Incidence and Distribution of Six Viruses Infecting Potatoes in Pennsylvania. D. M. Petrunak, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. F. E. Gildow, and B. J. Christ. Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 75:644. Accepted for publication 21 January 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0644B.
Two hundred eighty-two samples of potato (Solanum tuberosum L.) leaf tissue were collected from fields in five counties in Pennsylvania (Erie, Lehigh, Potter, Schuylkill, and Somerset) during 1987 and 120 samples were collected from three counties (Potter, Schuylkill, and Somerset) during 1988; samples were collected along a diagonal transect in each field, regardless of symptoms. Samples were tested for potato viruses S (PVS), X (PVX), Y (PVY), M (PVM), and A (PVA) and for potato leafroll virus (PLRV) by double antibody sandwich enzyme-linked immunosorbent assay. In 1987, the six viruses were identified in all counties; 38, 5, 21, 6, 11, and 5% of plants were infected with PVS, PYX, PVY, PVM, PV A, and PLRV, respectively. PVS, PYX, PVY, PVM, PYA, and PLRV were found in 14, 5, 15, 2, 10, and 4%, respectively, of 110 plants from virusindexed sources and in 58, 10, 27, 8, 12, and 5%, respectively, of 172 plants from nonindexed sources in adjacent fields. In 1988, only PVS and PYX, at 53 and 85%, respectively, were detected in commercial fields in Schuylkill County, and PVS, PYX, PVY, and PLRV, at 100, 3, 5, and 3%, respectively, were found in fields in Somerset County; no viruses were detected in samples from Potter County. These results support the need for Pennsylvania growers to adopt a limited generation seed production system and for all potato growers to use certified seed potatoes.