Transmission of Tristeza and Seedling Yellows Tristeza Virus by Small Populations of Aphis gossypii. C. N. Roistacher, Department of Plant Pathology, University of California, Riverside 92521. M. Bar-Joseph, Agricultural Research Institute, Volcani Center, Bet Dagan, Israel; and D. J. Gumpf, Department of Plant Pathology, University of California, Riverside 92521. Plant Dis. 68:494-496. Accepted for publication 14 December 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-494.

Transmission studies with three isolates of citrus tristeza virus, using 1, 3, 9, and 27 individuals of Aphis gossypii, showed a clear dosage response to infection. Infection was 1.1, 6.7, 23.3, and 56.7% for 1, 3, 9, and 27 aphids applied, respectively. These results are strikingly similar to earlier studies in South America using Toxoptera citricida. Extrapolation of the infection curve indicates that 100% infection would be expected if about 52 aphids were applied and a minimum of 33 living aphids were found after a 24-hr feeding period at 24 C. These results show a very high level of efficiency for A. gossypii in transmitting certain strains of tristeza virus in California.