Effects of regional crop rotations on autumn insect pests in winter oilseed rape

Abstract

BackgroundChemical control of insect pests in oilseed rape (OSR) is becoming increasingly difficult due to the development of resistance and restrictive insecticide approvals in Europe. At the same time, there is a lack of preventive and alternative control measures. Crop rotation mostly fails to control insects due to their mobility; however, changing regional cropping densities can dilute or concentrate pest pressure. In this study, we investigated whether the local occurrence of Psylliodes chrysocephala and Delia radicum, serious insect pests in winter OSR, is influenced by distance from the previous year's OSR fields and how changes in OSR rape cropping density at a regional scale (up to 10 km radius) affect pest pressure.ResultsAbundance of P. chrysocephala in yellow water traps decreased with increasing distance to previous year's OSR. Estimated catches in the first three weeks of migration were about 68–76% lower at 10 km distance compared to 1 km in autumn 2019 and 2020. However, in both seasons P. chrysocephala was able to disperse over distances of 10 km. Probability of root damage by D. radicum was affected by changes of OSR cropping area at a spatial scale of 2.5 km radius; it increased if acreage of OSR decreased. Furthermore, aphid infestation was lower when OSR was distant in the previous year.ConclusionThis study could enable field‐specific risk assessment and prediction of pest pressure. To decide about the effectiveness of cropping breaks at a regional level as a preventive crop protection measure, more knowledge on other pest species and antagonists is needed.This article is protected by copyright. All rights reserved.

Integrated pest control in oilseed crops—new advances from the rapeseed research community

“…14,15 Crop management factors such as undersowing companion plants was shown to reduce damage caused by CSFB in OSR 16 and rotation (or spatiotemporal separation of OSR fields via the proportion of OSR in the landscape) has also been shown to be important; CSFB, cabbage root fly (Delia radicum) and aphid abundance, damage or infestation decreases in crops with increasing distance from the nearest crop of OSR in the previous year. 17 Similar results were found for pollen beetle 18 and the cabbage seed weevil (CSW; Ceutorhynchus obstrictus) 18,19 importantly without negative impacts of distance on biocontrol by their specialist parasitoids. 18 Parasitism of OSR pests was high, 18,19 suggesting significant biocontrol potential.…”