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Site Factors Associated with Nectria Canker on Black Walnut in Michigan. C. S. Thomas, Graduate Research Assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. J. H. Hart, Professor, Department of Botany and Plant Pathology and of Forestry, Michigan State University, East Lansing 48824. Plant Dis. 70:1117-1121. Accepted for publication 24 July 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1117.

More than 75% of the black walnut trees (Juglans nigra) in some stands in southwestern Michigan have multiple cankers caused by Nectria galligena. A five-county survey of 189 survey sites indicated that high Nectria canker incidence was associated with terminal moraines and till plains and was especially more prevalent on black walnut trees growing near wetlands, kettles, or depressions than on trees growing on uplands (P< 0.01). Such lowland sites were more common on the till plains and moraines. Soil type, topography, and surface geology were characterized at 30 of the survey sites. Soil texture, rooting depth, and drainage features were not significant to disease incidence but some surface geology and topographic features were.