Japanese Maple with worsening dieback scar on tunk

[StephenHelman]

Hi everyone,

Just wondering if anyone could help diagnose a sickly Japanese Maple and suggest a treatment plan. (see photo)
It has dieback on the trunk that the tree seems to be fighting to try to heal over with new bark. It also has somewhat blackened roots.
I'm assuming it is some kind of fungal situation. The soil (standard potting mix, a bit old) is not ideal - I will repot it soon in something much more free-draining.

My main question is: should I just start with a repot & moisture management and see how it goes, or should I be trying to cut out the affected area?

Thanks very much,

Stephen

[shibui]

Photos need to be under 500K (maybe 1mb now?) to load.
I would like to see a photo before making too many comments but if the tree has survived and is trying to heal the scar it should be over the worst. Black roots does not sound good though.
Repot sounds like a good idea and now is a great time to do it.

[StephenHelman]

Thanks for the reply. Hopefully this picture works ok.
Thanks for the advice, I will try a repot in some freedraining mix and hope it bounces back.
I was wondering about pruning the roots (to remove the ones that cross behind the others), but might it be wise to wait until the tree seems healthier and the infection more under control?

Thanks very much,

Stephen

IMG_4277_3.jpg

[shibui]

Your maple seems healthy other than the dead part. I think you are right that the die back is old and the tree now actually has it under control. The black roots are turning black because they are dead. Sometimes dying roots can cause a bit of the trunk to die, sometimes when part of the trunk dies the roots that feed it also die because there is no longer anything to feed. This sort of die back seems to be par for JM. I have several with varying degrees of dead wood from infected roots, sunburn and physical damage to trunk or branches. It does not seem to spread after the initial problem is controlled.
There is nothing you can do to save those roots or to save that dead part of the trunk. Both are already well dead but the full extent is only now showing up which you have interpreted as worsening. The tree looks to be quite young so it is possible the scar on the trunk could heal over in time provided the wood does not rot away first. Try treating the bare wood with lime sulphur to preserve it then seal over the area with a wound sealer to promote new growth.
Repotting is a good idea. Better draining mix should help the tree manage better. You can prune roots as normal for JM but I would probably defer any real extensive root pruning until you are confident the tree is fully recovered.

[one_bonsai]

Probably best to ground layer it and rebuild the roots from scratch.

[Akhi]

If you let some sacrifice branch in the tree grow unfettered then chances are the trunk will heal itself. Mine did that well albeit was a branch rather than a trunk. The other alternative is to side layer a new seedling/s there So you can also get a branch if that’s fits your design.