What kind of grass do you have? If that's tall fescue then it's a fungus, probably brown patch. You are fertilizing too much, and at the wrong times for tall fescue. TF doesn't really produce thatch, you probably raked up a lot of dead blades.

If that's Zoysia, it's a fungus. You are also fertilizing too much for Zoysia.

In St. Louis any seeding of cool season grass should be done in fall, not spring.

Agree with tiemco. You're off to a poor start for this year. It is better to fertilize one time in the late spring (around Memorial Day) and two times in the fall (around Labor Day and around Thanksgiving). There is nothing magical about those dates other than I can remember them and I get those days off.

If you have a dense lawn, you should not need crabgrass preventer. If parts of the lawn are not as dense, you can use something that is strictly a preemergent herbicide and not mixed with fertilizer.

One of the reasons why you don't seed in the spring is so you don't encourage the crabgrass seed to sprout. It needs the same continual moisture that your grass seed need for germination. Except crabgrass germinates much faster and is designed by Mother Nature to fill fast and furiously during the heat of summer. Your new grass is not that sturdy.

It could be dog urine, if so we use Dog Rocks (dogrocksus.com) which is absolutely brilliant. natural & effective and so easy to use, good luck!

We had awful staining and dead patches on our lawn at the beginning of the year and went from garden store to garden store trying to find a remedy. Turns out it was our dog (like gardencare above!) we also found dog rocks (after lots of research) and they are doing a stellar job so far! Happy customer!

Dog rocks sound hilarious! I am old enough to remember the Pet Rock craze. I believe Dog Rocks are equally useless. Here is the "Technical Blurb" from their website.

Dog Rocks are a coherent Rock with a mechanically stable framework meaning no significant mineral particles are released into the petâÂÂs drinking water, in other words, Dog Rocks do not break down or leech anything into the petâÂÂs drinking water. Dog Rocks form a stable matrix and a micro porous medium in which active components are able to act as a water purifying agent through ion exchange. For this reason, when placed in water, Dog Rocks will help purify the water by removing some harmful trace elements.

That makes no sense at all. According to Texas A&M University, the reason dog urine burns grass is the sudden overdose of available nitrogen fertilizer. It is only an overdose because there are not enough microbes to process the urea in the urine. The solution is to scatter about 1 heaping handful of table sugar on the spot and moisten it. The sugar stimulates the beneficial bacteria in the soil to populate and the urine problem takes care of itself. Once the microbe population increases, you end up with dark green spots with tall grass.

There is nothing you can feed your dog to change the amount of urea in its urine.

Thanks tiemco and dchall. It's not dog urine related, we haven't had a dog for a few years. The fungus makes sense, is there a good fungicide out there that can be used this time of year or should I hold back on watering or both?

The mantra for watering is deep and infrequent. Deep means 1 inch all at one time. Infrequent means monthly in the cool months working your way toward once every 7 days as the days heat up. This is not a rule of thumb but guidance - if the temps are above 90 degrees F, then you should be watering more toward once per week. Between 80 and 90 should be about every 2 weeks. Lower than 80 and it's more like every 3-4 weeks. There are other factors including sunlight, humidity, cloud cover, shade from buildings and trees, soil type, soil depth, grass type, grass height, etc. Rather than trying to keep mental track of all that, it is best if you watch the grass for signs that it is drying out. As soon as any part of the yard looks dry, it is time to water the entire yard. If it has been fewer than 7 days in the summer, then water longer.

No plan is ever perfect. There are some fungal diseases which cause the grass to dry out and look like it has not been watered enough. If you are certain the soil is moist, but the grass looks dry, then you likely have a fungal disease.

Yes, there are fungicides. I use an organic approach so I don't know what the chemical fungicides are. I believe Immunox has been mentioned. Before you get one, read the entire label looking especially for the part about what the maximum temperature should be and rainfall. Summer is not a great time to treat for fungus because of the high temps.