Habitat and landscape heterogeneity positively influence biological control and natural enemy community composition in coffee agroecosystems

Background/Question/Methods

Agricultural intensification over the past several decades has resulted in serious environmental impacts, including habitat simplification and a correlated loss of biodiversity, leading to compromised ecosystem services such as biological control of pests. Structurally and biologically diverse agroecosystems have been shown to provide a level of autonomous biological control arising from naturally present enemy populations or from bottom-up effects of plant diversity. Our understanding of which components of tropical agroecosystems most influence biocontrol is limited. I studied how the effectiveness of biocontrol changes across an agricultural management intensity gradient embedded in different landscape backgrounds in coffee farms in Chiapas, Mexico, in order to determine which ecological components of the environment are most important in providing enhanced biocontrol. I sampled several biotic and abiotic variables as well as landscape context in 38 plots. In each plot I performed experiments to determine the predation rate of two important pests, the coffee berry borer (Hypothenemus hampei) and the green coffee scale (Coccus viridis). Furthermore, I measured the natural incidence of these pests and of different natural enemy guilds, including parasitoids, ants, and predatory beetles.

Results/Conclusions

The abundance of pests and natural enemies and predation rates of pests varied across plots of different management intensities and with different landscape complexity. Scale and borer predation were most influenced by local (habitat) characteristics including twig-nesting ant activity and vegetation heterogeneity, represented by an index based upon several vegetation characteristics including herbaceous ground cover and shade tree diversity, biomass, and density. Broca abundance as surveyed in the field was influenced by both local and landscape factors, being most negatively affected by decreased distance to forest and increased ant activity, especially of the tree-nesting Azteca instabilis. These results highlight the importance of maintaining structurally and biologically complex habitats and landscapes for achieving enhanced autonomous biological control.