EPIC-GILSYM: modelling crop-pest insect interactions and management with a novel coupled crop-insect model.
Modern intensive agriculture relies heavily on pesticides to control weeds, pathogens and insect pests. Forecasting and managing the impact of pests and pesticides on crop production is challenging. Since pest control tactics not only affect the target pest, but also initiate feedbacks within the field community, proper modelling of pest management requires functions in at least two trophic levels. To respond to this challenge, we integrated a process-based insect population dynamics model and a process-based crop model. The coupled model was then used to simulate eight field trials on five different sites across the US, testing the efficacy of five different pesticides against six different pests as well as the yield response. The results showed that the model performed robustly on different sites (five plots across the US) and under different climatic conditions (8 years spanning a period from 1985 to 2014). For armyworm and black cutworm, the simulated yields per hectare, the number of insects per plant and the response to insecticide treatments closely matched the reported numbers. For the European corn borer, the number of insects per plant differed slightly between simulated and field data, but the response to the insecticide treatment showed an adequate match. Simulations for the bean leaf beetle and stalk borer yielded similar results. The comparison between simulated and measured adult potato leafhopper numbers revealed that even though numbers did not match exactly in two of three years, they were in the same range, and the measured and simulated impacts were almost identical for all three used insecticides. Synthesis and applications. The novel coupled crop-insect model EPIC-GILSYM realistically simulates two trophic levels (insects and plants), their interactions, and the effect crop management has on both levels. It has been successfully tested against field trial data collected in eight different years on five plots in different parts of the US. With careful calibration and validation to other sites and climates, it may become a valuable tool in the assessment of insect pest impacts and appropriate control measures.