Abstract
Colletotrichum acutatum has been identified as a causal fungus of bitter rot of apples in Aomori. C. gloeosporioides, long known as a causal fungus of bitter rot, is predominant in the western part of the prefecture, where apples have been produced in monoculture. In contrast, C. acutatum is predominant in the eastern part of the prefecture, where a variety of fruits are produced. In most of the sampling sites in the western prefecture, C. gloeosporioides was found to be predominant in apples, and C. acutatum in the wild host plant Robinia pseudoacacia. Inoculation tests on apples indicated that C. gloeosporioides is slightly more pathogenic than C. acutatum.
