Several years ago a load was brewed in a two gallon pump up spray consisting of:
1. A generous teaspoon of Ally (small grain herbicide labled rate 1/10 of an oz. per acre, about what you can fit in a 22 Long Rifle casing).
2. Dicamba at around a 12 ounce rate.
3. 2,4D Ester about 3 pounds/acre.
4. A little Miracle Gro (what the heck).
5. Four drops of dish detergent as a surfactant.
This was a smoky bellybutton load. It was Agent Orange on crack. The spots that were sprayed looked like the moon for two years after which there were sparse green shoots. A 30 foot tall willow tree was killed by spraying a root. My wife's eyebrow still twitches a little whenever the subject comes up. This would address your needs but is not legal strictly speaking. The good thing is that the whole package has extremely low mammalian toxicity. Make sure you don't have any runoff onto anything you like.