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First Report of Anthracnose Caused by Discula destructiva on Cornus florida X kousa Hybrid Dogwood. V. I. Smith, Department of Plant Pathology and Ecology, Connecticut Agricultural Experiment Station, New Haven 06504. Plant Dis. 78:100. Accepted for publication 27 September 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0100A.

Leaves of Cornus florida L. X kousa hybrid dogwood cultivars Constellation (from a private yard in Wallingford, Connecticut) and Stellar Pink (from the Connecticut Arboretum in New London) exhibited large brown lesions on the margins and along the midribs. After 48 hr of incubation in a moist chamber, acervular conidiomata and conidia typical of Discula destructiva Redlin (I) developed in the lesions. The fungus was isolated from the tissue and positively identified by comparison with known isolates of D. destructiva. Because specimens of hybrid dogwood were scarce, Koch's postulates were completed by inoculation of intact leaves of susceptible C. florida L. 'Cloud Nine' with plugs of hyphae growing on potato-dextrose agar, followed by incubation for 72 hr in a dew chamber. Conidiomata and conidia of D. destructiva were observed on the new lesions. Although hybrid dogwood cultivars have been reported to be highly resistant to D. destructiva, conditions such as drought or transplant stress may predispose trees to infection by the anthracnose fungus. Long-term effects of anthracnose infection on the hybrid trees are not known. This is the first report of anthracnose infection on C. florida X kousa.

Reference: (I) S. Redlin. Mycologia 83:633, 1991.