Insecticide Baseline Sensitivity in Codling Moth (Lepidoptera: Tortricidae) Populations from Orchards under Different Management Practices

The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is a key "fruit-feeding" pest of apples and is known for developing resistance to various insecticidal products applied in apple orchards. Laboratory studies were conducted to determine insecticide resistance in codling moth populations collected from various apple orchards in Pennsylvania. In particular, male moths of C. pomonella were collected from commercial and abandoned fruit orchards and were tested for their sensitivity levels to azinphos-methyl and methomyl via adult topical bioassays. Larval sensitivity also was examined for different insecticides (e.g., acetamiprid, novaluron, rynaxypyr) via diet-surface topical bioassays. Adult C. pomonella populations expressed significant differences in their sensitivity to azinphos-methyl and methomyl. Concurrent estimates of azinphos-methyl insecticide effectiveness (i.e., adult topical assays) of moths in monitoring traps showed increased tolerance in individuals captured in commercial orchards rather than in abandoned orchards. Results of larval bioassays showed differences in sensitivity to various insecticide compounds as well as differences between compounds based on the timing of mortality. After the initial assessment, however, all insecticides (except fenpropathrin) exhibited greater toxicity with increasing time.