From margins to in-field: strategic deployment of flowering service plants for biological control

Abstract: Flowering service plants are critical for biological control because their (extra-)floral nectar and pollen are key food resources for many predators and parasitoids, in addition to hosting alternative prey. However, their beneficial effects may depend on their spatial deployment at the field scale. We present cases in Europe, Pakistan and China where flowering service plants are deployed within fields, compared to implementations at field margins. In Belgium, in-field flower strips sown every 27 m consistently reduced Aphis fabae abundance in sugar beet. In Pakistan, row intercropping of oilseed rape with wheat significantly reduced wheat aphid abundance through natural enemy enhancement. In China, Tagetes erecta deployed as clustered patches between tea tree rows significantly favored pest control compared to sowing around the field. In Germany, flowering weeds maintained at an acceptable level through intercropping attracted natural enemies at the crop vicinity, interacting with flower strips sown at field margins. The way to use flowering service plants may depend on the cropping systems and the socio-cultural and economic context. Overall, maximizing the benefits of flowering service plants to biological control invites not to leave them at margins and instead to insert them within the field