Acer Palmatum bark damage?

[Ugo]

Hi!

I would like to have your opinion on this discoloration and bark split on this acer, Im wondering what it can be?

The other side of the trunk seems perfect, same as all other branches.
The buds just start extending normally.



Image from December
As you can see the line on the trunk is pretty much the same height as the part that was going out the mulch


Thank you for your help
Ugo

 

[Shibui]

Looks like the black section is dead.
Sometimes that's from sunburn.
Sometimes it is an infection and I'd guess that's what happened here as it is just below a recent pruning cut. May or may not be related to the winter mulch.
Sometimes I get something like this if the roots are too wet through winter but that usually starts in the roots and comes up from soil level.

So far it is only a small section so the tree should be able to heal over the dead area as it grows this summer but keep an eye on it to see if it spreads further. Not sure if a fungicide will help.

 

[Canada Bonsai]

Black area = dead area. This section of the tree will end up looking like the 2 sections on your other tree that I circled in red. Luckily, that looks like a 0.25-0.5" trunk right now, and this problem will disappear as this area becomes a 2-4" diameter trunk flaring into the nebari.

This dead area can result from physical damage, die back from pruning, heat, cold, impact, pathogens, etc.

That looks like an overwintering space? What temperature are you keeping that space? The ground looks frozen or frosty in some areas. Where is the space heater located with regard to this tree?

I personally would not allow leaves to pile up like that around Japanese Maples, a species that people famously get depressed about due to spring-time fungal issues

edit: sorry @Shibui just saw your post after I hit submit. I fully agree of course.

 

[Ugo]

Good informations guys thank you.

I hope this little guy will be alright!!
I just inspected all the other trees that were in the cold shelter and no other show signs like that...
I must admit I allowed snow in the box once in awhile.
This tree is so small compared to the others but at that time I had no other solution then putting it in a cold shelter.

@Shibui Just in case I will isolate this tree from others and spray with 3%peroxide/water.
So far no bleeding from the scars, no expansion or anything and the other side of the trunk looks healthy.

@Canada Bonsai
Thanks for your comment.
Yes that is an overwintering space, this space goes to about -2c
As you mentionned I shouldn't let leaves inside the box... I guess I was just too lazy last year.
Even if I can't see any problem on my other Acer that were in there I will clean-up the space and spray with fungicide the inside just in case.
My small acer collection now has a proper place that will be kept at 2degC all winter so only conifers will go back in the box.
Its interresting that you pointed out the issue on my other tree.. its a tree I saved from trash and I was wondering what could have caused this type of damage when I got the tree.

 

[Crazy Diamond]

I think theres also a fungal infection tha necroses parts of the bark and the trunk leaving black parches right?

 

[Shibui]

-2C is no problem for JM. Mine all live outdoors all winter and get down to -5C (ambient) with no ill effects. Snow is not the problem for JM because it tends to insulate. Real cold may be but I'm not sure what temp may be too cold for JM.
Fungal infection, and most other health issues, are selective. One tree may be affected while another right next to it is not.
I'd avoid pruning just before winter where possible and seal cuts where you can't avoid pruning later.

Fingers crossed that this stays local.