Increasing prominence of community gardens in urban areas presents an opportunity to explore the unique ecosystems of managed, urban green spaces. These urban gardens are characteristically rich in biodiversity; both in the variety of crops planted, and the community of organisms, including people, that construct and inhabit the garden. We study how biocomplexity, the complex interactions that arise between members of a diverse community, may influence the spread of pests. In particular, our study focuses on Acyrthosiphon pisum (pea aphids) a significant pest of garden peas. Migration of aphids under the pressures of predators and pathogens was studied using a combination of lab experiments, surveys and modeling.
Results/Conclusions
Pea aphids (A. pisum) may be established and grow best at intermediate levels of host plant diversity (variety), possibly due to generalist natural control agents in low diversity plots and biocomplexity in high diversity plots. Aphid migration increased both in the presence of a coccinellid predator, and a fungal pathogen, separately. However, population growth was suppressed most when both control agents were combined. The general expectation is that natural enemy diversity may have a strong controlling effect on pest migration, thus generating the potential for strong spatially explicit dynamics in the system. We propose that biocomplexity may play an important role in effective biological control in urban agriculture.