I did a bunch of hack and squirt and girdle squirt last spring and summer. Some of the trees are alive and well some are 1/4 alive. Most the cambium layer are mostly dead around the wounds. Will the trees eventually die?

They’re likely dead they just don’t know it yet.

What tree species and herbicide ?

Sometimes it doesn't make sense how some treated trees can survive. May have been bad timing on when you treated them or a weak herbicide mix. I use the Craig Harper herbicide mix and it seems a lot of the time to not be potent enough, especially on larger trees.

No definite answer. Sometimes those that seem to be barely hanging on end up living and other times they eventually die. There have been multiple maples I have double girdled and sprayed and somehow, they still live to some extent.

Curious to other people's experience with that herbicide cocktail.

My main target has been killing all my gums off. I am not taking chances I’m hacking again with a different dose of chemicals. I’ve just never seen a tree with as much dead wood as some have survive.

I cordless drill a few 1/2" holes at a downward angle into the base or root swell and then fill the holes using a small pump sprayer with straight Gly or a 50/50 imulsion of crossbow/water to create individual pockets of poison. It works better for me than other methods.

I’ve had inadequate results from Harpers cocktail too, mostly on large gums and tallow trees.

Serious question. Didn’t Harvey Updyke use Spike 80DF to kill the Toomer’s oak trees? I remember the powers at be at Auburn tried their best to save them but they said at the time that it would be near impossible but would try any way. If that stuff is so good at killing large trees, how come it never seems like anyone ever uses it?

I used a 20% solution of Imazapyr on Tallow trees last fall. I need to ride over and check for regrowth. I also treated a few Sweetgum up to maybe 6-8” this weekend.

I used an impact driver with 3/8” auger bits for a while. I’ve gone back using a hatchet, it’s lighter and no worry about a battery losing power. I feel like the hatchet is faster and currently use a Fiskars. A lot of folks swear by the Eastwing.

Because that crap will run with the water as far as it can be taken and will injure or kill a lot of trees when taken up by the roots. I’ve dealt a long time with ALDOT, and can’t tell you how many times sign companies have had to buy trees on the DOT side of the fence when they used spike to kill trees around the signs or billboards.

I only started last year with hack and squirt. I used a mix of 41% gly, Garlon 4 and used vegetable oil. Most of the gums under 5” diameter are dead as a post. Are couple are looking very sickly.
As for appearances, I cut a few 6-8” diameter gums down in late March and cut them into manageable lengths. I didn’t get all of them out of the yard. I was up this past weekend and the lengths are growing new branches.

Good to know. Thanks for the response.