The problem is lack of water Period. OK. That seems like a long time to run the sprinkler for. You need to achieve 3/4 to 1" of water no matter how long it takes. Try a different rotor head that will throw more water, or change the nozzle in your current heads if you can. Honestly, running it for 45 minutes drenched the yard! Thats because we just received 3 days of soaking rain. It also doesn't explain why one of my problem areas received more water. If the problem was not enough water, it should be receiving less, right? Your talking about an 1/8" difference. If it would have been 1/2" or more difference then you might have an argument. What makes you think it's not enough water? Because you only applied an average of 3/16" of water. Can it be fungus? Chinch Bugs? No and once again, even if it was chinch bugs, you already treated for them. We have sandy soil in the Tampa Bay area. The problem areas you have are DEAD and are not going to get better over night. The good thing is that S.A. spreads by runners fairly rapdily. You could/should apply some compost to the dead areas to help/speed the process up. I strongly advise you read this whole thread again and follow the advise. By spring/early summer your problems should be much much better.

nematodes feed on ants, ticks, grubs, fleas, and too many insects to count yet they leave earthworms, toads, and beneficial ones alone. That should be enough. I've used only once and it seems to last a long time. I never seem to have major ant problem. They would build ant mound but they would never get huge like my neighbors and they seem to disappear overnight. It takes only one ant to be infected and bring it to the ant mound where it dies and nematodes would come out of the ant in large numbers... Nematodes are just very tiny worms...

I live right around the corner from you.(St.Petersburg, FL) I have Organically maintained my S.A. Floratam for 3 years now with excellent results. Ok, maybe a few shaky months hear and there but nothing detrimental. First! You should mow at the HIGHEST setting your mower will go and often. You dont want to remove more than 1/3 of the blade. I mow at 4.25" height year round and am mowing every 4-5 days right now. Recycle/Mulch mow (dont bag clippings or leafs) Use a Sharp, Balanced blade. I feed my lawn with Alfalfa @ 10-20lbs per 1000sqft and Soybean meal @ 12lbs per 1000 and Corn meal or cracked corn @ 10-20lbs per 1000 to keep any fungus at bay. The best method for watering is to wait until 30-50% of the lawn show signs of wilting before watering. Once a week is a good rule of thumb. You may not need to water that much in winter. Water deeply and uniformly early in the AM.(after 2am) with 3/4 to 1" water. See link below (tuna can test) to determine amount of water/timing. (I strongly recommend doing this) Below from UF IFAS Extension Most chinch bugs cannot complete their development when attempting to feed on Floratam and Floralawn. Beneficial Insects - Several predatory insects are often associated with southern chinch bugs. The most prominent predator of chinch bugs is the black big-eyed bug. (do a search for it) A predacious earwig, Labidura, is also a very good predator on all stages of the chinch bug. An adult earwig has been observed to eat as many as 50 adult chinch bugs in one night. Big-eyed bugs and anthocorids (another group of predators) are about the same size as chinch bugs and are often confused with them. Quite often these beneficial insects are misidentified as chinch bugs, and a pesticide is applied when it is not needed. Can you post some pics of your lawn? hope this helps.

For chinch bugs, used an old can and placed it in an area that was half dead half alive, filled it with water and soap and waited for any of them to float to the surface. I may have had one or two, but tough to be certain. For grubs, I chose a an area half dead half alive and just searched the soil diligently. Like I mentioned, I found a few, but definitely far from an infestation. I've read this is acceptable, but wondering if even seeing chinch bugs or grubs warrants action.