Arborvitae has bugs? - Ask Extension
Hello, I've had these arborvitae trees since we moved in 23 years ago in North Portland. They have always been healthy and green, even though we don't...
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Arborvitae has bugs? #866030
Asked April 26, 2024, 5:05 PM EDT
Hello, I've had these arborvitae trees since we moved in 23 years ago in North Portland. They have always been healthy and green, even though we don't water or fertilize them. But last week I discovered the bark on 2 of them appears to be peeling off. There also appears to be little holes in the bark. So my question is, does my arborvitae have a bug problem of some kind? If not, what is happening to the bark and how should I treat it? Thank you!
Multnomah County Oregon
Expert Response
Hi and thanks for your pictures and question about your arborvitae trees. There are several insects that bore into arborvitae as you can see in the attached website. They usually choose stressed trees, but since our recent drought and heat waves, nearly all our trees are stressed! In my area in Clackamas County, I have seen multiple arborvitae removed recently, and they all show signs of insect boring tunnels across the stumps.
https://pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/arborvitae-thuja-borer
It looks like the insects have gotten ahead of the natural biological controls like birds and wasps, but the tops of the trees still look fairly healthy. You might try keeping them watered this summer and see what happens. They don't like too much water, but giving them a soaking every 3-4 weeks when we don't get rain might help prolong them for a few years.
If you choose to go the chemical route, I would advise calling an ISA certified arborist to get a specific diagnosis and the proper chemical. You can find one at the following site:
https://www.treesaregood.org/findanarborist
Here's hoping you can save the trees,
https://pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/arborvitae-thuja-borer
It looks like the insects have gotten ahead of the natural biological controls like birds and wasps, but the tops of the trees still look fairly healthy. You might try keeping them watered this summer and see what happens. They don't like too much water, but giving them a soaking every 3-4 weeks when we don't get rain might help prolong them for a few years.
If you choose to go the chemical route, I would advise calling an ISA certified arborist to get a specific diagnosis and the proper chemical. You can find one at the following site:
https://www.treesaregood.org/findanarborist
Here's hoping you can save the trees,
