Residual Toxicity of Three Phosphorous Insecticides to the Boll Weevil12

The residual toxicity of 3 phosphorous insecticides to the boll weevil, Anthonomus grandis Boheman, was determined hourly for 24-48 hours by using field cages made of ice cream cartons. The cages were an improvement over those formerly used and should facilitate such studies of similar chemicals and insects. Azinphosmethyl at 0.25 lb per acre was effective for 12-24 hours and at 0.5 lb per acre, for more than 24 hours. Methyl parathion at 0.25 and 0.5 lb per acre was effective for only 2-4 and 4-6 hours, respectively. Malathion at 0.5 lb per acre gave residual kill for 4-6 hours; at 2 lb per acre it was effective for more than 24 hours.