Influence of Site Factors on Dogwood Anthracnose in the Nantahala Mountain Range of Western North Carolina. D. O. Chellemi, University of Florida-IFAS, North Florida Research and Education Center, Route 3, Box 4370, Quincy 32351. K. O. Britton, and W. T. Swank. USDA Forest Service, Southeastern Forest Experiment Station, Forest Sciences Laboratory, Carlton/Green St., Athens, GA 30602; and USDA Forest Service, Southeastern Forest Experiment Station, Coweeta Hydrologic Laboratory, 999 Coweeta Lab Rd., Otto, NC 28763. Plant Dis. 76:915-918. Accepted for publication 20 March 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0915.

Sixty-five 0.08-ha plots located within the Nantahala Mountain range of western North Carolina were surveyed for dogwood anthracnose, caused by Discula destructiva. The incidence of disease and disease severity (extent of foliar symptoms and limb dieback) within canopies of Cornus florida was determined for all trees with a diameter of 1.0 cm or greater at 1.37 m aboveground. The incidence of dogwood anthracnose ranged from 53 to 100%; the severity of foliar symptoms, from 3 to 65%; and limb dieback, from 8 to 65%. Plots were inventoried, and the relationship between dogwood anthracnose and 14 variables representing indices of host density, stand composition, and topography was examined. Host density or relative host density, expressed in stems per hectare or importance value, respectively, and azimuth accounted for a significant portion of explainable variation in dogwood anthracnose. Anthracnose was inversely related to absolute or relative measurements of host density. Disease was greatest in northeast-facing plots and lowest in southwest-facing plots. Elevation had a minor influence on disease incidence and limb dieback. Geographic features, as described by the landform index, had a minor influence on disease incidence.