Stinging nettles can be eliminated by first lopping them, and then a pitchfork can be used to remove the roots from the base. Any new sprouts can be pulled out before they grow into strong plants. Chemical treatment like spraying a weed killer may be necessary if the weed growth persists.
how to kill stinging nettles? – http://www.ehow.com/how_5642625_kill-stinging-nettles.html