Knowledgebase

European Mountain Ash is in trouble #884611

Asked September 09, 2024, 2:58 PM EDT

About a month ago, our 12-year-oldash started dying at the ends of its branches. Now, it has progressed. In previous years, it has been fine - growing, flowering, and producing lots of berries. It does have berries on it now. We cannot find any sign of insects. The trunk is in good shape - we have a mesh protector around it. What do you recommend? We really don't want to lose it. It is filled with robins in the fall eating the berries. Should we trim off the dead parts? Thank you!

Douglas County Colorado

Expert Response

Hi Susan,

I'm sorry to hear about your tree!  Based on your description and what I can see in the photos, I suspect your tree may be dealing with fire blight; a bacterial infection.  For ornamental trees and backyard fruit trees, cutting out the infected branches is the recommended treatment; certain preventative sprays could be applied next spring (in a series--one spray isn't sufficient) to try to limit further infections next season.

Mountain ash are particularly susceptible.

When removing the branches, be sure to remove down past the visible infection edge on the surface; bacteria have been detected up to 18" away from the symptomatic portions.  

This CSU fact sheet includes more information, including preventative product names should you decide to try them.

https://csfs.colostate.edu/wp-content/uploads/2024/01/Fire-Blight-Fact-Sheet-2.907.02.pdf

I hope this is helpful!

Cordially,

John

An Ask Extension Expert Replied September 09, 2024, 4:23 PM EDT
Wow!  Thank you, John!  You nailed it.  We read the fact sheet you sent us.  Sadly, now that we know what we are looking for, we examined the tree more closely and found damage throughout the tree including the trunk.  We will have to take it down.  So, more questions:

1.  Do we need to burn the remnants of the tree to prevent the bacteria from spreading?

2.  Can we leave the tree up long enough for the birds to eat the berries?  Will the berries hurt the birds or the virus be transmitted by way of the birds?  We have other ash trees.

3.  Can we plant a replacement tree in the same hole, or does the hole need to be treated?

Some history of the tree - it is a side branching of a main tree that died after a brutal winter about 10 years ago.  We babied the remaining part, making sure to wrap it during the winter and root feed it in the spring.  The main branch did not appear to have any of the fire blight.  We checked our crab apple tree and it appears to be fine.

Thank you, again, for the great service you provide.  Next, onto one of our Dwarf Alberta Spruces.... :-((

Susan

On Monday, September 9, 2024 at 02:23:19 PM MDT, Ask Extension wrote:


The Question Asker Replied September 10, 2024, 2:22 PM EDT

Hi Susan,

You could burn the trimmings from the tree if its legal in your area to do so, otherwise you can bag them and dispose of them in the trash--don't compost them at home. (Commercial compost piles are likely fine, as they get hotter than home piles).

You can leave the tree up; while the bacteria can be transmitted by bird feet from active infections, dry weather in the fall is an unlikely time for disease transmission--spring is the usual season for its spread.

You can plant a new tree in the same place, no treatment of the soil is necessary.  Just be sure to pick a resistant variety, which is by far the best way to deal with the disease.

Oak-leaf mountain ash (Sorbus x hybrida) has shown good resistance, as has American mountain ash (Sorbus americana), but there is also evidence that resistance depends some on the strain of bacterium as well, so even a resistant species may be infected under the right circumstances.

I hope this helps!

John


An Ask Extension Expert Replied September 10, 2024, 3:15 PM EDT

Loading ...