Without more information my first guess is that you might have rust. Years ago I had rust on roses, cannas, hollyhocks, and a few other plants. If so, here's a couple things to try. First, cut off all the infected foliage and get rid of it. Personally I would cut the whole clump down to the ground and dig and divide while you're at it. Don't put the clippings into a compost pile. Make sure that you clean up all the debris on the ground. You might check other plants and see if you have the same problem. Rust is a soil borne disease and is usually spread by rain and sprinklers splashing it up onto leaves and stalks. You'll see it mainly on the undersides of leaves. If you dig and divide, amend your soil with a good compost. Mulch with a good compost and keep an eye on the emerging plants. I kept my beds constantly mulched with homemade rough compost to keep the soil from splashing on the plants and buried soaker hoses under the mulch. I also used a summer oil spray on all the plants. Within two years I had it licked. In the Spring I raked up what was left of the old mulch and replaced it with fresh mulch. I tossed the old mulch just to be on the safe side. That was no small thing as our neighbor's entire back yard was one huge mess of rust and we were downwind of it.

The grass is dry. That can happen from not enough moisture or from rotten roots not letting the water up. Are you getting puddles of water in the dry areas? Puddles can allow fungal rot to set in. If no puddles then the areas are not getting enough water. That could be due to sprinklers not adjusted right, runoff from hydrophobic soils, sandy soils allowing moisture to run through, or simply the idea that you need more than 1 inch per week this time of year. My guess is your sprinklers are not adjusted right. That's more of an educated guess because I can see what appears to be a circular shape on the grass in your big picture. Mid way up from center to the right side of the picture is a nice colored circle(ish) green. Outside of that is the dry area. If you put cat food cans perpendicular to the circle and turn on the sprinklers, you will probably see that the cans are not filling evenly.

I live in Widefield/Colorado Springs and my gorgeous big lawn is having the same problems. The first year we moved in, the prev. owners had the sprinklers set to almost an hour per zone (6 zones), twice a day, 7 days a week. We cut it down to 30 mins per zone, 4 days a week am and pm. The majority of the grass was fine, but 4 ugly brown patches appeared, the largest being about 10'x4'. We thatched and reseeded some areas, with some success the following year. This year the problem is MUCH worse with about 12 big patches, a good 30% of the lawn affected. We've thatched, top dressed and aerated, and nothing is working. The grass just turns brittle and breaks when I walk on it. When I dig through it with my fingers, I see a thick thatch of grass roots, which I have to cut through and pull up to see soil. There are no bugs at all that I can see when I dig down. I'm going to use an insecticide just in case, but it is depressing looking at my huge, formerly lovely green, lawn!! HELP!!!

dchall_san_antonio(8 San Antonio), That’s a defense? Only on an internet forum where a few posters live safely in a bubble and can pat each other on the back unchallenged could that be considered a defense and even then it is weak. You Insult a highly credentialed source so you don’t have to address the points he made. Insult a second, un-mentioned resource to further dismiss any opposing positions as unworthy of an intelligent rebuttal while deflecting the need to actually counter the actual reference, claim a University is anti-organic with no link or reference, have the omnipotent power to project Dr. Parsons feelings of embarrassment, and finally simply mention an experience you claim cured a fungus solely because of corn meal and it just works because you said so? It is common to provide a link and credit to sources and required to be considered seriously. Who is the author of this peanut study and how did they respond to Dr. Parsons’s reply and he to theirs? Only by considering all positions, verifying the controls, data and conclusions, confirming it can be repeated consistently, can an independent person make an informed decision. Don’t want to address that so you dismiss any conflicting source? No controls on your assertions, no referenced controlled turf studies, something about peanuts I’d love to read, just trust you because you have over 10,000 comments? I was expecting another personal insult about boat payments. I have no dog in this fight but appreciate an open exchange of ideas when conducted respectfully. Please provide the link again to an actual peanut study confirming corn meal is an effective fungicide on turf. I’m sure you have a long list of degrees and certifications that put Dr. Parsons to shame and multiple examples and pictures posted of the great lawn you currently maintain and multiple pictures of all the lawns you have maintained over the years. I haven’t been able to find any though. Someone outside of your bubble might want to review actual sources and independently determine what practice to follow based on their budget and goals. Morpheuspa added a straw man, or at least threatened to build a straw man if he wanted to, that he could then easily beat, followed but the assertion, it just works while also dismissing the source never referenced in my original reply based on a supposed quote that apparently disqualifies this Dr. from series consideration on any and all previous and future subjects. With around 14,000 comments between them or “we” as they often refer to themselves it seems, just reading a few suggest the same disqualifying standard can be used against “we”. More power to a few that enjoys concocting material at the claimed low prices but time also has value and sourcing and mixing all those items and making multiple applications is not time well spent for all. I also didn’t realize this was exclusively an organic lawn care forum. Nothing wrong with organics, especially the true organic gardeners’ that don’t use herbicides or take other shortcuts, but many might prefer a simple management practice that leaves time to enjoy the yard. You two sure got it good; shutting down dissent simply by denigrating any challenge as unworthy of actually needing to address with counter studies and asserting your way is the best way simply by saying it’s so. You are likely to maintain your self-appointed position of superiority though because people like me will quickly tire of the noise and never make it to 10 posts much less 10,000. The forum will be worse for it though as resources that might have contributed useful information will find it isn’t a receptive place for a reasonable exchange of ideas.