Robin, nice to see another Northern MN member! Hoary Alyssum.... get some goats. Its not toxic to goats and mine chow it down. I keep goats, sheep, horses, llamas and cows all together in the pastures and they all eat different things- the goats go insane over the alyssum.
If you don't want goats, mow the stuff before it flowers. If it flowers, it drops like 15 quadrillion seeds and you'll never get it gone.
Spent a whole hour today laying in a pasture, waiting for a sparkling vampire to show up. Alas, I woke up and looked over, only to find a mound of horse crap. Sigh.