Tests with Dow ET-57 against Two Species of Cattle Grubs1

Abstract

Dow ET-57 shows promise as a systemic insecticide for livestock pests. In laboratory tests the compound was toxic to screw-worms (Callitroga hominivorax) and stable flies (Stomoxys calcitrans) when given orally or subcutaneously to guinea pigs at 100 mg/kg. It was less effective at 50 mg/kg and ineffective at 25 mg/kg. When administered orally at 100 mg/kg to 5 Hereford calves presumably infested with Hypoderma lineatum, it seemed effective, as only 4 larvae appeared and they died in the 2nd instar. A comparable group of 5 calves treated with ET-15 had 98 larvae develop. ET-57 administered orally at 100 mg/kg to 35 S. Dakota calves naturally infested with H. bovis and lineatum caused an estimated 97.2% control and completely prevented encystment of new larvae. Before ET-57 can be considered for practical control further research is required.