Biological control of a univoltine race of European corn borer, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), by Trichogramma in Switzerland is currently timed according to repeated, semi‐field observations of the post‐diapause development of the pest at one site. We developed a phenology model with the aims of replacing this costly labour practice and by considering the Swiss landscape. Observations collected over 29 years were used for model calibration and validation. We parameterized a time‐varying distributed delay model based on published laboratory observations of development durations at constant temperatures. The model was driven with hourly temperature recordings beginning on January 1. The calibration of the mean development rates and their variations was based on semi‐field data of larval and pupal development. The model, with its calibrated parameters and their variations, allowed the simulation of mean predictions and prediction intervals. We validated the model predictions of emergence with flight data (obtained via light traps) from several sites in western and northern Switzerland. The simulated mean emergence was 6.9 degree‐days earlier than the observed flight at the calibration sites and only 0.5 degree‐days earlier than the observed flight at other sites. Our simulation of pupation explained half of the variation in emergence time, whereas semi‐field observations of pupation explained three‐quarters of this variation. Our model simulations are not subjected to the local potential biases. Simulation errors from a year with an extremely dry spring were explained by the lack of consideration of humidity by the model. Our simulations provide a valid and less labour‐intensive alternative to observations for timing biological control in the maize‐growing areas of Switzerland and likely other areas of Europe.
Production of arable crops in Switzerland is subsidized for services performed within the Proof of Ecological Performance (PEP) program, the crop protection part of which is based on IPM principles. Within PEP, chemical insect control must rely on those approved insecticides that are deemed harmless for beneficial arthropods. Approved insecticides potentially impacting beneficial arthropods may also be applied, but only if unavoidable and with an official permit. In order to assess the ecological and economic sustainability of this PEP program, a reference insecticide strategy illustrating the current PEP requirements was compared with other strategies. For this purpose, a sustainability assessment taking account of ecotoxicological risks and economic viability in addition to the preservation of beneficial arthropods was performed according to the SustainOS methodology. The results show that the one-off use of Audienz (spinosad) to control cereal leaf beetle (Oulema melanopus)-a key pest in winter wheat-would significantly improve sustainability vis-à-vis the reference (Nomolt (teflubenzuron) plus Biscaya (thiacloprid)). However, in the case of the Colorado potato beetle (Leptinotarsa decemlineata), in potato crops, where Audienz is considered the reference, no alternative would exhibit better sustainability. Moreover, the study shows that strategies using Novodor (Bacillus thuringiensis) protect beneficial species well but have the drawbacks of increased yield risk and higher costs. The conclusions drawn from these analyses allow recommendations for modifications of the PEP requirements for these two pest insects. The SustainOS methodology, a multi-step process combining expert knowledge with quantitative assessments including a sensitivity analysis of key target parameters and a rule-based aggregation of assessment results, yielded valuable insights into the sustainability of different crop protection strategies.
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