LIBRARY STATE PLANT BOARD 7 May 194* ' E-722 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine NEW INSECTICIDES IN GRASSHOPPER CONTROL Compiled by E. J. Hinman and F. T. Cowan, 1/ Division of Cereal and Forage Insect Investigations For many years grasshopper control in alfalfa by the use of poisoned bait has been unsatisfactory. Complete kills have sel- dom been obtained, and persistent baiting has been necessary in order to reduce infestations sufficiently to guarantee the harvest of at least a partial crop of hay or seed from infested fields. Light infestations in alfalfa being grown for seed often cause serious reductions in yield. Before the last war alfalfa-seed production, especially in Montana and Wyoming, was carried on as a secondary phase in the production of livestock. The common practice was for the stockman to cut the first crop in June and leave the second crop for seed. If the seed did not set within a reasonable time because of grasshoppers or other insects or ad- verse weather, the crop was cut for hay or pastured. In any case it was seldom a total loss, and if a seed crop did set the rancher was well repaid for his efforts. During the war years the shortage of both alfalfa hay and seed became acute. This shortage was immediately reflected in the price of these two commodities. The average price in the United States for loose alfalfa hay for the period 1935-1940 was $9.34 per ton. The average for 1941-1944 was $15.08. Baled hay on the Los Angeles market brought an average price of $15.97 for the period 1935-1940 and $28.02 per ton for 1941-1944. Alfalfa seed sold at an average price in the United States of $9.46 a bushel for the period 1932-1940 and $17.09 a bushel for 1941-1944. Thus over the war years both the hay and seed approximately doubled in market value. In addition to the normal increase in price of al- falfa seed, approximately $4.00 per bushel was paid to the grower in government subsidies. This made a total of &21.09 a bushel, or more than twice the average price for the years preceding the war. 1/F. E. Skoog, Lee Seaton, J. R. Parker, 0. L. Barnes, and C. C. Wilson, all of this Bureau, assisted in conducting these tests. MAY 1 6 1947 - 2 - Stimulated by the increased return to be expected from alfalfa seed, many of the livestock men that had been growing the crop as a side line expanded their efforts to oroduce more seed. In Montana the acreage devoted to seed production during the war was 50 percent higher than it was prior to 1941. More attention was directed toward insect control in general and, in these western States particularly, toward better grasshopper control. These developments emphasized the need of increasing the efficiency of the poisoned bait or of finding a more effective method of control. The demand for more efficient control methods has continued to grow as the price of alfalfa seed and hay has increased and as the growers have realized the difficulty of obtaining complete control by baiting. It has been further stimu- lated by an increase in grasshopper populations in many, of the alfalfa- growing areas. Intensive efforts to meet this demand by improving baits and bait- ing methods have shown some favorable results and are being continued. The effectiveness of various new insecticides when applied directly to alfalfa in the form of dusts and sprays is also being determined. Favorable results have been obtained with some of these insecticides, and the purpose of this paper is to summarize the results of the ex- tensive tests made of them during 1946. Tests of various sprays and dusts were started at the Bozeman, Mont., laboratory in 1945 and continued in Arizona, South Dakota, vVyoming, and Montana in 1946. Further tests were conducted in Arizona by 0. l. Barnes of the Tempe station and in California by C. C. /ilson of the Sacramento station. Their results are included in this report. Most of the chemicals used in these tests were furnished by the Divi- sion of Grasshopper Control at Denver, Colo. The turbine sprayer- duster, dusting and spraying airplanes, and airplane hire were also furnished by that Division. EQUIPMENT AND METHODS USED AND CONDITIONS OF TESTS Laboratory Tests In the laboratory all dusting and spraying were done in an open- top sheet-metal drum 13 1/2 inches in diameter by 12 inches aeep. This drum was mounted on a turntable and revolved at 90 revolutions per minute during spraying or dusting operations. The inside was lined with wrapping paper, which was replaced after each application of in- secticide. All sprays were atomized into the chamber from a (Devilbiss) hand-atomizer nozzle mounted over the spray chamber. The spray was directed downward toward a point midway between the center and the edge of the drum. Spray dosages corresponding to the desired rate per acre were measured to an accuracy within 0.05 cc . At the lowest dosage at- tempted, corresponding to 2 gallons per acre, this measurement was accurate to within 13 percent. - 3 - All dusts ;vere applied with an improvised duster designed to handle the small amounts of materials used in these tests. Weighed amounts of dust corresponding to the desired rate per acre were used, and although the accuracy was probably not so high as in the spray tests it was believed to be adequate. Compressed air for both dusting and spraying was supplied by a small motor-driven diaphragm pump connected to the atomizer nozzle or duster through a pressure regulator. A pressure gage was located on the low-pressure side of the regulator. With this apparatus a constant air pressure up to 20 pounds could be maintained or dupli- cated in any series of tests. Soybean plants 3 to 6 inches high in 4-inch flower pots -were used as the test plants. The grassnoppers used were nostly late instars or adults of Melanoplus differentialis (Thos.) which had been reared in the laboratory. In most of the tests both the grasshoppers and the potted soybean plants were treated simultaneously. The grasshoppers were placed in the chamber along with the soybean plants just before the spray or dust was applied and removed as quickly as possiole after treatment. On removal from the chamber the grasshoppers were caged over treated or untreated plants in screened-top lantern chimneys for observation of mortality and other reactions. Fifteen grasshoppers were placed in each cage, and each phase ot" the treatment was dupli- cated so that 30 grasshoppers were used in each test. Field Tests Early-season field tests with various new insecticides were started by members of the Bozeman laboratory in the Salt River Valley in Arizona on .April 16, 1946, and carried through to May 13. Most of tnese tests were conducted in heavy stands of alfalfa and were de- signed to determine minimum effective dosages. Further tests were made in South Dakota on roadside infestations and in YJyoming and Montana on seed alfalfa. The spraying and dusting testj conducted by 3arnes in Arizona were mostly in alfalfa seed crops. ".Vilson's work in California was done, for the most part, in 10-foot strips of al- falfa left uncut in the fields, although some of his tests were made in mountain meadows consisting mainly of native grasses. Melanoplus mexi canus (Sauss.) was the most abundant species en- countered in the early-season tests in Arizona. At first all the hoppers were in the early instars, but before the tests were finished M. mexi canus was in the adult stage and some local migration was tak- ing place. Nymphs of M. differentialis were dominant in the roadside tests in South Dakota, and nymphs of M. differentialis and M. femur- rubrum (Deg. ) in the alfalfa-seed fields in Wyoming and Montana. - u - Kymphs and adults of ;;elanoplus differentialis and second-genera- tion nymphs of M. mexicanus were prevalent in the Arizona tests by Barnes. The do,Ti.nant species in California were K. devastator Scudd. and Camnala oellucida Scudd. In the early-season tests in Arizona applications of sprays and dusts from the ground we. e made with a power-driven, turbine-blower sprayer-duster. This machine delivered 8 gallons of spray per acre in 2-rod strips at a ground speed of 5 miles per hour. The same machine was used in the South Dakota and Wyoming tests. One-acre plots were used in all the tests employing ground equipment, a small rotary hand duster was used to apply dusts to l/10-acre plots in pre- liminary tests conducted by the staff of the Tempe, Ariz., station. Later the plot size was increased to 1/4 or 1/2 acre and the dust was applied with a multiple-nozzle newer duster. *11 dusts used in California were applied with a small multiple-nozzle power duster, and sprays were appLied with a single-nozzle, orchard-type power sprayer. In the first tests with airplane sprays in Arizona aoplications were made v.ith a 3ureau-owned ""hite Standard biplane equipped with a spinner-disk spray device, and in the later tests they were made with a privately owned N-3-N plane equipped with ordinary disk-type nozzles evenly spaced along a 30-foot boom. All airplane dust applications in Arizona were made with standard commercial equipment. All emulsion sprays were prepared by dissolving the insecticide in xylene, except in the later tests with technical chlordane for which No. I petroleum distillate was used as the solvent. *n oil-soluble emul- sifier (Igepal CA) £/ was added to this concentrate at the rate of 100 ml. I approximately 3.4 fl. oz.) per gallon. The concentrate was then diluted with water to the desired strength for spraying. All suspension sprays were maae from wettable powders. All dusts were factory-nixed. The results of all tests conducted by members of the Bozeman laboratory were evaluated by sweeping with an insect net on the treated and on an adjacent untreated plot before and after treat- ment. The ratio of the average number of grasshoppers per sweep on the treated plot to the number per sweep on the check plot would be expected to remain constant except for the effect of the treatment. The percentage kill was determined by dividing the reduction in this ratio by the ratio obtained before treatment and multiplying by 100. This method of evaluating results is an adaptation of Abbott's formula. 2/ A condensation product of ethylene oxide and an alkylated cresol. _ £ _ The results of the. Arizona tests conducted by the Tempe staff were evaluated by sweeping the treated plots before and after treat- ment and detenni-iin? the percentage reduction in number of live hoppers present. From 40 to 1J0 strokes with an insect net were made on each plot before treatment and at intervals of 1, 3> 4, and 6 days following treatment. The results of the California tests were evaluated by means of counts of live hoppers per unit area (1 sq. ft. or 1 sq. yd.) before treatment and of dead and live hoppers per unit area after treatment. CHLORDANE Laboratory and field tests were made with technical chlordane, a chlorinated hydrocarbon having the molecular formula CioH6Cl8« The manufacturer's trade name for this material is "Velsicol 1068," and it is commonly referred to as "1068." It is a viscous liquid which is considerably heavier than water (sp. gr. 1.70). It is insoluble in water but soluble in all proportions in organic solvents such as xylene, acetone, or light petroleum fractions. Although all the tests were made with technical chlordane, in this paper the material will be referred to as chlordane. Laboratory Tests In a laboratory test at Dozeman, Wont., which was repeated five times, unsprayed grasshoppers were confined with sprayed soybean plants and sprayed hoppers were confined with unsprayed plants. Sach combina- tion was prepared in duplicate. One cage of each pair was held at a constant temperature of 85.5^2 and 50 percent relative humidity while the other was held at approximately 74° and 49 percent relative humidi- ty. The emulsion spray was prepared by dissolving 5 fluid ounces of chlordane in an equal volume of xylene and adding 0.25 fluid ounce of Igepal CA. This solution was then diluted with water to make 4 gallons, and was applied as a spray at U*i rate of 0.5 pound of chlordane per acre. As shoum in table 1, the spray gave better kills when it was applied to the vegetation than when applied directly to the grass- hoppers. It also performed better at 85.5° than at 74°. An emulsion of identical formula was allowed to stand in a closed container at room temperature for 1 week. This emulsion was tested at the rate of 4 gallons per acre in comparison with a freshly mixed emulsion. In 24 hours the fresh emulsion had killed 95 percent of the grasshopp3rs, whereas the week-old mix- ture was only 59 percent effective. At the end of 72 hours the fresh spray had effected 100-percent kill and the mortality from the aged material had increased to 94 percent. After 1 week in a closed container the emulsion had definitely deteriorated, but not enough to destroy its Killing power and probable usefulness for field control. - 6 - Table 1. — Effect of chlordane on unsprayed grasshoppers fed on sprayed soybean plants, and on sprayed grasshoppers fed on un- sprayed soybean plants, and held at different temperatures. Dosage 0.5 pound per acre. Bozeman, Mont. , 1946 Temperature Mortality when spray was applied to — Plants Hoppers U F 8575 74.0 Hours Percent Percent 24 80 21 72 100 64 24 58 8 72 97 60 In most of the earlier tests the grasshoppers were caged with potted soybean plants in glass lantern chimneys with screen tops. Because of the consistently high kills obtained the possibility of fumigation in such cages was suggested. In a preliminary test to determine whether or not fumigation took place, unsprayed grass- hoppers were confined in a screen-topped glass lantern chimney with a soybean plant that had been sprayed vdth the emulsion at the rate of 0.5 pound of chlordane per acre, but were separated from contact with it by a screen partition. Within 48 hours 80 percent of the grasshoppers were dead. In another test to compare results in lantern chimneys with those in cages made entirely of wire screen, the emulsion sprayed onto the soybean plants at 0.5 pound of chlordane per acre gave 100 percent kill in the glass .cages and 84 percent in the better ventilated screen cages. At 1 pound of chlordane per acre the kill was 100 percent within 48 hours even in the screen cages. It is thus apparent that the emulsion or some component of it acted as a fumigant. Field Tests Field tests with chlordane were of two general types. Plot tests were carried out to compare this material with other insecti- cides and to determine the most desirable form and rate of applica- tion. When suitable procedures had been developed, treatments were applied to larger areas such as entire fields of alfalfa or areas of egg deposition. In such tests, once it had been determined that the expected mortalities actually occurred, attention was paid to other effects including undesirable results of the treatments. When this material was tested as an emulsion, the stock solution used was composed of e.jual parts by volume of chlordane and xylene, plus 3*4 fluid ounces of an emulsifying agent (Igepal CA) per gallon of the mixture. This solution was diluted with water to make 4 to 24 gallons of a spray as needed in order to apply the desired quantity of active ingredient per acre with the particular equipment to be used. The results of the plot tests are summarized in table 2. - 7 - 1 cd ■a 0, 9 51 c © 38 un UNO CM -d- •o a, n p si >> 4 © o r> CN CO CO CA © fa S Ch cn • • •• £ +> o c a -p 3 O >% c fa at © O -* T3 8 O O O CM 8. tiO •• •• id p fa 5 1 o CM CM cd CM CO CO C*- 00 CM NO -t C*N-^H < fa UNxO -J- as oo o o H £ n fa 18 © 0) E§ -tfCNCNH rlHH H rH H H H H H CM CM E-* ss / C|_| 1 0) «H UN cd p UN «H 2 o id fa 9 t3 Cm UN un un c- *H UN CO UN CM «H O C O aj • • • • P rH H H CO Cw • •H • • O H CM •P ■P rtHHH CO o PL, CO C u • • •• fj • s £3 £ Pi 1 • a> 1 • • I 2 © °fc © rH . tU) . . 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Single tests at 1.5 and 2.25 pounds per acre in California gave mortalities of only 25 and 40 per- cent, respectively, after 4 to 8 days. One pound per acre was the dosage chosen for further experimental work. Two dust applications of chlordane at 1 pound per acre averaged 60-percent kill in 24 hours. Twelve tests of chlordane in emulsion sprays at 1 pound per acre gave 88 percent average mortality. Two dust tests at 0.5 pound per acre averaged 55-percent mortality. Three out of four emulsion spray tests at 0.5 pound per acre averaged 62 percent. The results of the other test were obscured by a heavy migration of grasshoppers. At the same rate of application, emulsion sprays were evidently more effective than dusts. Chlordane dusts were applied with a conventional-type power duster, with a turbine-blower sprayer-duster, and by airplane. The results do not indicate tnat any one of the three is superior for applying this insecticide in the dust form. During the tests in Wyoming an opportunity was afforded to observe the effects of an emulsion applied with a high-pressure boom-type field sprayer. The dosage was 1 pound of chlordane in 60 gallons of spray per acre. The 24-hour kills were lower than from applications of 1 pound per acre of chlordane in 8 gallons of spray with the turbine- blower. After several days, however, no difference could be detected in the grasshopper control from the two methods of application. Comparable morning and evening applications of chlordane were equally effective. Chlordane, especially at 1 pound per acre, killed so many grass- hoppers within the first few days that very few were left to die later. Only when the populations on the plots were replenished by migrations or by further hatching did the continued effect of this insecticide be- come apparent. One plot in Arizona was treated with an emulsion spray at 1 pound of chlordane per acre on April 24. Grasshoppers continued to migrate onto and across the plot from a large, dry, weedy area across the road. Freshly killed grasshoppers could be found on this plot at any time until May 20, the date the crop was cut. Single applications of 0.5 pound of chlordane per acre in emulsion sprays to grassy egg-bed areas in South Dakota gave 90 percent initial kills of first-, second-, and third-instar nymphs of Melanoplus differentia lis , but showed little continued effect. Applications of 1 pound per acre killed nymphs as they continued to hatch ^on these egg beds for periods up to 1 week, when a 0.30-inch rainfall stopped the residual effect. - 9 - No undesirable effects were found in experiments which involved the treatment of entire fields of seed alfalfa. Honeybees that were moved onto a treated field after dark on the evening the treatment was applied showed no indication of poisoning or weakening of the colonies during the following 2-month period. The middle half of this field was sprayed at this time when in partial bloom, and the two «n4 portions were sprayed 1 to 2 weeks later when in about full bloom. The fact that all treated fields showed prospects of a good seed yield indicated that there was no destruction of any insects essential to the pollination of alfalfa. BENZENE HEXACHLQRIDE Tests were made in the laboratory and the field with benzene hexa- chloride, a light gray or nearly colorless powder with a very persistent musty odor. Laboratory Tests The first tests conducted in the laboratory at Bozeman were designed to establish optimum dosages and to determine whether benzene hexachloride acted as a contact or a stomach poison. These tests were conducted in conjunction with those already described for chlordane. The spray emil- sion contained 1/8 pound of benzene hexachloride (gamma isomer 10 percent) in 1 quart of xylene plus l/4 fluid ounce of Igepal CA and water to make 1 gallon. This spray was used at the rate of 4 gallons (| lb. of benzene hexachloride, or 0.05 lb. of the gamma isomer) per acre. The results are given in table 3 and show that benzene hexachloride was more effective when applied to the vegetation than when applied directly to the hoppers. Excellent kills were obtained with the l/2-pound dosage. Higher kills were also obtained at the lower temperature. Table 3» — Effect of benzene hexachloride on unsprayed grasshoppers fed on sprayed soybean plants, and on sprayed grasshoppers fed on unsprayed soybean plants, and held at different temperatures. Dos- age £ pound (0.05 pound gemma isomer) per acre. Bozeman, Mont., 1946 Temperature Mortality when spray Period of I was applied to — exposure Plants : Hoppers °F. Hours Percent 85.5 24 88 72 100 74.0 24 95 72 100 Percent 53 61 78 86 - 10 - A similar spray emulsion was allowed to stand in a closed container for 1 week at room temperature. It was then tested in comparison with freshly mixed emulsion at 1/2 pound of benzene hexachloride (0.05 pound of gamma isomer) per acre. The results based on five replications were practically identical and indicated that the material did not break down when stored in a closed container for 1 week after being formulated into an emulsion. The possible fumigating action of benzene hexachloride, as well as of chlordane, was tested by confining grasshoppers in screen-top glass lantern chimneys and in wire-screen cages over soybean plants that had been sprayed with the emulsion at the rate of 0.5 pound of benzene hexa- chloride (0.05 pound of gamma isomer) per acre. All the hoppers in the screen-top glass cages, but only 64 percent of those in the wire-screen cages, were killed within 48 hours. In a similar experiment witn 1 pound (0.1 pound of gamma isomer) per acre all the hoppers held in wire- screen cages v;ere killed within 48 hours. Apparently the emulsion or some component of it acted as a fumigant. Benzene hexachloride as a 10-percent dust was tested in 5 repli- cations in the laboratory. At 20 pounds per acre (0.2 pound of gamma isomer) it gave an average kill of 99 percent in 48 hours. Field Tests Although laboratory tests conducted at the Bozeman laboratory indicated that 1 pound of benzene hexachloride (0.1 pound of gamma isomer) per acre could be expected to give satisfactory control, pre- liminary tests in the field at 1 and 1.5 pounds per acre in an emul- sion and 1 pound in a suspension spray gave only mediocre results and the dosage was increased to 2 pounds. As shown in table 4, the results of most of the field tests were variable. The stock solution used in preparing emulsions contained 1 pound of the benzene hexachloride per gallon of xylene plus 3.4 fluid ounces of emulsifier (Igepal CA). To this solution enough water was added to permit the application of the desired dosage of active ingredient with the particular eauipment to be used. Throughout the season a total of 21 tests of 2 pounds of benzene hexachloride per acre were made in emulsion sprays, suspension sprays, and dusts. Under the different conditions of the tests the reductions in populations ranged from 4 to 100 percent, with a general average of 64 percent. A total of 17 tests at a dosage of 3 pounds per acre (0.3 pound gamrr.a isomer) gave from 32 to 100 percent reduction, with an aver- age of 71 percent. In Barnes 1 tests in Arizona the dosage was increased to b, 7.5, 8, and 10 pounds of benzene hexachloride, with a correspond- ing gamma-isomer dosage of 0.6, 0.75, 0.8, and 1.0 pound per acre. In two tests a 30-percent dust applied at 20 pounds per acre (0.6 pound of 1 d n S i cd 1 -d ■a vO a • • •• o a >> cd •h fci -d . • c +> -4" O H •• •• P O C 0) d o >i TJ -H <2 0) .p •d fc r^ © 00 • • •• (0 £ >> o cd > -d <: H 09 ■P 09 09 E-i a> © -d a> C 1 «H £ © cd *h o cd *3 J? ° B^JC h 03 O © n •» ft *- .. o >» © cd P ■^ ^ a § & Q Of) © h d p U 03 •H t. 4aiA HH^fAHHHHHOI^HNHC^ cm u-\ 5rHrH(NcNtNHcNCNC\|C^C^CN^C\cn CO © H « cd o t»o to •a 00 • X» Si COtOOOtOCOtOtOQOOOvOvOO CM CM CM CM I F-O »f\-4C0 • I o>o r~ co cm c^ cm C^- C- CM -i) CM t^- c- i o T c*- i o «TN r-\ vO vO >o eoaaaaaaeaeaoo • ^ • •• ••••• >^j <^j CX, cd a) a ft CX cd CX cd O O O O H r-t H H i o H CD I O Cm C O •H © £ § •a I 09 d CO O Q O •d *d *d 9 o o o tJ T3 T3 H H H O I m © o w d co S ft CM ^H rH CM to H ^O C*>vO sO O CO CM O itNnO O vOC^-ir\vOC*--d--4-tX) -4CMCMHC*>HHH i>- a 00 •H C\J CO iH «0 © P CO © H goo o o & o o • t3 *^ *& *0 * "O *0 ex cd o H -iK\v-ilCVHCV-^ft g% o*C o^t O^s. Ot o o o o o CA41AHH g •H © i CO n >i © 1 T> CO H -O d a, • • •• o a CO t>> c -3 © S fM -4- •H <0 ♦ • «• p O C 09 3 O >> © !p CO -a *4 C"\ & • • •• © u >j © © > T) < rH 09 -P CO © e-« » © © -P -^ ^ 5 © P. Q 09 09 h =* -P £g ^^ 1 © •H O CO t- * on N o o o 3& r-\ C-4 ^t r4 r-< r-4 r-i C*- CM to a> (N © -p CO .o © r-l t»0 CO -p CD © '-*VrnlC\MCY^!0*-*\i-*V I i • i II 1 1 rH t. k © (4 0) >> 1 P © to h • 5 a. o •a d t. L, h o O © Oh a. c « « o O c •iH c rH CO o •H c •H ♦ » -P 3 D] CO co 1 3 CO J - 13 - gamma isomer; gave an average Rill of 76 percent in 3 days. A 40-percent dust at 20 pounds per acre (0.8 pound of gamma isomer) gave 83-percent kill in 3 days in a single test. Three tests of a 50-percent dust at 20 pounds per acre (1 pound of gamma isomer) gave an average kill of 86 percent in 3 days. A dosage of 7.5 pounds of benzene hexachloride per acre (0.75 pound gamma isomer) in a suspension spray applied by plane gave 80-percent kill in 1 day and 86-percent kill in 4 days. In V/ilson's tests in California, 4 pounds of benzene hexachloride (0.4 pound of gamma isomer) gave an average kill of 66 percent in two trials. Thus it would appear that the application of 2 pounds of benzene hexachloride (0.2 pound of gamma isomer) per acre could be expected to kill between 60 and 65 percent of the hoppers, and that 3 pounds per acre approached an effective dosage. The larger quantities used gave very good kills in most instances, but may not be economical or much more effective than the 3-pound dosage. Comparisons of the effectiveness of benzene hexachloride in emulsion sprays, suspension sprays, and dusts of varying percent- ages may be made from the data in table 4. At 2 pounds per acre (0.2 pound gamma isomer) 9 tests in emulsion sprays gave an average kill of 70 percent, 3 tests in suspension sprays gave an average kill of 56 percent, and 8 tests as a dust gave an average kill of 61 percent. Three tests of 3 pounds (0.3 pound gamma isomer) in an emulsion gave an average kill of 90 percent, whereas 14 tests of the same dosage in dusts gave an average kill of 67 percent. Three tests of 4 pounds in a suspension spray gave an average kill of 50 percent. From these results it would appear that the emulsion sprays are more effective than either the suspension sprays or the dusts. However, it is necessary to use almost 1 gallon of xylene to dissolve 1 pound of the crude benzene hexachloride. At a dosage of 2 pounds per acre approximately 2 gallons are required. This amount of xylene approaches the point where the spray containing it is dangerous to plants. The results show that a 3-pound dosage of benzene hexachloride in xylene emulsion is quite effective, but that the danger of xylene injury to plants is too great to warrant its use. If this insecticide is to be applied as an emulsion, it will apparently be necessary to find a better solvent or one that is less injurious to plants. The data do not permit good comparisons between the several types of ground equipment used in these tests. The applications made by ground equipment did, however, give somewhat higher kills than those made by plane. In 19 tests with ground sprayers the average kill was 67 percent, and in 25 tests of dust applied by ground equipment it was 66 percent. In 4 tests of sprays applied by plane it was 59 percent, and in 5 tests of dust applied by plane it was 49 percent. The data provide some evidence that benzene hexachloride is more effective if applied in the evening or during cool, damp weather. In the early-season work in Arizona three morning tests at 2 pounds per acre in an emulsion spray gave an average kill of 65 percent, - u - whereas three evening tests with the same spray and dosage averaged 77-percent mortality and one test at noon gave only a 38-percent kill. .Vilson in California noted that benzene hexachloride apparently gave better kills on cool days. Little or no continued kill beyond 48 hours was noted in the early spraying and dusting tests in Arizona. The heavier dosages applied by Barnes apparently continued to be effective for 3 to 4 days and tnose applied by Wilson continued to kill for 6 days. METHOXY ANALOG OF DDT Laboratory Tests The technical grade of the methoxy analog of DDT, 1-trichloro- 2,2-bis(p-methoxyphenyl)ethane, was tested in the laboratory at 3ozeman,llont. , in 1946 along with benzene hexachloride and technical chlordane. The results indicated that 2 pounds of this material per acre would be effective when applied in an emulsion spray, but when applied at this rate in 5 replications as a 10-percent dust it gave an average kill of only 34 percent. Higher kills were obtained when the material was applied to the plants than when applied to the grasshoppers, indicating that it kills mainly as a stomach poison. 3etter results were also obtained when treated plants and hoppers were held at low temperatures. In tests to determine its stability in an emulsion, this material showed no decreased kills after being allowed to stand in a closed container at room temperature for 1 week. It was not tested for fumi- gating action in the laboratory. Field Tests The methoxy analog of DDT was thoroughly tested under field con- ditions in Arizona, California, and TJyoming, and the results are shown in table 5. Preliminary tests of emulsion sprays in the field proved that a dosage of 2 pounds per acre was ineffective. Five tests by Barnes conducted somewhat later, using 2 pounds per acre in a 10-percent dust, gave an average mortality of 49 percent. In seven tests with both sprays and dusts applied at the rate of 3 pounds per acre the average kill was only 48 percent. Four pounds per acre as an emulsion averaged 80 percent kill in three tests. Four and one-half pounds per acre killed an average of 56 percent when applied both as dusts and as sprays. From these results it would seem that the methoxy analog of DDT at comparable dosages is less effective than benzene hexacnloride . Comparisons can be nade of the methoxy analog of !;DT at different percentages in emulsion and suspension sprays and dusts. At 3 pounds per acre in emulsion sprays the average kill was 52 percent in 6 tests. CD 3 Q , rH 1 ctf 3 l/\ Tj a, • • •• o P« i CO .si X) a> C P -d- O J -a -h cO CD P -a «i en CD bo • • •« a) £ >. 0) cd > -a < rH CO -p CO CD E-« CD & (h o ££ a) P Q © Jh 3 CD .« P- *H „ o >> CD etS P P m <0 CO O, « 3 09 Q CO CD «-. 3 p P. <0 •H U «aj CD ^ CD •P S j •H o a) Eh »0 CO CD . -P n'h o •H O rH CO Q, ■P C 1 a 3 S c o •H P > o, C-i fft p c CD O u CD Oh CD O CD Ou ft CD O f-. CD a. o u CD a. .8 - 15 - cM CO CD U V < •g 8 M O C •H C o •H P crj O -a xO -j- c- c~- -4- i^ -J- CN a o O rH ^ CN H rH rH rH Cm aJ ir\ P CO CN (^(nc^^^^ C aJ a < S rH tSJ (Tj O bO PQ CO >» XI H , crj jd bo H X ITMfNrH o • . C o N •H nO CN I C IfN t> IT\ •H • CN CO vO -P CO CD Eh gas • • • crj (X crj -4 O u-\ O t> o oo nO so o a P, CTJ H H H H O O O o H X O T3 CD C c0 . . H O O o 0-, g •H CO rH rH C O ^ O CO rH •H C •• CO CD •• -P rH CX.P CO 3 CO CO 3 3 3 r- ■» '3 rr\ s~i CN CN 4Htn ir\ -4 en R 00 o -4-sO rH C^rH «m cd C\J CN CN a^ . CD O Eh PI >-0 O O XI CN CN CN I •H M C •H CO P co • • • HHrIN cm cm co o p c I u . O XJ cO <-\ CO o o o o >jCM r^c^CN Xt aJ •H e en CO 00 C>- rH CN Cm cm pU^ CO § . eg HO O PQC0 CO XI bo c o «M r1r>C0CM to aJ CO CO m I o >^ CO p CO CD 00 »T\C0 00 I en sO CO p CO CD e a • • cO P. M|C*-i|C\rMKV rH I I I o H4-MM-MW h Ih M CD 5 CD P P co 3 CO 3 3 x) -d u M M -d CD CD c (5 i crt O O ac cu CU M o o p CO 5 - 16 - One test of this dosage in Arizona, applied as a 15-percent dust, killed 27 percent. A similar test in California resulted in a 4-percent kill. Four pounds per acre in an emulsion gave an average kill of 80 percent in the 3 Wyoming tests. In one similar test in Arizona the results were obscured by migrations. Four and one-half pounds per acre in a 15-percent dust gave an average kill of 56 percent in 5 tests in Arizona and California. One suspension spray was applied by plane but the results were obscured by migrations. These results indicate that the methoxy analog of DDT is more effective when applied in an emulsion spray than when applied as a dust or as a suspension spray. At 3 pounds per acre the results were not satisfactory. At U pounds in the Wyoming tests it began to show effective results, but the amount of xylene necessary to dissolve U pounds (approximately 2jjj gallons) burned the alfalfa noticeably. No difference in results was apparent when the methoxy analog of DDT was applied with various types of. ground equipment, and in two of the three tests in which it was applied by plane migrations obscured the results. In the remaining test in which it was used at 4.5 pounds per acre in a 15-percent dust, a kill of 69 percent was recorded. This was somewhat higher than the average of four tests of the same dust concentration and dosage applied with ground equipment in California. There was some evidence that the methoxy analog of DDT gave better kills when applied in the evening. Four tests with the 3- pound dosage in an emulsion applied in the evening gave an average of 54 percent, whereas two tests with the same dosage applied in the morning averaged 47- percent kill. A CHLORINATED CAMPHENE A chlorinated camphene containing 67-69 percent of chlorine and designated experimentally as Hercules 3956, is a gummy, amber-colored substance in the crude state. It is readily soluble in relatively small amounts of xylene and No. 1 petroleum distillate, although it does not go into solution rapidly. A small quantity of this material was received at the Bozeman laboratory early in the spring of 1946. Unfortunately it arrived too late to be given routine tests in the laboratory and was not in suf- ficient quantity for field testing. A larger supply was received later and was tested in a small way in the field late in the season at Hardin, Mont. Small quantities were also received at the Tsmpe, Ariz., and Sacramento, Calif., laboratories and tested in the field insofar as materials and time would allow. The results are shown in table 6. Only four tests were completed in Montana, all at the rate of 4 pounds per acre. Two of these were with an emulsion spray and the - 17 - CD so cd N0 IT> O Cn 03 © U » 33 01 o5 T3 (I) -P cd & •H (0 > .Si cd a) a -p en O Cm •H ctJ • • • • •P O C CO 3 O b © -p cd n fn T3 <: rH CO -P (0 CD E-< to (0 j CD cd P -P u cd CO a. (2 3 co Q CO CD £h 3 -P f-. cd •H U «& & 9 ■P CD e > •rH o to N CM rH rH rH H «m Cm cd CO p T3 «W CO § «M -4- -4- Cm CN CV sO 00 -* >c\ >s CTN xO -O vO >> £> XI H rH rH X> cd cd a g c cd ca u m -p •H CO o Cu c c H O r- b -4 O CM o o CO u> 00 IT\ < a •H a c rH o rH cd c •H o •H CO CO +J CO -P CO •p CO • • • • CD • > CO CD 6 e e £ e-t S O CD H • • • • • -d 6-< a cd a cd a rHiWHOiHCVMlCV CO rH U% CD • • 1 1 1 1 u H rH H H O o 1 u U CD u U CD CD >s CD -P 4-> cd o 4J CO CO rH H CO 3 3 a X> o -d co fn ■O J-. rn M CD T3 CD CD CD 3: o S § o o ex. Vc k ex. ex, ex. c O o CM o o CM rH •H •H CO M •• M CO 3 ■*-> +J +- rH CO CQ CO 3 A 3 3 Q Q t3 other two were with a 20-percent dust. The average kill for the two spray tests was 97 percent and for the two plots receiving the dust, 95 percent. In Arizona the average kill in two tests with 20 pounds per acre of a dust containing 10 percent of ^ ochnical e hlor