A virus‐like disease of apple was observed for the first time in Canada in 1974 in a three year old planting. The disease was characterised by stem pitting, necrosis and breaking or separation of scion/rootstock at the graft union. Foliage was sparse and leaves were chlorotic and diffusely mottled. Using both frozen and freshly harvested leaves of infected apple trees from rootstock suckers as inoculum, a virus was transmitted to herbaceous indicator hosts. Based on host range symptoms, serology and electron microscopy, this virus was identified as tobacco ringspot virus. Initial counts of nematodes in the rhizophere of apple trees affected with union necrosis showed high densities of Xiphinema americanum Cobb., a known vector of nepoviruses. Reports of similar symptoms have indicated that the disease, apple union necrosis and decline was associated with the recovery of tobacco ringspot virus from infected rootstocks. This is the first report associating a union incompatibility condition of apple and tobacco ringspot virus.