Pierce's disease, named after N.B. Pierce , seems to be restricted to portions of North America with mild winters. The disease is less prevalent where winter temperatures are colder, such as at higher altitudes, farther inland from ocean influences, and at more northern latitudes. Since the mid-1970s, many other strains of Xylella fastidiosa have been discovered, and almost all of these cause leaf scorching of woody perennials such as American elm, maple, mulberry, or plum. In some plants, such as peach and alfalfa, the bacterium slows and stunts plant's growth. Vines develop symptoms when the bacteria block the water conducting system and reduce the flow of water to affected leaves.
Water stress begins in mid-summer and increases through fall.
Typically, the leaf dries progressively over a period of days to weeks, leaving a series of concentric zones of discolored and dead tissue. About mid-growing season, when foliar scorching begins, some or all of the fruit clusters may wilt and dry up. The bacteria can move internally from cell to cell in blackberry as in grape, but nt within California mugwort. All of these plants are important breeding plan ts of the blue-green sharpshooter in Northern California.