Pierce's Disease (bacterium - rickettsia-like): Early summer symptoms include delayed shoot growth, leaf mottling, and dwarfing of new shoots. Late summer and fall symptoms are burning, scalding, or drying of leaves; wilting or premature coloring of fruit; and uneven cane maturity. Ribier is very susceptible, usually dying within two years. Thompson seedless and most other French (Vinifera) varieties die within two to five years. American (Lambrusca) varieties often live longer than five years. No effective control is known. Pierce's disease is spread by several types of leafhoppers, by the spittlebug, and by grafting. Seventy-three plant species serve as disease reservoirs and hosts for these vectors.

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