Pierce's Disease Bacterium: Mechanism of Transmission by Leafhopper Vectors.

The bacterium that causes Pierce's disease of grapevines is isolated most consistently from the foregut of its leafhopper vector Graphocephala atropunctata. As seen in light and scanning electron microscopy of infective leafhoppers, the bacteria are attached to the cibarial pump and the lining of the esophagus in the foregut where they appear to multiply. These findings suggest that the bacterium is transmitted from the foregut by egestion during feeding by infective leafloppers.