A STRAIN OF FRUITTREE LEAFROLLER, ARCHIPS ARGYROSPILUS (LEPIDOPTERA: TORTRICIDAE), TOLERANT TO AZINPHOS-METHYL IN AN APPLE ORCHARD REGION OF THE OKANAGAN VALLEY OF BRITISH COLUMBIA

Abstract

Probit analysis of the dosage response of first instar, fruittree leafroller larvae to azinphos-methyl indicated that a strain from a commercial orchard in East Kelowna, B.C. was 7.8 times more tolerant than a susceptible strain. Azinphos-methyl applied to experimental apple blocks in the same area did not provide satisfactory control. Leafroller damage as high as 10.5% was found in several orchards which had received multiple azinphos-methyl and other organophosphorous insecticide treatments. The development of an organophosphorous resistant strain of fruittree leafroller in this orchard area is strongly suggested. Bacillus thuringiensis applied at the pink stage of apple blossom development gave adequate control of fruittree leafroller in East Kelowna field trials and will be suggested as the control material for commercial orchards in this area.