Population-dynamical model to optimise agricultural landscape management for natural pest control

Abstract: Pest-regulating insects, such as predatory hoverflies (Diptera: Syrphidae), rely on
diverse habitats to complement their resource needs. While predatory hoverfly larvae feed on
aphids, adult hoverflies require floral resources. In agricultural landscapes, both types of
resources are often spatially separated and are often only temporally available in one habitat.
Therefore, supplemental habitats are required to cover the annual cycle of a hoverfly
population. Our landscape-based population-dynamic model assessed the dynamics of
hoverflies and their aphid prey in various habitats and shows the relative importance of these
habitats for aphid suppression in crops. This model is unique as it combines predator-prey
interactions, hoverfly life stage structure, seasonality and habitat structure. Our findings
highlight the need for a minimum of three habitats to cover the annual hoverfly population cycle needed for sufficient aphid suppression: a woody habitat for early- and late-season food supply, early and late crops for interim aphid prey supply, and flower sub-habitats, such as (wild)flower margins, to provide floral resources simultaneously with aphids.