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Disease Detection and Losses

Natural Infection of Nuts of Castanea dentata by Endothia parasitica. R. A. Jaynes, Connecticut Agricultural Experiment Station, New Haven 06504; N. K. DePalma, Connecticut Agricultural Experiment Station, New Haven 06504. Phytopathology 74:296-299. Accepted for publication 20 September 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-296.

An average of 14% of the nuts harvested from a planting of American chestnuts in which chestnut blight was prevalent was infected with Endothia parasitica. The percentage of nuts infected from individual trees varied greatly, but samples from 32 of 37 trees had one or more infected nuts. Signs of infections by the pathogen appeared after storage at 4 C followed by incubation at 18- 25 C, but the infections apparently were initiated while the nuts were on the tree. Infections were confined to the shell and appeared not to effect seed germination or seedling growth; pycnidia were commonly produced. Nuts of other chestnut species and hybrids from the same location appeared not to be infected. Immersion of nuts in water at 50 C for 30 min shortly after harvest diminished, but did not eradicate, E. parasitica. Transportation of nuts of C. dentata grown in areas where E. parasitica is present could be a means of transmitting the pathogen long distances to areas presently free of the disease.

Additional keywords: hypovirulence, seedborne pathogen.