( Tetranychus blmaculatus Hat*vey) shared that a 0.3-percent DDT emulsion was effective. This spray caused no damage to guayule, mariola, or related plants even after repeated . 13 - applications. Other recommended materleds such as sulfur, tartar emetic-glycerol, DN-111 (a dlnitro-o-cyclohexylphenol salt) and Triton B-I956 (a phthalic glyceryl alljyd resin) were less effective. The susceptibility of the Mexican mealybug; ( Phenacoccus gossypii T, and C) to 0,3-percent DOT emu-lsion vas found to vary with the form. The Immature stages were effectively controlled after 7 de^e, and females with egg masses were the most resistant, A residual effect is indicated, since leaves sprajed with this emulsion killed most small forms soon after hatching. When guayule plants sprayed with 0,3-percent DKT emulsion were enclosed in cheesecloth cages, all insects, mites, and spiders were killed, DIT dusts were effective against crickets and sowbugs when applied to their habitats. Kerosene solutions ccaitalning from 2.5 to 5 P©i*- cent of DDT applied with a paint gun were very effective against bed- bugs, houseflies, mosquitoes, and spiders. Literature Cited (1) Baker, H,, and Porter, B. A, 19^5. Results of tests with DDT against fruit insects in 19^. U, S, Bur, Ent, and Plant Quar. ET-637, 9 pp, (Processed, ) (2) Hills, 0, A. 1933. A new method for collecting samples of insect populations. Jour. Econ. Ent. 26: 906-9IO, lllus. (3) 19^5. ffemorandum of information on Insecticides used against Iprgus bugs on sugar beets grown for seed, U. S, Bur, Ent. and Plant Quar, E-635, ^ pp. (Processed.) (U) Parker, R, L, 19^. Control of the common red spider, (Scientific note) Jour. Econ. Ent, 37: 292, (5) Smith, F. F., Lung, P. H., and Boswell, A, L, 19^. An air-pressure tank for use in the field application of liquid sprays. U. S. Bur. Ent. and Plant Quar. ET-218, k pp. (Processed,) - Ik - Steiner, L. F,, Arnold C« H,, and Sunmierland , S. A. 19kk, Laboratory and field tests of DDT for control of the codling moth. (Scientific note) Jour, Econ. Ent, 37: 156-157. Weigel, C. A. 19^U. DDT against some pests of vegetable crops. (Scientific note) Jour. Econ, Ent, 37: 150, and Johnson, G-, V, 19^0. Tartar emetic sprays against red spider, (Scientific note) Jour, Econ. Ent. 33: 579-530. - 15 Figure 1. — Cage used for insect- toxicity tests with DDT dusts. - 16 - Figure 2. — Equipnient used for spraying guayule with DDT emiolEion: Left, paint gun being used to spray guayule; right, compressor 77ith air hose attached. Figure 3« — Left, type of plant and collar used in experiments for control of red spiders and mealybugs on guayule; right, cage used to Confine whiteflies and other insects on guaynle after being sprayed with DDT emulsion.