The mulberry anthracnose fungus, Colletotrichum acutatum, overwinters on a mulberry tree

摘要

Colletotrichum acutatum, a causal fungus of mulberry anthracnose, has been observed on the leaves of a particular mulberry tree in Tsukuba. To elucidate its life cycle on the tree, the fungus was isolated throughout the year from various asymptomatic organs; leaves, bark, xylem and winter buds were periodically collected from November 1995 to January 1997. The fungus was detected from the bark and bud scales in winter, but not from the xylem or the inside of winter buds. When leaves were still attached to the shoots, the fungus was also isolated from blades and petioles of asymptomatic leaves, as well as diseased leaves and the bark. Based on the difference in isolation frequency from epidermis-scraped bark and intact bark, the fungus was considered to survive on the bark either superficially or slightly internally. These results indicate that the fungus overwinters on the tree and can repeat the infection cycle year after year, suggesting a strong association of the fungus with this particular tree. C. acutatum survived better on detached shoots in winter than two other mulberry anthracnose fungi, C. dematium and Glomerella cingulata.