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. These fungus problems contain many variables and have different effects on the plant.
Definition of Fungus
The study of plant diseases is known as plant pathology. Infectious diseases are caused by living organisms called pathogens. One category of a pathogen is fungi. Each fungus has a different life cycle and host (or plant) specific to a genus or species. Azaleas have several different fungi that affect their growth and appearance.
Azalea gall is widespread around the country. It is caused by the fungus Exobasidium vaccinii in azaleas and the fungus appears on its leaves. Weather conditions affect the severity of the symptoms. Spores are produced during spring and summer and are dispersed by the wind or rain to healthy leaves. This usually occurs during cool, wet weather. The symptomatic galls are not visible until the following year.
Petal blight is caused by the fungus Ovulinia azaleae. Its severity and occurrence on azaleas is also highly dependent on the weather. If it is wet and cool during the flowering period, symptoms may become more severe. The symptoms are tiny, pale white spots on colored petals and rust colored spots on white petals. The spots can grow quickly and the infected petals become soft and watery until the whole blossom falls off.
Azalea gall can be manged by handpicking and disposing of the leaves 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.
If petal blight has been a continuous problem in the past, applying a fungicide is recommended just as the buds begin to show color. A second application can be applied if the weather conditions are good throughout the blooming period.
All azalea varieties are susceptible to fungus. One type of native azalea is the deciduous variety. It's important to care for the plants to prevent issues like fungus from occurring. 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 should be easy to avoid.