Phomopsis galls of hickory
Phomopsis galls of hickory are caused by one or more species of Phomopsis. The galls appear as a cluster of nodules tightly pressed together. When cut open they consist of woody tissue that is a bit disorganized in comparison to the normal wood. Phomopsis galls can be found not only on hickory but also on oak, maple and elm. Galls occur on affected trees throughout the eastern states but are more common in the north than in the south. Phomopsis galls on hickory range in size from very small to one inch or more. Affected hickories usually occur singly or in clusters of several trees. Ungalled hickories can occur nearby.
Genetic variability, among other factors likely plays a major role in the occurrence of this disease. Galls of affected trees may develop for several years then die. Multiple galls seem to cause a general loss of vigor and heavily affected branches and trees can dieback. The disease cycle on trees has not been throughly studied, therefore, control remains unknown.