Flower fields and pesticide use interactively shape pollen beetle infestation and parasitism in oilseed rape fields

Pollen beetles (Brassicogethes spp.) are the main pests of oilseed rape (OSR, Brassica napus) in Europe and responsible for massive yield losses. Upcoming pesticide resistances highlight need other means crop protection, such as natural pest control. Sown flower fields aim to counteract decrease insect biodiversity agricultural landscapes by providing resources ecosystem service providers. However, optimal age size increase control is still unclear. We conducted experiments on 31 OSR located along a gradient landscape-scale semi-natural habitat (SNH). were adjacent which differed age, continuity size, or calcareous grasslands. Pesticide-free areas established examine interactive effects use field characteristics. The abundance pollen beetle adults larvae, parasitism superparasitism rates recorded at increasing distances sites. Flower grasslands increased when compared neighbouring fields. threshold effective 35% could be reached pesticide-free maintained continuously least 6 years. In pesticide-sprayed areas, declined with distance field. Furthermore, larger than 1.5 ha able improve more smaller Synthesis applications. To promote (OSR), large should several years, create stable habitats enemies. continuous maintenance preferred, ploughing resowing after 5–6 years decreased positive can abrogate parasitism. This study highlights that sown have potential OSR, but this depending its hindered use.