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Phytophthora Root and Crown Rots of Peach Trees in the Eastern Great Lakes Region. W. F. Wilcox, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. M. A. Ellis, Department of Plant Pathology, The Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691. Plant Dis. 73:794-798. Accepted for publication 3 May 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0794.

Phytophthora megasperma, P. cryptogea, and P. cactorum were isolated from necrotic root and crown tissues of declining and dead peach trees on nine, four, and one farm(s), respectively, in New York and Ohio. Symptomatic trees in many of these orchards had been diagnosed previously as suffering from winter injury or root asphyxiation following an excessively wet autumn and spring. When woody peach seedlings were transplanted into artificially infested potting soil and flooded for 48-hr periods at 2 wk intervals, P. cactorum and most isolates identified as P. cryptogea were highly virulent, causing >90% root rot and a 60100% incidence of crown rot; isolates of P. megasperma displayed more variable levels of virulence, causing 1980% root rot and a 060% incidence of crown rot. These results indicate that root and crown rots caused by P. megasperma, P. cryptogea, and P. cactorum may be significant causes of decline and death of peach trees in New York and Ohio.