TOXICITY AND FIELD EFFICACY OF AVERMECTINS AGAINST CODLING MOTH (LEPIDOPTERA, TORTRICIDAE) ON APPLES

Avermectin compounds were tested in laboratory and field residual bioa ssays and field efficacy studies to determine their toxicity and effec tiveness against codling moth, Cydia pomonella (L.), larvae. In the la boratory, the LC(50) for MK-0244 was 0.08 ppm. MK-0244 was approximate to 9, 30, and 104 times more toxic than abamectin, azinphosmethyl, an d abamectin 8,9-oxide, respectively. Abamectin and MK-0244 were equall y effective in reducing larval entries into apples; however, >50-fold increase in concentration of both was required to prevent stings. In c ontrast, only a 2-fold concentration increase of azinphosmethyl was re quired for similar effectiveness. Variable sting and entry damage redu ction was observed on young versus older apples when treated with aver mectins and azinphosmethyl. Older apples treated with avermectins were protected from entry damage for 14 d after application, whereas azinp hosmethyl-treated apples had no stings and entries for 7 d and entry d amage through 14 d. Under field conditions, single applications of aba mectin and MK-0244 versus multiple applications per codling moth gener ation were equally effective in preventing entries, although the level of control obtained with either treatment was not commercially accept able.