Control of Larvae of the Screw-Worm in Cattle with Insecticidal Sprays1

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Abstract
For 2 consecutive days cattle were artificially wounded, and the wounds were infested with newly hatched larvae of the screw-worm, Cochliomyia hominivorax (Coquerel). On the 3rd day, the cattle were individually sprayed with 2½ gal of 1 of 19 insecticides (2—4 animals/treatment). At 1 day posttreatment, wounds were examined for live larvae. Treatments were grouped according to effectiveness as follows: complete control of 1- and 2-day-old larvae 0.25% Bayer 37289 (O-ethyl O-2,4,5-trichlorophenyl ethylphosphonothioate), 0.1% Bayer 38333 (O-2,4-dichlorophcnyl O-ethyl methylphosphonothioate), 1% bromophos (O-(4-bromo-2.5-dichlorophenyl) O,O-dimethyl phosphorothioate), 0.05% isobenzan, 0.1% fenthion, and 0.45% Shell SD- 8447 (2-chloro-l-(2,4,5-trichlorophenyl) vinyl dimethyl phosphate); complete control of 1-day-old larvae only—0.01% Bayer 29952 (O-ethyl O-[p- (methylthio)-phenyl] methylphosphonothioate), 0.25% coumaphos, 0.1% ethion, 0.25% Hooker HRS-1422 (3,5-diisopropylphenyl methylcarbamate), and 0.25% Imidan® (O,O-dimethyl S- phthalimidomethyl phosphorodithioate); incomplete control—O.1 % Banol® (6-chloro-3,4-xylyl methylcarbamate), 0.01% Bayer 38156 (O-ethyl S-p--tolyl methylphosphonodithioate), 0.25% Bayer 39007 (O-isopropoxyphenyl carbaryl, 0.5% carbaryl, 0.05% dimetilan, 0.1% Dowco 175 (2,4-dichlorophenyl propyl methylphosphoramidate), 0.1% Shell SD-8448 (2-chloro-l-(2,4,5-trichlorophenyl)vinyl diethyl phosphate), and 0.01% Stauffer N-2790 (O-ethyl S-phenyl ethylphosphonodithioate).