Abstract

Responses of tufted apple bud moth, Platynota idaeusalis (Walker), neonates in direct spray and leaf residue bioassays with the organophosphates azinphosmethyl, chlorpyrifos, microencapsulated methyl parathion, phosmet, and phosalone; the carbamates methomyl and thiodicarb; and the pyrethroid fenvalerate were measured for a laboratory strain and for populations collected from orchards at the Pennsylvania State University Fruit Research Laboratory in Adams County, Pa. The relative ranking of pesticide toxicity for the laboratory strain wassimilar in both bioassays: pyrethroid > carbamates > organophosphates. However, certain organophosphates such as chlorpyrifos and microencapsulated methyl parathion were much more effective in the leaf residue than direct spray tests. Highest resistance levels (field LC50,/laboratory LC50,) were found for the organophosphates in both tests (3- to 17-fold), especially with azinphosmethyl (17-fold). Carbamates and pyrethroids had low resistance levels (1- to 4-fold). Resistance levels to azinphosmethyl were high (17- to 24-fold) within commercial and experimental apple orchards scattered throughout Adams County.

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