St Augustine needs a very specific herbicide so you don't kill the St Aug. I'm not familiar with Scott's products for southern lawns, but, as neilaz said, use a fertilizer to fertilize and a liquid herbicide to spot spray weeds. But contrary to what neilaz said, Weed B Gone is not the product. It will kill St Aug. Weed B Gone is great for any other grass; just not St Aug. No, St Aug will not crowd out broadleaf weeds. It will do a pretty good job with bermuda but some other grassy weeds give it trouble. You are in luck, though, there is a very effective herbicide. This one DANG. I didn't realize that picture was that huge!! If you use it right (shake first and then spray as a mist) it works very well. If you use too much the St Aug will yellow for a week or so before coming back. But the weeds will not come back. When the weeds die out, you can buy a few flats of St Aug and scatter them around in the bare spots. Keep them watered well for the first 3 weeks until the roots knit in with the underlying soil. Then start to back off. Use organic fertilizer like alfalfa pellets (rabbit chow) heavily and the St Aug will spread about 5 feet in all directions. Then in the fall after the hot weather is over, it will spread another 5 feet in all directions. You should have pretty good coverage, if not density, by November. Then next year the density will catch up due to the spreading in among itself. Key is to never let it dry out. St Aug does not go dormant like some other grasses. When it dries out it goes straight to dead. Water it deeply and infrequently. Deeply means a full inch all at one time. Infrequently means monthly in the winter transitioning to weekly in the hottest heat of summer. If you have particularly dry and windy days that evaporate the water more quickly, you might have to go to a 5-day schedule. Once the grass is established, there is never a case where you should water daily for a few minutes at a time. I use an oscillator type sprinkler - the new turbine drives, not the old mechanical linkage. These things are great. They provide a very slow application. Mine takes 8 full hours to get an inch of water. Your timing will vary depending on humidity, wind, soil type, grass height, shade, clouds, and temperature. Oh and raise your mower all the way to the highest setting for St Augustine. It looks much more plush and needs much less water. I have a St Aug experiment going on. It has not been mowed since October of 2011. In some places the grass height is 30 inches. And in those places it has not been watered since Oct 2011. Here is a pic of that. Yes I know...pretty funny to see St Augustine that tall. It's an experiment, not neglect. Notice there are no weeds either. My yard is surrounded by weeds, so that is one of the results of the tall grass experiment.

I might seem brutal but I'm going to be frank. Some of what you did is "wrong," by the general consensus of GardenWeb writers over the years. Here goes... 1. I've manually pulled large amounts of dandelions and other weeds with a long steel weed puller. I'd say I've filled about two of those roll out to the curb trash bins completely with pulled weeds. However, this may be a losing battle as there's still a large amount of weeds still sprouting up. I've gotten most of the bigger ones, though. The weed puller is good for dandelions but not for clover or henbit. My hanbit has amazingly weak roots but yours had taproots from heck. Hmmmm? 2. Because of the losing battle, I talked with a person at Home Depot and they suggested using weed and feed. I applied that to the lawn and I gotta say, I don't think it did anything. There were still just as many weeds a week later and I don't see and dead or dying ones. I started doing some research on-line about weed and feed and it seems like it may be some pretty nasty stuff and I may not use it again as I have a 2 year old daughter at home. Your experience is exactly what we read here year after year. As you have spent the money and learned, Weed N Feed doesn't work. Weed killing and grass feeding work best when done as separate tasks. Fertilize first and spot spray for weeds using Weed B Gone about 2 weeks after fertilizing. The weed plants die best when they are growing well after being fertilized. Now is a good time to fertilize. The grass will thicken up and then in early June you can spot spray the individual weeds. Clover and henbit should die quickly or after a second spraying. Crabgrass is probably best to let live this one last season. 3. I recently just had the lawn aereated. A better time to aerate is in the fall, but really there was no harm done. 4. After the lawn was aereated I went out and threw grass seed down on the bare patches. No harm there either but not much benefit either. Grass seed will not sprout unless it gets continual moisture for a couple weeks. That means it needs a short drink of water three times a day, every day. Not coincidentally, crabgrass seeds need exactly the same care to sprout. This is one reason why seeding in the spring does not give you the results you expect. If you seed in the fall, crabgrass is dying about then. Follow bpgreen's suggestions for watering and mowing for this one last season. Ignore any crabgrass or grassy weeds you have until September. Fighting it now is a losing battle and is just frustrating. But I disagree with him that you have Kentucky bluegrass. Why? Because if you did it should be much thicker. I've certainly been wrong guessing grasses from pictures, but I guess my point is that if you get a good Kentucky bluegrass going this coming fall, even with modest neglect it should get nothing but better and better in the coming years. Yours is getting worse and worse. That is what fescue does when it is neglected. If you want it to look better and better, then I would suggest killing with something after the summer heat breaks. That day/time is different everywhere so I can't pick a date for you but I'd guess it would be late August or early Sept. The idea would be to kill it with something like RoundUp, wait a week and spray anything that did not die the first time, remove all the dead grass with a power rake and leaf blower, spot-fill any low spots you want fill, scatter the best Elite Kentucky bluegrass seed you can afford (not available at Walmart), roll that seed down with a water filled roller, and water it daily like I outlined above for 10-15 minutes, three times per day. When it sprouts, set your mower for 3.25 inches and mow when the grass gets tall enough. Fertilize after you have mowed two times. Fertilize again on Thanksgiving. Next year fertilize on Memorial Day, Labor Day, and Thanksgiving. Next year it will seem to sleep, the following year it will creep, the third year it will leap out of the ground like it's on rocket fuel.

I don't think you can spray meticulously enough to not kill the good with the bad. If the nuisance is a weed......and there's not that much of it...why not think to dig it out. I'm not a fan of one type grass....most seed bags contain a blended mix of Kentucky Bluegrass, perennial ryegrass and fescue....in the ratio of 40/30/30.....which gives a lawn the best chance of each giving its best and standing up to most conditions that might not stand up well to the individual type. Spraying a glyphosate...such as RoundUp, will kill everything green it touches...including the good. Instead of trying to get rid of the invader, why not try to bring the other stuff up so it shades out the bad and treat the lawn with organic matter each spring.....and each fall. If this is too much on the wallet, then do it in the spring for sure....and repeat this every spring...whether you believe it needs it or not. This will increase organic mater and invite moisture to be retained. then over seed every spring.

I had a pretty sad law 1.5 years ago when I bought this house. I really knew how bad when the HOA sent me a "love note", "fix the bad areas now". Actually, the worse was the strip of lawn between the sidewalk and street. I ripped up that area and dumped 4 bags of black cow, then some alfalfa pellets, spread it out, water, then put down Lowes sod. It is really a vibrant dark, thick green this year!. That black cow is a bit expensive 4.90 per bag, but it seemed to work well. - Mowing at a higher setting really helps the weed control and my lawn looks better. - I put down CGM a month ago, which might had been a bit early but from what I read. It takes a few years for it to really help with weed control. I bought it off the web, 68 dollars for 60 lbs. Can't find it locally. - Tomorrow I will get soy-bean-meal (50lbs for 18 dollars) and put it down next week. - I did get some fungus in one area that does not get a lot of light and used corn meal to control it. Results were mixed but that area is finally growing back. Organic seems to be not so difficult so I'm going to try and stick with it for at least 5 years. The alfalfa is easy to get, but I have to order the SBM. The CGM is the most difficult to get here in FL. Good Luck!