Azalea ailments

By Wayne Hobbs Environmental Horticulture Agent
Posted 5/9/18

GREEN COVE SPRINGS – To wrap up on the topic of azaleas, let’s discuss some of the common diseases you may encounter on your shrubs. Ranging from little spots to swelling leaves, the azalea is …

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Azalea ailments

Posted

GREEN COVE SPRINGS – To wrap up on the topic of azaleas, let’s discuss some of the common diseases you may encounter on your shrubs. Ranging from little spots to swelling leaves, the azalea is susceptible to several pathogens and you must have an idea on its identity and cause to get the proper treatment.

Look-Alikes

One thing to remember with all plant diseases, is that what may seem like a fungus or bacteria may be something else entirely. If leaves become yellowed or discolored it could likely be a nutrition deficiency and cultural issues can cause dropped leaves or die-back. Remember to also give your azalea proper care, avoiding hedging, keeping overhead irrigation off of their leaves, and not planting them in coastal areas. If you are unsure of what is happening, share a sample and images of the plant with your local UF/IFAS Extension Office for identification and advice on care and treatment (if necessary).

Petal Blight

In cool, wet springs, this fungal disease appears as white spots on colored blooms or as rust-colored areas on white blooms. If left unchecked, it can rot the entire flower as it spreads. As the blooms dry, the spores of the disease stay there and wait for the next year.

While we are past the active season for this disease, it is a good idea to rake up spent blossoms around the shrubs and then remove any old flowers on or around the shrubs again 3-4 weeks before next year’s bloom.

Azalea Leaf and Flower Gall

Much more dramatic but less damaging than other diseases, azalea leaf and flower galls form as swollen, misshapen areas on flowers, leaves and stems. This often happens when azaleas are in deep shade with poor air circulation.

To control the disease, remove any galls as soon as they appear.

Mushroom Root Rot

A disease that proves to be mostly fatal in azaleas is mushroom root rot. This is most common when the shrubs are planted in areas where organic matter such as old stumps or tree debris is actively decomposing in the soil. The fungus lives within the soil but then can grow into the roots of the azalea, limiting the ability to absorb water and nutrients.

Plants will often decline heavily from this disease and if you pull up a root from the bush you can often find the fungus by scratching the bark off of major roots or the crown and looking for the white, thread-like material growing underneath. Treatment comes from not planting azaleas in sites where buried organic debris can be found.

If you have any horticultural, agricultural, 4-H, or family and consumer science questions, contact the University of Florida/IFAS Clay County Extension Office online at http://www.clay.ifas.ufl.edu or call by phone at (904) 284-6355.

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