Grapevine water stress can exert profound effects on the abundance of the green leafhopper Empoasca vitis (Göthe) (Hemiptera: Cicadellidae) in vineyards. Three experiments were carried out using potted grapevines in controlled conditions to investigate the mechanisms involved in this phenomenon. Grapevines were subjected to different levels of water stress, monitored by a pressure chamber, and E. vitis adults were confined on them prior or after the induction of water stress. At the end of each experiment, the number of leafhopper eggs laid in grapevine leaves and that of hatched eggs were counted. Empoasca vitis females preferred to oviposit into leaf veins and petioles, but tendrils and internodes (with a diameter of less than 2 mm) were also used. Moderate water stress levels (stem potential values from –0.9 to –1.0 MPa) reduced the reproductive potential of E. vitis and egg survival (hatching rate of 60%). High stress levels (values from –1.6 to 1.7 MPa) had a marked negative effect on egg laying and egg hatching (hatching rate of 33%), and hence reduced the subsequent abundance of nymphs and adults. Severe stress levels (values from –1.6 to 1.7 MPa) dramatically reduced the survival of eggs (hatching rate of 5%), and subsequently the size of progeny. The positive effect of a moderate water stress on E. vitis control was discussed in relation to yield and grape quality.
