Dogwood anthracnose leaf damage
Joseph O'Brien, USDA Forest Service, Bugwood.org
Dogwood anthracnose is a disease of flowering and Pacific dogwood (Cornus florida and C. nuttallii). An anthracnose fungus, Discula destructiva, has been identified as the causal agent.
Keywords: fungus, blighted leaves, necrotic veins and leaf margins, blotches, spotted bracts, girdling cankers, twig dieback, Cornus florida, Cornus nuttallii
|Distribution Map||Distribution Source Image|
Infection of dogwoods is favored by cool, wet spring and fall weather, but can occur throughout the growing season. Drought and winter injury weaken trees and increase disease severity. Bracts may become spotted or blighted if rainy conditions prevail during flowering. Leaf symptoms, which include tan spots that develop purple rims, begin in the lower crown and progress up the tree. Leaves may also have necrotic veins and leaf margins, large necrotic blotches, and shot holes. On both dogwood hosts, leaves that are entirely blighted do not abscise in the fall. Infections often progress down the petioles of blighted leaves into shoots, resulting in cankers. Girdling cankers cause twig dieback, which is most common in the lower crown following years of extensive spring or fall leaf blighting. Twig dieback results in succulent shoots proliferating on the lower trunk and main branches of affected trees. These branches are very prone to infections that may progress into the main stem. Multiple cankers can girdle individual branches or kill the entire tree. Consecutive years of heavy infection have resulted in extensive mortality in both woodland and ornamental dogwoods.