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Field Evidence for Kousa Dogwood Resistance to Anthracnose Caused by Discula sp.. C. R. Hibben, Brooklyn Botanic Garden Research Center, Ossining, NY 10562. F. W. Holmes, Shade Tree Laboratories, University of Massachusetts, Amherst 01003. Plant Dis. 74:828. Accepted for publication 21 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0828C.

Anthracnose symptoms were observed on Comus kousa Hance and C. k. var. chinensis Osborn (trees 15-20 yr old, 12-18 cm trunk diameter) in a private arboretum in eastern Massachusetts (1). Conidiomata in necrotic leaf tissue were identified as Discula sp. Discula sp. was isolated from symptomatic leaves and pathogenicity was confirmed by infecting C. kousa seedlings. About 80% of the 500-600 Kousa dogwoods in the arboretum had received irrigation from overhead (5 m) sprinklers for about 10 hr twice a week during the dry summers of 1987 and 1988. These conditions were ideal for foliar infection. In adjoining areas without sprinklers, Kousa dogwoods had little or no infection whereas C. florida L. had severe anthracnose. In 1989, the sprinklers were not used and all Kousa dogwoods were free from anthracnose symptoms. This field evidence confirms the resistance of Kousa dogwoods to anthracnose (2), except under unusual moisture conditions conducive to foliar infection.

References: (1) F. W. Holmes and C. R. Hibben. J. Arboric. 15:290, 1989. (2) F. S. Santamour, Jr., et al. Plant Dis. 73:590, 1989.