If you can transplant some of those volunteers into small pots, even a paper cup, you could give the plants to people who want to start enjoying the Monarchs. Or plant them along paths or roadways. Even others who rear Monarchs might be glad to have them. It's a shame to rip them up and let them go to waste. The one thing I know for sure is that you never have too much mikweed. More like you can never have enough because the more you have, the more cats you will have.

I've been transplanting mine and they're doing fine.

With at least 45 Monarch cats from what ma have been only a single female that survived our hard freeze, I looked up how many eggs a Monarch cann lay. The first hit on the summary page included enough to see 500 -- one attt a time. I didn' look further, but it confirmed my feeling that there will never be enough milkweed for all of them,

Or you could mow them constantly and hope they stop growing.

http://akdavis6.wixsite.com/monarchscience/single-post/2017/03/15/Is-tropical-milkweed-really-medicinal-answer-yes-and-thats-really-really-bad-for-your-garden