LIBRARY TA -. IT BOARD April I9U5 E-6H7 United States Department of Agriculture Agricultural Research Administration • " Bureau of Entomology and Plant Quarantine DDT FOR CONTROL OF THE SUGARCANE BORER , \ : THE^RICE.STIMTCBUG, AND A GRASS WEBWORM. By J, 117. Ingram, E. K. Bynum, W. B. Haley, and L. J. Charpenticr, Division of Cereal and Forage Insect Investigations Sugarcane Borer Although experiments conducted at Houma, La. , in- 19^3 indicated that DDT (l~trichloro-2,2-bis(p-chlorophenyl)ethane) was less effective than -pryolite in controlling the sugarcane "borer, ( Diatra ea saccha ralis (F. ))— ', it was further tested in I9UU against first- and second- ■ generation borers. Two experiments. comparing 10 percent DDT-pyrophyllite dust with cryolite^/ ajri ^ fluosilicates were conducted during April and May against the first generation. Twentieth-acre plots were. arranged in a Latin square* In one experiment 6 "by 6;plots of C.P. 28/1 9 cane and in the other 5 "by 5 plots of C.P. 29/103 'cane were used. Each treatment was applied four times at weekly intervals at . the rate of approximately 8 pounds of the dust per acre-application. Control was determined from counts of the surviving "borers in treated and untreated plots (table l). On the C.P. 23/19 cane synthetic cryolite gave a control of 85 percent, natural cryolite 63 percent, and DDT-pyrophyllite only 11 percent. In the tests on variety C.P. 29/103 cane synthetic; cryolite gave a control rf Si percent, natural cryolite 80 percent, and: DDT-pyrophyllite only 3^ percent. Table 1.— Survival of first-generation sugarcane borers in two varieties of Cane following treatment with DDT, cryolite, or fluosilicate. Treatment Synthetic cryolite-sodium fluosilicate^/ (80:20) Synthetic cryolite Potassium fluosilicate-/-pyrophyllite (75*25) Natural cryolite DDT pyrophyllite (DDT 10$) Check, no treatment Difference reauired for significance: Odds 19:1 ' Odds 99:1 1/ NagSiFg and ^SiFg each 97$. 2/ Last 3 applications only. .1 /Ingram, J. W, Tests of DDT dust against the sugarcane borer, the yellow sugarcane aphid, and the Argentine ant. (Scientific Note) Jour. Econ. Ent. 37:lUU-lU5. I9UU. ,2/The synthetic and natural- cryolite used in the tests reported in this paper were analyzed by the Division of Insecticide Investigations IP/? 2 iQjfflfi fouJl(i to contain 90.1 and 89.7 percent of Na3AlF£,, respectively. Average number of "borers per pl< Dt C.P. 28/19 C.] ?. 29/103 )) 6.7 — ' 7.0 . (1U.8±/ 15,7 — 17.5 ll.U ' Ul.7 ...; 38. U U7.0 58.0 1.6.1+- 12.0 22. U 18.1 - 2 - In June and July a similar experiment was conducted for the control of second-generation "borers. A 6 "by 6 Latin-square arrangement was used on C.P. 36/191 cane. Four weekly applications were made at the rate cf approximately 10 pounds of the dust per acre-application. Based on percentages of joints "bored in the treated plots as compared with the checks (table 2), synthetic cryolite applied on regular schedule gave a control of 6l percent and natural cryolite '50 percent. In the plots dusted with DDT 12 percent more of the joints were "bored than in the un- dusted check plots. This difference was not 'significant, "but the DDT- treated plots showed significantly heavier "borer injury than the plots treated with any of the other insecticides. Table 2. — Comparison of DDT with various cryolite schedules for control of second-generation "borers in sugarcane variety C.P. 36/191 Treatment Application Average joints bored schedule Percent Angle Synthetic cryolite Hatural cryolite DDT-pyrophyllite (10$) Check, no treatment Difference required fo: Odds of 19 Jl Odds of 99:1 Regular 6.2 lU.l Delayed 1 we ek U.o 11.2 Regular plus one applica- tion 5,6 12,5 Regular •- s.o 15,9 Regular 19.0 25. h — 16.1 23,1 ^lificance: « 3.5 In September and October a 10 percent DDT-pyrophyllite dust was compared with synthetic cryolite in two replicated experiments, one at Houma and the other at Raceland, La. , of six plots per treatment on sugarcane planted the previous August. This cane was similar in size and growth to that prevailing in the spring at the time of dusting for the control of first-generation "borers. Four weekly applications were made at the rate of approximately 8> pounds per acre-application. From the number of live "borers surviving (table 3) on variety C.P. 3^/120, synthetic cryolite gave a control of 8£ percent, and almost three times as many borers were found in the DDT plots, as in the untreated plots J on variety C.P. 2S/19 synthetic cryolite gave 95 percent and DDT 9 percent control. The increase in borers .in the DDT plots in the first experiment may have been due to its effect .on Trichogramma and other natural enemies of the borer under conditions of a heavy infestation, when Trichogramma is usually more abundant. . 3 - Table 3 •~*~Survi val of sugarcane "borers on two varieties of summer- planted cane, following treatment with DDT and cryolite, - Average number of "borers per t)lot Treatment C.F. 3U/12w C*F. 28/19 Synthetic cryolite l.S 0*5 DDT-pyrophyllite (10$ DDT) Hi. 3" g.g Cheeky no treatment 15? 2 9?7 Differences required for .significance? Odds of 19:1 10.7 5.3 Odds of 99:1 ik.G 7.2 In September and October DDT spray was compared with synthetic cryolite dust in a replicated experiment on variety C,F. 29/120 sugarcane planted in August* As in the previous experiment, this cane was similar in size and grov/th to that prevailing in the spring. The DDT spray,, which was made up of 20 pounds of ,10 percent of DDT-pyrcphyllite and f^ ounces of a sticker-spreader per 100 gallons of water,, was applied at the rate of 50 gallons per acre. The synthetic cryolite dust was applied at the rate of 8> pounds per acre. Each material was applied four times at weekly intervals on four 1/20-acre plots. Cn untreated check plots an average of 63 "borers survived. On the plots dusted with synthetic cryo- lite an average of 9*5 "borers survived as compared with ^5 on the plots sprayed with DDT* Control with cryolite was thus £5 percent hut with DDT spray only 29 percent* ' In' the experiment conducted in 19^3 the number of leaves infested with. the yellow sugarcane aphid ( Sipha flava (Forbes)) was six times as great in plots treated with DDT as in untreated check plots and over twice as great as in plots treated with synthetic cryolite*-/ In the first-generation experiments with D3T in 2$% there was very little yellow aphid injury, "but in the second-generation experiments the aphid infestation was noticeably greater in DDT-treated plots than in pints receiving any other treatment* Sice Stinkbug A DDT-pyrophylllte dust was tested in a cage experiment on the rice stinkbug ( Solubea pugnax (F*)) in 19*14. On September 23 six screen-wire cages about 3 "by 3 "by 3 feet in size were each stocked with 10 adult stinkbugs and a bunch of Faspalum urvillei panicles. The Faspalum stems were inserted in a jar of water through a small hole in a paper cover* Three of the stocked cages were carried into the open and, dusted with 10 percent DDT-pyrophyllite at about the rate used in', making 'a 10-pound- per-acre application on sugarcane. All the cages were then placed on antproof "benches in a screened insectary. - u - mil 3 1262 09238 7090 The results shown in tatle h indicate that DDT dust may have con- siderable promise for use in the control of tho rice stinkbug. This dust gave an 8>S«5 percent control of adults 2 days after dusting, and 32. H percent after h days. The lateness of the season prevented addi- tional experiments with this "bug. Table U. — Results of cage tests of DDT-pyrophyllite dust on the rice stinkbug Cage No, Percentage mortality after 1 day 2" days 3 days h days l IC days Nymphs found 1 2 3 Average 1 2 3 Average Dusted cages 70 70 90 90 90 100 100 IOC 90 100 100 100 S3 90 97 97 Untreated cages 10 10 1© IC 10 10 10 10 20 30 30 7 13 17 . 17 100 100 100 100 100 100 None None k dead 15 live 10 live 15 live Grass Webworm A grass webworm ( Pachyzancla phaeopteralis G-uen,) defoliated many lawns and pastures in southern Louisiana in September and October. On a lawn near Houma a strip about 50 feet wide and 3C0 feet long was dusted with synthetic cryolite while the dew was on the grass at the approximate rate of 10 pounds per acre. A similar strip was dusted with 10 percent DDT-pyrophyllite, applied at the rate of about 10 pounds per acre while the dew was on the grass, and a third strip was sprayed with ordinary kerosene emulsion at the approximate rate of 1 gallon to each squafe yard of surface after the dew had' dried. The emulsion was made by dissolving 1 pound of laundry soap in 1 gallon of water and adding 1/2 gallon of kerosene while stirring vigorously; 1 part* of this emulsion was then mixed with 50 parts of water by volume for application to the lawn. These treatments were all applied on September 28, Two days later many live larvae and no dead ones were found in the untreated* and the cryolite-treated areas, many dead- ones and ne live ones in the DDT- treated strip, and about 30 percent of the larvae were dead in the strip treated with kerosene emulsion. Nine days after the application the untreated areas and the areas treated with synthetic cryolite or kerosene emulsion were brown from defoliation -while the DDT-treated area was of a normal green color. This difference was still apparent the last cf November, On October 3 parts of another webworm-inf ested lawn were treated with a IC percent DDT-pyrophyllite dust at the rate of about 10 pounds per acre. Over 90 percent of the larvae were killed by the DDT treatment in areas examined, and only live larvae were found in untreated areas. Carpetgrass ( Axon opus compressus ( Swart z) Beauv.) was the main lawn grass in both this and the preceding location.