Empoasca vitis (smaller green leafhopper)

E. vitis is a phloem-feeding leafhopper, which is unusual among the sub-family Typhlocybinae where many species are mesophyll specialists. Few signs of damage caused by feeding appear on tree hosts but feeding on grapevine and kiwi fruit causes veinal browning, as well as marginal rolling and burning, symptoms often referred to as scorching (Tavella and Arzone, 1989). Damage on these plants is proportional to the number of individuals and the duration of their stay.

Integrated Pest Management

Although chemical control is usually advocated for the control of E. vitis, the possibility of using the natural enemy Anagrus atomus has been discussed by a number of authors. Cultural control measures have also been studied for E. vitis. The susceptibility of plants to E. vitis can vary among different grape cultivars and action thresholds should be adjusted considering these parameters (Linder et al., 2003; Fornasiero et al., 2011).

Although E. vitis is considered to be a significant pest, there have been few assessments of crop loss caused by the leafhopper. The second generation of this pest is considered to be the most important in terms of damage to plants (Pavan et al., 2000; Jermini et al., 2009). Symptoms of E. vitis are different among cultivars, with leaf margins typically turning reddish in red cultivars and yellowish in white cultivars. Infestation can also cause the leaf lamina to partially dry out. Higher oviposition rate were positively correlated with leaf density (Pavan and Picotti, 2009). At similar E. vitis infestation levels, water availability can influence the impact of the pest, with higher symptoms levels in water-stressed plants (Pavan et al., 2000).

Candolfi et al. (1993) conducted field studies in Switzerland during 1991 to determine the impact of E. vitis on leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves in grapes. Gas exchange was measured on the discoloured (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 feeding symptoms. The stomatal conductance of the red leaf section of infested main leaves was lower than on undamaged control leaves. The red leaf section of infested main leaves showed lower transpiration rates than those of the green parts of the same leaves or of undamaged control leaves. The gas exchange processes of lateral leaves were not affected by feeding. The number of E. vitis on main leaves was correlated with visual estimates of damage symptoms. At 71.8 E. vitis-days/leaf, up to 40% of the main leaf area of infested plants was discoloured from the borders toward the centre. Lateral leaves showed no feeding symptoms. Shoot diameter, pruning weight and carbohydrate reserves in the wood were not affected by E. vitis. Lateral leaf area growth was significantly stimulated on plants infested by E. vitis. No decreases in yield and fruit quality were observed with leafhopper-loads up to 71.8 E. vitis-days/leaf. However, in other situations high infestation levels were associated with yield losses and sugar content reduction (Pavan et al., 2000).

E. vitis is also reported to be an important pest of tea (Camellia sinensis) in Asia (e.g. Adarsh et al., 2002; Hazarika et al., 2009). Xu et al. (2005) proposed economic thresholds. The impact of the insect on tea is variable among tea cultivars (Huang et al., 1998) and in case of severe attack a yield reductions of up to 30% have been reported (Xu et al., 2005). Using the electrical penetration graph (EPG) technique, Jin et al. (2012) studied the feeding mechanism of E. vitis on tea and suggested that the leafhopper acts as a cell rupture feeder.

The early introduction of leafhoppers to single plants in cages significantly reduced the yield of potato tubers (Rygg, 1981).