In my last article, I discussed powdery mildew on dogwoods. In this article, I want to talk about a different disease that can infect dogwood trees — spot anthracnose.
One of the most common leaf diseases of flowering dogwoods, spot anthracnose usually attacks the flower bracts first. Next comes the leaves, young shoots and finally the fruit of dogwoods.
Symptoms are small or 1/8-inch tan spots with reddish-purple borders appearing on the plant. When the infection is severe, the spots can cause flower bracts and leaves to become wrinkled and distorted.
And this fungus survives from year to year on infected twigs, fruits and other tissues.
The attacks happen primarily during wet spring weather. Frequent rains or extended periods of high humidity are needed for disease development. When dry weather follows bud swell and bloom, the symptoms are rarely seen on the flower bracts.
In most cases the disease doesn’t result in significant damage, but severe and repeat infections each year can significantly weaken a tree.
To manage the problem in the landscape, thin the canopy to increase air movement. Another excellent option is planting species and cultivars with some degree of resistance to the disease.
Disease-tolerant and resistant varieties include:
- Kousa dogwood (Cornus kousa) “National” and “Milky Way Select”
- Flowering dogwood (C. florida) “Cherokee Brave,” “Cherokee Chief,” “Welch’s Bay Beauty,” “Cherokee Princess” and “Springtime”
- Rutger’s hybrid — Stellar Pink”
The worst infections of spot anthracnose have been reported on Cornus Florida “Rainbow” and “Cherokee Daybreak.”
If the disease becomes severe, fungicides may be used in the spring starting at bud break and continuing until leaves are fully expanded. Fungicides available include chlorothalonil, mancozeb, maneb, propiconazole, thiophanate-methyl or copper fungicides. Fungicides for spot anthracnose will also control dogwood anthracnose (canker anthracnose). Apply all chemicals according to directions on the label.
The source of the information was derived from Clemson University Cooperative Extension.
Michael Wheeler is county extension coordinator for the UGA Cooperative Extension office in Hall County. You can contact him at 770-535-8293, www.hallcounty.org/extension. His column appears weekly and on gainesvilletimes.com/life.