AbstractCryphonectria parasiticagrew on American and Chinese chestnut total aqueous and tannin extracts from winter and summer bark. Differences in the amount of conidial germination and growth on extracts of the two species were small.C. parasiticatannase (tannin acyl hydrolase) was found to be more abundant intracellularly, had a pH optimum of 5.5, and a temperature optimum for activity of 30°C. Total tannase activities on American chestnut total aqueous and tannin extracts were higher than on the respective Chinese extracts