Please help! I am so upset about my garden. I grow swamp milkweed and lots of Missouri native plants for pollinators. For years, my family has welcomed monarchs, protected the larvae, and released the new monarchs! Last year, a pest started eating my milkweed. I cannot see any bug, and it seems like the stalks are being eaten from the inside. Everyday, new stalks/branches are cut off the plant and I find them on the ground. It has already started happening this year to my brand new monarch stalks that are only a few inches tall! Plus, the same thing is now happening to my false indigo plant. How do I stop this from happening and also not ruin the milkweed for the monarchs! Please help!

Sounds like stem borers. I've never seen them but apparently milkweed and False Indigo both have their own versions.

Cut open some stems and look for grubs.

Thank you! I had not heard the term "borer" before, and it actually put me on a new path to try and figure this out. I will cut stems open today to look for grubs.