Pathclear perhaps? Seems to kill off everything in its way.
Available at all gardening shops; B & Q etc

"Dgethin" wrote in message
...
I have been trying to kill a patch of rhubarb, weed killer won't do it, so
I have been trying to dig it out (down to 4 foot), and it still goes down
further than that.
Is there a easy way to do it.