Landscape heterogeneity and farming practice influence biological control

We measured the impact of natural enemies on the population development on the bird cherry-oat aphid (Rhopalosiphum padi) on conventional and organic farms, By pairing farms with similar landscape features but different farming systems, we were able to separate the effects of farming practice and landscape features on the influence of natural enemies on R. padi abundance. Natural enemies had a greater impact on R. padi establishment on organic farms than on conventional farms. Irrespective of farming system, landscapes with abundant field margins and perennial crops were associated with low R. padi establishment. After establishment, there was no difference in ground-living enemy impact on R. padi population growth rate between farming systems, but impact was greater in landscapes where arable land was contiguous.