Transmission Efficiencies of Field-Collected Aphid (Homoptera: Aphididae) Vectors of Beet Yellows Virus

Alate aphids (Homoptera: Aphididae) were collected at weekly intervals in 1988 in six California sugarbeet fields-three on each side of a boundary line which separates overwintered spring harvest beet fields in Solano County from fall harvested fields in Yolo County. Alate aphids landing on a yellow board during a 45-min morning collection period were captured live and tested for ability to transmit beet yellows virus (BYV) by allowing individual aphids to feed on healthy sugarbeet seedlings immediately after capture. Test plants were evaluated for BYV infection by enzyme-linked immunosorbent assay (ELISA), and aphids were preserved and later identified. Myzus persicae (Sulzer), Aphis fabae Scopoli complex, and Rhopalosiphum padi (L.) were the principal aphid species which transmitted BYV. Five additional captured aphid species were found to be carrying BYV, including Macrosiphum rosae (L.) and Amphorophora spp., which are reported as BYV vectors for the first time. Geographically distinct isolates of A. fabae complex were collected from fields in Fresno, Monterey, Santa Barbara, Tehama and Yolo counties; M. persicae was collected from Yolo County and R. padi was collected from Fresno and Yolo counties. A laboratory colony of R. padi was also obtained from New York. All aphid collections were tested for their relative efficiency in transmitting BYV. Differential transmission ability was found among geographically isolated aphid colonies of the same species and also among the different genera. A. fabae complex aphids from Santa Barbara County were the most efficient BYV vectors, followed by M. persicae, A. fabae complex from Fresno County, and R. padi from Fresno County.