Association of Nematodes with Dogwood Canker and Stem Malformations on Other Trees

Two nematodes, one stylet-bearing and allied to the Aphelenchoides fragariae complex and the non-stylet species Panagrolaimus subelongatus, were isolated from the disrupted bark on main trunks and branches of young flowering dogwood (Cornus florida L.) trees exhibiting symptoms of “dogwood canker” disease. Similar nematodes were isolated from burls on the trunks of Siberian elm (Ulmus pumila L.), Higan cherry (Prunus subhirtella Miq.), red oak (Quercus rubra L.) and black locust (Robinia pseudoacacia L.), whereas only the Panagrolaimus species was found in abnormal tumorous growths on the trunks of the Green Mountain cultivar of sugar maple (Acer saccharum Marsh. ‘Green Mountain’). Nematodes were recovered 2 months after inoculation into young dogwood stems in June, 1983 but none could be detected after the inoculated trees had been subjected to winter temperatures as low as −22°C (−4°F) even though nematodes in established cankers survived under the same conditions. Inoculations made in July, 1984 into callus tissue developed after wounding in 1983 or 1984 produced canker-like symptoms but the nematodes were not reisolated in 1985. The total number of nematodes per canker was low and older cankers often yielded no nematodes, even though the canker persisted.