Coral Bark Japanese Maple problem
I have a mature coral bark maple where all the leaves from one major branch of the tree have gone brown. Is this a root rot?
Washington County Oregon
Thank you for your question about your maple tree. It is difficult to diagnose a plant problem without a picture of the tree, but maple trees are especially susceptible to a soilborne fungus known as verticillium wilt. The fungus kills one branch or group of branches at a time. I've attached a photo of a maple with this problem.
Here's a link to an OSU handbook page about it. This suggests that you have the soil tested for the fungus. You can do so at the OSU Plant Clinic, whose information can be accessed here.
Again, without a picture, I can't tell you whether this is the issue, or whether your tree is just drought stressed. But this should give you something to investigate.
Here is a photo of the affected tree. The left side has been brown for a month even before the right side began to show much color from dry conditions. I have been watering, but not deeply.
Thank you. I suggest you cut off a branch that you know/believe to be dead, to see if the 'veins' in it are the dark colors like the photo I sent you. You can also cut the branch lengthwise, to see if there are dark streaks like the ones pictured in the article I sent you a link to. If you find them, it would be wise to have soil tested.
As this Master Gardener article explains (although about Japanese maples, which are also susceptible), there are some things you can do whether or not you have this fungus diagnosed. But you'd want not to plant another plant there only to have it die, too, wouldn't you?
I cut one branch and scored the bark. There is no moisture in this branch. Photos attached show minor dark streak. I'm thinking your diagnosis is correct but will send a sample of soil. I Should probably cut this half of tree down before leaves fall.
There is not enough of the dark 'scoring' to indicate verticillium wilt. I suggest you wait to cut anything off until you get a soil test result. Cutting half of it may doom the tree for sure!