Epidemiology of Pierce's disease in Texas vineyards

Although many issues face the production of grape in Texas, Pierce’s disease is the limiting factor in the eastern two thirds of the state. As the disease now occurs in all major growing areas of Texas, production may be interrupted in nearly any vineyard. Research into the epidemiology of Xylella fastidiosa, the causative bacteria, has been ongoing in grape since 2003 by scientists in plant pathology, horticulture and entomology. The worst problems occur where European grape varieties are grown in areas of high rainfall. Some 29 species of insects that either transmit or are likely capable of transmitting the bacterium have been identified in the state and these are generally more abundant in wetter areas. Three subspecies of X. fastidiosa are known to be in Texas: X.f. fastidiosa, X. f. sandyi and X. f. multiplex. X.f. fastidiosa is most commonly associated with grape, but the other two subspecies are commonly found in insects assayed via PCR for the presence and genotype of the bacterium. Grape varieties have differential susceptibility to X. fastidiosa and are the primary means by which grapes are produced in high risk areas. Epidemiological dynamics change depending on the varieties used, the presence of systemic insecticides, the history of the vineyard, vector density and location of the vineyard.