wushaw pointed you in the right direction re mesquite.. use the Brush Busters formula... they have a pamphlet that can be downloaded from the net with details, etc...
Fear not using either REMEDY or RECLAIM. I have used both with much greater success that noted below... more like 95%.
I use hand spray application. Reclaim is a foliar spray.. be SURE to wet ALL leaves... any twigs you miss WILL live... and seem to be connected to their own special root. I go thru the mesquite patch several times a year and "re do" those that for some reason got missed, or only half sprayed in spite of my best efforts. I've gone from applying 1000 gallons of spray mix annually to 30 this year.
I am now down to the annual crop of sprouts from seeds. There was an A&M study that planted mesquite beans in sterile soil and provided good growing conditions. They pulled each sprouted bean... 15 years later they were still pulling new sprouts... tenacious stuff!!!
I have sprayed Reclaim into a mesquite tree with brambles growing in it... and a hackberry bush imbedded in it.... 2 weeks later the mesquite leaves were all withered/dead but the bramble was shining green in the mesquite twigs and hackberry was 100% healthy... grass underneath OK as well... although there does seem to be some inhibiting of weeds/broomweed where the spray drifts to ground around the plant.
Remedy is sprayed completely around the trunk of small smooth bark trees.
In theory, Reclaim is best in late spring early summer.
I'd study the literature, look at the calendar, look at your size of trees and density and application capability, then choose the one that best fits YOU. I have had fine results spraying reclaim in early fall. For some reason, I tend to use Reclaim more than Remedy but have no scientific reason for it.
In my opinion, knowing your territory, I don't think you can affort to NOT spray mesquite, regardless of cost.
CTW, go 50hp or better if you can, hydrostatic transmission if you can, tooth bar on FEL, at least 2 remotes in rear, lights to rear, cab... gosh! it's fun to spendsomebody else's money

If you have some BIG mesquites, PM me.
This is what Brush Busters says:
----------------
How to beat mesquite
The Brush Busters "
How to Beat Mesquite" program promotes only two "select" treatments for controlling mesquite (McGinty and Ueckert 1995). One is a "stem spray" containing 15 or 25% Remedy herbicide in a diesel fuel carrier. The second is a "leaf spray" containing 1/2% Reclaim herbicide + 1/2% Remedy herbicide. Results from the large demonstration/research plots treated in 1995 showed the following:
1) The stem spray method (l5% Remedy + 85% diesel fuel) was capable of treating up to about 300 mesquite/acre before approaching the cost and quantity of herbicide applied using the most effective broadcast aerial treatments. Cost per mesquite plant treated averaged 11 cents (range 6 to 15 cents). Cost per acre averaged $18.50 (range $6.20 to $25/acre). The average mesquite density was 196/acre (range 43 to 327/acre).
2) The leaf spray method treated over 400 mesquite/acre before reaching this same threshold. Cost per mesquite plant treated averaged 8.2 cents (range 5 to 15 cents). Cost per acre averaged $l6.76 (range $6.80 to $34.20/acre). The average mesquite density was 244/acre (range 45 to 461/acre).
3)Mesquite rootkill after 2 years averaged 80% for the leaf spray and 80% for the stem spray.