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Occurrence of Rhizomorphs of Armillaria in Soils from Declining Red Spruce Stands in Three Forest Types. P. M. Wargo, Principal Plant Pathologist, USDA Forest Service, Center for Biological Control of Northeastern Forest Insects and Diseases, Hamden, CT. A. C. Carey, G. T. Geballe, and W. H. Smith. Former Graduate Student, School of Forestry, Yale University, New Haven, CT; and Research Associate, and Professor of Forest Pathology, School of Forestry, Yale University, New Haven, CT. Plant Dis. 71:163-167. Accepted for publication 23 September 1986. 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, 1987. DOI: 10.1094/PD-71-0163.

The occurrence of rhizomorphs in soil around dead trees was determined in stands of declining red spruce in hardwood, transition, and montane boreal forest types that differ in elevation. Rhizomorph incidence and population density were significantly lower in the higher elevation transition and montane boreal forest types. These data suggest that previously reported infrequent colonization of declining red spruce at high elevations is due to low levels of inoculum of Armillaria in forest soils. High lead concentration and low pH of the organic layer of soils in the higher elevation spruce-fir stands in the Northeast were correlated with low levels of inoculum, but these factors alone do not explain the variation in occurrence of the fungus.

Keyword(s): heavy metals, root disease.