Bob NH said:
If you go the Round-up route to kill it all, get the concentrate and mix your own. Those 1-gallon premixed things are very expensive for what they cover.
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If yr gonna buy concentrate, buy 'glyphosate' generic concentrate (the ingred in roundup) from another company. HiYield makes a prod that's 41% glyphosate. I think residential roundup is like 2% glyphosate, so a gal will last you forever.
However, I gotta say that in 2 years of using it, I hate it. I outfitted a pair of salad tongs with foam paintbrushes so that I could dip and carefully grab individual leaves to 'spot' kill. Didn't work too well.
It's easier to just pick the plants out by hand. Get em as soon as they emerge.
2 step process: put down pre-emergent. Then handpick young plants as they emerge.