A zero-inflated Poisson mixture model to analyse spread and abundance of the Western Corn Rootworm in Austria

The Western Corn Rootworm (WCR, Diabrotica virgifera virgifera) has become one of the main maize pests in Europe. Our objective was to develop a model for mapping spread and abundance of WCR in Austria as a function of the natural spread, climatic conditions and the maize share in crop rotations. Records of a total of 5,338 WCR monitoring traps spread over Austria are available for the period 2002-2015, with 2,520 (47.2%) showing zero counts. We developed a spatial zero-inflated Poisson mixture (ZIP) model to relate WCR counts to climatic conditions and maize shares and account for zero-inflation, and spatial correlation in the count data. The model was validated by a 40-fold cross validation procedure and applied to Austrian cropland on a spatial resolution of 1 km. Results show that increased probabilities of WCR occurrence and abundance are associated with higher maize shares in crop rotations combined with a positive influence of higher winter temperatures and summer precipitation. The developed model provides a scientifically sound basis for analysing impacts of future climate change scenarios and crop rotational maize restrictions on the spread and abundance of WCR. It supports the development of WCR control measures.