Tailoring the species composition and in-field deployment of flower strips for functional insect biodiversity and biological control

Abstract

Flower strips in agroecosystems contribute to insect conservation and can favor biological control of crop pests. First, we compared a flower mixture tailored to attract and support natural enemies of aphids, to a subsidized mixture, on the attraction and support of functional insect biodiversity. Second, we tested the in-field deployment of flower strips set at 27 m intervals with sugar beet crop to enhance the regulation of aphid pests, independently of the flower mixture. The tailored mixture showed a more consistent flowering cover, and a significantly higher presence of aphids serving as alternative prey/hosts, than the subsidized mixture. The abundance of natural enemies was low in the flower strips and was not significantly different between the two mixtures, while non-predatory hoverflies were numerous, and significantly more abundant in the tailored mixture. The abundance of Aphis fabae was significantly reduced on sugar beet bordered by in-field flower strips. The abundance of Myzus persicae followed a similar trend, but with a high variability leading to non-significant differences between fields. Predators on sugar beet were mainly ladybird beetles and hoverflies, which abundance was significantly correlated with the abundance of Aphis fabae. By tailoring the plant species composition of mixtures, we demonstrate that flower strips can support both natural enemies and non-predatory insects, offering potential for multifunctional habitats. Their deployment within fields significantly contributes to protecting crops against aphids. As such, tailored and in-field flower strips represent strategic tools to design pest suppressive agroecosystems.