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Azalea Malus infested #749952

Asked May 14, 2021, 2:40 PM EDT

My Azalea Malus has a wasting disease where leaves are eaten down to central stem and plant is looking very sickly and dying back with only a few blooms this year. I found a green worm which may be the cause (see photo). It's a very old plant (maybe 80 years old) but has never had this before and old growth has always regenerated with young vigorous Azaleas coming up next to it before this disease hit it. The young sprouts have the same issue.

Multnomah County Oregon

Expert Response

Thank you for your question, Bonita.  The strange upward growths on the branch appear to be witches broom, whose cause is unknown.  Rhododendron-Witches' Broom | Pacific Northwest Pest Management Handbooks (pnwhandbooks.org)  While there may be a disease acting on your plant, a diagnosis cannot be made without your submitting plant tissue and, perhaps, a soil sample to the OSU Plant Clinic (| College of Agricultural Sciences | Oregon State University).

The photo with the larva on it shows lichens growing.  The lichens are not harmful to the plant, but often grow on plants that are in distress and failing from other causes.  I am unable to identify the species of insect with just this photo.  Although you can send it to the OSU Insect Identification lab (OSU Insect ID Clinic (oregonstate.edu)), I would suggest that your azalea may have out-lived its (healthy) life span.  It looks as though it has not had regular pruning, and it may be in soil that is not acidic enough to allow it to uptake nutrients.  

I am sorry I cannot be more helpful.  Good luck!

An Ask Extension Expert Replied May 14, 2021, 4:48 PM EDT

Thank you for your quick response to my Azalea issue. I’ll follow through with pruning the overgrown old branches away and try to amend the soil to make it sustain this venerable old plant. The new growth sprouting at the base has healthy wood without moss though many of their leaves are also eaten back to the stems. Some branches here and there have normal leaves thankfully. Appreciate your advice.

 

Bonita

 

From: Ask Extension <<personal data hidden>>
Sent: Friday, May 14, 2021 1:49 PM
To: Bonita Sells <<personal data hidden>>
Subject: Re: Azalea Malus infested (#0019883)

 

The Question Asker Replied May 17, 2021, 3:30 PM EDT

If you are intending to keep it, I suggest you get a soil test to ensure that it has the correct (acidic) soil pH and enough nutrients.  Analytical Laboratories Serving Oregon | OSU Extension Catalog | Oregon State University   Another one of your plant's problems may be its inability to uptake nutrients.  Good luck!

An Ask Extension Expert Replied May 17, 2021, 4:05 PM EDT

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