Xylella Fastidiosa - Pierce's Disease

Pierce's Disease

Pierce's disease was discovered in 1892 by Newton B. Pierce (1856–1916; California's first professional plant pathologist) on grapes in California near Anaheim. It became a real threat to California's wine industry and overall economy when the glassy-winged sharpshooter (its vector), native to the southeast United States, was discovered in the Temecula Valley in California in 1996. It triggered a unique effort from growers, administrators, policy makers and researchers to work together in finding a solution for this immense threat. No cure has yet been found, but the understanding of Xylella fastidiosa and glassy-winged sharpshooter biology have exponentially increased since 2000, when the California Department of Food and Agriculture, in collaboration with different universities, such as University of California, Davis; University of California, Berkeley, and University of California, Riverside, and University of Houston-Downtown started to focus their research on this pest. The research explores the different aspects of the disease propagation from the vector to the host plant and within the host plant, to the impact of the disease on California's economy. All researchers working on Pierce's disease meet annually in San Diego in mid-December to discuss the progress in their field. All proceedings from this symposium can be found on the Pierce's disease website, developed and managed by the Public Intellectual Property Resource for Agriculture (PIPRA).

There are no resistant Vitis vinifera varieties, and Chardonnay and Pinot noir are especially sensitive, although muscadine grapes have a natural resistance. Pierce's disease is presently found in the southeastern United States, Mexico, Costa Rica, and Venezuela, and possibly in other parts of Central and South America. There are isolated hot spots of the disease near creeks in Napa and Sonoma in northern California.

Currently, work is underway at U.C. Davis to breed PD resistance into Vitis vinifera. The first generation was 50% high quality vinifera genes, the next 75%, the third 87% and the fourth 94%. In the spring of 2007, seedlings that are 94% vinifera were planted.

When a vine becomes infected, the bacterium causes a gel to form in the xylem tissue of the vine, preventing water from being drawn through the vine. Leaves on vines with Pierce's disease will turn yellow and brown, and eventually drop off the vine. Shoots will also die. After one to five years, the vine itself will die. The proximity of vineyards to citrus orchards compounds the threat, because citrus is not only a host for the sharpshooter eggs, but it is also a popular overwintering site for the insect. Likewise, oleander, a common landscaping plant in California, serves as a reservoir for Xylella.