The effect of three organo‐phosphorus insecticides on certain arthropods which infest livestock

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Abstract
SUMMARY: The organo‐phosphorus compounds fenchlorphos, trichlorphon and coumaphos, used at 0·25%, killed Dermanyssus gallinne on poultry and perches, and Leiognathus (Liponyssus) sylziarum on poultry: both showed persistent acaricidal value without avian toxicity.Fenchlorphos at 100 mg./kg. and trichlorphon at 20–100 mg./kg. were systemically effective against larvae of Lucilia sericata on sheep. Coumaphos was non‐insecticidal, but toxic to sheep, when given orally at 15–20 mg./kg. Sprzying with 0·25% coumaphos protected sheep against L. sericata larvae for 8–10 weeks.Fenchlorphos administered orally at 110 nig./kg. killed larvae of Hypoderma boris which had been implanted into calves. Trichlorphon (2·0%) applied externally killed all larvae within 28 days: coumaphos (2·0%) similarly applied was larvicidal within about 15 days.The toxic dose of fenchlorphos for calves was 500 mg./kg.; trichlorphon at 300 mg./ kg. and coumaphos at 20 mg./kg. were toxic to sheep.