Beet western yellows luteovirus in western Oregon: pathosystem relationships in a vegetable-sugar beet seed production region

uring the 1980s, crisphead lettuce, butterhead lettuce, and spinach crops in western Oregon (Fig. 1) became increasingly damaged by beet western yellows luteovirus (BWYV) (5,8) infection (15), a previously insignificant problem in this area. Utilizing double antibody sandwich enzyme-linked immunosorbent assay (DASELISA) methodology (2), we identified potential BWYV inoculum sources in vicinities of affected lettuce and spinach fields (15) based on the known host range of BWYV (5–9) and prior agroecosystem investigations of BWYV in the Pacific Northwest (20,29,30,32–34,37,38). In current and prior (14,15) studies, we identified three principal subreservoirs of BWYV inoculum in the Willamette Valley: multiseasonal plantings of vegetable crops, biennial plantings of sugar beet seed fields (21), and numerous BWYV-susceptible weed species prevalent in this agroecosystem (14), including native, introduced, and escaped annual and perennial species. We also endeavored to understand beet western yellows (BWY) disease-cycle components in western Oregon and to document the presence and determine the effects of BWYV in representative western Oregon sugar beet seed fields (17). The incidence of potential aphid vectors on one or more of 30 western Oregon plant species or forms commonly infected by BWYV was also separately examined (16). The purpose of this paper is to present interactions within the BWY pathosystem that cause risks to BWYV-susceptible crops in western Oregon.