I sprayed 75 gallons of Roundup (glyphosate)about 2 weeks ago on my Bermuda yard. Weeds are turning yellow. Normally I would say you are too late but this year we have had so much cold weather the Bermuda is still dormant. Not for long though. If you are gonna do get it done now. Spray only the recommended strength.

Snow, I hope you're still here with us. Sorry it took so long for anyone to respond. I, for one, normally try to avoid questions from the southern folks because I don't know much about those types of lawn grasses. In reading your questions, I see I could have tried to answer yesterday. It's possible several other cool season folks also avoid warm season questions waiting for those more knowledgeable. I'm glad davidandkasie tried to help you out and hope you didn't lose patience with us. As mentioned, the types of weeds you have determine the treatment. You can post pictures for us to try to identify, but the best idea is to take samples to your nearest cooperative extension service for positive identification. Or, you can try to identify them yourself here or here. You must be careful of the herbicide you use. There are some that will damage St. Augustine, and there are some labeled for certain varieties of St. Augustine. You'll have to carefully read the labels and will have to know what variety of St. Augustine you have. The above sounds like a damaging amount of water, I must say. Store-bought molasses will take care of the fire ants. Just a bottle off the market shelf (unsulfered, the kind you eat) applied with a hose end sprayer.

Might be a Sedum sp. The waxy leaves tend to resist herbicides.

Temps were in the low-mid 70s during day and low 50s at night when applied, only applied it in test areas, followed directions that stated to water down lawn before applying, lightly applied only in test areas (e.g., 2' x 2'), did not water for a couple of days after that (if I recall correctly it stated don't water after that so the granules stay stuck to the weeds). Believe me, I followed the directions. The only clue I had on the packaging about what may have happened is the fescue isn't established enough, although at least some of it should be considering it was planted from seed and thriving the summer of 2006, just some overseeding to fill in spring 2007. I think the packaging says don't apply until you've mowed new grass at least a few times but my lawn had been mowed many times more than that.