Infected Japanense Green Maple? Help?

[southernleaf]

Hi everyone, I have a 6 year old maple bonsai I acquired 2 years ago. I am in Austin, TX and I noticed this wound forming about a week ago. I did a heavy pruning in September that involved removing one main branch. I’m attaching before and after photos with a couple close ups of the potentially infected area. This photos were taken between September 2020 and Feb 2021. You can see a hole opening up above where a main branch was cut, which is my focus area in this thread. The weird looking grey color is the wound paste that I applied after the September pruning.
My questions are
1) is this an infection and if so, what am I dealing with?
2) what is the best remed?
3) how can I ensure that this doesn’t happen again?

PS I am fairly new to bonsai and this is one of two trees I have so this is definitely a learning opportunity for me. Thanks in advance for any thoughts or advice!

 

[0soyoung]

I don't see anything particularly unusual, but so you sanitize your cutting tools before and after use? This is the best general practice to avoid infecting your tree(s). These infections are often only apparent when fruiting bodies are displayed or the infection had progressed significantly. So, you bring home a tree, prune it, then subsequently use the same cutting tool on another few trees. Later that year of next, one discovers that they have a number of trees with the same infection. Wipe the cutting surfaced with a paper towel moistened with some isopropyl alcohol (70% or more) or some sanitary wipes before and after use on a tree (before/after every cut on a know diseased tree).

Carbohydrates made by the foliage come down the tree in the inner bark (a series of tubes called the phloem). With Japanese maples, the flow is much like how a thick (viscous) fluid will flow down the tree if you just poured it on the top of the tree. Right below a branch, the tissues on the trunk are fed by the flow from the bottom of the branch, so when the branch is removed, the trunk tissue below the branch point tends to die, especially when the branch was pruned late in the season (i.e., close to the time of leaf drop). The green bark of a Japanese maple turns black when the cambium dies. Possibly this is what you are seeing.

 

[Wires_Guy_wires]

I hate maples. So don't trust me a 100% and wait for some experts. But experts love being experts, so I trust them to correct me if I'm wrong

But I see no necrosis, no spread towards the rest of the trunk. I see nice callus. This makes me thing there's no worrying infection of bacteria or fungi.
Other than the gooey cut paste, I don't see anything worrying right away.
I do see some wood being affected, which I would personally treat with some lime sulphur. I'm not sure if maples love diluted more than straight from the bottle. It's just to prevent/kill fungi.

Next time when cutting a branch, try to make a sloped cut instead of leaving an upwards pointing stub. This'll help dispose of water, it will increase the wound size but it can also heal in a nicer way. A flush or concave cutter works very well to do this. Those two are essential tools in my book, everything else can be found in a generic hardware store.

 

[southernleaf]

Thanks for the advice everyone. Almost 2 months has passed, so I wanted to post an update. I applied some lime sulphur on top of the wound paste as a preventative, and the tree is doing well. It spit off a bunch of new growth in the training areas after spring finally reared its head here in Texas. I will use this thread to post more pics as the tree develops over the coming years. Thanks again!

 

[leatherback]

Just to add..

I would guess that when removing the side-branch you nicked the back above and just did not notice it; maybe it remained covered with bark making it less obvious. What you see is healing of that damage.

 

[ajm55555]

I hate maples

Why?

 

[Wires_Guy_wires]

Why?

They lose their foliage in winter, they are susceptible to almost any pest, they are susceptible to a lot of bacterial issues.
Norway maple has plagued my gardening experience for years by jamming thousands of seedlings in my growing beds.

 

[ajm55555]

they are susceptible to almost any pest, they are susceptible to a lot of bacterial issues

I agree... but... they're beautiful

 

[southernleaf]

Update ~10 months later. Tree seems to be doing well. Looking forward to seeing it pop out again over the next few months. Open to any thoughts/reactions folks have on styling/training technique or methods given what you can see in the pic.

My near-term goals are to 1) thicken up the base trunk, 2) thicken up the secondary trunk shooting out to the left, 3) more clearly establish the leader, and 4) improve overall balance. Here is how we’re trying to attack it:

1) thicken up the base trunk: allow 2-3 long branches coming out of the lower areas to grow unrestricted
2) thicken up the secondary trunk shooting out to the left: let that long branch continue growing (should I tie or wire it down so that upward energy prioritizes the main leader on the primary trunk?)
3) more clearly establish the leader: tie down the highest competing branches into 90 deg angles. I thought about pruning these, but figured I’d keep them to promote thickening up the leader line)
4) improve overall balance: rotate the planter’s positioning 1/4 turn week/week during the growing season (the sunshine onto our balcony has a fairly sharp angle to it during the afternoons; our balcony faces west)

Thoughts? What opportunities am I missing? What have I misunderstood?