LIBRARY STATE PLANT BOARD April 19^5 E-6k8 UNITED STATES DEPARTMENT OF AGRICULTURE AGRICULTURAL RESEARCH ADMINISTRATION BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE COMPARATIVE VALUES OF NEW INSECTICIDES FOR USE AGAINST LYGUS SPP . AND TBE SAY STINKBUG By Or in A. Hills and K. B. McKinney Division of Truck Crop and Garden Insect Investigations Incidental to the development of a control program against hem- ipterous insects affecting sugar beets grown for seed, a considerable number of laboratory tests of various insecticides have been made at Phoenix, Ariz., to determine their comparative value as contact in- secticides against Lygus spp., primarily Lygus oblineatus (Say), and the Say stinkbug ( Chlorochroa sayi Stal) . It is the purpose of this circular to make available additional information regarding the value of some of these new materials as contact insecticides. The results of these tests, made in small laboratory cages, are not always indicative of the value of an insecticide under field con- ditions. Most of the insecticides that produced high insect mortal- ities in laboratory cages have been tested in the field with good results, but in some instances materials have shown considerable prom- ise in laboratory tests and have not given good results under field conditions . Methods The laboratory tests were made by confining the insects on branches of suitable food plants in small cylindrical screen-wire or cloth-covered cages. Applications were made either by applying liberal and uncalibrated quantities of the insecticides directly to the insects and plants through the cage covering or by applying calibrated quan- tities to the plants only before the introduction of the insects. The cages used in these experiments were approximately 3l2 inches in diameter by 7 inches high. They were built onto the lids of 1-pint ice-cream cartons, and the stems of the food plants in most cases ex- tended through a hole in the floor of the cage into the carton below, which contained water. In some of the later experiments branches of one of the fig marigolds , Mesembryanthemum sp . , were used as a food plant, and it was found unnecessary to place the stems of this plant in water. Insects for all experiments except those involving nymphs of the Say stinkbug were gathered from the field and put in the cages on dusted plants, or were put on clean plants and dusted later. The variously MAY 1 4 ^45 - 2 - treated cages of insects were then placed on laboratory shelves in randomized blocks for further observation. In the case of nymphs of the Say stinkbug the test insects were reared in a constant -temperature cabinet in the laboratory at a constant temperature of 82 *\ Most of these nymphs were in the third and fourth ins tars at the time of treat- ment. The insects were put in the cages on predusted plants and the cages placed on shelves in a second constant -temperature cabinet. They were arranged in randomized blocks, each shelf constituting a block, and carried at a temperature of 82 . Tests Against Lygus Bugs The predominant species of Iygus occurring in the Salt Blver Valley of Arizona are L. oblineatus (Say) and L. hesperus Knight; these species occur intermixed, although at certain seasons of the year and on certain plants one or the other often predominates. The following tests were made with field -run insects which were predomi- nantly L. oblineatus . Both adults and nymphs were used, and in most cases the two forms were placed in separate cages. Experiment No. 1 . — Six organic compounds furnished by the Di- vision of Insecticide Investigations were tested in this experiment. Each material was furnished mixed with equal parts of talc or sulfur. Each mixture was applied directly onto the insects through the walls of the cages, eight lots of adults and six of nymphs being used in each case. Twigs of Atriplex semibaccata E. Br. were supplied as food. The mortalities after 1, 2, and 3 days, as shown in table 1, were inapprec- iable except in the lots dusted with phthalonitrile . - 3 - -4- On U © 1 > o o -p On Sh & O P o o CO -P CD CD -P © d «H O •H -P O ) cd d on m >s cd d OJ Mortality of adults after— CO >: 33 d on CQ >. 55 d OJ d •d CO CO CO -p o © CO a CO 1 S3 CO -p 5 -p CD rH -H ft d CD -p CO CD -P 3 «H Sm CD ■P 1 c o On O rH On O OJ O CO CO On On ON. 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Satisfactory reductions in insect populations were obtained, but there were some indications that this material might be damaging the flowers since there was a lower per- centage of viable seed than was expected. Experiment No. 2 .- -Previous laboratory and field experiments had indicated that mixtures of sulfur with pyrethrum extract-impregnated dusts were effective against I^ygus . Other workers in the Bureau had used magnesium oxide with certain materials to give additional toxicity. Experiment No. 2 was made to determine the value of "heavy" and "light" magnesium oxide as an insecticide, and also to determine the insecticidal value of mixtures of magnesium oxide and sulfur, and magnesium oxide- pyreth2"um extract -sulfur dusts. Several dusting sulfurs as well as wettable sulfurs used as dusts were also included in this experiment. Each material was applied to 11 cages containing adults and to 12 cages containing nymphs . The food plant used in each case was Chenopodium murale L. The powders were applied liberally to the insects and plants through the meshes of the cages with a hand dust gun. The results are given in table 2. a ID >» J 1 IP. o +J >> 'a > a) > ro +> o •H >» 4 I * OJ o S >» at •ct H n :>> IT •d i i u tp. 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O >> CM 1 X -H rH «H Xl I CD 1 3 5S hS O a t o o o o K .M CD 1 H "tf*-H CO «H O U I OHO © O Pm CD O 1 >> > U t> XI 3 O o CJ o o aj O h d o d •H -d 1 O *H 1 -H * CD U P o d o o o ■P o U CD <1> xi Pi CD X! rH cd as •P Xi CH CD P P< CD CD •h n, m cd 3° cd U o C E-i ■P 1 ■H •H P a CvJ P P P ro - 8 - Experiment go. k. --This test included two of the dinltro compounds commonly used as insecticides, one dinitro compound (U,6-dinitro-2-tolyl acetate) the insecticidal value of which was unknown, DDT, and a dust impregnated with secondary terpene -alcohol thiocyanyl acetate. In this experiment these materials were tested in rather dilute form and also in concentrations considered suitable for field use. The conditions of the tests with the dilute and concentrated materials were as nearly the same as possible. Five cages containing Iygus adults and five cages containing nymphs were used for each material in each case, Chenopodium morale "being used as a food plant. The materials to he tested were all in powder form and were applied to the plants within the cages before the insects were in- troduced. Definite quantities were applied by removing the tops from the cages containing the plants and placing the encaged plants in a settling cham- ber. Here the materials were applied as a dust at the rate of 0.5 gram per square foot, which is the equivalent of approximately 50 pounds per acre. Results obtained from the use of the dilute materials (table h) indicate that only dinitro-o-cresol was effective in the weaker dilutions. Later a pyrethrum. extract -sulfur dust (table 5) was substituted for one of the 4,6-dinitro-2-tolyl acetate dusts, since there seemed to be no difference in the results obtained from the two methods of preparing this material. Good results have been obtained with the pyrethrum extract- sulfur dust both in laboratory and field tests, and it was included here for comparison with the other materials. Results shown in table 5 indicate that 5-percent DDT and 1-percent dinitro-o-cresol were equally as good as the pyre thrum-sulfur dust although somewhat slower in their action. - 9 - u © 6 m -p © © ■P © •d •H O +» O © © o o ■8 ! © •8 i >» -p ■H £3 • co -* H © O H P ■3 En 1 O h © >»-P •d •d © o p m •p o © at © I © I CM •8 © I CO © I cvi I m p 1 ,© ■p a © o u © ■8 ■p © © u © p 3 co CO H CVJ CM CO CO CO © p" H Pi >*. 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A 1-percent dinltro-o-cresol dust was also tested on sugar beets grown for seed in field plots. Good kills of Iygus were obtained, but such severe burning occurred that this material cannot be recommended for use on seed beets. Experiment No. 5. — This test included sabadilla, DDT, and 2-chloro- fluorene dusts; the pyre thrum extract-impregnated sulfur dust used in previous experiments was also included here for comparison. Two pro- prietary sabadilla insecticides were tested. Each was labeled by the manufacturer as containing 20 percent of sabadilla seed. Each of these materials was tested in 20-percent and 5-percent concentrations. In addition one of the materials was tested in the 5 -percent strength in combination with sulfur. Three DDT preparations were tested, all of which contained 3 percent of DDT. The first was DDT in pyrophyllite; the second DDT, pyrophyllite , and sulfur J and the third a DDT- sulfur preparation made up by fusing DDT in sulfur and regrindlng. The last was an experimental preparation made up by one of the commercial insecticide manufacturers. Three 2-chlorofluorene dusts were tried; the first contained 20 peroent of 2-chlorofluorene in talo, the second 10 peroent of 2-ohlorofluorene in talc and pyrophyllite, and the third 10 percent of 2-ohlorofluorene in talc and sulfur. Mesembryanthemum sp. was used as a food plant, and calibrated quantities (0.5 gram per square foot) of the dusts were applied to the encaged plants in a settling chamber before the Introduction of the insects. Only Iflgus adults were used, and each treatment was replicated eight times. The results of this experiment are presented in table 6 and show that both sabadilla and DDT were effective against Iprgus adults. The sabadilla killed much more rapidly both at the 20-percent and 5-percent strengths than did the DDT. These data also Indicate that the sabadilla insecticide from one source of manufacture was slightly superior to the other. Differences between 20-percent and 5-percent concentrations were small, and sulfur as a diluent was little if any better than pyro- phyllite. DDT dusts containing sulfur gave somewhat better results than DDT in pyrophyllite, and the material prepared by fusing DDT and sulfur and regrindlng was slightly better than the mechanical mixture of DDT, pyrophyllite, and sulfur. Dusts containing 10 percent of 2-chlorofluorene gave better results than the 20-percent material, probably owing largely to an improvement in the physical qualities of the dust by the addition of the diluent. The 10 -percent dust containing sulfur did not give such good results as the 10 -percent dust containing only talc and pyrophyllite. - 12 - Table 6. — Mortality of Lygttg adults In laboratory insecticide tests. October 30 to November Lygus rTTT 19^4 Material tested (peroent by vt. Of final mixture) Inseots used Mortality after — 1 day 2 days 3 days 4 days 5 days Wumber Peroent Peroent Peroent Peroent Percent Sabadilla: 20* plus unknown inert 80* l/ 117 74 5* plus unknown inert 20$ plus pyro- phyllite 75* l/— 119 82 20* plus hydrated lime 20^ plus talc 60* 2/ 122 100 5* plus hydrated lime 5* plus talc 15* plus pyro- phyllite 75* 2/ — 119 5* plus hydrated lime 5* plus talc 15* plus sulfur 75* 2/ 118 DOT 3*: 86 99 86 89 100 93 99 88 92 100 96 99 90 94 100 97 99 91 95 100 98 100 Plus pyrophyllite 97* Plus pyrophyllite 27* plus sulfur 70* (mechanical mix) 110 121 Plus sulfur 91% (fused and reground) 128 33 ^5 62 6Q 7* 84 81 89 95 84 95 98 92 96 100 Table 6. — (Continued) Material tested Insects used Mortality after — (percent by wt. of final mixture) 1 day 2 days 3 days k days 5 days Number Percent Peroent Percent Percent Peroent 2-Chlorof luorene : 20* plus talo 80* — 119 10* plus talo 40* plus pyrophylllte 50* 118 10* plus talo 40* plus sulfur 50* — 118 Pyrethrum extract dust 3/* Plus sulfur 50* plus pyrophylllte (0.2* pyrethrins) - — - — - 120 Untreated check — 121 56 20 100 13 70 28 100 16 81 3h 100 5 22 90 36 100 16 29 92 k2 100 23 l/ Supplier Ho. 1 2/ Supplier Ho. 2 3/ See table 2, footnote 1. - 13 - Experiment No. 6. — In this experiment the insecticidal value of sabadilla and DDT dusts containing sulfur was compared with similar dusts in which pyrophyllite was used as the diluent. The value of add- ing a fntwii amount of petroleum oil to these dusts was also tested, as was the insecticidal value of a sulfur dust containing a dithiocyanate . When the oil-impregnated dusts were "being made up, the dry ingredients were first thoroughly mixed, the oil was then atomized onto the dust a little at a time, and the dust was remixed until no more oil could "be added without impairing the physical qualities of the dust. Sulfur does not absorb oil so readily as some of the other powders used as insecticide diluents, and therefore not so much oil could "be put into materials con- taining sulfur. An automobile lubricating oil having an S.A.E. rating of 10 was used for this work. Both the DDT and the sabadilla were used in 1-percent strengths in all these dusts. At these concentrations these materials were considered weak insecticides, but these strengths were used to accentuate any differences which might occur from the addition of the sulfur or oil. The dithiocyanate dust was made up at a strength consider- ed suitable for field use (3.6 percent). The conditions of this experiment were similar to those of experi- ment No. 5. Mesembryanthemum sp. was used as a food plant, Iygus adults were used as test insects, and before introduction of the insects 0.5 gram of each material was applied to the plants in a settling chamber covering an area of 1 square foot. Each material was applied to seven replicate cages. The results of this experiment, given in table 7, indicate that neither the DDT nor the sabadilla was improved by the addition of the petroleum oil. Sulfur as a diluent seemed to improve the DDT dusts, but not the sabadilla dusts. Good kills resulted from the use of the dithio- cyanate and sulfur dust, but no increased mortality was indicated after the first 2U hours. This dust was later tried in field plots of seed beets for Iffgus control, with fairly good results; it warrants further trial. - Ik - Table 7* — Mortality of Ijgus adults in laboratory insecticide tests, Norember 13- 25, 19^ Material tested (percent by wt. in final dust mixture) Insects used e • Mortality after -- .1 day : 2 days: 3 days: 4 days: 5 days Rumber Percent Percent Percent Percent Percent 102 103 106 107 33 18 21 16 51 29 *7 3* 57 38 57 66 50 69 76 57 79 73 DDT, 1* in pyrophyllite plus: Sulfur 89* plus petroleum oil 2$ Petroleum oil 3* 103 Sulfur 90* 106 Alone Sabadilla 1$ plus: Sulfur 9k plus hydrated lime 1* plus talc 3$ plus petrol- eum oil 1* - — 102 Hydrated lime 1$ plus talc 3$ plus pyrophyllite 91* plus petroleum oil ty 106 Sulfur 95 it plus hydrated lime 1* plus talc 3* 10^ Hydrated lime l£ plus talc 3$ plus pyrophyllite 95* 10^ Dithiocyanate dust 28*-/ plus sulfur 72* 105 17 18 12 8 95 Untreated check 105 30 29 26 17 96 8 1*3 39 3* 2k 97 15 *3 kk 38 32 98 25 *5 52 39 99 36 1/ A proprietary material containing 13.5* of beta -beta' -dithiocyanodiethyl ether, 80* of talc and 5* of magnesium carbonate. - 15 - Tests Against the Say Stinkbug The results of tests against adults of the Say stinkbug have already been reported in part by Hills, l/ Stevenson et al . 2/ have also reported the results of cage tests with 2 -percent DDT against adults of Chlorochroa sayi and two other species of stinkbugs as well as Lygus sp. Sxperiment Ho. 1 . — This experiment included two of the commer- cial dinitro insecticides, 10-percent DDT, and 20-percent 2-chloro- fluorene. Adults of the Say stinkbug were used as test insects. Ten cages of insects were used for each material . Atriplex elege-ns (Moq . ) D . Dietr. was used as a food plant . Liberal quantities of the ma- terials were applied as dusts to the plants and insects tLi-ough the meshes of the cages. The data from this experiment (table 8) show that the 1-percent dinitro-o-cresol and DDT were equally effective against this insect, but that the bugs were killed much more rapidly with the dinitro-o- cresol than with the DDT. Twenty -percent 2-chlorofluorene was shown to be ineffective against this insect, and mortalities obtained with the 1-percent dinitro-o-cyclohexylphenol dust were somewhat lower than had been obtained in previous tests. The dinitro-o-cyclohexylphenol dust used in this experiment, however, was 1 year old, which may have been at least partly responsible for the comparatively low mortalities accompanying its use. Table 8. — Mortality of Chlorochroa sayi adults in laboratory insecticide tests, August 17 to 23, 19^3 Material tested (percent by wt. ) Insects used Mortality after- - 1 day 1 2 days k days 6 days Number Percent Percent Percent Percent Dinitro-o-cyclohexylphenol 10 in special volcanic ash — 100 Dinitro-o-cresol 10 in special volcanic ash 100 DDT 100 in pyrophyllite 100 2-Chlorofluorene 200 in talc- 99 Untreated check 100 U6 60 65 72 Q9 90 92 92 Ik 53 86 98 5 12 22 U6 1 7 15 30 - 16 - Experiment Ho. 2. --This experiment included proprietary dinitro compounds and DDT. Since the 20-percent 2-chlorofluorene dust did not give good results with the Say stinkbug in experiment No. 1, it was omitted from these tests. A fresh supply of the dinitro-o-cyclohexyl- ph->nol dust vas obtained and its toxicity compared with that of the 1-year- old material used in experiment No. 1. The conditions of this experiment were similar to those of experiment No. 1, as 10 cages of insects were used for each material and Atriplex elegans was the food plant. Insecti- cides were applied liberally as dusts to the plants and insects through the meshes of the cages. The results are given in table 9 and indicate that a freshly pre- pared dinitro-o-cyclohexylphenol dust is superior to 1-year-old material. These data also show that dinitro-o-cresol is much more prompt in its action than dinitro-o-cyclohexylphenol, but that the end results of these two materials are not significantly different. Results obtained with the DPT in this experiment were very similar to those of experiment No. 1. Plant -tolerance tests indicated that the dinitro-o-cresol caused much more foliage burn than did the dinitro-o-cyclohexylphenol. In limited field trials of dinitro-o-cyclohexylphenol against the Say stinkbug in seed beets fairly good results were obtained. Table 9. — Mortality of Chlorochroa sayi adults in laboratory insecticide tests, September 1 to 6, 19U3 Insects used Moribund at l£ hours Mortality after -- Material tested 1 day 2 days 3 days k days 5 days Dinitro-o-cyclohexyl phenol 1$ in special volcanic ash: Number Percent Percent Percent Percent Percent Percent Material 1 year old 90 27 53 60 62 66 Fresh material 88 9^ 97 98 98 98 Dinitro-o-cresol 1$ in special volcanic ash 99# — 93 65 88 90 90 90 90 DDT 10# in pyrophyllite 90 13 *3 75 93 95 1 2 6 9 10 - 17 - Experiment No. 3- — This was the first experiment against nymphs of the Say stinkbug. Five insecticides vere selected which had given good results against adults of this species or against Lgrgus. Six replicate cages were used for each insecticide. Branches of Chenopodium murale were used as food plants, and the insecticides were applied to the plants in a settling chamber at the rate of 0.5 gram per square foot, before the introduction of the insects. The stinkbug nymphs used in this exper- iment were reared specimens and after introduction on the dusted plants the cages were held in a constant -temperature cabinet at 82° F. The results, which are given in tahle 10, indicate that all materials were fairly effective against nymphs of the Say stinkbug except the 2- chlorofluorene. The kills obtained with dinitro-o-cyclohexylphenol were not quite so good as those obtained with the pyrethrum extract -sulfur, dinitro-o-cresol, or DDT. However, field tests with these two materials have shown that dinitro-o-cresol causes considerable foliage "burn and is not safe to use on sugar beets grown for seed, whereas dinitro-o- cyclohexylphenol can be used with safety. The results obtained with DDT indicate that this material is slow in its action against the nymphs of the Say stinkbug, which corroborates results of previous experiments with adults of this insect and also with lygus where lower concentrations of DDT were used. The 20-percent 2-chlorofluorene was shown to be ineffective against the Say stinkbug nymphs. Table 10. — Mortality of Chlorochroa sayi nymphs in laboratory insecti- cide tests, January 2k to 29, 19^ Material tested (percent by wt. of final dust) Insects used Mortality after — 1 day 2 days! 3 days! k days I 5 days Number Percent Percent Percent Percent Percent Pyrethrum extract dust-' plus: Sulfur 50$ plus pyro- phyllite (0.2# pyrethrins) Dinitro-o-cresol 1$ in spec- ial volcanic ash Dinitro-o-cyclohexylphenol 1$ in special volcanic ash DDT 10$ in pyrophyllite 2-Chlorofluorene 2C# in talc Untreated check — . — . .- 60 87 92 95 97 98 57 61 77 83 88 93 60 k3 63 70 75 78 59 20 66 83 90 95 58 k 10 10 20 28 56 7 12 16 18 27 1/ See table 2, footnote 1. - 18 - Experiment Ho. k . --In this experiment comparisons were made of dusts containing a di t hi ocyai; ate, pyre thrum extract, and "both of these insecticides. The conditions of this experiment were similar to those of Experiment 3. Chenopodium murale was used as the food plant, insecti- cides were applied t6 the plants only in a settling chamber at the rate of 0.5 gram per square foot before the introduction of the insects, nymphs of the Say stinkbug were used as the test insect, and five replicate cages were used for each treatment . The results of this experiment are given in table 11 and indicate that only fair results were obtained with dusts containing the dithio- cyanate. Excellent results were obtained with the dust containing pyrethrum extract, even when the pyrethrins content was reduced to 0.1 percent. This dust was more effective than one containing both insec- ticides. Tests in field cages as well as in test plots against adults of the Say stinkbug have shown that pyrethrum extract -sulfur dust containing 0.2 percent of pyrethrins knocked down a high percentage of the insects but a large number recovered. Table 11. --Mortality of Chlorochroa sayi nymphs in laboratory insecti- cide tests, February 7 to 12, 19^ Material tested (percent by wt. in final dust mixture) Insects used Mortality after -- 1 day | 2 days [ 3 days | h days 5 days Number Percent Percent Percent Percent Percent Dithiocyanate dust 30^r- / plus: Pyrophyllite 70$ Sulfur 70$ ■ 50 62 lh 78 80 Qk 51 kk 56 66 68 72 2/ Pyrethrum extract dust 5$- plus: Dithiocyanate dust 30$ plus sulfur 50$ plus pyrophyllite (0.1$ pyrethrins, 3.6$ 50 88 90 9h 98 100 Sulfur 50$ plus pyrophyllite 50 100 100 100 100 100 Sulfur 50$ plus pyrophyllite (0.2$ pyrethrins) 50 100 100 100 100 100 h9 10 15 26 33 37 1/ See table 7, footnote 1. 2/ See table 2, footnote 1 - 19 - Summary and Conclusions Twenty-seven new materials were tested as insecticides in laboratory cages against Iffgus spp. and the Say stinkbug. Some insecticidal value was indicated for the following: Against Iygus spp.: *Phthalonitrile , magnesium oxide (alone and ir combination with sulfur and pyrethrura extract -sulfur dusts), *phenoxathiin-sulfur,*lime-sulfur, 2-chlorof luorene, *dlnitro- o-cresol, *DDT, sabadllla, dithiocyanate dust. Against the Say stinkbug: *Dinitro-o-cyclohexylphenol, ilnitro-o- cresol, and *DDT. The materials starred (*) were later tried in the field against these insects on sugar beets grown for seed. Phthalonitrile satisfacto- rily reduced Iygus populations but apparently damaged the sugar beet flowers and caused a reduction in the percentage of viable seed produced. The phenoxathi in- sulfur compound on small field plots did not give sat- isfactory kills of lygus . A dust containing lime -sulfur and sulfur gave somewhat better results against Iffgus than dusting sulfur alone but was not enough better to Justify the additional expense. Dinitro-o-cresol gave very good kills of Lygus but caused a severe foliage burn. DDT produced the highest Iffgus mortality of any of the materials tried in the field and produced no detrimental effect on the plants. Plots treated with this material produced a better quality of seed than any plots treated with the pyrethrum extract -sulfur dust, recommended for I^ygus control on seed beets. Dithiocyanate-sulfur dusts gave fairly good results in the field against I^ygus , and this material should be given further trial. Dinitro-o-cyclohexylphenol produced satisfactory kills of the Say stinkbug and did not damage the foliage or flowers. DDT gave fair results against the Say stinkbug in experimental plots, al- though these data are limited. UNIVERSITY OF FLORIDA I I II II I I I I 3 1262 09238 7108