Symptoms of ash anthracnose Courtesy Michigan State University Extension Service

Anthracnose diseases occur on many landscape trees; though they tend to be most severe on ash, dogwood, maple, oak, and sycamore. They are typically foliar diseases but twigs, branches, and buds may also be affected. Twigs and branches may develop cankers or dead areas that girdle the stem, causing death of distal parts of the stem. Premature leaf drop commonly occurs on infected trees. Anthracnose is not fatal (except for dogwoods in some circumstances); however, severe defoliation from anthracnose year after year can seriously weaken trees. Weakened trees become more susceptible to environmental stresses and secondary pathogens.

In ash trees, buds, leaves, and sometimes twigs can become infected. In early spring, infection of buds or expanding leaves results in irregular brown blotches and distortion of leaflets. These blotches are often associated with leaf margins. Infections that occur once leaves have already expanded result in small brown circular lesions. As these lesions enlarge, they may coalesce. Infected leaflets frequently drop from the tree leaving a carpet of leaflets on the landscape below. Although shoots may become stunted, infection on ash does not result in conspicuous twig or branch cankers.

Text courtesy Kentucky State University Extension Service

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