fungus or mold on azalea bushes #412745

Asked July 08, 2017, 6:28 PM EDT

I have scores of azaleas (different colors) - perhaps 60+ years old - and have noticed many, many of them have some kind of fungus on them which appears to be killing the branches, and sometimes the entire plant. Some plants are 8 ft high. I just became aware of this in last couple of months (it may have been existence long before), and seems to be spreading. Both sun and shade. No pesticides or fertilizers have been used. Need to know what kind of treatment I need to do. I'm attaching a photo. Thanks.

Montgomery County Maryland

Expert Response

The blue patches you see on the branches are called lichens. These are a combination of algae and fungus. Lichens do not cause decline in trees and shrubs and do not require any treatment.

You can prune out the affected branches. Pruning will stimulate new growth and eventually give you a fuller shrub.

Dead wood can be pruned out at any time. Green growth should be pruned immediately after the azaleas bloom in the spring.


Thank you for the response, so quickly, too.   I am concerned, because there are literally dozens of azalea bushes that have this condition, and the mold or lichens "infect" a branch and eventually that entire branch dies, sometimes killing the plant, but usually just a large branch.   I have lived here for about 40 yrs (North Chevy Chase) and have never seen this before.   Is there any other possible cause?    Is there anywhere where I can bring a branch to an expert to have it looked at?

The Question Asker Replied July 10, 2017, 1:06 PM EDT
There are other possible causes of branch decline in azaleas: botryosphaeria dieback, borers, and winter injury are among them.

You can take a branch sample to your local extension office:

Montgomery County Extension
18410 Muncaster Road
Derwood, MD 20855
Hours: Monday - Friday 8:30 - 5:00
Phone: (301) 590-9638


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