Abstract:Two leafroller spades are major pests of apple in British Columbia, Archips argyrospilus (Walker) and Archips rosanus (Linnaeus). Field observations showed that both species overwinter in the egg stage and that larval emergence times are similar. Experiments demonstrated that both species are susceptible to sprays of azinphos-methyl, diazinon, or trichlorfon applied at either the pink bud or petal fall stages. Dipel (Bacillus thuringiensis) failed to control larvae of either species.
A 2-year study was conducted in an organic, essentially pesticide-free orchard and in one which followed a complete pesticide program to assess populations of beneficial arthropods. There were far more beneficial species in the pesticide-free orchard both on the trees and in the cover crop. Spiders increased dramatically in the organic orchard and relatively few spiders were found in the sprayed orchard. Pest species were below treatment thresholds in both orchards with the exception of codling moths. By the second season, codling moth injury was so severe in the organic program that the non-pesticide program had to be abandoned.
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.
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