Dogwood – Diseases
Nothing can panic a homeowner like the threat of disease to their prized dogwoods. Dogwood trees in Atlanta have had several problems this spring. Brown, distorted leaves and severe leaf drop are common complaints. Fortunately, the problems are probably not life-threatening. But how can you tell?
Dogwood leaves tell the story of their afflictions. Knowing Atlanta’s weather history explains why the symptoms are so severe. The wet July last year caused dogwood root systems to grow shallowly in the soil. Dry weather this past May weakened the roots further – making the trees very susceptible to common diseases. Here’s what to look for:
POWDERY MILDEW was very common on dogwoods this spring. Look for a faint, dusty covering on all or part of the leaves. The affected leaf areas eventually die. Some leaves will be distorted. This can contribute to the scorched appearance of the foliage. Symptoms of either powdery mildew or water stress usually involve most or all of the foliage on the tree. Water stress and/or powdery mildew are the most common ailments of dogwoods this year.
TREATMENT: Protect new foliage by spraying a labeled fungicide throughout the summer. The powdery mildew fungus overwinters on twigs and trunks so spray again at bud break next spring. Remove all leaves under the tree this fall.
SPOT ANTHRACNOSE occurs on dogwoods in early spring. The disease is worst during a rainy April. Leaves will have lots of pinhole sized spots. The spots will be numerous and may distort the leaf or cause the blooms to look dirty.
TREATMENT: Protect new foliage in wet spring weather by spraying a labeled fungicide, from bud break until leaves are fully opened. Stop when summer begins.
DOGWOOD BLIGHT (Discula destructiva) causes medium-sized dead spots that enlarge to kill most of the leaf. It starts on the lower branches and works upward. Shaded trees in a very moist environment are susceptible and may die after several years. This disease has done severe damage to dogwoods in the eastern and northeastern mountains. Trees in open lawns SELDOM, IF EVER, get this disease. Although the disease has been identified in a few spots in Atlanta, it is very unlikely that it could be widely distributed.
TREATMENT: Protect new foliage by spraying with a labeled fungicide, from bud break until beginning of summer. Resume spraying again when fall temperatures cool. Remove all leaves from under trees this fall.