Plant Pathology Infobytes
March 22, 1996
Time For Flowering Dogwood Disease Control
A home or forest landscape filled with flowering dogwoods in full bloom is one of the most beautiful sights Mother Nature has to offer. However, diseases occasionally reduce dogwood bloom quality, especially if cool, wet conditions persist in the spring. Spot anthracnose is the most common disease of flowering dogwoods and causes symptoms on flower bracts and foliage.
Spot anthracnose of dogwood should not be confused with "killer anthracnose," a disease which has killed many native flowering dogwoods in northern Georgia, eastern Tennessee, northern Alabama, and other areas of the Southeast. "Killer" anthracnose has been detected in only one location in northeast Mississippi. Thankfully, this particular strain of anthracnose has not become established in the state.
Spot anthracnose does not kill dogwoods, but the disease is capable of detracting from the beauty of the bloom crop. This disease frequently is widespread on dogwoods in the forest and home landscape during wet springs since moisture is necessary for the anthracnose fungus to infect young floral structures. Diseased flower buds may be stunted and malformed with bud death in severe cases. Although all flowering dogwoods are susceptible to spot anthracnose, white varieties are usually affected most, although pigmented varieties may also be severely affected.
Spots on flower bracts and leaves are small (pinhead size or slightly larger), circular, and have reddish brown to purple margins. The center of spots tends to be yellowish brown. Heavily spotted bracts and leaves are often distorted in appearance and may be smaller in size than healthy blooms and foliage. Numerous spots may blend together into large blighted areas. Young shoots and berries are also invaded by the spot anthracnose fungus.
Badly diseased bracts and sometimes leaves are shed, and while anthracnose won't kill trees, repeated early defoliation from year to year may reduce flower bud numbers and possibly increase plant sensitivity to later periods of moisture and temperature stress.
In the home landscape, spot anthracnose can be controlled by applications of fungicides.
Start fungicide application at bud break and repeat every ten to fourteen days until bracts fall. Spraying trees after spot anthracnose symptoms have appeared is of little value.
If you have questions about spot anthracnose of dogwood or other pests which may affect this popular landscape plant, please feel free to check with us at your county Extension office.
Infobytes newsletter was written by the late Dr. Frank Killebrew, Extension Specialist.