check into fungus problems. Over watering on top of the massive rain we have had this spring has fungus written all over it. (I live in Ft Myers, it rains about 1/4 to 1/2 inch a day) Ill try to find you some sites for a cure. You will find alot of people that will tell you to spread corn meal, it will work but its kind of pricy unless you know someone in Kentucky that is going to be driving down here. Copper based products will probably be the best soultion.

Hello Cathy. I have the same problem with my lawn and living in SFLA the rain is what has caused this. Stop watering right away. The rain water plus the additional water you give it will only kill it further. Do a search for my username and you will find a lot of info since any problem I have, it is posted here. From brown spots to fungus etc... Down in SFLA it has been raining almost every day so my st. Augustine is just brown in some spots, lime in color in others, etc... Hopefully all my posts help.

Because it has a fungal disease. Those dark spots on the dead blade are a dead giveaway. Where do you live? What is your watering schedule? How often and for how long?

That is weird that all over the net nobody recognizes fungal disease in St Aug. The first and last pictures show it crystal clear with the lesions running up and down the brown tipped blades. I have had rousing success fighting fungal disease with ordinary corn meal applied at 20 pounds per 1,000 square feet. Call your local feed stores to check availability. The cost should be well under $10. They might think you want corn gluten meal. You don't. The difference in price will tell you they are selling you the wrong product. CGM sells for roughly $30 per bag. When corn meal decomposes it attracts a fungus which attracts a predatory fungus causing the predator to over populate. Once the initial host fungus is gone, the predator goes after the disease fungus. Your alternative is to use chemicals. I can't help you with that. I've never needed them. But if you use chemicals first, then you cannot come back and try the corn meal later. The chemicals will kill off the predatory fungus from the soil. Try the corn meal first. If, after 3 weeks you don't like the results, either apply the corn meal again or try chemicals. Corn meal was the only thing that worked for me and was good enough to convince me to go full organic with my fertilizer. If you are happy with the corn meal after 3 weeks, you might just use it every month this summer to make sure you got it all. Corn meal is an organic fertilizer, so apply to the entire yard. Otherwise as the grass comes in over the dead areas, it would be much darker green. Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.