Aphids and their enemies in pumpkin respond differently to management, local and landscape features

Natural enemies of agricultural pests can be limited by high farming intensity and the scarcity of important resources such as flowers and alternative prey. Thus, organic farming and the presence of seminatural habitats adjacent to crop fields or in the surrounding landscape may enhance pest control. However, studies in vegetable crops investigating combined effects of field management, adjacent habitats and landscape complexity are still rare. We measured natural field densities of aphids and their enemies in 18 pumpkin fields in Southwest Germany. Increasing flower abundance in field margins tended to decrease aphid densities and significantly increased densities of natural enemies, especially of lady beetles, parasitoids, lacewings and aphid gall midges. Organic management and landscape complexity (measured as proportion of agriculture in 1 km radius) had no clear effect on pest control. Our results indicate that abundant flower resources in field margins are the most promising tool to enhance natural aphid control in pumpkin.