Made a sort of discovery. I have epazote (worm seed, skunk weed) which recently germinated and now is growing well in the garden. I'd gotten a start back in 2008, and it has faithfully reseeded. According to this article,
https://gardenerspath.com/plants/herbs/grow-epazote/
it contains ascaridole, a worm repelling chemical. Maybe I'll feed some to the chooks when the plants get more leaves, and see if it's effective. It's also known to reduce flatulence, and is also used in bean dishes in Southern Mexico and Central/ South America. If I save some seeds, would anyone want some to try? It will take over, do plant in a pot, or a wild area which you can let be wild.