What kind of grass do you have? If it is St Augustine then you might have a disease. If it is bermuda, you likely have other issues. If it is fescue or Kentucky bluegrass, then we'll need a picture.

What kind of grass?
What is your watering regimen (frequency and duration)?
How high/low do you mow?
When were the last 2 times you fertilized and what did you use?

Can you post a picture?

I've never had good luck with Actinovate against disease, but I have excellent results, year after year, with ordinary corn meal at 20 pounds per 1,000 square feet.

Thank you dchall for your comments. I hope the following information will help.
I have a fescue lawn.
The watering schedule is Sun, Tues, and Thurs for 15min per station.
The mower is set at 3-4" cut.
The last time I fertilized was February with steer manure. I just recently moved into this home.

How are you applying the corn meal? Are you using a hand held spreader?

Your mowing is fine.

Your watering is wrong. Don't feel too badly. Most Californians water wrong. I grew up in Riverside, and lived all over SoCal until I was 30, so I have a pretty good feel for that. Keeping the soil continually moist can trigger the disease as well as other issues. This time of year in Marysville you should be watering no more than once every 2 weeks. Then in June or July, when daily temps are in the 90s, you can bump that to watering every week. Time how long it takes to fill several empty cat food or tuna cans and water for that duration every week. Allowing the soil surface to dry out completely should keep any disease away and stop your weed pressure.

You cannot go cold turkey from 3x per week watering to watering every 2 weeks. You'll have to wean the grass off the high intensity schedule. Start by watering more deeply (longer) and skipping a watering session. Watch the grass for signs of wilting. If you see that, water immediately but water longer.

Hello dchall

Thank you again for your comments. I live in a farming community of Woodland which is 20-25 miles northwest of Sacramento. The day time temps now run mid 80s to low 90s. I will follow your advice and change my watering habits. Based on your comments, I will eliminate one watering cycle and watch for wilting. Can you advise what you think the disease is that I might have? Should I used corn meal as you suggested and how should it be applied?

thanks again for your help

I throw corn meal by hand on my small yard. You can use either a drop spreader or a broadcast spreader.

With temps in the 80s you should be watering every other week, but you'll have to water deeply 1 inch. Put come cat food or tuna cans out and time how long it takes your sprinkler to fill them. That time is going to be the time you water every time. Every sprinkler is different. Mine takes 8 full hours to get an inch. My neighbor's takes 20 minutes. When the daytime high temps start sticking in the 90s, move to watering once per week. If you get some dry days or temps in the 100s, go to watering every 5 days. Watch the grass for wilting, though.

when applying the cornmeal to my lawn, should I apply it to the entire lawn or only those areas affected with brown spots. Also, should I water the cornmeal in right away or wait for the normal watering cycle.

thank for all of great council.