Ovicidal Activity of Thompson-Hayward TH 6040 in the Stable Fly and Horn Fly After Surface Contact by Adults13

Abstract

Adult stable flies, Stomoxys calcitrans (L.), deposited eggs that did not hatch when the flies were exposed in the World Health Organization kit to paper impregnated with Thompson-Hayward TH 6040 (N-4-chlorophenyl)-N'-(2,6-difluorobenzoyl) urea). The approximate LC₅₀ for inhibition of hatch was 0.17%. Also, 88% of the eggs did not hatch when the stable flies were exposed for 7 days to 7-day-old spray residue of TH 6040 (1%) on a steer, and 60% did not hatch after a similar exposure to 14-day-old spray residue. Adult horn flies, Haematobia irritans (L.), treated topically with 1–2 µg TH 6040/µl acetone likewise deposited eggs that did not hatch though larvae developed within the egg. When horn flies were exposed to the treated steer, hatchability was inhibited after a 48-h exposure to 35-day-old spray residue.