Use of insect pest thresholds in oilseed rape and cereals: is it worth it?

Abstract

BackgroundIntegrated pest management (IPM) uses thresholds to minimize pesticide use, and field monitoring of damaging organisms is an important component to evaluate whether or not thresholds have been breached. However, monitoring requires time and knowledge which impacts costs and benefits. In this study, we evaluated the effects of using insect pest thresholds on time effort, frequency of insecticide treatment and economics in comparison with common farm practices (business as usual) in winter wheat (WW), winter barley (WB) and winter oilseed rape (OSR). This study was done over 2 years (2018 to 2020) on 24 conventionally managed farms in North Rhine‐Westphalia (Germany).ResultsFarmers spent significantly more time (42 min ha−1/season) monitoring insect pests in OSR than in WW (16 min ha−1/season) and WB (19 min ha−1/season). The use of insecticides in OSR was significantly reduced by 42% in comparison to business as usual. In cereal crops, the use of insecticide treatment was reduced by 50% but this was not significantly different to business as usual. Yields were not significantly reduced when crops were managed in accordance with IPM, and negative differences were small and not significant. However, economically, the costs of monitoring can only be recovered when labor costs and commodity prices are low and insecticide cost is high.ConclusionInsect pest thresholds can help link the policy and environmental goals of insecticide reduction and the agronomic goal of production security. In the future, the time and cost required for monitoring should be reduced through intelligent solutions and tools, increasing the economic viability of monitoring and IPM. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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

“…Novel work to define spray thresholds based on OSR physiology is presented 8 and use of thresholds in OSR was shown to significantly reduce insecticide use by 42% in comparison to 'business as usual', however, increased costs for monitoring can make this uneconomical. 9 Better monitoring methods and risk assessment/decision support tools are therefore needed. These are in the pipeline; improved understanding of immigration behavior and the factors that drive infestation of the cabbage stem flea beetle (CSFB; Psylliodes chrysocephala) 10,11 and pollen beetle (Brassicogethes aeneus) 12,13 will help to inform models to predict the timing, risk and spatial distribution of these insects, perhaps enabling targeted applications via precision agriculture.…”

“…when pest populations have breached a certain threshold, will help to reduce selection pressure for insecticide resistance. Novel work to define spray thresholds based on OSR physiology is presented 8 and use of thresholds in OSR was shown to significantly reduce insecticide use by 42% in comparison to ‘business as usual’, however, increased costs for monitoring can make this uneconomical 9 . Better monitoring methods and risk assessment/decision support tools are therefore needed.…”