Enhancing natural enemies in sugar beet fields: The impact of flower strip types and landscape elements

• Flower strip types differ in flower-volume and -composition early in the season. • Most aphid predators were found in autumn-sown annual and perennial flower strips. • Hoverfly communities differ between autumn-sown annual and perennial flower strips. • Nearby forests help support aphid antagonists in otherwise open landscapes. Flower strips (FS) enhance predators that can help regulate aphids. In sugar beet crops, early-season aphid populations can spread viruses, so timely FS resources are key to attract aphid predators to reduce virus transmission. This study aims to identify the optimal FS type(s) for supporting aphid antagonists in early spring, track their abundances in the different FS types, and analyze the landscape factors influencing antagonist presence. We selected three different seed mixtures, each sown on 10 sugar beet fields managed without insecticides. FS types were compared to sugar beet strips in fields without insecticides, and conventionally managed fields, both served as controls. We assessed the strips by counting flowers and collecting insects with a sweep net in mid-April, early May, and early June. Autumn-sown annual and second-year perennial FS produced greater and earlier flower volumes than other treatments. Over time, the flower compositions of these two FS types also became increasingly distinct from each other. Aphid antagonists were more abundant in these FS types compared to spring-sown annual FS and controls. Hoverfly communities differed between autumn-sown and perennial FS. Braconidae were positively linked to forest cover within 500 m, while hoverflies showed a negative association with forest at the 2000 m scale. Overall, autumn-sown annual and perennial FS are better suited for conservation biocontrol of aphids in sugar beet systems than spring-sown annual FS. Hoverfly composition differences may lead to variation in aphid suppression. From a landscape perspective, forested areas near fields within otherwise open landscapes are important in supporting beneficial insects.