By Bill Kleiman
On the left is invasive black locust, Robinin pseudoacacia, that is still alive even though I sprayed them from a boom with 2% glyphosate and 1% Habitat. That herbicide mix killed all the other plants including reed canary grass.
On the right is one of many dead black locust that I sprayed nearby with 1% Milestone. The Milestone did very well on the black locust and appeared to kill every other forb in this area too. [note that 1% is too high a concentration as Chris Hauser points out in the comment on this post.]
grassland restoration network 
A 1% Milestone spray mixture seems very concentrated. If a field is boom sprayed at a standard spray volume of 40 gal per acre, then the field will receive 51 oz of Milestone per acre, which is about 7 times the maximum labeled rate of 7 oz per acre. If a field is boom sprayed at the lowest labeled per-acre volume, 5 gallons per acre, you’d be within the labeled application rate, but you might not get good foliar coverage.
If the application “appeared to kill every other forb in this area”, it is likely due to a concentrated spray mix. At more typical rates (4-7 oz per acre), there are many dicot species that are tolerant to Milestone, including plants in the Scrophulariacea, Fagaceae, Caprifoliaceae, Rhamnaceae, and many other dicot families. At high rates, more forbs will be killed, even from families that are normally tolerant.
I’ve been using aminopyralid herbicides for about 15, and I almost always boom spray Milestone and Milestone VM (now called Capstone) at a concentration of 1 oz per 10 gal. At this concentration, a spray volume of 40 gal per acre gives 4 oz of Milestone per acre, and I almost always get good results on sensitive dicots, but low impact to non-sensitive dicots.
Keep up the great work!