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Ecology and Epidemiology

Effects of Photochemical Oxidant Injury of Ponderosa and Jeffrey Pines on Susceptibility of Sapwood and Freshly Cut Stumps to Fomes annosus. R. L. James, Plant pathologist, Forest Insect and Disease Management, State and Private Forestry, U.S. Forest Service, 11177 W. 8th Avenue, Lakewood, CO 80225; F. W. Cobb, Jr.(2), W. W. Wilcox(3), and D. L. Rowney(4). (2)(3)(4)Associate professor, forest products pathologist and statistician, respectively, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 70:704-708. Accepted for publication 3 January 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-704.

Ponderosa and Jeffrey pine sapwood samples and freshly cut stumps from trees with different amounts of oxidant injury were inoculated with Fomes annosus. With stumps, percentage of surface cross-section area infected and extent of vertical colonization were determined 1 mo and 610 mo after inoculation, respectively. Increase in surface area infection with increased oxidant injury, expressed as upper-crown needle retention, was statistically significant for ponderosa pine (P=0.01), but was not for Jeffrey pine. Also, the rate of vertical colonization was greater in stumps from severely oxidant-injured trees than in those from slightly injured trees. The relationship between injury and colonization was significant for Jeffrey pine (P = 0.05) and for ponderosa pine at one site (P = 0.03), but nonsignificant (P = 0.18) for ponderosa pine at a second site. Increased susceptibility of stumps to F. annosus appeared to be associated with decreased oleoresin exudation and decreased colonization by other fungi (especially Trichoderma spp. and blue stain fungi). Laboratory tests indicated that decay susceptibility of excised sapwood to F. annosus apparently was not affected by oxidant injury with Jeffrey pine, but weight loss of ponderosa pine sapwood was correlated with decreased injury (greater needle retention). On the other hand, weight losses of Jeffrey pine caused by Polyporus versicolor and of ponderosa pine caused by Poria monticola were correlated with increased injury (increased needle chlorosis).

Additional keywords: root disease, air pollution, epidemiology, decay susceptibility.