Influence of flowering cover crops on Anagrus parasitoids (Hymenoptera: Mymaridae) and Erythroneura leafhoppers (Homoptera: Cicadeliidae) in New York vineyards

摘要

We tested the hypothesis that providing nectar-producing cover crops will enhance the biological control of grape leafhoppers (Erythroneura spp.) by Anagrus wasps in commercial vineyards in New York, U.S.A. We established three cover crops between vine rows in a commercial vineyard: buckwheat (Fagopyrum esculentum (Moench)), clover (Trifolium repens L.) and mowed sod (Dactylis glomerata L.). There was no effect of cover crop on adult Anagrus in 1996, whereas in 1997 adults were more abundant withinedge vines with buckwheat compared to vines with clover or sod; adults were more abundant at the vineyard edge, especially early in the season. Parasitism of 'sentinel' leafhopper eggs was higher on vines with buckwheat compared to parasitism on vines with clover or sod in 1996; a similar, nonsignificant trend, was observed in 1997. Neither the abundance nor the distribution of leafhoppers was influenced by cover crops, although in 1997 there was a trend toward greater numbers of nymphs on edge vines with buckwheat. In a cage experiment, parasitism by Anagrus of leafhopper eggs on grapes was greater when adults had access to flowering buckwheat rather than buckwheat without flowers. In a laboratory study, longevity of female Anagrus was increased whenprovided with honey or sugar water compared to water only or nothing. Our results suggest that parasitism of grape leafhoppers by Anagrus may be enhanced by providing floral resources within vineyards in New York, although it is unclear whether this will produce meaningful reductions in pest abundance.