Reducing insecticide use in winter oilseed rape by in-field to landscape-scale agroecological pest management

Abstract

Reducing insect pest damage in field crops while minimizing insecticide use poses a significant challenge for farmers in Europe. Initiated in 2019, the six-year territorial project R2D2 aimed to explore the effectiveness of an agroecological crop protection approach in the context of widespread resistance of winter oilseed rape (WOSR) autumn beetles to pyrethroid insecticides. Over an area of 1371 hectares, ten farmers collectively developed a generative experimentation based on modifying cultural practices and implementing conservation biological control to gradually phase out insecticide use. Two years later, these farmers had made significant shifts in their pest management strategies by implementing a coordinated array of pest control measures from the field to the landscape level. These changes led to a complete cessation of systematic insecticide applications on WOSR and a 37% reduction in the insecticide Treatment Frequency Index (TFI) for this crop. Despite these promising outcomes, the total TFI across all crops, as assessed at the territorial level, remained unchanged. One of the main reasons for this is the increase in aerial insecticide applications on winter barley following the ban on neonicotinoids, as well as on spring pea to combat rising pea beetle pressures across the territory. For these two crops, effective alternatives to insecticides must be identified. More time is needed to instigate fundamental changes in farming systems and to enhance natural pest regulation through conservation biological control. Farmers’ support strategy should focus on identifying and overcoming barriers to the implementation of transformative systems.