The effects of reduced tillage and earlier seeding on flea beetle (Phyllotreta spp.) crop damage in spring oilseed rape (Brassica napus L.)

The restriction on seed treatments containing neonicotinoid insecticides in the European Union has brought crop protection into focus for oilseed rape (Brassica napus L.). In spring sown oilseed rape, neonicotinoid seed treatments have mainly been used for protection against flea beetles (Phyllotreta spp.), and there is now a need to evaluate alternative control methods. We investigated the effect of reduced tillage and altered seeding date on flea beetle crop damage in spring oilseed rape in eight field experiments over three years in south central Sweden. The average proportion of cotyledon area damaged by flea beetles was not affected by the tillage treatment. Proportion of crop damage was, however, lower in early seeded compared to late seeded plots (0.21 compared to 0.28). We conclude that earlier seeding holds promise to be incorporated into an integrated pest management program for flea beetles in spring oilseed rape, whereas further research on reduced or zero tillage strategies for flea beetle control is warranted.