Season-long releases of partially sterile males for control of codling moth (Lepidoptera: Tortricidae) in Washington apples

Season-long field studies were conducted in Washington apple orchards that compared the following: (1) twice per week releases of partially sterile codling moths, Cydia pomonella (L.), treated with either 100 or 250 Gy, and (2) combinations of mating disruption plus the release of partially sterile (100 Gy) codling moths, to control wild codling moth populations. No significant differences in the level of fruit damage at either midseason or han,est were found between any of the treatments, or between the treatments and the inside controls. Damage in all plots was <0.1%. In both studies, trap data suggest that the movement of the 100 Gy-treated moths into the other treatments and the inside controls may have masked treatment effects. However, fruit damage was significantly lower in all treatment plots when compared with control plots located outside of the treatment areas. Results indicated that the release of partially sterile male (and fully sterile female) codling moths does not result in increased fruit injury and that the lower dose of radiation used to partially sterilize males results in insects that are more active, disperse greater distances and are generally more competitive.