Azaleas and Mildew

Deciduous azaleas, called the royalty of the American garden, have brilliantly colored, fragrant flowers that are quickly shed, especially as autumn approaches. Your enjoyment of their blooms could be cut even shorter if your plants are infected by mildew.

Symptoms

• An azalea infected with powdery mildew will first have pale patches of thread-like fungus growing on the upper side of its leaves. The mildew can spread to flower buds and other parts of the plant. Eventually, entire leaves may be covered in powdery mildew, according to Alabama Cooperative Extension Services.

Problems

• Powdery mildew may cause an azalea's leaves to turn yellow or become deformed. Some plants drop infected leaves early. An infected plant will grow more slowly than a healthy one. Powdery mildew can grow on azaleas' buds, in which case the flowers will not be as attractive.

Control

• Mildew-resistant cultivars are available, as is the mildew-resistant species R. viscosum, according to Ohio State University Extension. If your azaleas develop powdery mildew, all dead portions should be removed and---with debris of fallen leaves---discarded. Pruning may be necessary to increase air circulation. A fungicide spray may halt the growth of mildew.