By Natalie Swinhoe, Anthropology and Evolution, Ecology, and Biodiversity, 2015

Pierce’s Disease in grapevines is a major threat to California’s viticultural economy. Caused by the bacterial strain Xylella fastidiosa, the disease blocks water transfer in the xylem of stems, leading to water stress and eventual death. Until the 1990s, the only carriers for the disease were native Blue-Green Sharpshooters, Graphocephala atropunctata. However, between 1994 and 2000, a devastating outbreak occurred in Southern California, destroying more than 1000 acres of vineyards (Ringenberg et al., 2014). This epidemic was caused by a new nonnative vector- the Glassy-Winged Sharpshooter, Homalodisca vitripennis (Tumber et al, 2013). Compared to the Blue-Green Sharpshooter, the Glassy-Winged Sharpshooter has a much greater capacity to spread Pierce’s Disease because it can fly further and feed on a larger variety of plant parts (Alston et al., 2013, Baccari and Lindow, 2010).

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