Agroecologist and UH West Oʻahu Assistant Professor of Sustainable Community Food Systems, Albie Miles and UC Berkeley colleagues published the article “Landscape diversity and crop vigor outweigh influence of local diversification on biological control of a vineyard pest,” in Ecosphere, a journal of the Ecological Society of America.
The authors conducted a two-year ecological study of wine grape vineyards in California to inform the development of new strategies for natural pest control and pesticide reduction. The objective of the study was to determine the influence of vine vigor (crop nutrient status and growth rates) and local-scale and landscape-scale habitat quality on biological control of the Western grape leafhopper by its key natural enemies, Anagrus wasps. Their findings indicate that, in this agroecosystem, landscape diversity – the quality and abundance of surrounding native ecosystems – mediated pest populations and outweighed the influence of local-scale habitat provisioning (see images above). The authors conclude that pest populations were best controlled by a combination of enhanced biologic control – driven by the quality of insect habitat in the surrounding landscapes – and low crop vigor, which is less attractive to the pest. The implications of the findings suggest that the conservation of California native plant habitat, the selective planting of native plant species and the efficient management of crop nutrients (nitrogen fertilizer) can all contribute to enhanced natural pest regulation and a reduction in pesticide use.
“Landscape diversity and crop vigor outweigh influence of local diversification on biological control of a vineyard pest”
Abstract: The influence of local and landscape habitat diversification on biological control of the Western grape leafhopper (Erythroneura elegantula Osborn) by its key parasitoids Anagrus erythroneurae S. Trjapitzin & Chiappini and Anagrus daanei Triapitsyn was studied in wine grape vineyards. At the landscape scale, Anagrus rely on alternative host species in non-crop habitats outside of the vineyard to successfully overwinter, while at the local scale vineyard diversification can provide resources, such as shelter and floral nectar, which improve parasitoid performance. In a two-year experiment, plots with and without flowering cover crops were compared in vineyards representing a gradient of landscape diversity. While the cover crops did attract natural enemies, their populations were unchanged in the crop canopy and there was no difference in parasitism rate, leafhopper density, crop quality, or yield. Vineyards in diverse landscapes had higher early-season abundance of Anagrus spp., which was linked to increased parasitism and decreased late-season populations of E. elegantula. Leafhopper densities were also positively associated with crop vigor, regardless of landscape or cover crops. Flowering cover crops did increase abundance of some natural enemy species as well as parasitism rate in vineyard landscapes with intermediate levels of diversity, indicating a local landscape interaction, although this did not lead to reductions in E. elegantula densities. These findings indicate that, in this agroecosystem, landscape diversity mediates and in many ways outweighs the influence of local diversification and that E. elegantula densities were regulated by a combination of biological control and crop vigor.
Dr. Albie Miles
Dr. Miles received his Ph.D. in Environmental Science, Policy and Management from the University of California, Berkeley in 2013. His natural science research explores the synergies between farming system biodiversity and the provisioning of globally important ecosystem services from agriculture. His social science research explores the socio-economic and political obstacles to a more ecologically sustainable and socially equitable food system. Dr. Miles has held posts at the United Nations Food and Agriculture Organization (FAO) and the Center for Agroecology and Sustainable Food Systems (CASFS) at the University of California at Santa Cruz.