That is a tough one. you will be on the cutting edge of tree science if you figure it out. i would try something myself. Get that hole dry before you seal it.

There have been many discussions on this topic. The majority agrees the tree "compartmentalizes" internally and offers the most protection without removal of rotten wood, insertion of drain holes/tubes and filling with foreign materials or applying sealers. I would refer you to the writings of tree expert Dr. Alex Shigo, who basically states that trees will be better off, and may actually live longer, without any of these things.

NO SEALING ...

all you will do.. is seal in the moisture.. already in it ... and as soon as the tree flexes.. your seal will be damaged ... and more water will get in behind ...

if it threatens anything.. its time to think about removal ...

if its out in a field... watch it fail .. might take a decade or two ... to finally go down.. but who cares.. its not like its hanging over the house or something ...

might change my mind with a pic of the scenario ...

ken

This hole is a foot and three inches across and eight inches deep with mushiness already. I will argue the tree IS NOT capable of sealing it off before the next President has a chance to finish her second term in 2024. Thus if left unattended it is a death sentence for a tree in a residential setting.

You are probably right toronado, the tree may not be able to seal itself off, BUT, as Ken said, using a sealer will seal in moisture and make the situation worse. Tree sealer does NOT seal out water, EVER (assuming we are talking about a living tree rather than dried lumber) !

I agree with Horster that the tree will likely be better off without "insertion of drain holes/tubes and filling with foreign materials or applying sealers." I also second what Ken said; if the tree could cause problems if it fell, it's time to consult an ISA-certified arborist, or, think about removal.

Brandon, you bring up a good point about possible removal. plus I wouod love to see a pic of the tree, the wound and what is around it.

FWIW, I was looking at my invasive weed tree in the back yard. 3 years ago the tornado broke a section off leaving a jagged splintery wound. I waited for the heat of summer to dry it out and for encapsulation to begin then just plum painted parts of the wound. lord knows what is going on deeper in the trunk, I will happily slice it some day in the future, but the exposed painted wood is not rotting and ecapsulation is continuing.

OP, there are techniques to basically prune all the main leaders on a large, over-mature tree back to laterals, thereby reducing size somewhat, while retaining basic benefits of said tree in landscape. This is the new frontier of arboriculture-now that we've made so much progress on how to get trees in our landscapes to attain size and maturity. Now the challenge is how to get them to die with dignity, so to speak. You may be able to hire an arborist to do "drop-crotch" pruning (I know-get's chuckles every time) thereby achieving this moderate size reduction. I'm afraid there's quite a bit more to it than I'm, going to be able to share here on this forum, but advanced arborists might know what to do.

+oM

i wouldnt need to pay a tree surgeon ..

it all boils down to how many boat payments you want to make to some tree peeps ...

if you are like me... and one payment will be a struggle.. take it down ... and be done with it ...

if you have extra boat payments laying around the house.. and want to see what can be done.. spend away ...

or.. its out in the field.. and you simply watch ...

ken

I re-read, OP (your screen name is too long, lol) and noticed you said rotting into trunk. In my earlier haste, I thought I'd read a single branch was developing a decay pocket. This sounds more advanced and in view of this, the pertinent question becomes one of target: Is there a target below the area where branch/total tree failure could have an impact? Child's sandbox, picnic table, part of your or others' house, etc?

If out in the clear, and you can stand to watch things progress, then yes, leave it be. Let things happen as they will. But please, no misguided heroic efforts to delay the inevitable.....in that they won't anyway.

+oM

Considering location (Kamloops - interior BC), the size of the tree you describe, and the rate at which the wood is decaying, i think you have a willow or cottonwood. In either case, there is not much you can do about slowing decay with those species...the heartwood was probably already softening even before you took the branch off. That said, I've seen large cottonwoods hold up very well with just sapwood left. It's not a great situation but it does seem to work. If it's a willow, I wouldn't trust it.

Yes, a cylinder is a very strong shape. And trees' live wood is all around the outer portion of the cylinder, so a hollow tree is not only oftentimes alive, but can truly be said to be perfectly healthy. It's just that if there's been this much decay, there's apt to be weaknesses and other trouble spots you maybe don't even know about. The danger is to any potential targets on the ground, and there is simply no way to stop, undo, or in any other way mitigate what's already gone on with the tree.

+oM