Towards eradication of codling moth in British Columbia by complimentary actions of mating disruption, tree banding and sterile insect technique: Five-year study in organic orchards

Abstract

In 1992, the Okanagan-Kootenay Sterile Insect Release (SIR) Program was initiated in British Columbia, Canada, to eradicate codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) from its montane, fruit-growing valleys. Widespread damage in 1994, and failure to maintain sterile:wild (S:W) overflooding moth ratios at the 40:1 target in spring, led to intensive use of supplemental insecticides to control spring populations post-1994. During 1995–1999 population control with this modified SIR Program was compared with an alternative strategy to supplement SIR with pheromone-based mating disruption+tree banding in organic orchards. Weekly catches in pheromone traps indicated mean S:W moth ratios in both insecticide- and pheromone-supplemented orchards were near identical in spring, and confirmed ratios were more often suboptimal (<40:1) in May–June compared with July–August. By 1997 no damaged fruit were found in any orchard, and by 1999 no wild moths, nor overwintering larvae were captured in any pheromone-supplemented orchard. However, wild moths and overwintering larvae were still detectable in 15–20% of insecticide-supplemented orchards in 1999. Catches of wild moths and overwintering larvae declined fastest in SIR orchards supplemented with pheromone and banding. Given sterile moths compete poorly with wild moths in spring when S:W ratios rarely reach target levels, a pheromone+banding program applied in spring, combined with release of sterile moths in summer only, is recommended, especially for organic orchards. A multi-tactic SIR program should reduce codling moth populations at least as effectively as SIR supplemented with insecticides. This approach should ensure sustainable management of codling moth with potential to eliminate wild populations sooner than using sterile moths alone, and possibly their use in combination with neurotoxic insecticides.