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Peach Rosette Mosaic Virus, Symptomatology and Nematodes Associated with Grapevine ‘Degeneration’ in Michigan. D. C. Ramsdell, Assistant Professor of Plant Pathology, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; R. L. Myers, Technician, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 64:1174-1178. Accepted for publication 8 April 1974. DOI: 10.1094/Phyto-64-1174.

Peach rosette mosaic virus (PRMV) was present in five out of 21 (23.8%) of surveyed mature Vitis labrusca ‘Concord’ grapevines at two of seven locations exhibiting grapevine ‘degeneration’ in Michigan. All ‘degeneration’ vines were delayed 2-3 wk in breaking dormancy, and exhibited weak growth and berry cluster shelling compared to healthy vines. The presence of PRMV was detected by sap inoculation from surveyed vines to herbaceous indicator hosts and confirmed serologically. Vines infected with PRMV exhibited abnormalities in leaf morphology; short, crooked cane internodes; narrow angles of cane branching and an ‘umbrella-like’ vine growth habit. Yield of PRMV-infected vines was drastically reduced, compared to apparently healthy PRMV-free vines. No other sap-transmissible virus was detected in any of the surveyed vines. PRMV-positive vines had medium populations of Xiphinema americanum or high populations of Criconemoides xenoplax nematodes associated with root zones. PRMV-negative ‘degeneration’ vines at five of the seven locations surveyed had mean vine populations of 134 X. americanum and 152 C. xenoplax per 100 cc soil per vine. Vines at these locations also yielded low populations of four other plant pathogenic nematodes. Nonsap-transmissible viruses not yet detected, and/or high levels of X. americanum or C. xenoplax associated with nonPRMV-infected ‘degeneration’ vines could account for symptoms expressed by these vines.