Incidence of Apple Union Necrosis and Decline, Tomato Ringspot Virus, and Xiphinema Vector Species in Hudson Valley Orchards. D. A. Rosenberger, Assistant Professor of Plant Pathology, New York State Agricultural Experiment Station, Geneva. M. B. Harrison, Associate Professor of Plant Pathology, Cornell University, Ithaca, NY 14853; and D. Gonsalves, Associate Professor, New York State Agricultural Experiment Station, Geneva 14456. Plant Dis. 67:356-360. Accepted for publication 24 September 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-356.

Graft-union symptoms of apple union necrosis and decline (AUND) were observed in 22 orchards involving seven scion varieties propagated on MM 106 rootstock. Dandelions and individual trees in four orchards were indexed for tomato ringspot virus (TmRSV) by enzyme-linked immunosorbent assay. TmRSV was detected in the inner bark from 159 of 309 trees indexed and in 89% of trees with graft-union symptoms of AUND. Twenty-five percent of the dandelions in the four orchards were infected with TmRSV. The mean numbers of Xiphinema nematodes (X. americanum and X. rivesi) extracted from 100-cc soil samples were 84 and 181 for samples from beneath trees and from sodded row-middles, respectively. Nematodes transmitted TmRSV from soil samples to cucumber bait plants.

Keyword(s): tobacco ringspot virus.