Systemic Insecticides Applied as a Topical Pour-On and as an Oral Drench for Cattle Grub Control

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Abstract
In south Mississippi during 1960-61 Ruelene® (O-4-tert-butyl-2-chlorophenyl O-methyl methylphosphoramidate) formulated as a 2 Ib/gal. emulsifiable concentrate, at dosages ranging from 38 to 120 mg./kg. and administered as a pour-on treatment resulted in 98.9% control of the common cattle grub, Hypoderma lineatum (de Villers). On nonweaned calves, using the pour-on method. Co-ral® (O, O-diethyl O-3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl phosphorothionte), 2% suspension in water, 250 ml. per animal, gave 84.7% control, and Ruelene, 50 mg./kg., gave 80.1% control. The average gains in weight of the Co-ral-treated group was significantly less than that of the other treatments indicating that this dosage of Co-ral to calves 4 to 6 months of age is too high. Differences in gains in weight of groups of mature Hereford heifers treated with pour-on applications of Ruelene (75 mg./kg.) and Co-ral (2% and 4% suspensions in mineral oil) were not significant. No grubs appeared in three groups of nonweaned Hereford calves treated as follows during 1961-62: pour-on applications-(1) Ruelene 60 mg./kg., (2) Co-ral. 2% suspension in mineral oil, 125 ml. per animal; oral drench-(3) Famophos® (O, O dimethyl, O, p-(dimethyl sulfamoyl) phenyl phosphorothioate) formulated as a 20% wettable powder and administered as a suspension in water at a dosage of 25 mg./kg. A second pour-on test gave grub control among several groups of nonweaned calves as follows: Bayer 29493 (O, O-dimethyl O-[4-(methylthio)-m-tolyl] phosphorothioate). 2% solution in mineral oil, 125 ml. per animal, 97.6% control; Ruelene, 50 mg./kg., 95.9% control; Co-ral, 2% suspension in mineral oil, 125 ml. per animal, 82.4% control. Differences in gains in weight in the 1961-62 tests were not significant, Co-ral (2%) administered at a rate of 125 ml. per animal in mineral oil (instead of 250 ml. in water as applied the previous year) did not affect gains in weight of nonweaned calves.