kiss garden, you are to be complimented on identifying a problem while you might still be able to solve it. 1) If this condition occured soon after you (or someone else) did something to the lawn, or a particular environmental (hail?) condition occured - there might be your answer. 2) For insects, do a soap flush around the EDGES of the yellowing patches. Make sure that you include both good and bad. Identify the species and estimate the quantity to determine if control is necessary. 3) If these check out OK, seek out disease. Look for colored spots on individual leaves; pull on a tuft of grass and if it feels slimy, pulls out easily and there are lots of dead leaves, these are all indications that a disease is present. Is the ground more wet or dry than in the healthy areas? 4) If nothing thus far, it may be a deficiency. An overall yellowing of all the leaf tissue indicates a shortage of "greening" nutrients - nitrogen and iron are the commonest. If veins are green but the tissues in between are not, if tissues are green but veins are not, if there is a green triangle near the base of the leaf etc. etc. Each and all of these mean something. Get hold of a good KEY to the identification of pests, diseases and environmental conditions and do the "CSI Plants". You will have a great deal of fun and maybe write your own TV series. Texas A&M published a comprehensive key some years ago and someday I must try to obtain a copy of it.

Pictures are usually needed but I think you have identified the culprit - fungal disease. I live in San Antonio, TX. I believe we have a similar issue with chemical fungicides. They must be applied when the temperature is not going to be above 80 degrees and no rain or irrigation for 7 days. Well, when is that??? January 3rd??? I had given up on finding a solution when I heard a guy on the radio suggest using ordinary corn meal on plants with fungal disease. I tried it on a rose plant and it was cured in a week. Nobody was more surprised than I was. Next week I listened to that radio guy for 3 hours. That day I went out and bought 50 pounds of corn meal at my local feed store. The rest is history. Since then I have never been afraid of a fungal disease. I have watched my garden carefully and have even identified the cause of my fungal disease issues. It is my wife leaving garden clippings on the lawn for a few days. Dew forms and the normal air flow is choked off by the pile of clippings. She had one favorite place to put the clippings so I just pretreated it with corn meal every spring. Now I have her putting them in the compost pile or on the concrete until they can be disposed of. The application rate to get rid of disease is 20 pounds per 1,000 square feet. You should apply to the entire lawn so you don't end up with green spots where you applied it. Corn meal is an organic fertilizer, too. Having said that and rereading your original message, if you have already used a fungicide, then corn meal may not work. Corn meal relies on the fungal health of the soil. If you have sprayed a fungicide then you have no fungal health left. You might want to apply compost first. Give the compost 2 weeks to work and then use corn meal. Then give the corn meal 3 full weeks to work. I would reapply after 3 weeks whether you have seen progress or not. The second app at the third week will thrive on the back of the first dose and should supercharge the antifungal effect. Most people wonder how corn meal works to kill fungus. The original TAMU work showed that corn meal contributes to the growth of the Trichoderma fungus. Trichoderma is a naturally occurring, predatory fungus that feeds on the cellular structure of other fungi. Normal soil has Trichoderma but not in high populations. Corn meal is decomposed by another fungus that multiplies the population of Trichoderma.

Otherwise it's a great looking lawn! You are still watering too much. I'm 500 miles south of you and got an inch of rain exactly 15 days ago. I watered two spots today for the first time since the rain. Most of the lawn still does not need water. At this time you should be backing off beyond the 7 days and looking at 10 or 15. With much cooler weather the soil does not dry out as quickly. Oh and the other thing you should be doing is putting down corn meal instead of asking so many questions. There is no substitute for getting it down NOW. Be sure to treat the entire lawn and not just the spots. You can't really tell how big the disease is affecting the soil. Plus the corn meal will really green up the spots you treat, so you'd go from brown to deep green.

Phased, I'm not a fungus expert. I'm a solutions expert. Corn meal seems to work on all the popular diseases except red thread, rust, and dog barf (yes, it's a type of fungus). I don't know why those seem to be immune. Dog barf goes away with a water hose, so that's the only treatment you need. Some diseases go away with shampoo just washing the disease microbes off the blades of grass. gotsqueeze, it's way too late to add seed for this season. But I like your thinking the problem through. I agree that the daily water needed for new seed might be a problem. Certainly if you were watering too long to the point of soggy soil it would be a problem.