Incidence of Apple Union Necrosis and Decline, Tomato Ringspot Virus, andXiphinemaVector Species in Hudson Valley Orchards

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Abstract
Graft-union symptoms of apple union necrosis and decline (AUND) were observed in 22 orchards involving 7 scion varieties propagated on MM106 rootstock. Dandelions and individual trees in 4 orchards were indexed for tomato ringspot virus (TmRSV) by enzyme-linked immunosorbant 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 4 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.