Contributors: J.R. Baker, Extension Entomology Specialist; D.M. Benson, Plant Pathology, Professor; L.F. Grand, Plant Pathology, Professor; R.K. Jones, Extension Plant Pathology Specialist; M.A. Powell, Extension Horticulture Specialist; D.L. Stephan, Extension Entomology Specialist; J. Scott, North Carolina Department of Agriculture; H. Singletary, North Carolina Department of Agriculture

DOGWOOD DISEASES

FOLIAR SYMPTOMS OF DOGWOOD ANTHRACNOSE
Photo courtesy of the Dept. of Plant Pathology, North Carolina State University
Dogwood anthracnose, a disease caused by a newly identified fungus, Discula destructiva, has been confirmed on flowering dogwood in the Southeast. The disease was first reported in the Northeast (New York and Pennsylvania) in the early 1980s. It since has been reported in Maryland, West Virginia, and Virginia. In 1987, anthracnose was found in northwest Georgia, northwest South Carolina, eastern Tennessee, and western North Carolina. The disease was reported in 1988 in the following North Carolina counties: Avery, Buncombe, Cherokee, Clay, Cleveland, Graham, Haywood, Henderson, Jackson, McDowell, Macon, Swain, and Transylvania. By 1990, the disease had spread to Ashe, Alleghany, Burke, Caldwell, Madison, Mitchell, Polk, Rutherford, Watauga, Wilkes and Yancey counties. It has not become established in any additional counties since 1991.

Mortality of Pacific dogwood (C. nuttallii) has occurred in Washington, Oregon, Idaho, and British Columbia. Recently the disease has been found on flowering dogwood in Alabama and Kentucky.

Initial symptoms are small purple-bordered leaf spots or larger blotches, especially on leaf margins. These initial symptoms can be confused with spot anthracnose, caused by Elsinoe corni, or other foliage diseases. Blighted leaves do not abscise in the fall and frequently remain on the twig until spring.

DOGWOOD ANTHRACNOSE CANKER
Photo courtesy of the Dept. of Plant Pathology, North Carolina State University

The fungus can spread to the twigs, causing dieback and, in some cases, damage to the trunk. New branches may develop on the trunk and larger branches and frequently become infected. The fungus may grow into the trunk or branch where a brown, elliptical, annual canker forms at the base of the dead branches. Multiple cankers can girdle branches or an entire tree causing death.

The fungus produces masses of spores (conidia) on infected leaves or bark on twigs and branches and presumably spreads by splashing rain and possibly by birds. The disease is more widespread and severe in cool moist locations at about 1800 feet of elevation.

Control is centered around cultural practices and fungicidal sprays. Maintenance of healthy, vigorous dogwoods is recommended (see Ten Essential Steps for Maintaining Healthy Dogwoods above). Pruning and disposal of diseased twigs and branches, removing new branches that develop on the trunk, and raking and disposal of leaves may be of some value. Pruning low branches of taller trees and thinning other understory plants to improve air movement may also help. This disease is more severe in forested areas near streams than in the landscape. Fungicides should be used only as a supplement to a cultural control program. Applications may be required in the spring, during leaf expansion, and during the fall if moist weather favors infection. The current North Carolina Agricultural Chemicals Manual should be consulted for recommendations on control.

Dogwood Anthracnose Control Key

1 A) If the tree(s) are in the following counties, see No. 2: Ashe, Alleghany, Avery, Buncombe, Burke, Caldwell, Cherokee, Clay, Cleveland, Graham, Haywood, Henderson, Jackson, Macon, Madison, McDowell, Mitchell, Polk, Rutherford, Swain, Transylvania, Watauga, Wilkes, Yancey.
B) If the tree(s) are not in one of the counties listed above, apply the 10 essential steps described in the text above, with the exception of the fungicide.
2 A) If elevation is 3,000 feet or above, use the 10 essential steps or plant another tree species.
B) If elevation is below 2,999 feet and in one of the counties listed in No. 1, go to No. 3.
3 A) If severe disease in local area, use the 10 essential steps or plant another tree species.
B) If no severe disease in local area, go to No. 4.
4 A) Dogwood in full sun. Apply the 10 essential steps except no fungicides and monitor.
B) Dogwood in partial shade, go to No. 5.
C) Dogwood in full shade, go to No. 7.
5 A) South-facing slope, apply the 10 essential steps except no fungicide and monitor.
B) North-facing slope, go to No. 6.
6 A) If moist or wet site, use the 10 essential steps or use another tree species.
B) If site not wet or moist, apply the 10 essential steps except no fungicide and monitor.
7 A) South-facing slope, go to No. 8.
B) North-facing slope, use the 10 essential steps or use another tree species.
8 A) If moist or wet site, use the 10 essential steps or use another tree species.
B) If site not moist or wet, apply 10 essential steps--with the exception of fungicide--and monitor.

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Last Modified: 07/10/96