A process-based life cycle model of the cabbage stem flea beetle on winter oilseed rape: Effects of temperature

The cabbage stem flea beetle (CSFB) is an economically important pest of oilseed rape crops that has increased in importance over recent years. Here we present the first attempt at a process-based model of this species using delay-differential equations (implemented in the R package stagePop) to simulate the abundance of each stage of the life cycle. We split the life cycle into 6 distinct stages: eggs, larvae, pupae-diapause (pupae, pre-aestivation adults and aestivating adults), pre-oviposition adults, reproductive adults and non-reproductive adults (past reproductive age), with temperature-dependent stage durations and death rates. We use adult trap data to inform on the initial conditions for the model and drive the model with a generic air temperature time series. To validate our model we compare the results with expected timings based on the scientific literature and field data on larval abundance. We use the model to investigate the effects of increasing the yearly average air temperature, and the effects of unusually warm seasons on CSFB population seasonal abundance patterns. Due to a lack of data there are key processes (e.g. temperature dependence of larval development) and parameter values that are uncertain. However, we believe the model, and its future iterations as more data are obtained, has the potential to be used as part of a decision support system for farmers and advisors, enabling more informed decisions on drilling and IPM strategies based on the within season weather conditions.