Fungus on Azalea Leaves


Azaleas are flowering shrubs that are part of the genus rhododendron. They are popular because they bloom in the spring in a variety of colors. They are different than a rhododendron because of their size and flower growth. Azaleas are generally healthy plants when their basic needs are met, However, they can be subject to a number of different fungus problems affecting the leaves.

Azalea Gall

Azalea gall is widespread around the country and it appears on leaves. Weather conditions affect the severity of the symptoms. Spores are produced during spring and summer and are dispersed by the wind or by rain to healthy leaves. The symptomatic galls are not visible until the following year. Azalea gall can be hand picked and disposed of before they turn white. Most native and horticultural azalea and rhododendron plants are susceptible. Plants growing in poorly aerated soils are more subject to infestation.

Rhododendron Leaf Spot

This fungus can cause leaf spots on azaleas as well as other types of rhododendrons. Small, tan, round spots with yellow borders appear on the leaves throughout the year. Extremely infected leaves drop off right away. This rarely causes major damage to the health of the plant unless they are young or weak. Keep the plant vital by fertilizing, irrigating, mulching and paying attention to the pH of the soil. Prune plants to ensure that sun and air get through to help the leaves dry quickly. Leaf spot is more prevalent after wet springs but rarely require fungicide control.

Powdery Mildew

Powdery mildew appears as a dusty white coating on leaves. In some cases it can be removed by rubbing the leaves. However, it can be misidentified as dust that has built up. Powdery mildew usually has more circular spots. As these spots expand, they will constantly produce mildew. Symptoms usually appear late in the season and are more prevalent in high humidity. Indoors, symptoms may occur at any time of year and is also affected by humidity and temperature. Injury to plants include stunting and distortion of leaves. Nutrients are removed by the mildew and may result in a decline in the growth of the plant. Fungicides are available, but not all fungicides can be used on all plants. Read the packaging directions carefully before applying any chemical.


Rust attacks the leaves of rhododendrons and deciduous azaleas and appears as yellow abscesses primarily on the lower side of the leaves. Usually, rust appears late in the summer and chemical control is not very practical. It is recommended to simply dispose of infected leaves immediately.


All varieties are susceptible to problems including leaf issues. One type of native azalea is the deciduous variety. It's important to care for the plants to prevent issues like fungus from occurring in the first place. The deciduous varieties of azaleas do well in full sun, well drained soil, and established plants do not need fertilizer. Pruning is recommended right after the flower blooms to avoid cutting off next year's blooms. If given proper care, fungus and other problems can be easy to avoid.

Keywords: Azalea Leaves, Azalea Leaf fungus, Fungus

About this Author

Sheri Engstrom has been writing for 15 years. She is currently a gardening writer for Demand Studios. Engstrom completed the master gardener program at the University of Minnesota Extension service. She is published in their book "The Best Plants for 30 Tough Sites." She is also the online education examiner Minneapolis for