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
image by "Alexander Hall" is Copyrighted by Flickr user: Joe Shlabotnik (Peter Dutton) under the Creative Commons Attribution license.
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.
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.
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.
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.
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.
- American Rhododendron Society: Insect and Disease Control
- Maintaining Healthy Rhododendrons and Azaleas in the Landscape
- Rhododendron Diseases
- Rhododendron Species
- Rhododendron Botanical Classification
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Cat Carson has been a writer, editor and researcher for more than 10 years. She has professional experience in a variety of media, including the Internet, newspapers, newsletters and magazines. Her work has appeared on various websites. Carson holds master’s degrees in both writing and cultural anthropology, and is currently working toward her doctorate degree.