Symptoms and Fungal Associations of Declining Chamaecyparis nootkatensis in Southeast Alaska. P. E. Hennon, USDA Forest Service, Forest Pest Management and Pacific Northwest Research Station, P.O. Box 21628, Juneau, AK 99802. C. G. Shaw III, and E. M. Hansen. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, 240 W. Prospect, Fort Collins, CO 80526; and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331. Plant Dis. 74:267-273. Accepted for publication 18 October 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0267.

The roots of 35 dying and healthy Alaska yellow-cedar trees (Chamaecyparis nootkatensis) were excavated to study symptoms and organisms associated with decline and death. Dying fine roots and necrotic lesions on roots and boles were common on cedars with declining crowns. Of 1,864 isolations, 1,047 from both healthy and dying cedars yielded fungi. However, when cedar seedlings were inoculated with the 11 most commonly isolated fungi, only Cylindrocarpon didymum caused necrotic lesions, and no fungi killed seedlings. Vesicular-arbuscular mycorrhizae and Mycelium radicis atrovirens were common (83 and 79%, respectively) in cortical cells of 42 fine root samples. Phytophthora gonapodyides was recovered in soil samples from beneath cedar trees but too infrequently to be considered responsible for mortality. These results suggest that pathogens are not the primary cause of Alaska yellow-cedar decline.