Evidence that Tomato Ringspot Virus Causes Apple Union Necrosis and Decline: Symptom Development in Inoculated Apple Trees. D. A. Rosenberger, Associate Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. J. N. Cummins, and D. Gonsalves. Professor, Department of Horticultural Sciences, and Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. Plant Dis. 73:262-265. Accepted for publication 4 October 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0262.

Rootstocks of cultivar Delicious/MM.106 apple trees were inoculated with tomato ringspot virus (TmRSV). Inoculum consisted of bark patches from TmRSV-infected MM.106 rootstocks of Delicious apple trees with distinct graft union symptoms of apple union necrosis and decline (AUND). Two of 31 trees inoculated in 1981 developed graft union symptoms after 2 yr and 26 additional trees had symptoms after 3 yr. TmRSV was detected serologically in rootstocks of most trees with symptoms of AUND. Only one of 37 control trees was infected with TmRSV 4 yr after planting. Inoculated trees were subjected to various crop-load, nutritional, and water stress regimes, but none of these factors affected the incidence or severity of AUND symptoms.