Why are my arborvitae’s dying? - Ask Extension
Hello. My arborvitae are experiencing rapid mortality and I don’t know why. Whatever is happening is targeting the arborvitae as the other evergree...
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Why are my arborvitae’s dying? #907928
Asked June 30, 2025, 6:51 PM EDT
Hello. My arborvitae are experiencing rapid mortality and I don’t know why. Whatever is happening is targeting the arborvitae as the other evergreen trees on the property are not effected. I had a soil test done, nothing glaring indicating a soil problem. I would like to replace them, however, I would like to figure out what is happening before buying new plants.
Macomb County Michigan
Expert Response
Hello
This looks like drought stress. Do the shrubs get deep watering when we enter dry periods, such as we have had over the last 3-4 summers and falls? Past droughts affect trees and shrubs, slowly killing them over several seasons. We tend to notice when the whole shrub finally has died and the needles turn gray and drop off.
The new growth at the base would indicate some roots are still alive.
Examine the shrubs that begin to show dying needles for signs of chewing by animals on the branches and main trunk, or other injury such as large cracks, missing bark, unusual growths, oozing sap.
Root rots can kill shrubs. Injuries to the root zone or trunk allow diseases to enter, gradually killing shrubs.
Flooding can also kill shrubs; does this area ever flood? If so how long do the shrubs stand in flooded soil?
There are a couple ways to have a plant pathologist give you a diagnosis:
1- Send branch samples to MSU Plant and Pest Diagnostic lab. You need to fill out the sample form, and submit branch samples with needles just beginning to show problems. You may also want to dig a sample of the roots from the dead shrub and submit those with the branches. Include pictures and plant history details on watering, how long the shrubs have been planted, any chemicals applied nearby including weed killers. There is a fee schedule on the lab website. https://www.canr.msu.edu/pestid/
2-Hire a certified arborist, one who has received training and passed certification, to come on site and examine the whole area and give you a diagnosis. You can find certified arborists by zip code here— http://www.treesaregood.org
Some references for you-
https://extension.psu.edu/arborvitae-diseases
https://www.extension.purdue.edu/extmedia/id/id-477-w.pdf
This looks like drought stress. Do the shrubs get deep watering when we enter dry periods, such as we have had over the last 3-4 summers and falls? Past droughts affect trees and shrubs, slowly killing them over several seasons. We tend to notice when the whole shrub finally has died and the needles turn gray and drop off.
The new growth at the base would indicate some roots are still alive.
Examine the shrubs that begin to show dying needles for signs of chewing by animals on the branches and main trunk, or other injury such as large cracks, missing bark, unusual growths, oozing sap.
Root rots can kill shrubs. Injuries to the root zone or trunk allow diseases to enter, gradually killing shrubs.
Flooding can also kill shrubs; does this area ever flood? If so how long do the shrubs stand in flooded soil?
There are a couple ways to have a plant pathologist give you a diagnosis:
1- Send branch samples to MSU Plant and Pest Diagnostic lab. You need to fill out the sample form, and submit branch samples with needles just beginning to show problems. You may also want to dig a sample of the roots from the dead shrub and submit those with the branches. Include pictures and plant history details on watering, how long the shrubs have been planted, any chemicals applied nearby including weed killers. There is a fee schedule on the lab website. https://www.canr.msu.edu/pestid/
2-Hire a certified arborist, one who has received training and passed certification, to come on site and examine the whole area and give you a diagnosis. You can find certified arborists by zip code here— http://www.treesaregood.org
Some references for you-
https://extension.psu.edu/arborvitae-diseases
https://www.extension.purdue.edu/extmedia/id/id-477-w.pdf
