If they are indeed the Blueberry type, cutting them at ground level will usually do the trick. But then you have stumps. If they are redberry, I don't think it works as well. If you are going to spray, Tordon seems to work the best but its hard to get enough solution on big trees especially if they are in a thicket. Like mesquite, you need to cover all the foliage. I have always wanted a drone to spray. I have only used Sendero on small trees that I come across spraying mesquites and like you say it works well. Chemical is quite a bit more expensive.
The velpar spot spray or Pronone power pellets (or spike) will work real good sometimes, at other times you get no effect. Your soil type and moisture has a lot to do with it.
The pellets are what I prefer because they are easiest to apply. Put a bunch out on the up hill side of the thicket a day or so before it rains an let them dissolve through the root system. Winter is a good time to use because the soil stays moist longer. My chemical guy doesn't recommend them in my black soil but they work okay and I can leave a can in the four wheeler and have it handy when I am out checking cows and have a few extra minutes to throw some out.
I have never tried burning them after the leaves turn brown. Its a slow process to kill them and if you can get all the leaves brown, they are in the dying process. Once they die let them stand until next year. Then they are easily pushed over and don't leave a stump. If you leave them long enough the wind will knock over a lot of them and then your sure the complete plant is dead.
If you treat with a chemical, be aware that like mesquites you need to treat once and then come back in a couple months and get the ones you miss or only got a partial kill. Good luck and be patient.
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