In recent years there have been advancements in vineyard irrigation management to optimize water use, improve wine quality and help manage arthropod pests. Vine water status has a major impact on leafhoppers (Erythroneura spp.): Adult leafhoppers lay more eggs on vines that are well-watered, and leafhopper nymphs which hatch on such vines have greater survivability. Water stress has the greatest effect on leafhopper eggs, and first and second instar nymphs. Improvements in wine quality have been achieved with water deficits between berry set and veraison. This is the period of rapid cell divison in the berries, and vine water stress at this time results in smaller berry size, loose clusters and improvements in wine color and flavor. The post berry set period corresponds closely with the oviposition period and hatch of the second leafhopper brood. We conducted experiments in vineyards (cv Cabernet Sauvignon) in the San Joaquin Valley (SJV) and in the Paso Robles (PR) region, where the dominant leafhopper species was the western grape leafhopper (Erythroneura elegantula). Both studies involved treatments which reduced the irrigation level between berry set and veraison compared to standard irrigation. At each site, the deficit irrigation treatments had a significant effect in lowering the second generation leafhopper populations. In 2000, second generation nymphal counts were down by about 50 % at the SJV site and were reduced to near zero at the PR site. At the SJV site the effect even carried into the third leafhopper generation, even though at that point the severe deficit irrigation had ceased. Deficit irrigation lowered yield at each site, but at the PR site had the benefit of increased grape berry sugar accumulation. At both sites deficit irrigation had a positive effect on wine color.
Species 1: Homoptera Cicadellidae Erythroneura elegantula (western grape leafhopper)
Keywords: grapes, leafhoppers
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA