Overview

Rhododendrons (Rhododendron) are flowering shrubs in the heath family (Ericaceae). Rhododendron plants are native to North America, Asia, Europe and Australia. While rhododendrons are generally hardy plants, they are susceptible to few diseases.

Rhododendron in bloom

Types

One of the most common rhododendron disease is rhododendron wilt, also called Phytophthora root rot (Phytophthora cinnamomi). Other common rhododendron diseases include petal blight (Ovulinia azaleae) and powdery mildew.

Effects

Rhododendron wilt effects include yellowing leaves, drooping foliage and stunted growth. Petal blight causes tiny rust- or white-colored spots to appear on the petals, while powdery mildew creates a white or gray coating on the leaves.

Considerations

Most rhododendron diseases are caused by fungal or bacterial pathogens. Many common rhododendron diseases occur during wet weather conditions in the late spring and early summer months.

Other Problems

Rhododendron plants often suffer from iron deficiency, which causes the leaves to yellow between the veins. Rhododendrons are vulnerable to several pests, including the lace bug, root weevils and black vine weevils.

Maintenance

Rhododendrons should be planted in high locations that offer excellent soil drainage. Dying and dead foliage should be removed from the vicinity of other plants to avoid spreading the disease.