The impact of two predatory guilds, epigeal and aerial natural enemies, on levels of cereal aphid control in winter wheat was examined on farms with contrasting proportions of grass margins, one of the most popular agri-environment options in England. In year 1, by 14 d after inoculation the aerial natural enemies alone had caused substantial reductions (88%) in numbers of cereal aphids compared to where no natural enemies were present. In contrast, epigeal predators achieved a 31% reduction, although this reached 88% after 28 d. In year 2, both aerial and epigeal natural enemies achieved over 87% control after 14 d. Aerial natural enemies were largely comprised of predatory Diptera and Linyphiidae (Araneae). Levels of control were positively related to the proportion of linear grass margins within 250, 500 and 750 m radii of the study arenas. There was weaker evidence that hedgerows decreased aphid control by epigeal predators. This study demonstrated that an agri-environment option can be used to improve an ecosystem service on arable farmland.
