Our native dogwood (Cornus florida) is an important harbinger of spring in many parts of the U.S., and a popular ornamental tree in home gardens. The upturned white or pink flowers are arrayed along delicately tapering branches, which extend horizontally from the trunk in tiers. It's this shape that makes it stand out in the landscape. From flowers to form, the dogwood has an exquisite beauty that is the essence of spring to many people.
Unfortunately, this beloved tree is susceptible to a disfiguring, often fatal disease called dogwood anthracnose. Anthracnose is the common name given to a number of fungal diseases that affect all types of plants, including trees, shrubs, perennials and vegetables. There is more than one anthracnose that affects native dogwoods, however dogwood anthracnose does the most damage.
Robert L. Anderson, USDA Forest Service, bugwood.org
Robert L. Anderson, USDA Forest Service, bugwood.org
Dogwood anthracnose, the aptly named Discula destructiva, causes lesions on leaves and flowers, then twigs, and eventually the branches and trunks of a tree. It starts as small, purple-ringed spots on young leaves. These expand into brown blotches that can kill the leaves, which don't fall right away, but cling to the branches. It then spreads to twigs and branches, usually on the lower part of the tree, causing cankers that can ultimately kill it. It infects both wild and cultivated dogwoods.
Mary Ann Hansen, Virginia Polytechnic Institute and State University, bugwood.org
Dogwood anthracnose is found in the U.S. from Maine to Mississippi, and west to Missouri and parts of Kansas. It also appears in the Pacific Northwest and parts of Canada. Cool, wet, humid spring weather favors development of the disease.
C. florida and its pacific relative, Pacific dogwood (C. nuttallii), are host plants for the virus, however other species of Cornus are vulnerable, including redosier dogwood (C. sericea).
Charles Hoysa, Virginia Cooperative Extension, bugwood.org
Ways to prevent or control dogwood anthracnose:
Site a tree where its requirements for light, moisture, soil quality and soil pH are met. Growing a dogwood in an unsuitable location will stress it, leaving it vulnerable to diseases and insects.
Plant in an area with good air circulation.
When watering, keep water from splashing on the leaves.
Remove affected leaves, twigs and branches from the tree and clean up any on the ground. Put them in the trash, do not compost. Good sanitation can keep the disease from spreading to the main trunk, where it can be fatal.
Consider professional fungicide applications if a tree is newly infected to try to save it or delay its demise. A severely affected tree should be removed entirely and not turned into wood chips or mulch.
Finally, there are cultivars such as 'Appalachian Spring', and hybrids 'Ruth Ellen' and those in the Stellar series, that are resistant to dogwood anthracnose. Other dogwood species that are less susceptible to the disease include kousa dogwood (C. kousa) and pagoda dogwood (C. alternifolia).
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By Dan Heims, President, Terra Nova Nurseries, Inc.
Photographs courtesy of Terra Nova Nurseries, Inc.
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