We have a Mountain Ash tree with leaves turning yellow. It isn't just one spot, it's happening all over the tree. This patch is even more bright yello...
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Mountain Ash with yellow leaves #407615
Asked June 16, 2017, 1:49 PM EDT
We have a Mountain Ash tree with leaves turning yellow. It isn't just one spot, it's happening all over the tree. This patch is even more bright yellow than it was just a couple of days ago.
Dickey CountyNorth Dakota
Expert Response
Good morning,
I'm not exactly sure what's going on with this tree, based on this single photo. However, I'm wondering if it is suffering from a malady called fireblight. Fireblight is a bacterial problem that affects all plants in the Rose family. It can kill trees outright, or it can kill them slowly over several years.
The best approach right now is to prune out the dead branches, about 8-10 inches below any canker that might be visible. Then, this winter, continue pruning those stubs back to the nearest branch attachment point along the previous branch or the main stem.
If you need more information, please let me know. Best wishes with your tree,
Thanks for the additional pictures. I'm still not completely sure what's going on. It could be the beginning stages of fireblight; what we would expect to see is leaves that turn brown and droop - as if they were burned in a fire. However, it could also be that the affected branches are simply broken from storms or high winds. Even drought or over-watering could give these same symptoms.
I wish I could give you more direction. You may want to check with your local county Extension agent.
Here is the answer I got from NDSU Extension:
This looks like a case of "summer leaf drop, " as we discussed in our previous message. Trees lose water through their leaves and can shed some of its leaves as a means to conserve moisture. Mountainash trees prefer a moist soil, and they struggle under dry times. It has definitely been a dry time.
This is what I see:
The leaves are yellow, but have minimal disease spotting.
There are no insects curling the leaves.
The yellowing leaves are sporadic and often found in the shadier regions of the tree (these are the least important leaves since they produce the least amount of food for the tree).
There are no dying back of branches.
No branch cankers are evident.
Perhaps one small inner branch is dying back. This is no great cause for concern.
Overall, the tree is green and healthy.
This looks like summer leaf drop. The tree is sweating and coping with the situation by shedding a few leaves. It would appreciate a drink of water. Some mulching around the base would help, too.
Let me know if you have any follow-up questions. I will be happy to help.
Regards
Tom Kalb
Extension Horticulturist / Plant Sciences
