Diseases in Azaleas

Overview

A popular shrub with showy blooms in colors ranging from deep magenta to red to white, azaleas are hardy evergreen plants that can create breathtaking color bursts during their short spring blooming season. A member of the rhododendron family, azaleas are particularly popular in the South. These generally healthy plants are susceptible to some diseases but most are easily controlled.

Root and Crown Rot

Most commonly caused by too much water--flooding or poor draining--crown and root rot are caused by a fungus. Also known as water mold, this fungus will cause the plant to wilt, leaves will curl and droop and roots will look black and soft. This fungus may also affect the lower portion of the stem, in which case it is called crown rot. Symptoms are a brown discoloration of the plant's stem near the soil and it can be caused by poor drainage, over watering or initially planting azaleas too deeply. Similar symptoms of both root and crown rot may be brought on by drought. There is no fungicide on the market that can cure this disease, but if caught early enough, treat with fungicide to delay further damage.

Petal Blight

This common fungus affects the flowers on an azalea and will appear first as small white spots on colored flowers or brown spots on white flowers. As the fungus progresses, the spots will get bigger and the bloom will become soft and watery. Rotting flowers may stick to leaves or branches of the plant. Remove and dispose of affected blooms and treat plant with fungicide.

Leaf Gall

Caused by a fungus, leaf gall is a common illness, but one that does not necessarily require chemical care. The fungus presents itself in early spring when buds and leaves become distorted--they may turn white, get fleshy or curl. As the disease progresses, the leaf gall becomes a white powdery substance and then hardens into a brown "gall." Remove and destroy galls of affected plants. If a large number of plants are affected, apply fungicide.

Rust

Caused by a fungus, rust presents itself as red-orange spores on leaves or cankers on the bark. This fungus could kill your whole azalea plant, so treat it as soon as you spot it. The best defense is to remove and dispose of affected areas.

Premature Leaf Drop

Premature leaf drop may be caused by twig blight or powdery mildew, both of which may turn up late in the season. Twig blight is the more critical and additional symptoms include wilting as well as red-brown discoloration on the bark. The best defense is pruning back the affected bush and disposing of diseased sections. Powdery mildew presents itself as white powder on the leaves, which may drop early. Remove and dispose of affect leaves and consider a fungicide treatment if the condition does not clear up.

Keywords: Azaleas and rhododendron, Azalea disease, Treating diseased azaleas

About this Author

J.D. Chi is a professional journalist who has covered sports for more than 20 years at newspapers all over the United States. She has covered major golf tournaments and the NFL as well as travel and health topics. Chi received her Bachelor of Arts in professional writing from Carnegie Mellon University and is working toward a master's degree in journalism.