Glassy-Winged Sharpshooter

The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is a relatively large leafhopper belonging to the Cicadellidae family. GWSS is native to the southeastern United States and northeastern Mexico. Although it was first reported in California in 1994, it likely arrived in the state in the late 1980s as egg masses on ornamental or agricultural plant foliage.

The range of GWSS includes many habitats, including agricultural crops, urban landscapes, native woodlands, and riparian vegetation. The host list includes over 360 genera of plants. Since the insect feeds on the nutrient-poor xylem fluid of the plant, it must consume large amounts of fluid in order to gain enough nutrition to grow and reproduce. Consequently, the adults and nymphs excrete large amounts of liquid while feeding, which gives the fruit and foliage a whitewashed appearance. Host preference changes according to the availability and nutritional value of host plants at any given time.

GWSS is a significant vector of Xylella fastidiosa, the xylem-limited bacterium that causes Pierce’s disease of grapes. Although Pierce’s disease has been in California for over 100 years, native vectors do not transmit the bacterium as extensively as GWSS. GWSS is a serious threat to California vineyards because it moves faster and flies greater distances into vineyards than native sharpshooters. It also builds up large populations and can feed on the tougher, lower parts of grapevine stems. When the GWSS feeds on a plant that is infected with X. fastidiosa, it acquires the bacteria, which multiplies within the insect’s mouthparts. The sharpshooter then transfers the bacteria to other plants when it feeds. Symptoms include chlorosis and scorching of leaves, with entire grapevines dying within one to five years.

In California, in addition to strains of X. fastidiosa that cause Pierce’s disease, there are also strains that cause other plant diseases such as oleander leaf scorch, almond leaf scorch, mulberry leaf scorch, sweet gum dieback, and cherry plum leaf scorch. Outside of California, other strains of the bacterium cause phony peach disease, plum leaf scald, leaf scorches in sycamore, elm, maple, and oak, and citrus variegated chlorosis. In Europe, X. fastidiosa causes olive quick decline syndrome. At this time, there is no cure for any of these diseases. 

(Edited excerpt from Glassy-winged Sharpshooter and Pierce’s Disease in California: Background and History, produced by the Pierce’s Disease Program at the California Department of Food and Agriculture)