Leafhoppers in the Erythroneura genus are sensitive to grapevine water status, and recent work suggests that water stress at critical times during the season can increase leafhopper mortality. We have experimented with deficits between berry set and veraison because this corresponds to the onset of the second generation of leafhoppers. In addition, deficits during this period result in smaller berries, which tends to improve quality characteristics of wine, such as color and flavor. Our results from the 2000 field season with sites in the San Joaquin Valley and the Paso Robles region found a significant reduction in leafhopper nymphal density when irrigation was reduced to an average of 50% of evapotranspiration (ETc), and a reduction to near zero when the average reduction was 20% of ETc. The reduction was associated with a decrease in leafhopper oviposition rate between treatments. In the current season, we are working in the Paso Robles region with a split plot design to determine the length of time and intensity of deficit in order to achieve a significant reduction in leafhopper nymphal density and improvement in wine quality.
Species 1: Homoptera Cicadellidae Erythroneura elegantula (Western grape leafhopper)
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