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Potential Role of Winter Rapeseed Culture on the Epidemiology of Potato Leaf Roll Disease. P. E. Thomas, Research Plant Pathologist, Vegetable and Forage Crop Production, Agricultural Research Service, U.S. Department of Agriculture. An N. Hang, Gary Reed, G. C. Gilliland, and Guy Reisenauer. Associate Agronomist, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser; Superintendent, Hermiston Agricultural Research and Extension Center, Hermiston, OR; Elect. Technician II, and Scientific Programmer, WSU-IAREC, Prosser, WA 99350. Plant Dis. 77:420-423. Accepted for publication 14 December 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0420.

Rapeseed was an efficient overwintering host of beet western yellows virus (BWYV), one of two viruses that has been associated with potato leaf roll disease. However, rapeseed was not an overwintering host of potato leafroll virus (PLRV), which also causes the disease. Although all unprotected potato plants in the test area were infected with PLRV, no rapeseed plants were infected with PLRV among 3,040 plants assayed in 72 cultivars over a 2-yr period. In contrast, BWYV infected many plants of all winter rapeseed cultivars in the fall, survived winter in these plants, and spread to nearly all remaining plants of every cultivar in the spring. Although small differences in incidence of infection and in BWYV antigen content of infected plants were detectable among the rapeseed cultivars, all cultivars were highly susceptible to the virus. Two aphid vectors of BWYV and PLRV, the green peach aphid (Myzus persicae) and, rarely, the potato aphid (Macrosiphum euphorbiae), were found on rapeseed plants in the Columbia Basin of Washington in both fall and spring, but neither aphid species survived winter on rapeseed. Both species returned to rapeseed in an early spring migration, colonized the crop, and began to migrate away from rapeseed as the crop ripened in early summer.