Xylella fastidiosa, a xylem-limited bacterium that causes Pierce's disease of grapevine and other plant diseases, has numerous symptomless hosts. The multiplication and spread of X. fastidiosa within grapevine (Vitis vinifera) and four other reported plant hosts that were preferred plants for insect vectors (Himalayan blackberry, Rubus discolor; California mugwort, Artemisia douglasiana; watergrass, Echinochloa crusgalli; and Bermuda grass, Cynodon dactylon) were assessed after vector inoculation. The bacterium was detected by culture and enzyme-linked immunosorbent assay. The incubation times required before first detection in grape, blackberry, mugwort, and watergrass were 4, 32, 30, and 18 days, respectively. The maximum bacterial concentration (CFU per gram) and percentage of infection in these species were > 10(8) (100%), 1 x 10(7) (58%), 2 x 10(6) (20%), and 4 x 10(5) (31%), respectively. Systemic movement of X. fastidiosa distal to the inoculation site was detected only in grapevine and blackberry. The bacterium was never detected in inoculated Bermuda grass. The wide range in the capacities of these hosts to support the bacterium's multiplication and spread suggests that the epidemiological importance of plant host species for the spread of Pierce's disease varies greatly.