Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops
1 Maintenance of floral diversity throughout the growing season in vineyards in the form of summer cover crops of buckwheat (Fagopyrum esculentum Moench) and sunflower (Helianthus annus Linnaeus), had a substantial impact on the abundance of western grape leafhoppers, Erythroneura elegantula Osborn (Homoptera: Cicadellidae), and western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and associated natural enemies.
2 During two consecutive years, vineyard systems with flowering cover crops were characterized by lower densities of leafhoppers and thrips, and larger populations and more species of general predators, including spiders.
3 Although Anagrus epos Girault (Hymenoptera: Mymaridae), the most important leafhopper parasitoid, achieved high numbers and inflicted noticeable mortality of grape leafhopper eggs, no differences in egg parasitism rates were observed between cover cropped and monoculture systems.
4 Mowing of cover crops forced movement of Anagrus and predators to adjacent vines resulting in the lowering of leafhopper densities in such vines.
5 Results indicate that habitat diversification using summer cover crops that bloom most of the growing season, supports large numbers of predators and parasitoids thereby favouring enhanced biological control of leafhoppers and thrips in vineyards.
Document Type: Research Article
Affiliations: 1: University of California Cooperative Extension, 1131 Harbor Bay Parkway. Suite 131. Alameda, California 94502, 2: University of California, Davis. Entomology Department and 3: University of California, Berkeley. Environmental Science Policy and Management Department, California, U.S.A.
Publication date: 01 May 2000