Field-scale and landscape-scale drivers of insecticide use in oilseed rape crops across France

Adapting production systems to reduce their impact on human health and the environment through a reduction in pesticide use is a major challenge. Identifying the main environmental determinants of the use of these phytosanitary products represents a major step, particularly in crops known to be very sensitive to pests such as oilseed rape crops. This study aims at analysing how insecticide use in oilseed rape depends on a combination of effects of agricultural practices others than insecticides applications, pest population levels at large scale and properties of surrounding landscape, and possible interactions between these variables. To do so, we combined (i) data on agricultural practices in 162 oilseed rape fields of the French national network DEPHY farms (ii) pest data from the French national epidemiological monitoring database Epiphyt, and (iii) data on the composition and configuration of the landscape surrounding the focal oilseed rape fields. We found that the level of insecticide use in oilseed rape fields was lower when oilseed rape was sown earlier or when there was no ploughing between oilseed rape and a following winter cereal. We also found that insecticide use was lower in landscapes with smaller oilseed rape fields. In addition, we detected effects of the landscape proportional cover of oilseed rape and woodland that were conditional to the regional pest pressure. Under low regional pest pressure, insecticide use was lower in landscapes with low proportional cover of oilseed rape and high proportional cover of woodland but the direction of these effects was reversed under high regional pest pressure. This study demonstrates that in addition to adjusting local agronomic practices, the landscape context of farms is an important driver of insecticide use in oilseed rape crops, and thus highlights that reducing pesticide use in this crop will require to action multiple levers at multiple spatial scales. • We related insecticide use in oilseed rape with practices, landscape and pest pressure. • Sowing early and reducing ploughing was associated with lower insecticide use. • Less insecticides in landscapes with smaller oilseed rape fields. • Regional pest pressure effect was modulated by landscape properties. • Reducing pesticide use in oilseed rape requires to action multiple levers and scales.