LAUSR

BACKGROUND Agricultural landscapes provide resources for arthropod pests as well as their natural enemies. In order to develop integrated pest management (IPM) practices, it is important to understand how spatiotemporal location influences crop colonization and damage severity. We performed a three-year (2016-2018) field experiment in winter oilseed rape (OSR, Brassica napus) fields in Estonia, where half of the fields were within 500 m of the location of the previous year's winter oilseed rape field, and half outside this zone. We investigated how distance from the previous year's OSR crop influences the infestation and parasitism rates of two of its most important pests - the pollen beetle (Brassicogethes aeneus) and the cabbage seed weevil (Ceutorhynchus obstrictus). RESULTS When the distance from the previous year's OSR crop was > 500 m, we recorded significantly reduced pest pressure by both B. aeneus and C. obstrictus, in study fields. Biocontrol of both pests, provided by parasitic wasps, was high in each study year and commonly not affected by distance. Mean parasitism rates of B. aeneus were > 31%, occasionally reaching > 70%; for C. obstrictus, mean parasitism was > 46%, reaching up to 79%, thereby providing effective biocontrol for both pest species. CONCLUSION Spatiotemporal separation of OSR fields can reduce pest pressure without resulting in reduced parasitism of OSR pests. This supports a spatiotemporal field separation concept as an effective and sustainable technique for IPM in OSR. This article is protected by copyright. All rights reserved.