Weather and landscape drivers of the regional level of pest occurrence in arable agriculture: A multi-pest analysis at the French national scale

Limiting crop pests while favouring environmentally friendly practices is challenging. It is required to identify the main drivers of infestation for multiple pests at different scales. In particular, large scale approaches are missing, while they could contribute to increase the predictability of pest infestation. In this study, the French national Epiphyt dataset (part of the national epidemiological monitoring service) was used to assess the relative importance of weather and landscape drivers on the between-region variability in the level of occurrence of some agricultural pests. Using a regional resolution, we analysed the proportion of occurrence of slugs, cereal aphids and oilseed rape pests over 181 small agricultural areas (‘regions’) across France in 2018. The mean proportion of occurrence per region was 0.17 for slugs, 0.25 for cereal aphids and 0.61 for oilseed rape pests. Weather variables were more explanatory than landscape ones for the proportion of occurrence of slugs and oilseed rape pests while the two types of variables had a similar level of explanation for the regional proportion of aphid occurrence. Slugs were favoured by high winter temperatures, high soil wetness index and important proportions of hedgerows in the region but negatively influenced by high winter rainfalls. Cereal aphids and oilseed rape pests were negatively influenced by the regional proportion of grassland. Additionally, the winter air humidity and the proportion of perennial crops in the region decreased the proportion of occurrence of oilseed rape pests. We detected no effect of the proportion of host crop or the proportion of organic farming in the region. This study emphasises that, in line with findings derived from more local studies, weather characteristics are an important driver of the regional level of pest occurrence in arable fields; it also highlights that the proportion of grassland at the regional scale could be a key tool to design insect-pest suppressive landscapes.