Groups Of Arborvitae Plants Yellowing And Turning Brown And Dying

Question From: J. Pekarek - Vancouver, Washington, United States
Q: Hello, I am concerned for my arbs. I have 12 to 15 foot arbs all around my back yard in a "u" shape, approx. 170 feet in total length. A couple of years ago random patches of them started very slightly yellowing, unfortunately we thought nothing of it. Last summer the problem got worse. The foliage started yellowing and some of the plants turned brown and died. This is happening in patches of whole plants, two or three are affected then the next two or three are healthy and green and so on. We were told it was a type of bug and applied some copper type spray at the advice of a yard specialist. Well this year it is much worse and at least 10 of the arbs are dead and about 20 others are displaying this problem. We hired a commercial shrub care company and they have sprayed 3 times now and there seems to be no improvement in 3 months now. I was recently told this could be a root problem. How can I find out what this really is and stop it?
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A: James, I am not a trained tree doctor,a certified arborist. so unfortunately I cannot help you. If you have a root problem, there are procedures that can be done. Trees planted too deep can be helped with the use of an air spade. Also applying the beneficial fungus mycorrhizae, to the root area would help. My certified arborist is a member of the Tree Care Industry Assoc. ( and The certified arborist Assoc. I suggest you contact both associations for recommendations. A good tree specialist should be a certified arborist and a current and active member of both groups. Do be sure to keep them well watered, but don't drown them. Good Luck and please let me know how it goes. Best Nancy