What is killing my red maples?
I have three red maples 20+ years old in line with each other spaced 20 feet apart. 4 years ago the first one in line started have dead branches at the top the next year more died so I trimmed them out. By the 3rd year 3/4 of the tree was dead and the next tree had started dying the same way this year the first tree is completely dead and the second inline is half dead the 3rd tree had not yet shown signs of dying.
Thanks for using Ask a Master Gardener with your Maple tree question. Thanks for sending the photos along with your question.
You trees are Crimson King Norway Maples. They have deep red leaves during the growing season. A Red Maple has green leaves with a bright red fall color.
Norway maples are susceptible to a soil born fungal disease called Verticillium Wilt. The fungus blocks the vascular system of the tree preventing water and nutrient movement within the tree. When this happen, a branch will wilt, followed by death of that branch. As the disease progresses, the entire tree is likely to succumb to the fungal pathogen.
The way to diagnose at the site is to take a branch that is showing symptoms and cut at an angle to expose the vascular portion of the branch. The tissue will show green streaking in maples and brown in other species. To confirm the disease, you need to have it cultured at a lab. The Ohio State University has the C. Wayne Ellett Plant and Pest Dignostic Clinic. You can find information on sending samples at:
There is a fee associated with this service.
Here is a fact sheet about verticillium wilt from Michigan State University:
Another issue that can cause loss of trees are girdling roots. These are roots that encircle the trunk of the tree, causing a lost ability of the tree again to move water and nutrients through the plant. That normally results in a one sided loss of branches above the girdling root. The trunk of the tree will exhibit a flat spot on the trunk above where the root has grown to stop the expansion of trunk size. Again, this does not usually cause the entire death of a tree.
I do see some holes in the branches in the photo you sent, however, I feel that those were insect attacks that occurred once the tree was in a weakened state. The photo of the interior of the branch shows no sign of insect infestations.
Since the trees were in a line, it is possible that the roots of the trees have grown together, called grafting. If so, then they are sharing the disease organism from one to the next. However, as you might notice in the fact sheet, the third tree may not develop symptoms of the disease for some time. The wet conditions of this winter and spring definitely does not help the health of any of the trees.
I trust this has been helpful to identify your issue. Sorry that there is not a fungicide that will help prevent or stop Verticillium Wilt. Thanks for the question.