What is killing our arborvitaes? #772720 - Ask Extension


What is killing our arborvitaes? #772720

Asked September 22, 2021, 3:30 PM EDT

Hi - we had a 13 large - beautiful arborvitaes installed by a reputable Landscape company last September (4) and this May (9) - they all have done beautifully until one week ago — when I noticed one of them on the side looked odd so I walked over to the row of them and walked behind the row and five of them appeared completely dried out and dead on the Northside and healthy and vibrant on the south side. They are planted in our garden in a shaded area so the sun is not hitting them hard. When I touched the bush the needles all fell off - the branches completely dried out— they also have a strange color to them on the north side — almost like they have been spray painted. There is no yellow or brown branches. And the all began dying off like this within days. This all began last week. What is very curious is that our neighbor had just had their back yard and trees sprayed for mosquitos and that day we had a very strong north wind - so strong that my husband came into the house because the fog from the spray was so dense. The trees starting dying off a week after this spray. I have called the Mosquito company and they came out yesterday and said - their spray would not kill trees/shrubs. They do have something they use on the ground that would kill Trees/shrubs but the representative said that should not have been in their tanks. I had the Nature Designs landscape company come out — specifically the owners and after two inspections they told me it is not a bug/mite that this appears to be an environmental spray or toxin spray. Now I feel stuck between no one wanting to clearly identify what the problem is as the bushes are still in warranty by the landscape company - however this was an expensive project, and I assume they do not want the liability. The Mosquito spray company does not want the liability either. I have kept the bushes watered and the ones that were installed last September came through the winter just fine. I am hoping someone can help me determine what is/has killed my beautiful shrubs.. they seem to be loosing more needles and drying out daily — on one side only. Our home is in Maple Grove on a Natural Wetland and the shrubs are inside our fenced yard.

Hennepin County Minnesota

Expert Response

This must be heartbreaking. 
There is an agency where one can report pesticide drift.


Mosquito sprays unless they are unusual aren’t toxic to trees.


The very windy day was also very hot and dry so it may have been too much for the trees that aren’t well established yet. Some transplant shock is expected. Did your nursery person have any advice on how to restore your trees to health? 
The university plant disease clinic only tests for pathogens. They can analyze why the tree died but not the how if it is chemical exposure. 
This is not an endorsement but Brartlett does testing although I don’t know anything about their service. 

I wish I had an answer for you. Those are large trees and it is heartbreaking to potentially lose them.

Claire Kari Replied September 22, 2021, 6:10 PM EDT
Hi Evelyn — thank you for such a quick response.. Yes we are sick about this.    We spent a lot of money having good quality trees installed and they looked fabulous all summer (and last winter for the first ones that were put in) — up until last week.    The landscaping company does not believe this is transplant shock or even a bug as they have checked in on the project several times over the past year and especially this summer during the drought.   They believe it is from a toxic spray.   We are very suspect of the mosquito spray or possibly our neighbor using Roundup.    I am going to check out Bartlett - and see what their service provides.   Ofcourse getting anyone to take responsibility is like wishing I could turn myself into a unicorn..    

The one thing my husband and I discussed is — if these trees were purchased from say a Home Depot - we could have ripped them out and brought them back for a refund as they are under warranty….   Our landscaper does have a warranty but it will not cover them due to a chemical spray.   This is just so frustrating.   And we are so committed to the natural area that we live in that we do everything possible to preserve trees and other natural vegetation….  Thank you for your help.   It is not likely these trees will survive.

Take Care

Michelle Swanson 

On Wed, Sep 22, 2021 at 5:10 PM Ask Extension <askextension@eduworks.com> wrote:
Swanson Replied September 22, 2021, 7:41 PM EDT

So frustrating for you. The plant disease clinic at the U can diagnosis herbicide damage. They can also rule it out. Hopefully something will be useful.

Claire Kari Replied September 22, 2021, 11:07 PM EDT

One more thought that is probably a dead end too is the landscape company should have to prove herbicide damage to void the warranty. They are making you try to prove it wasn’t. 

Claire Kari Replied September 23, 2021, 7:49 AM EDT

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