Toxicity and field efficacy of avermectins against codling moth (Lepidoptera: Tortricidae) on apples

Avermectin compounds were tested in laboratory and field residual bioassays and field efficacy studies to determine their toxicity and effectiveness against codling moth, Cydia pomonello (L.), larvae. In the laboratory, the LC50 for MK-0244 was 0.08 ppm. MK-0244 was approximately 9, 30, and 104 times more toxic than abamectin, azinphosmethyl, and abamectin 8,9-oxide, respectively. Abamectin and MK-0244 were equally effective in reducing larval entries into apples; however, >50 fold increase in concentration of both was required to prevent stings. In contrast, only a 2-fold concentration increase of azinphosmethyl was required for similar effectiveness. Variable sting and entry damage reduction was observed on young versus older apples when treated with avermectins and azinphosmethyl. Older apples treated with avermectins were protected from entry damage for 14 d after application whereas azinphosmethyl-treated apples had no stings and entries for 7 d and entry damage through 14 d. Under field conditions, single applications of abamectin and MK-0244 versus multiple applications per coding moth generation were equally effective in preventing entries although the level of control obtained with either treatment was not commercially acceptable.