Workshop "Multitrophic Interactions"
Georg-August University Göttingen, March 22 - 23, 2012
organized by: Teja Tscharntke and Stefan Vidal (Department of Agroecology)
Landscape effects on natural enemy interactions and on the efficiency of biological pest control
Emily A. Martin, Björn Reineking, Bumsuk Seo, Ingolf Steffan-Dewenter
Landscapes are recognized as important drivers of biodiversity distribution in agricultural systems. In particular, they can influence the distribution of natural enemies involved in biological pest control. To date, however, it is unclear whether landscape effects on higher trophic levels are associated with differences in the degree of pest suppression, overall damage avoidance, or crop yield. In addition, interactions between natural enemies, for instance linked with omnivory of certain guilds, may also differ according to the landscape and influence the degree of effective pest control.
In this study, the effects of landscape context on natural enemies and on their interactions are examined through the lens of their consequences for crop yield, herbivory and pest density. In the agricultural landscape of the Haean catchment, South Korea, a total of 7 enemy exclusion treatments were installed on cabbage plants (Brassica oleracea var. capitata), in 18 fields distributed throughout the landscape. Cage treatments were designed to exclude combinations of natural enemy guilds, including ground-dwellers, flying insects and birds. Results show that enemy exclusion induced higher crop damage and pest densities, as well as lower biomass, than open controls. The strength of these effects also varied depending on the landscape, implying that quantification of the biological control potential requires consideration both of practical, “service-oriented” crop-level variables, and of a broader landscape perspective on these variables.