October 1945 E-672
United States Department of Agriculture Agricultural Research Administration
EXMERLMENTS WITH DDT AGAINST INSECTS ATTACKING GUAYULE
By V. E. Romney, T. P. Cassidy, and G. T. York,
Division of Forest Insect Investigations
Guayule (Parthenium argentatum Gray) is a shrub being grown
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 Lytus bugs, red spiders, whiteflies, mealybugs, thrips, and aphids.
This paper reports results from tests conducted at Salinas, Calif.,
during the period January 1944 to February 1945 to determine the
effect of DDT (1-trchloro-2,2-bis(p-chlorophenyl)ethane) on these
The DDT was applied both as a dust and as a sp ay. Dusts were
made by dissolving I part of DDT (technical) in 2f parts of acetone
and using this solution to impregnate pyrophyllite, the amount of carrier depending upon the percentage of DDT required in the dust.
The pyrophyllite wetted with the DDT-acetone solution was spread
over paper and allowed to dry for 24 hours and then ground in a ball
mill for 2 to 3 hours.
For sprays the DDT was used in the form of an 3mulsion. An l/
emulsion concentrate was made up according to the following formula (figures in parts by weight): DDT 15, acetone 30, .methylcyclohexanol 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 warmed
together over a water bath, the DDT was dissolved 1:i the warmed
mixture, and then the sulfonated vegetable oil-ammo:ila mixture was
added slowly with stirring. According to the manufacturer, the
vegetable oil contained 75 percent of sulfonated ca;3tor oil. For use the concentrate was diluted, usually at the rate of I 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 amount of DaYT varied.
I/ This is a modification of a formula given in Soap and Sanit.
Chem. 19 (7): 103 (example 1). 1943.
Nov 2 1
Preliminary Cage Tests
For preliminary tests with DDT dusts the cylindrical cage illustrated in figure 1 2/ was used. The cage was made of 16-mesh screen wire and measured 33 inches in diameter by 5yy- inches tall. The base was a pint ice-cream carton which had been treated with hot paraffin to enable it to retain water. Nettleleaf goosefoot (Chenopodium morale 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 sides of each cage. Excess dust was blown by mouth from the floor of the cage after each treatment. Most 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 IT dusts in a frame building, then moved immediately
into a screened insectary during January 1944 when maximum temperatures ranged from 650to 750 F. and minimum temperatures from 350 to 410,
Results from cage tests using 5-percent DDT dust against adults
of Lygus hesperus Knight after 24 hours showed 90 percent dead, 8 percent down, and 2 percent normal, compared with 5 percent dead, 29 percent down, and 16 percent normal for 1 he 2.3-percent DDM_ dust. After 43 hours the 2.5-percent DDT dust killed 94 percent and 6 percent were down, showing that this plant bug is highly susceptible to DDT.
Tests conducted with the western spotted cucumber beetle (Diabrotica undecimpunctata Mann.) showed that this insect is more susceptible than L to the DDT dusts. The 2.5-percent dust killed 91
percent of the beetles after 24 hours, and after 43 hours all were dead, while none were dead in the checks.
Similar tests replicated seven times showed adults of the false
chinch bug (Nysius ericae var. minutus Uhler) to be highly susceptible to 5-percent M ust a-ter 24 hours, while in two replications larvae of the diamondback moth (Plutella maculipennis Curt.) were less susceptible, although all larvae were either dead or down on thie bottom of
the cage after 24 hours.
Aphids were less susceptible to DDT than the insects mentioned
above, although kill was practically complete within 5 to 7 days after treatment. The effect of 5-percent DDT dust on the turnip aphid (Rhopalosiphum pseudobrassicae (Davis)) illustrates the effect of DDT on aphids. This species was found reproducing in the tips of Brassica
2/ Designed by the senior author and Orin A. Hills in 1939.
sp. Infested tips were dusted with 5-percent DDT and then enclosed :Ln cheesecloth. The treatments were replicated five times. After 3 days 65.1 percent of the aphids were dead or down, after 5 days 97.9 porcent, and after 7 days 100 percent. In the checks from 1.3 to (.3 percent were dead or down. Aring the experiment maximum torporat oe averaged 65.40 F. and minimum temperatures 40.30. Similar ocu.tI ::.th respect to time required to kill and general susceptibility were obtained with the green peach aphid (_Mgs persicae (Sulz.)) and the pea aphid (Macrosiphum pisi Kltb.).
Field Experiments for Control of Lygus Bugs
Two experiments for control of Lygus hesperus on guayule were ccnducted under field conditions beginning in June. In experiment 1 DDT was applied as dusts and sprays, each in two concentrations, with replications of each test. A 5 by 5 Latin-square arrangement was used with plots 40 feet square. The dusts were applied with rotaryj hand dusters. The sprays were applied with equipment illustrated in figure 2, which consisted of a paint gun and an air compressor (5), wi~h a gasoline motor for power. An air pressure of 65-75 pounds per square inch was maintained. In the sprayed plots only 8 of the 16 rows in a plot were treated, but the dusts were applied to the entiro plots. Six days after treatment counts were made with a sampling cage (ills 2). The results, given in table 1, show 93 percent kill or highher fr"-om all treatments. These large reductions in Lygus numbers, ffected by single applications of DDT, caused highly significant incroases in the viability of guayule seed over that produced in the untreated check plots. The 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.
Table l.--Effect of DDT on Lygus hesperus populations under field conditions and the effect on the viability of guayule seed. Salinas,
Calif., June 16 to July 20, 1944
Concentration : Dozage of : Mortality of : Average of DT : mixture : adults and : germination
per : nymphs : of guayule
: acre : : seed 1/
Percent Pounds Percent Percent
2.5 33.9 98.0 34.4
5 33.1 99.6 32.4
0.15 74.6 98.8 33.7
.3 74.6 99.6 29.8
Difference required for
significance at 5-percent level................. 12.4
1/ Germination in untreated checks, 16.1 percent.
In experiment 2 about 3 acres composed of many small plots were sprayed with a 0.134-percent DoT 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 4 days after treatment. Kill of adults and nymphs averaged 95.8 percent, which corroborates results from other tests showing the effectiveness of DIDT against Lygusw bugs.
Two plots cf ims beans (65 by 104 feet) were treated with 5-perenat DDT dvust with a rotary hand duster at the rate of 40 pounds per acre on August 15. Counts made 2 weeks later with a sampling cage showed an average of 1.7 I adults and no nymphs per foot of row in the treated plots, compared 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.
Experiments for Control of Greenhouse Pests
Red spiders.--The problem of controlling mites and insects on guayule under greenhouse conditions has been of major concern. The shrub is a good host of the two-spotted mite (Tetranychus bimnaculatue Harvey), as identified by 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 mariola (Parthenlum incanum H.B.K.) or crosses of marilola with guayule under greenhouse conditions, it burned the leaves.
Weigel (7) reported poor results against Tetranychus spp. in several tests with DDT in aerosol form, spray suspensions, and dusts. However, in most cases he measured the effects after 48 hours, which is too soon for maximum results wilh 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 increase of European red mites (Paratetranychus pilosus (C. and F.)) after treatment. Baker and Porter (1) also state that at dosages used against the codling moth (Carpocapsa pomonella (L.)) the DDT did not control orchard mites. Tuvse workers, among 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 difficult 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 application.
In tests for red spider control the DDT emulsions we.- -pplied
with a paint gun 'fig. 2) with air pressure set at 40 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 spreaylng wts done outside the greenhouse, and as plants for each treatment were sprayed they wer moved into position on a bench in the greenhouse. Tests with emulsions were arranged as randomized blocks with 3 to 8 replicates.
Five experiments were conducted during the period March 1944 to February 1945 to determine the effect of DDT emulsions and other recomaended chemicals against Tetranychus bima-ulatus. 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 b inocular microscope.
Table 2.--Effect of DDT and other materials on Tetranychus bimaculatus
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 :instar :mites
P Number Number Percent
Experiment 1, three replicates
Checks, water, once 5 2,065 1,343 4.6
12 951 678 6.3
DDT emulsion, 0.3 percent: *
Once 5 1,514 6 88.1
12 945 14 92.7
Twice 5 1,209 5 99.3
Once 5 1,741 253 66.1
12 1,228 219 57.8
Twice 5 1,856 149 79.3
Experiment 2, eight replicates
Checks, water 6 22,606 8,149 1.4
0.1 percent 6 13,072 269 89.8
0.3 percent 6 14,069 7 98.1
Experiment 3, seven replicates
Checks, water 6 1,633 630 7.7
DDT emulsion, 0.3 percent 6 1,439 1 96.4
Experiment 4, five replicates
Checks, water 9.5 2,545 791 4.7
DDT emulsion, 0.3 percent:
Regular formula (in water) 9.5 1,106 21 89.2
In 0.01-percent Vatsol OT 9.5 1,023 11 91.6
In 1-percent Triton B-1956 9.5 1,038 6 93.6
DN-111, f lb. per 100 gal. 9.5 2,657 97 55.5
Triton B-1956, 2 percent 9.5 2,303 46 81.8
1/ On mariola plants.
Table 2. -4Continued)
: Time :Total :Total :1,il.
: between 1l es :liv e m ton:of Spray treatment : treatmnt :2 :larger : 0
: and aes in :than fi rot:and
: counts : ief :inota :mites
: :darples.: :
Days Number Number Percc't
Experiment 5, ex reply ct
Checks, water containing
acetone 0.6 percent and
Vatsol OT 0.01 percent 8 81299 3,693 2.3
DDT emulsion, 0.3 percent:
Regular formula 8 21, 828 3 97.0
Less ammonia 8 2,500 6 95.9
Less DDT 8 4 659 2,013 13.6
Less methylcyclohexanol 8 2,527 8 96.6
Less sulfonated vegetable 8 4,103 1,573 30.1
Sulfonated vegetable oil in
0.01-percent Vatsol OT 8 5,433 2,040 17.1
DIT 0.3 percent with acetone in
0.01-percent Vatsol OT 8 4,240 2,227 16.5
In the first experiment 9 guayule plants containing these mites were sprayed with 0.3-percent DDT emulsion. Results on 3 of those plants were recorded after 5 days, and on 3 others after 12 days, while 3 plants were sprayed a second time on March 26 and the results recorded 5 days after the second treatment. The same arrangement 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 maximum temperatures averaged 890 F. and ranged from 78.50 to 950; minimum temperatures averaged 66.90 and ranged from 610 to 760. The high kill of mites and eggs after one application of DDT emulsion indicates a
residual effect o~a~en ~ce ita Toapplications almost
eliminated the c. it .oi i Aesfudn
thes ~ Izit~wer nev~ hi ~o~<1,&~ a ot'~ho wre abnormally
sluggish. The tatreei orlerj~~t arlY" so effective
as the DM. Both as biecs .v idl slight plant
i~nJUry a caused by t tra eti,, vwil cI~i inoe on plant
sprayed with DDT.noe p t
Experiment 2 shoiw -ei defective resoitpe thhe O. -rent
DDTI emulsion as applied to ite on xiaricla 7;C~t ands ic tl less kill with the0.-prcn e~malsion. peaett3 o~obrates
the results off experts and 2 with reespect t.,th effecti-veness of 0,3-percent DIX iiWin Again the nui~oer off _,a, mtes a ,L-ger
than first instar was rer~ 1 cfw,
Experiment l4 was oor4iu:ted to determine teQ~r1Iee~cie
nes of IN-111 (a dinitro--oyolohexylpnenjo'k sa't) -'Iton B-1956 (st pbhthalic 8lyvcery;L aklvd r4;7tr,), 483gete yPx~e I) andDY
emulsions, both tiae regularii rornnP-ila an,-A wit t &1!tio !cff &: t agent. Inf oted guayvt 1-2ii,, were 131ra3yed wit ,roit1-D i,
of each material uzed, 1)I L y inaiiU& t (;ratup&X Stae 82. 1?.
and ranged from 770 t9';MiniMUM tbe~r ra emd.5,5 n
ranged from 580 to 6~Teewas ani obvious tfie nei ~ut
tween the checks and tn r -AsOttstc~aaysssoe thecombined kill of mites and eggs sprayed with I-11l to be Gignifioantly l0ss than with the other treatments, Owing to an apparent lack of ovicidal effect. When based on kill of mites, however, there was no statistical difference in effectiveness of the various treatments,
Experiment 5 was conducted f'rom February 3 to 11, 1 945, to evaluate the various components of the DDT emulsion used to control red spiders in 1944. One ingredient in this formula was deleted at a time and the remaining mixture was tested, The ohecks were sprayed with water containing 0.6 percent of acetone and 0.01 percent of Vateol OT, since these ingredients were Oommon to all treatments in this experiMent. The awniint of material sprayed on the six plants in each treatment ranged from 370 to 391 ml. After treatment the plants were idntained in a greenhouse section at 700 to 800O F. The data (experiment 5, table 2) show that the DDTY is the principal toxic ingredient, and that neither aMMOnia nor -methylayolohexanol appreciably increases thL, toxicity. The sulfonated vegetable oil appears to be very inprtant in combination with MT. but alone it killed only a small percentage of eggs and miteoi. An emulsion of DDT with acetones and Vatsol OT alone is undesirable, since the MrY readily eartsout upon dilution with water.
Some information relative to the rate of kill in experiment 5 was obtained by placing collars around each plant, as illustrated in figure 3. Dead mites were collected from the collars 43, 96, and 144 hours after treatment. Around the plants sprayed with the regular DDr formula 884 dead mites were collected after 48 hours, 670 after 96 hours, and 562 after 144 hours. During the first 48hour period more than three-fourths of the dead mites on the coUars were larger than first in3tars, but during the second period this condition was reversed, and during the third period 92.5 percent were newly hatched.
Samples from six lots of technical DIr from the same compcriy were used in preparing 0.3-percent emulsions to determine whetIh); or not the DIYT in the various lots varied in toxicity to the twospotted mite. Six guayule plants were sprayed vith each emulsion, The 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 agent was user with the regular formula.
STAki-h PLANT BOARU
Table 3.--Toxicity of various lots of DDT to Tetranychus bimaculatus
8.5 days after spraying with 0.3-percent I= emulsion
: Average number per guayule leaf ::Kill of
Lot : Dead mites and : Live : Viable :mites and
: collapsed eggs : mites : eggs :eggs
1 26.1 .59 .63 95.5
2 23.6 .45 .72 95.3
3 19.8 .65 .92 92.7
4 19.5 .22 .43 96.8
5 17.0 .67 .56 93.3
6 13.1 1.12 .78 87.3
Difference required for significance
1/ Plants sprayed with 0.6-percent acetone and 0.01-percent
Vatsol OT were used as checks, and 3.5 percent of the mites and eggs were dead on the plants.
Mealybugs --An experiment was begun on May 5 to determine the effectiveness of 0.3-percent DDT emulsion on the Mexican mealybug (Phenacoccus gossypii 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 wee sprayed all 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 insect. The immature stages were effectively controlled. Females without egg masses averaged 48.1 percent alive, and those with egg masses 77.4 percent. Males in cocoons averaged 22.1 percent alive. About half of the egg masses were at least partly destroyed by the treatment. Since the population consisted largely of immature stages, an
average of 87.2 percent control was effected for all stages. Seven days after spraying there were on the 5 treated plants 27 females without egg masses, 62 females with egg masses, 267 males 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 DDT emulsion on nynphs
hatching from recently deposited egg masses of Phenacoccus gossypii was tested by treatment of two plants on May 12. Seventeen daWs 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 DDT 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 guaulje plants
became infested under green house conditions with Aleyrodes spiraeoides Q. and Trialeurodes vaporariorum (Westw.) (whiteflies), Myzus persicae (aphid), Tetragchus bimaculatus (mite), Frankliniella occidontalis trehernei Morg., Thrips tabaci Lind. (thr-ips), E asca arida DeL, (leafhoper), and spiders. Nine plants selected from the group at random were sprayed with 0.3-percent 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 engaged with cheesecloth, and placed on another bench.
Fourteen dL ft er treatment the cages were inspected by untying the tops and couantit all forws 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 founi in the cages on the sprayed pln t; Seventeen days after treatment 10 leaves collected at random fwm each of these plants were examined for insects under a bioculr iroscope. One whitefly pupa, which appeared to be alive, was found on the treated leaves and all 3ther forms on them were dead, while any live insects and mites were found on the leaves from the check plats.
Control of Miscellaneous Pests with DDTI
The field cricket (Gryllus assimilis (F.)) was found to infest greenhouses during the fall rainy season at Salinas. Infestations were often large, and controlled by dusting lightly with either 5or 10-percent DDT in locations frequented by them. Crawling of the
crickets over the dusted surfaces was apparently lethal. A bait made with 1 part by weight of 10-percent DDT dust and 10 parts of commercially sweetened bran was also found to be effective against crickets. 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 4 days and 94 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 (Cimex lectularius L.) were sprayed with a 5-percent DDT-kerosene solution-y -ueof the paint gun illustrated in figure 2, with air pressure set at 90 pounds. All cracks on the inside of the building and the wooden cots were sprayed. This treatment controlled the bedbugs.
The windows, ceilings, and walls of rooms sprayed lightly with a 2.5-percent DYDT-kerosene solution were found to be lethal to houseflies (Musca domestica (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.
Preliminary cage tests showed that adults of L4 hesperus
Knight, the western spotted cucumber beetle (Diabrotica undecipunctata Mann.), and the false chinch bug (Nysius ericae var. minutus h1 Ie), and larvae of the diamondback moth (Plutella macul:.pennis Curt.) were highly susceptible to DDT dusts. Aphids were susceptible to IDDT dusts, but maxiLmm kill did not occur until 5 to 7 days after treatment. Those teted included the turnip aphid (Rhopalosiphum peudobrassicae (Davis)), the green peach aphia (zus ercae
(Su.) T-and The pa aphid (Macrosiphum pisi Klatb)7
Field teste iovt'd Lygue hosperue to be very fuacoptible to dusts and emulsions containing DI, and since dust aret more convenient to apply, they are recommended for control of this insect.
Experiments conducted under greenhouse conditions for control
of the two-spotted mite (Tetranychus bimaculatus Harvey) showed that a 0.3-percent DDT emulsion was effective. This spray caused no damage to guayule, mariola, or related plants even after repeated
applications. Other recommended materials such as sulfur, tartar
emetic-glycerol, DN-111 (a dinitro-o-cyclohexylphenol salt) and
V Triton B-1956 (a phthalic glyceryl ak~yd resin) were less effective.
The susceptibility of the Mexican mealybug (Phenacoccus 'gossypii
T. and C.) to 0.3-percent DDT emiulsion was found to vary with the
form. The immature stages were effectively controlled after 7 dF.as,
and females with egg masses were the most resistant. A residual
effect is indicated, since leaves sprayed with this emulsion killed
most small forms soon after hatching.
When guayule plants sprayed with 0.3-percent DDT emulsion were
enclosed in cheesecloth cages, all insects, mites, and spiders were
DDT dusts were effective against crickets and sowbugs when applied
to their habitats. Kerosene solutions containing from 2.5 to 5 percent of DDT applied with a paint gun were very effective against bedbugs, houseflies, mosquitoes, and spiders.
(1) Baker, H., and Porter, B. A.
1945. Results of tests with DDT against fruit insects in 1944. U. S. Bur. Ent. and Plant Quar. ET-637, 9 PP. (Processed.)
(2) Hills, O. A.
1933. A new method for collecting samples of insect populations.
Jour. Econ. Ent. 26: 906-910, illus.
1945. Memorandum of information on insecticides used against Lygus bugs on sugar beets grown for seed. U. S. Bur. Ent. and Plant Quar. E-635, 4 pp. (Processed.)
(1) Parker, R. L.
1944. Control of the common red spider. (Scientific note) Jour. Econ. Ent. 37: 292.
(5) Smith F. F., Lung, P. H., and Boswell, A. L.
19d44. An air-pressure tank for use in the field application of liquid sprays. U. S. Bur. Ent. and Plant Quar. ET-218, 4 pp. (Processed.)
(6) Steiner, L. F., Arnold C. H., and Sunmerland, S. A.
1944. Laboratory and field tests of DDT for control of the
codling moth. (Scientific note) Jour. Econ. Ent.
(7) Weigel, C. A.
1944. DYT against some pests of vegetable crops. (Scientific
note) Jour. Econ. Ent. 37: 150.
(8) -------------- and Johnson, G. V.
1940. Tartar emetic sprays against red spider. (Scientific
note) Jour. Econ. Ent. 33: 579-580.
Figure l.--Cage used for insect-toxicity
tests with DDT dusts.
UNIVERSITY OF FLORIDA
I Itll fl Ill Ul II 1t I II IItl
3 1262 09238 7355
Figure 2.--Equipment used for spraying guayule with DDT emulsion:
Left, paint gun being used to spray guayule; right, compressor
with 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 guayule after
being sprayed with DDT emulsion.