Disease Note.

Root Rot of Red Pine Caused by Heterobasidion annosum in Wisconsin. G. R. Stanosz, Departments of Plant Pathology and Forestry, University of Wisconsin, Madison 53706 . M. A. Guthmiller, Departments of Plant Pathology and Forestry, University of Wisconsin, Madison 53706 and W. H. Kearby, Wisconsin Department of Natural Resources, Rhinelander 54501. Plant Dis. 79:859. Accepted for publication 28 May 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0859A.

Root rot of merchantable red pine (Pinus resinosa Aiton) was investigated in one plantation in Adams County in the fall of 1993 and a second plantation in Iowa County, Wis., in the spring of 1994. Dead and living symptomatic trees were present along the margins of openings in each of the previously thinned stands. Living symptomatic trees exhibited thin crowns, reduced twig growth, and short, chlorotic needles. Root symptoms included resinosis, pink to light brown discoloration of sapwood affected by incipient decay, and stringy white pocket rot of roots in an advanced state of decay. Basidiocarps collected from trees and stumps were identified as those of the root rot pathogen Heterobasidion annosum (Fr.:Fr.) Bref. (syn. Fames annosus (Fr.:Fr.) Cooke). Isolates from fruiting bodies and decayed roots were identified based on the production of the asexual state Spiniger meineckellum (A. Olson) Stalpers (syn. Oedo-cephalum lineatum Bakshi) and by comparison with known isolates. Red and jack pines (P. banksiana Lamb), grown for 2 years in a nursery and a third year in pots, were inoculated by insertion of colonized wood wedges into wounds made in lower stems (1). All of the inoculated trees (15 of each species) were girdled and killed within 8 weeks and the fungus was reisolated. This is the first report of H. annosum in Wisconsin. Additional mortality occurred at each location during 1994, but limited observations have not confirmed presence of this pathogen at other sites in the state.