Black spots on Trunk

[girv]

Hey everyone - Very new to this forum and new to bonsai in general so looking for some help. I have a Green Leaf Japanese Maple I picked up at home depot early summer when they had some big sales, and got it for a great price. Since it was sitting in the parking lot, there was lots of leaf scorch and once I repotted I also trimmed the tree down quite a bit and defoliated. I now know this was probably a bit too much to do all at once, but the tree has done well and pushed out a ton of new growth. From here I want to let it grow out a bit before doing anything else, and I will post a question on styling plans later on.

For now, my main concern is a bunch of black spots on the top half of the trunk/main branches and am having a hard time diagnosing. Please see attached pictures, and if anyone can add some color here it would be greatly appreciated!

 

[AlainK]

If the twigs/branches are OK, I wouldn't worry too much. The bark is beginning to age. In periods of stress, one place can react negatively and others positively. In the course of the seasons, if you turn the pot around every other week/month, dry periods, fresh air, wind, sun, sleet, ... it will make your tree great again.

If the "black spots" grow fast, I would paint them with Bordeaux mix. I say "paint": to me that's Bdx mix + water + alcohol or chlorine made into a soft paste applied with a paint-brush.

If the black spots don't develop, I'd spray the tree with Bdx mix after leaf fall, then again before budbreak. This is the best option if the tree is in a - rather - healthy condition in late October.

 

[0soyoung]

Black-ish coloration in the bark of acer palmatums = death of the cambium underneath.

In the second photo, it looks like cambium die back around a puncture wound. If it stays the same size or begins shrinking in size, it is not a worry. If it enlarges noticeably over the next couple of weeks, the area is infected. If so, it is likely that part of the remedy will be to remove the bark of and around this area and apply some kind of antiseptic treatment.

Likely, it is nothing to worry about, but do you sanitize your cutting tools before and after use? Wiping blades with 70% isopropyl alcohol (or stronger) is a good idea to prevent propagating pathogens from one tree to another.

 

[girv]

Black-ish coloration in the bark of acer palmatums = death of the cambium underneath.

In the second photo, it looks like cambium die back around a puncture wound. If it stays the same size or begins shrinking in size, it is not a worry. If it enlarges noticeably over the next couple of weeks, the area is infected. If so, it is likely that part of the remedy will be to remove the bark of and around this area and apply some kind of antiseptic treatment.

Likely, it is nothing to worry about, but do you sanitize your cutting tools before and after use? Wiping blades with 70% isopropyl alcohol (or stronger) is a good idea to prevent propagating pathogens from one tree to another.

Thank you for the feedback! Like I mentioned, I am still very new to this(got my first tree two years ago, really started to do research and get more trees this year) so having been making tons of mistakes to only realize afterward. I now clean my cutting tools, but was not early on.

There is probably around 6-12 spots like this on the tree, but I haven't noticed any of them growing over the last few weeks. I will continue to monitor.

 

[Deleted member 21616]

Wiping blades with 70% isopropyl alcohol (or stronger) is a good idea to prevent propagating pathogens from one tree to another.

This is news to me Thank you!

Do you wipe down your tools with alcohol (i think i can get 99% at Walmart in Canada), and then simply wipe down/dry the tools with a cloth before using? Or do you wash away the alcohol before using? I'm wondering if residual alcohol on the tools could harm the tree?

I have been applying mineral oil on my (kaneshin, carbon) tools after usage to prevent rust during storage, and gently wiping down the tools (usual with whatever t-shirt i'm wearing around the garden) before making any cuts. Does this make sense? would you have any other suggestions for storage in addition to alcohol for disinfection/sterilization?

 

[0soyoung]

been making tons of mistakes to only realize afterward

This is how one becomes an expert.

This is news to me Thank you!

Do you wipe down your tools with alcohol (i think i can get 99% at Walmart in Canada), and then simply wipe down/dry the tools with a cloth before using? Or do you wash away the alcohol before using? I'm wondering if residual alcohol on the tools could harm the tree?

I have been applying mineral oil on my (kaneshin, carbon) tools after usage to prevent rust during storage, and gently wiping down the tools (usual with whatever t-shirt i'm wearing around the garden) before making any cuts. Does this make sense? would you have any other suggestions for storage in addition to alcohol for disinfection/sterilization?

Any isopropyl alcohol 70% or stronger will do. Just dampen a paper towel with it and thoroughly wipe the blades is all you need to do to satisfactorily sanitize them. It is much better to wipe than to dunk them in a container of alcohol, say. Do this before use and when moving to another tree. If you have strongly suspected or known infections, wipe after every cut. Many 'wet'/'sani' wipes are made with 70% iso (check the label). You might find a container of these more convenient. A little residual alcohol won't harm your trees.

When you are done, wipe with alcohol, let dry (a matter of seconds) and then oil them for storage.

I am careful to do this with anything new in my garden. However, truth be known, I am lax about sterilization as long as all my trees are healthy and there are no signs of infection.. But at the first sign ...

 

[Deleted member 21616]

@0soyoung Thank you sir! As always, advice worth gold from you, thank you!

 

[MariaM]

You can also sterilize the blades with a lighter,

 

[leatherback]

You can also sterilize the blades with a lighter,

be carefull. Not all steel likes repeated heat/cool cycles.