Several azalea diseases are really problems created by location or soil conditions. Azaleas have shallow root systems. Their roots require access to air and a constant supply of moisture that doesn’t soak the roots. Of course, there are some true diseases that may bother your plant as well. The chart below identifies both azalea diseases and general problems. Just look for your symptom in the left column. If you don’t locate your problem, you may want to consult the page on azalea pests.
| Azalea Symptoms |
Azalea Diseases & Treatment |
| Leaf Centers burn or bleach |
Too much direct sunlight. Azaleas prefer light shade under trees. Transplant. |
| Plants are lanky and have few blossoms. |
Too much shade. Prune to shape or transplant. |
| Flower petals develop brown spots which spread. Petals feel slimy when touched. Eventually flowers fall off. |
Petal Blight. Spray with a fungicide when flowers begin blooming. Replace any mulch at the base of the plant during Fall. Spores overwinter in soil. |
| White powder-like spots on leaves. |
Powdery Mildew. Spray with fungicide or use a systemic fungicide. Hot, dry weather (above 75 degrees Fahrenheit)will also kill this mildew. |
| Green leaves have yellow veins. |
Iron Chlorsis: too little iron in the soil. Apply iron fertilizer to roots or spray leaves with an iron solution. |
| Plant turns yellow, wilts/collapses. |
Root Rot – A condition that causes plants to rot in the ground — usually due to poor drainage. Amend your soil with organic materials; plant it in a raised bed; or pot it. But, fair warning, once root rot has truly set in, it might be best to dispose of the plant. |
| Foliage burns on outside edge or tip of leaf. |
Windburn if on new foliage, salt burn if on mature growth. Transplant to a more sheltered location. |
| Small yellow or pale spots occur on upper leaf surface. Eventually lower leaf surface is covered with yellow and orange spores. Early leaf drop in severe cases. |
Leaf rust. This disease occurs mostly during the late summer and fall in the eastern United States. Deciduous varieties are particularly susceptible. Weekly applications of a fungicide is recommended with the appearance of the disease. |
| Leaves become swollen, curled, and galled. |
Leaf and Flower Gall. Remove and destroy infected parts before they turn white and produce spores. Spraying remaining foliage with a fungicide may help. |
| Irregular dead spots first show on leaves. Spots enlarge becoming black. Leaves fall off. |
Web Blight. This disease primarily effects evergreen azaleas and can cause complete leaf-loss. Spray or use a systemic fungicide. |