Grapevine leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves influenced by the grape leafhopper, <i>Empoasca vitis</i>

Abstract

Abstract The impact of the grape leafhopper, Empoasca vitis , on leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves of the grapevines, Vitis vinifera L., was studied. Gas exchange was measured on the discolored (red) and the green parts of infested main leaves and on leaves from uninfested vines. Photosynthesis and mesophyll conductance were severely reduced on main leaves showing leafhopper feeding symptoms. The stomatal conductance of the red leaf section of infested main leaves was lower than on undamaged control leaves. Additionally, the red leaf section of infested main leaves showed lower transpiration rates when compared to the green parts of the same leaves and to undamaged control leaves. Gas exchange processes of lateral leaves were not affected by leafhopper feeding. Leafhopper‐load on main leaves was correlated to visual damage symptoms. At 71.8 leafhopper‐days per leaf up to 40% of the main leaf area of the infested plants was discolored from the borders towards the center. Lateral leaves showed no feeding symptoms. Shoot diameter, pruning weight and carbohydrate reserves in the wood were not affected by leafhoppers. Lateral leaf area growth was significantly stimulated on plants infested by leafhoppers. No decrease in yield and fruit quality with leafhopper‐loads up to 71.8 leafhopper‐days per leaf were observed.