Here is a picture of two new spots which appeared this spring.

Weather update: I'm worried that this year the active disease cycle will occur earlier than normal. It hasn't been above 90 here for maybe a week or so, when we are often 95+. Nighttime lows are also in the low 60s, and we have been getting a TON of rain (every other day) for the last maybe two weeks. With all that moisture and cool temperatures I am worried the fungus will become active earlier than normal.

I get that each spring that I do not spray insecticide. Are there a bunch of little black bugs about the size of a pin head? Rake the dead grass with your fingers and see if you see them running.

I've not noticed any bugs, unless they only appear seasonally. I dethatched the whole yard this spring with a metal rake and did not notice anything then as well.

Is this evidence of large patch infection?

That is excellent evidence of a fungal disease. I was very busy in July and missed this post. What I would have suggested to apply was corn meal at 20 pounds per 1,000 square feet. The problem with zoysia is that it is so slow to recover that you can't always tell if the corn meal worked. Since 2002 corn meal has worked for me on several different fungal diseases in St Augustine.

Update: May 2015

Last fall I over seeded tall fescue in the areas of devastated zoysia. Thus week I've noticed some patches of the fescue seems to have died. I just looked but didn't find any indicators of active fungal disease. It might just be lack of water, we had about a three week dry spell in NC, and I'm not used to watering cool season grasses. I looked for evidence of distress on the zoysia in these border regions, but all I found was some yellowing and a failure to thrive:

I posted my soil test results in another thread (fairly acidic and low potassium). The site is about 50% shade so I know the zoysia is going g to struggle.

Is large patch active in the late spring at all? The turffiles page says to apply preventative fungicide towards fall when temps begin dropping again.

Last summer I spread cornmeal, but had an active large spot infection again in all three zones.

So how's this zoysia working out for you? Is it as easy to manage as all the brochures said? I only ask that as a caution to others who might be considering zoysia. It is not all its cracked up to be.

I assume you had the disease come in after the corn meal or you wouldn't have mentioned it. Now I'm just gathering information to see what the situation was. I have read reports of corn meal not working, so I'm trying to understand why or what the circumstances were. Was is exceptionally rainy? What was your watering schedule? How often and for how long? Did you fertilize before the disease hit? What month did it hit? How long after the corn meal did it hit?

In my area, I actually love the zoysia when it's not diseased. It naturally fills in gaps by spreading, it has never suffered from lack of rain (I hate irrigating), it needs extremely infrequent mowing and makes no seed heads, it's very fine textured with no clumps and is a pleasure to walk on, it backfilled high traffic areas, and it actually spreads even in >50% shade.

The Bermuda front lawn is fantastic, bit it gets full sun. My Bermuda will also cross over three feet of sidewalk and ten feet of mulch in a fortnight so it's a bit of a hassle to keep out of beds.

My notes say I added cornmeal early August last year. Late August I found the active infection, and so I spread Disarm G at the end of Aug and Sept. I also sprayed daconil between those applications but it had been in the tank for a year.

I don't think I will try organic this year. I was considering alternating daconil mixed with propicanozle and disarm g during the appropriate season. I am having trouble determining timing, and whether or not it will be effective.

Culture should improve this year. Last year's lime made a dent, bit morpheuspa suggested a more fast acting lime this year, and potassium sulfate to help harden it off.

If it survives the fall, I'm wholly open to moving to an organic regime next year.

BTW, I didn't chose the zoysia, it was in place when we moved in last year. I am attempting to avoid fescue though because it needs more water, mowing, and I find it clumpy and gappy, even in lawns that look nice.

Excellent, thanks for the info.

Something I might have mentioned in my earlier posts on this topic, but when you apply preemptive doses of chemical fungicide, or even postemptive apps also will kill the beneficial fungi living in your soil. Those beneficials will eventually return to the soil when the fungicides stop working, but that can take time especially if you hit it several times in the same season. When the beneficial fungi stop being beneficial, then your soil chemistry can get off leading to other issues. So what I suggest is applying either compost (1 cubic yard per 1,000 square feet) or compost leachate (almost any dilution) about 3 weeks following the app of the fungicide. Compost leachate is not compost tea. Compost leachate is much easier to make. All you do is plunge a half gallon of compost into 4 gallons of water (5-gallon bucket), screen out the compost for reuse later, and then pour or spray that water around. All that does is wash the beneficial microbes off the compost and distribute them on the yard. That will give the soil a head start in reestablishing the microbiology that should be there.

Then as much as possible, deep and infrequent watering is how you prevent the fungal disease in the lawn.

Thanks! What time of fall should I apply the leachate? I have a full compost bin which should finish converting in the summer heat.

I almost never water that yard. I aerated last year, but this year I will try a few baby shampoo apps - the flat clay soil may hold water.

We dethatched with a metal rake last year (holy mackerel it made a big straw pile), and will probably do so again in July.

Instead of dethatching you might try spraying molasses on the grass at a rate of 3 ounces per 1,000 square feet. The molasses fires up repopulation of the bacteria that will decompose the grass clippings and fallen grass for you. I cringe any time someone wastes an organic material. I hate to see people burning off their piles of wood or even lawns. Raking up thatch seems like such a waste.

Thanks, that's an interesting idea. We fill our composted with what we can. Our city also has weekly yard waste pickups which go to municipal compost so I don't fell too bad about that.