Arborvitae issues

Asked August 17, 2018, 6:53 PM EDT

I have an arborvitae fence and over the last 2 seasons, I have lost 50% of the trees. The remaining trees are systematically turning brown slowly and appear to be dying as well. What might be causing this and what can I do to reverse this trend?

Oakland County Michigan

1 Response

Hello,
Loosing over 50% of your arborvitaes is certainly concerning. There are many factors that cause Arborvitae’s to begin browning. Most common are improper planting, lack of water, too much water, proper drainage, insects, diseases and winter burn. Without a picture it is hard to get an idea of the problem or problems that could be affecting your Arbs. There is more information needed from you that may help with making a determination. Are these newly planted or well established? How were they planted? If they were balled and burlap was the material removed? Root issues will develop if trees are not properly planted. Next, how often do they receive water? Water is essential for the establishment of your arborvitae especially after transplanting and throughout the growing season. Evergreens need to be getting least on inch of water per week in well-drained soil right up to the time the ground freezes. The soil should be moist not wet since over watering can be just as detrimental as under watering. You may want to do a quick test to determine your soil moisture by digging down about 4 inches and feel if the soil is dry or too wet. Adding about 3 inches of mulch will help keep the soil at an even temperature and help maintain moisture. Keep the mulch at least 3 inches away from the trunk of the tree to avoid excess moisture against the bark which can cause rot and encourage insects.

If not protected, winter winds can be extremely drying to the foliage and dehydration may result in browning. More information can be found here:

https://hort.uwex.edu/articles/winter-burn/

http://msue.anr.msu.edu/news/tips_for_preparing_landscape_trees_and_shrubs_for_winter

Arborvitaes are known to have spider mites and they can cause a lot of damage if not kept in check. To check for mites hold a white piece of paper under a branch a give it a shake. You may see some drop on the paper and you may notice the dark, oval mite against the white background. Look around for any webbing around the branches this could be another indicator of insects. More information on mites:

https://ento.psu.edu/extension/factsheets/spruce-spider-mite

Since you have already have a large amount of decline it would be beneficial for you to have an onsite analysis made by an arborist.

To find an arborist in your area go to the following website and click on the link find an arborist. You then type in your zip code and it will bring up a list of certified arborists in your area that can help with a proper diagnosis. Make sure you select a certified arborist, they have had the proper education in diagnosing tree diseases.

http://www.treesaregood.com/

I have included more information regarding Arborvitaes and I hope you find it beneficial.

Stress-related conifer dieback:

https://www.extension.purdue.edu/extmedia/id/id-477-w.pdf

http://horticulture.oregonstate.edu/system/files/onn011001.pdf

https://ipm.missouri.edu/MEG/2011/10/The-Blast-Furnace-Summer-of-2011-turned-some-Evergreens-to-Everbrowns/

Arborvitae Problems:

http://ccenassau.org/resources/arborvitae-problems

I realize this is a lot of information but it will help you understand the problems and assist you in converstation with an arborist.
If you have any more questions don't hesitate to contact AaE again.