Predatory arthropods in apple orchards across Europe : Responses to agricultural management, adjacent habitat, landscape composition and country

Local agri-environmental schemes, including hedgerows, flowering strips, organic management, and a landscape rich in semi-natural habitat patches, are assumed to enhance the presence of beneficial arthropodsand their contribution to biological control in fruit crops. We studied the influence of local factors ( orchardmanagement and adjacent habitats) and of landscape composition on the abundance and community composition of predatory arthropodsin apple orchardsin three European countries. To elucidate how local and landscape factors influence natural enemy effectiveness in apple production systems, we calculated community energy use as a proxy for the communities’ predation potential based on biomass and metabolic rates of predatory arthropods. Predator communities were assessed by standardised beating samples taken from apple trees in 86 orchardsin Germany, Spain and Sweden. Orchardmanagement included integrated production(IP; i.e. the reduced and targeted application of synthetic agrochemicals), and organic management practices in all three countries. Predator communities differed between management types and countries. Several groups, including beetles (Coleoptera), predatory bugs ( Heteroptera), flies (Diptera) and spiders (Araneae) benefited from organic management depending on country. Woody habitat and IP supported harvestmen ( Opiliones). In both IP and organic orchardswe detected aversive influences of a high-quality surrounding landscape on some predator groups: for example, high covers of woody habitat reduced earwigabundances in German orchardsbut enhanced their abundance in Sweden, and high natural plant species richness tended to reduce predatory bug abundance in Sweden and IP orchardsin Spain. We conclude that predatory arthropodcommunities and influences of local and landscape factors are strongly shaped by orchardmanagement, and that the influence of management differs between countries. Our results indicate that organic management improves the living conditions for effective predator communities.