I have a number of different nasty plants that want to take over my pastures. I don't know their proper names, but I've got a few I've learned. Nutsedge is one. It's a grass that none of the livestock likes. Oh the goat will eat a little, but not enough to control it. It spreads rapidly, choking out the good grasses. Round-up doesn't kill it. So I use a mattock to dig out the major clumps and weedwack off the seed heads as they start to develop. It comes back every year because the birds spread the seeds.
Mexican elderberry is a pain. If I don't kill it when I see it, it sends out side roots that starts more plants all around it. The goat eats some of this but not enough to control it. Since it shoots up from roots readily, Round-up is needed for good control. I've pretty much eliminated the big patches from the pastures, but it comes back because birds spread the seeds.
There's a couple types of grass that the livestock won't eat. And of course, these grasses are the type that spread rampantly, sending out aggressive runners. The easiest way to keep their numbers down is to graze off the pasture then go around and spray the noxious clumps with Round-up. Easy to see and find them when everything else is short. I never get it all because I don't want to kill off all the edible grasses too, but at least I keep it from taking over the pasture.
Don't know the name but these ferns spread aggressively via underground runners. And when you pull them out, you never get all the pieces so it comes back.
But if I pull out a section, plant sweet potatoes as a cover, then pull individual ferns as they reappear, I can gradually eliminate it. I'll also seed pasture grasses or transplant grasses in with the sweet potato vines. Eventually the livestock gets to graze it.