What Is the Discoloration on Azalea Leaves?

Identification

• Azaleas are susceptible to the leaf rust disease caused by Pucciniastrum vaccinii. Infection commonly occurs during mid-summer. Symptoms are more pronounced in plants that stay wet for extended periods of time.

Damage

• The disease starts with the appearance of yellow, 1/8-inch diameter spots on the upper sides of foliage. Rust-colored pustules filled with fungal spores appear on foliage undersides immediately below these spots. Fungal spores are spread throughout the plant and to other plants with water and wind. Gradually, the entire plant appears discolored. Severely infected leaves start to fall.

Control

• Keep plant clear of fallen leaves as spores overwinter in affected foliage. Try to use resistant plant varieties. Avoid overhead irrigation that keeps plants wet for extended periods. Fungicides are usually not required for disease control.