Relation between Collybia fusipes root rot and growth of pedunculate oak

Collybia fusipes (Bull. ex Fr.) is the cause of a root rot on oak, mainly p edunculate oak, Quercus robur L., and northern red oak, Quercus rubra L. Th e disease is associated with a deterioration of the crown of affected trees in some, but not all, stands. We investigated the relationship between the level of root damage induced by C. fusipes and past growth of the infected trees at four sites of pedunculate oaks and one site of red oaks in northe astern and central France. The severely infected oaks showed poor growth fo r 15-50 years depending on the site. At one site where C. fusipes was not a ssociated with a deterioration of the affected tree crowns, the basal area increments of severely root damaged oaks has nevertheless been poor for mor e than 30 years. Severe infection by C. fusipes was associated with a 30-50 % reduction of basal area increment in the last 10 years preceding the stud y at all the sites. In contrast, in all the sites, trees lightly damaged by C. fusipes had basal area increments similar to the undamaged trees. The d ata would be consistent with a disease that develops slowly on vigorous tre es and affects their growth only late in the infection process.