Arborvitae Fungus/Mold?

Asked June 22, 2020, 10:45 AM EDT

We have three 12-14' healthy arborvitae that all of a sudden have a white coating on many branches. They otherwise look green and healthy, so not sure what the problem is as most other online help suggests a browning or dying of needles. I've attached two pictures to help. Any suggestions would be greatly appreciated on what it is and how to treat. Thank you.

Ottawa County Michigan

3 Responses


I apologize for the delayed response, your question was accidentally queued to a person who is not available.

My references do not show any diseases or insects to match your photos. Could something have been sprayed nearby that drifted onto your arborvitaes?

If this substance has not continued to spread that is probably what occurred. If it is continuing to occur, is there a spray being applied nearby every so many days?

You may send your pictures with a history of the plant—watering, do sprinklers wet the leaves, sun exposure, any chemicals or fertilizers applied— to MSU Plant and Pest Diagnostic lab for their opinion.

I’m sorry I couldn’t be more help.

Thanks for the response and it may very well be a residual spray from hemlock trees that alternate between the arborvitae. We had them treated earlier this year, but for some reason we did not notice the whitening on the arborvitae until recently. It does not seem to be spreading, and we’ll see if the upcoming storms help eliminate the “problem”. Thanks for checking it out.

Glad to hear they are doing OK. Reply here if more problems with them, and I’ll do my best to get you a timely response.