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Effects of Fertilization on Hypoxylon Canker of Trembling Aspen. George E. Teachman, Soil Scientist, Michigan Department of Natural Resources, Mt. Pleasant 48858. Douglas J. Frederick, Associate Professor, School of Forest Resources, North Carolina State University, Raleigh 27650; and William E. Perkis, Graduate Assistant, and Martin F. Jurgensen, Professor, Department of Forestry, Michigan Technological University, Houghton 49931. Plant Dis. 64:284-286. Accepted for publication 16 October 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-284.

Aspen (Populus tremuloides) on two sites in Michigan were fertilized in May 1977, then inoculated with Hypoxylon mammatum in June; canker incidence and length were recorded in August and October. Incidence was highest and average length greatest in August for both sites, although the relationship among fertilizer treatments varied. Canker incidence was not independent of fertilizer treatment in August but was in October. There was no significant difference between incidence level in August and October on either site, even though the number of cankers declined for nearly all treatments. Canker length declined from August to October for all treatments except K, NK, and PK, but the decrease was not significant. No significant differences in canker incidence or length and fertilizer treatments between sites were observed. N fertilizer favored Hypoxylon infection and canker development during the summer, whereas P and K treatments restricted canker incidence and development.