Emerald Green Arborvitae sudden browning

Question: I have a row of 7 arborvitae in a landscape bed along my back property line.  I have had these arborvitae for 21 years in my suburban yard.  They have been beautiful and green and have been a great privacy screen since I live on a corner lot.  They have been this way for 21 years up until Labor Day time frame this year when an end shrub started turning brown, then it's neighbor shrub started to do the same, and then a third one did the same.  The browning started near the top of the shrubs until it encompassed the whole shrub.  This has taken place just in the past 30 days!!

I am posting 2 photos.  The all green row of shrubs is from June 2024 and the photo of the browned shrubs is from Oct. 1, 2024.  Help!

responder: An Ask Extension Expert Replied October 02, 2024, 10:07 AM EDT
response: Dear Janet I am very sorry to hear about your situation.  The most common cause of arborvitae turning brown all over and dying is root rot caused by Phytophthora, a fungus. Early in the process, when only a few roots are affected, the portion of the tree they supply with water will die. As the entire root system becomes involved the entire tree dies. If you dig up an infected tree, the roots are black, brittle, shortened and break easily. During a hot summer like this year, a tree with an affected roots typically dies very suddenly.   Regretfully, this fungus persists in the soil for many years making treatment with fungicides very difficult.  Because you have such an established planting, I suggest you contact a Certified Arborists immediately. They will be able to confirm the diagnosis, the stage of the disease, and whether any treatment can be effective.  OCISA | Find an Arborist (ohiochapterisa.org)  All the best, Roxanne

responder: The Question Asker Replied October 02, 2024, 10:40 AM EDT
response: Roxanne,   Thank you for your reply.  I will take your suggestion and contact an arborist.    A couple more thoughts/questions for you, if I may:   I was wondering about my seemingly unaffected 21-year-old globe-shaped shrubs in front of the arborvitae...2 barberry and 4 old gold cypress (I think).  They seem okay.  Since it is October, will winter/freezing temperatures help my arborvitae by killing any fungus?  I am just hoping for a miracle here with these arborvitaes.  I am worried about the cost of replacement AND the possibility of remaining fungi killing off any new planting next year.  It almost seems hopeless.  I have thoroughly enjoyed these shrubs for 2 decades!   Janet Martin   From: ask=<personal data hidden> on behalf of Ask Extension  Sent: Wednesday, October 2, 2024 10:07 AM To: Janet Martin  Subject: Re: Emerald Green Arborvitae sudden browning (#0156822)

responder: An Ask Extension Expert Replied October 02, 2024, 11:42 AM EDT
response: Janet If it is Phytophthora, I do not believe it will affect the barberry or gold cypress. Regretfully winter temperatures will not stop the fungus, it is indeed the cause of your issues. If is the fungus, the prognosis for your plants will largely depend on the progression of the disease, which the certified arborist should be able to ascertain. Roxanne