Transmission of the virus of Pierce's disease of grapevines by leafhoppers

In single-insect transmission of virus from infected to healthy grapevines, the most efficient vectors tested were Neokolla circellata (65 per cent), Cerneocephala fulgida (33 per cent), and Helocbera delta (32 per cent). Lower percentages were obtained with Draeculacephala minerva, Friscanus friscenus, N. severini, and Pegaronia confusa. No infections were obtained with P. triunata or N. confluens var. pacifica. N. circelleta was the only one of four species tested that gave a significant transmission of virus from infected grapevines to healthy alfalfa (35 per cent). In single-insect tests, no transmissions from infected to healthy alfalfa were obtained with five species, or from infected alfalfa to healthy grapevines with P. conjuse, Some of the vectors that proved inefficient were short-lived when confined on grapevines and alfalfa in the greenhouse. Species of leafhoppers of the subfamily Anthysaninae, two species of fulgorids, and unidentified species of cicadas failed to transmit the virus. In transfers from infected to healthy grapevines, the minimum latent period was 2 hours in Neokolla circellata and Carneocephala fulgida, 7 hours in Draeculacepbala minerva. In the greenhouse, some adults of the blue-green sharpshooter, reared on infected grapevines, retained the virus throughout adult life, in one case for 122 days.