SUSCEPTIBILITY STATUS OF BOLL-WEEVILS FROM LOUISIANA TO 11 INSECTICIDES

Topical bioassays of 11 insecticides were conducted with the R. T. Gas t Insect Rearing laboratory colony (GAST-LAB) and 22 field collections of boil weevils, Anthonomus grandis grandis Boheman, from 11 parishes in Louisiana. The order of toxicity of the insecticides tested agains t the GAST-LAB colony from most to least toxic was cyfluthrin > zeta-c ypermethrin > fipronil 4-tri-fluoromethylsulfinylpyrazole-3-carbonitri le] > deltamethrin > azinphosmethyl > cypermethrin > methyl parathion > Pirate(R) ethyl)-5-(trifluoromethyl)-pyrrole-3-carbonitrile] > oxamy l > endosulfan > malathion. There was no conclusive evidence of resist ance to any of the 11 insecticides bioassayed against field-collected boil weevils, although LD(50)'s for cypermethrin, cyfluthrin, malathio n, and oxamyl were highly variable. The LD(50) values for deltamethrin , endosulfan fipronil, oxamyl, Pirate(R), and zeta-cypermethrin will s erve as baseline data for future studies.