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First of all you're watering too often. Second you're watering at night. Third, are you fertilizing? Fourth, are you sure your sprinklers give you even coverage? I walk my dog at night and can't tell you how many sprinkler geysers I see night after night.

I'll start with watering because it's the most important thing. With temps in the 90s you should be watering only once a week. You can measure your sprinklers with tuna cans or cat food cans. Set several out in the yard. Be sure to put them in the yellow areas and in the greenest areas. Turn on the sprinklers and time how long it takes to fill all the cans. Memorize that number. Of course if it fills the cans on the green area in 15 minutes and takes another hour to fill over the yellow areas, then you need to balance your sprinkler heads. They might be clogged with debris or calcium or just be different heads.

Once you know what your target watering time is, then you can start to back off on the frequency. Water to that depth and skip a night/day. Watch carefully. If the grass does not look dry in the afternoon, then skip the next day, too. If it does look dry, water it immediately for that target time. Eventually the grass will extend itself until you don't need to water but once every 7-10 days. Then in the fall back off to once every 2 weeks, then 3 weeks, and then once a month in the cool months.

Watering at night is not always a problem. If you're watering once a week at night, it should be fine. If you're watering every night, then you get into disease issues.

You should have fertilized in late spring. Memorial Day is a good time and easy to remember.

Hello! I think we have a similar problem here in Georgia. We have an emerald zoysia lawn that is nice and thick. Recently we have had a valve fail on our irrigation and until we can fix it ourselves we are manually turning on a zone at a time and it has usually been evening while still daylight. Could evening watering and overwatering be our problem? Also, we have missed two fertilizations. We discontinued Trugreen last year and have been picking up a couple of big bags at Sam's club of Scott's and Pennington Weed and Feed but as I type this they are stacked in the garage because we have been busy. The grass has looked great until this showed up about two days ago. I don't think we have fertilized since summer 2013 although we did put a lot of pelletized lime down last fall while it was still warm. It is cut every week by a professional.

This post was edited by MrsPaw on Sat, Jul 19, 14 at 18:16

The yellow area is beyond the magnolia.

A close up. The green and yellow are quite bright when viewed in person. The yellow is still moist and pliable, not grey/white and straw-like. Thank you for any help you can give!

Thanks Lou. We have been watering a lot and it has been a wetter summer. Our watering habits have changed because we have to turn it on manually until we fix a valve on one of our zones and probably a solenoid. We have been doing this in the evening because we have more time then but I'm thinking we should water less frequently and strive to do it in the morning? One more thing: this yellow showed up two days ago when we started to get quite a bit of rain.

MrsPaw. First of all see if you can return the unopened bags of weed n feed. You don't have any weeds. If you want to fertilize, use a fertilizer. If you want to kill weeds, spot spray them with something like weed-b-gone.

Secondly, if you are watering every day, you definitely need to back way off from that. Before I get into that detail, how often are you watering? If you were watering once every week to 10 days then I would not be concerned about watering in the evening. If you are watering 3x per week or more, then I would be very concerned about evening watering.

Thanks dchall, we have been watering at least every other evening when it does not rain, probably because we have been doing it "consciously", not automatically. And we will turn on a zone and enjoy a beer on the patio and probably let it go too long. So we will take your advice and back way off on the watering and start taking bids to get the automatic system back up. It is so easy to get ripped off and my husband is proficient at replacing rotors and underground pipe repair that we don't like to hire.

My husband also wonders if some boxwood clippings that sat in the area for about a day may have been toxic to the grass. If that is even possible, they have been cleaned up.

I appreciate your note about the weed and feed. We are generally weed free and I have successfully spot treated yellow nutsedge so I will take that to heart. We have owned five homes, this is our first zoysia yard and we really love it and want to preserve it.