Victoria L. Smith, Ph.D. 1994. Dogwood anthracnose severity is influenced by
timing of spring rains. Frontiers of Plant Science 46(2): 2-3.
Abstract: The
health of landscape dogwoods (Cornus florida) has been monitored for eight growing
seasons. Most anthracnose lesions (caused by the fungus Discula destructiva) appear
on the leaves during the period of rapid leaf expansion in the spring; very few new
lesions appear after the leaves are fully expanded, about six weeks after leaf emergence.
This indicates that most of the anthracnose infections occur in the spring and early
summer, when the leaves are expanding, and suggests that the best time for application of
protectant fungicides is during this time. Defoliation or death of a dogwood tree due to
anthracnose has not been observed, and cankers caused by anthracnose are extremely rare.
Powdery mildew, however, is emerging as a serious defoliating disease, especially when
trees are stressed by other causes, such as drought or injury. Hybrid dogwoods (C.
florida X C. kousa) are very resistant to both anthracnose and powdery mildew,
but have weak crotches and tend to split as the trees age.
For a free copy please contact Victoria Smith, CT Agricultural Experiment
Station, P.O. Box 1106, New Haven, CT 06504 or vlsmith@caes.state.ct.us
Abstract: The
health of landscape dogwoods (Cornus florida) has been monitored for eight growing
seasons. Most anthracnose lesions (caused by the fungus Discula destructiva) appear
on the leaves during the period of rapid leaf expansion in the spring; very few new
lesions appear after the leaves are fully expanded, about six weeks after leaf emergence.
This indicates that most of the anthracnose infections occur in the spring and early
summer, when the leaves are expanding, and suggests that the best time for application of
protectant fungicides is during this time. Defoliation or death of a dogwood tree due to
anthracnose has not been observed, and cankers caused by anthracnose are extremely rare.
Powdery mildew, however, is emerging as a serious defoliating disease, especially when
trees are stressed by other causes, such as drought or injury. Hybrid dogwoods (C.
florida X C. kousa) are very resistant to both anthracnose and powdery mildew,
but have weak crotches and tend to split as the trees age.