- Winter 1999 "Update" Newsletter Article -
IPM studies track relationships of arthopods, pests
Copyright © 1999. All rights reserved.
Arthropod sampling research being conducted through Fresno State's Viticulture and Enology Research Center (VERC) continues to reveal new bits of information on relationships between beneficial insects and unwanted pests in the vineyard.
Brief reports from two research projects have just been published by the California Agricultural Technology Institute (CATI). Both reports stem from work conducted under the university's integrated pest management (IPM) program overseen by entomology professor Mark Mayse.
The first report is titled "Arthropod Community Dynamics in New Varietal Vineyards." It outlines results from sampling work done in four vineyards in California's San Joaquin Valley, approximately 30 miles northwest of Fresno. The sampling covered beneficial insects such as spiders, beetles and parasitic wasps, and pests such as leafhoppers and omnivorous leafrollers.
Purpose of the project was to compare and contrast population densities in wine grape cultivars relatively new to the San Joaquin Valley. Those cultivars are Cabernet Sauvignon, Ruby Cabernet and Chardonnay. One portion of the data showed that "highest spider counts, along with lowest leafhopper nymph counts and essentially no omnivorous leafroller larvae, were found in the established Ruby Cabernet vineyard."
Another phase of the study included collection of leafroller larvae and pupae from leaf samples. The larvae and pupae were examined for parasitism by parasitic wasps.
"This activity yielded an estimate of roughly 50 percent parasitism of OLR larvae/pupae, ...far above the more commonly reported 10 percent level," the authors noted.
The second report published is titled "Abundance and Diversity of Arthropods Associated with Conventional and Organic Vineyard Practices." This continuing study is focusing on a six-acre Barbera vineyard on the farm laboratory at California State University, Fresno.
Sections of the vineyard were given certified organic and conventional viticultural treatments. Between the two important pests of variegated leafhopper (VLH) and western grape leaf- hopper (WGLH), the VLH proved to be the most common. However, a key finding in 1996 was that no significant differences in VLH nymph densities were detected between the organic and conventional plots. During 1997, as the summer growing season progressed, VLH nymphs started declining around the same time spider densities began to increase slightly.
More details on pest populations in these vineyards can be obtained by viewing the reports in the Research Publications section of this web site.
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