Susceptibility of codling moth in southwestern Ontario apple orchards to currently recommended insecticides

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Grigg McGuffin, Kristy Nicole
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University of Guelph

This research examined the susceptibility of codling moth ('Cydia pomonella' L.) from 2008-2010 to registereded insecticides-azinphosmethyl, phosmet, thiacloprid, acetamiprid, methoxyfenozide, novaluron, spinetoram, and chloranthraniliprole used in Ontario apple orchards. Discriminatory concentrations were determined for application in future resistance monitoring for adult topical and larval diet bioassays. Azinphosmethyl and phosmet were generally less toxic than all other insecticides. Thiacloprid, acetamiprid, chlorantraniliprole, methoxyfenozide, and novaluron had moderate toxicity. Spinetoram was the most toxic. Some field populations exposed to azinphosmethyl and thiacloprid had lower mortality in adults and larvae compared to insecticide-susceptible populations. Larvae exposed to methoxyfenozide also had lower mortality, but were still susceptible to chlorantraniliprole. Results suggested the presence of tolerance to these registered insecticides in some Ontario codling moth populations. It was conclude that newer classes of insecticides, such as spinosyns and anthranilic diamides need to be incorporated into codling moth control programs with continual insecticide resistance monitoring. Control programs should also include rotation between different insecticide classes during a growing season and utilization of mating disruption to reduce selection for insecticide resistance.

Codling moth, Southwestern Ontario, Apple orchards, Insecticides, Resistance