how do I get rid of a couple hundred yuca's in the middle of my garden

I have volunteer yuca's sprouting in the middle of my garden. Before planting we dug down and got out a HUGE root system (1 1/2 feet long, and 3-4 inches in diameter) Thought that would take care of it, but, NOOOOOO! Seemed to have just ticked it off and it's sending up mega baby yuca's. I don't find a few nicely spaced on the edges of the yard, but these are the yuca's from Hell!!!