Organophosphorus Compounds as Residual Treatments for Adult Mosquito Control

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The residual action of Malathion and Parathion deposits against laboratory-reared adult Anopheles quadrimaculatus was evaluated in animal-baited huts under simulated field conditions near Savannah, Georgia. Malathion at 100 and 200 mg/sq. ft., Malathion:DDT at 100:200 or 200:100 mg/sq. ft., Malathion:dieldrin at 100:25 or 100:50 mg/sq. ft., Parathion at 12.5 mg/sq. ft. and Parathion:DDT at 12.5:200 mg/sq. ft. produced essentially 100 per cent mortalities of dieldrin-resistant females for the entire 4- to 5-month observation period. Dieldrin at 25 or 50 mg/sq. ft. and DDT at 200 mg/sq. ft. yielded mortalities of 26 to 54 and 36 to 75%, respectively, over the same time interval. Dieldrin-resistant and susceptible strains of A. quadrimaculatus moved into untreated huts from attached entrance cages in similar numbers but 42 per cent of the resistant specimens escaped into window traps as compared to 12 per cent of the susceptible strain.