If this is for a flower bed (which is where I have the most problem with
spurge) there is a product called Preen which you can get at your local
garden shop or Home Depot that stops spurge from growing. You'll need
to kill it off with Round-up first, but the Preen will keep it from
coming back. This stuff is only for use around ornamental flowers and
shrubs, do not apply it to your lawn.

BTW, spurge is about the only plant I've seen that puts up a really good
fight against Round-up. It normally takes several applications 3 or 4
days apart to really completely wipe the stuff out. Often I hit it a
couple of times with RU and then when it seems to be mortally wounded
I'll pull up as much as I can then hit it with the Preen. Just pulling
it up by hand never works very long. Spurge has so many thin fine roots
that you invariably leave some of it behind and it is so tough to kill
that it can regenerate from a very small root mass. My routine is to
nuke it with Round-up, wait 3 ~ 4 days, nuke it again and put out some
Preen, then wait another 3 ~ 4 days and pull up by hand whatever I can
and reapply Preen as directed on the label.

David wrote:

Anyone know what product works best for killing spurge? Weed B Gone sure
isn't doing the job.