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Effects of Oxidant Air Pollution on Susceptibility of Pine Roots to Fomes annosus. R. L. James, Former research assistant, Department of Plant Pathology, University of California, Berkeley 94720, Present address of senior author: Forest Insect and Disease Management, State and Private Forestry, U.S. Forest Service, 11177 W. 8th Ave., Lakewood, CO 80225; F. W. Cobb, Jr.(2), P. R. Miller(3), and J. R. Parmeter, Jr.(4). (2)(4)Associate professor, and professor, respectively, Department of Plant Pathology, University of California, Berkeley 94720; (3)Plant Pathologist, Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, stationed at Riverside, CA. Phytopathology 70:560-563. Accepted for publication 6 December 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-560.

Oxidant air pollution injury to foliage of ponderosa and Jeffrey pines increased the susceptibility of roots to infection and colonization by Fomes annosus under field and fumigation chamber environments. Roots of ponderosa pine trees severely injured by oxidant air pollution became infected proximal to the inoculation point significantly more often than did roots of healthy trees. Proximal colonization rate of F. annosus in inoculated ponderosa pine also was much greater in trees severely affected by air pollution. Exposure of container-grown ponderosa and Jeffrey pine seedlings to ozone in fumigation chambers increased infection and colonization by the pathogen. More seedlings (78% of both species) fumigated with ozone were infected than were nonfumigated seedlings (62 and 53% for ponderosa and Jeffrey pine, respectively). Colonization of host tissue of both species by F. annosus was directly related to ozone dose and seedling injury. These results indicate a very substantial, probable effect of oxidant air pollution on the rate of increase of F. annosus in coniferous forest stands subjected to chronic injury.