Hi and was hoping could help diagnose and treat issue having with azalea in my front yard. Transplanted about a month ago as had been behind a Japanese maple for years in my yard and moved to the front in a new bed I prepped with top soil and peat moss. It looks to be rust but wanted to make sure and it’s on so many leaves I’m hesitant to strip them all off. Pictures attached. There is a mushroom growing near the base of that matters at all though seems to be withering. Thanks for your help!
Franklin County Ohio
Thanks for using Ask a Master Gardener with your question about your Azlaea.
It is possibly a fungal leaf spot, but without a lab verification , I would just be guessing. You are welcome to send a sample to the C. Wayne Ellett Plant and Pest Diagnostic Clinic.
I do not think you really need to as the environmental conditions needed for a fungal growth is not really being met right now and the new growth I see from the photo look like clean leaves. Dry conditions when the leaves are not wet for a long period of time does not allow the fungal spores to germinate and rust is a fungus too.
You could also have some leaf scorch from having moved the plant in summer. Roots would have had to be cut to transplant which results in loss of water to the leaves. I would suggest leaving the leaves on the plant as not all the tissue is involved and the remaining leaf tissue that is green is producing energy for the plant to become re-established. Removing the leaves at this time might result in plant death since you do not have enough new leaves emerging after the transplanting to yet support the plant.
With that being said, here are a couple of fact sheets concerning issues with Rhododendrons and Azaleas. You may look at the descriptions and see if you feel it is something that needs treated. A fungicide will not cure a leaf but stops the spread to new, uninfected leaves. And again, the leaf needs to be wet for several hours for any fungus to grow. Rust would have spores that you can rub off with your fingers.
Since I cannot handle the leaf and can only view it from the nice photos you sent, you might need to compare the descriptions in the fact sheets. Try not to make the descriptions of the diseases match, rather what you actually see is the important issues. Let your inspection then give you the description of the issue.
The mushroom probably has nothing to do with anything and may have just been a fungus in the soil, amendments, or mulch, as long as the mushroom is not coming from the stem of the plant.
Hope this helps, thanks for your question.