Is it too late for this Mulberry tree?

[Initial Z32]

Bought my house 5 years ago and spent the first few years gut rehabbing it. Third year I started working on the yard, there were carpenter ants in about 7 red oak trees so I had them all removed and I fogged the yard with Talstar and Gentrol the day of, I fog the yard frequently for mosquitos using these two pesticides. My Mulberry tree is one of my favorite parts of the yard, when I fog I fog into any openings I see to make sure there aren’t any carpenter ants but it doesn’t look like this tree is doing so well. I think it might have split while maturing and the previous owners didn’t do anything about it and I noticed these holes and markings as well as the hollow looking center of the stump. What can I do now to get this tree back to good health? Our dog loves rolling around in the yard and we get a kick out of seeing him come back inside looking like Braveheart lol

 

[Jed1124]

So first and foremost the carpenter ants are not doing anything to your trees but living in the decayed wood. They don’t damage the trees in any way. The decay may be a problem though.
I would be cautious when using Bifenthrin, especially if you or your dog are eating the mull berries. It’s not labeled for edibles and has a decent residual.
The Mullberry can be cabled and braced. It looks like it could also benefit from some reduction pruning. This work would generally need to be done by a certified arborist.

 

[pdqdl]

So first and foremost the carpenter ants are not doing anything to your trees but living in the decayed wood. They don’t damage the trees in any way.

While I agree with your assessment that carpenter ants are not doing damage, I don't think that is exactly accurate. Their tunneling does in fact reduce structural integrity, and it does accelerate the spread of wood decay.

Reduction pruning is a good call. That tree is seriously decayed, and it does present a serious risk of collapse. I'd save up some money and have it removed. When it collapses, it will certainly crush the fence. There are no treatments to reverse the decay that has happened.

Bifenthrin applications seem to be pretty indiscriminately applied. Why so often? Monitor for the carpenter ants, then treat only the areas you find. Blanket fogging the yard and trees will also be killing off insect predators, which don't generally re-populate as quickly as the pesky bugs you are after. Boxelder bugs and other similar pests are sometimes worth it, but you are probably doing as much harm to your outdoors as any good. If you are after mosquitoes, then just eliminate water sources where you can. They can easily track you down in the evening from the neighbors, so there is little gain in fogging the area for that problem.

 

[Jed1124]

While I agree with your assessment that carpenter ants are not doing damage, I don't think that is exactly accurate. Their tunneling does in fact reduce structural integrity, and it does accelerate the spread of wood decay.

Carpenter ants live in and tunnel through decayed wood. Their tunnels introduce airflow into the system, and from what I understand can and do improve codit.
The wood they live in has poor structural integrity to begin with.
Breaking down the cellulose that the mycelium lives on slows decay.
They do not advance into sound heartwood.