Halting large patch disease in zoysia

phasedweasel(7b)August 1, 2014

Good morning. I have a zoysia backyard which has suffered from large patch for at least the last three years. The largest spot was about four feet across when we moved in, and has grown to be probably about twelve feet across this summer. Before now, I was a new homeowner (and new father) and had not spent much time on lawn maintenance besides mowing and watering. This year I would like to bring my cultural practices up to par and halt the spread of the disease, so that next year the lawn can begin to repair.

The lawn: Central North Carolina, zone 7b. ~50% shady, more towards the fence. Direct sun is received in late morning to early afternoon. The soil turns to red clay an inch or two deep. My spring soil report from the state ag office says the pH is 5.0, the potassium index is 46 (just under what they suggest as optimum), and the phosphorus index is 92 (substantially above optimum).

Where the grass is not diseased it is quite healthy and beautiful. I will try to work with zoysia at least for the next year because it withstands our foot traffic well, can be mowed and watered pretty infrequently and remains extremely weed free.

This spring (June) I took the following maintenance actions:
- Dethatch the lawn with a metal rake (the raked up thatch pile was unbelievable large, it was like we were making hay!)
- Lime (~50 lbs per 1000 sq feet)
- Core aerate
- Fertilize (15-0-15, slow release, ~5 lbs product per 1000 sq ft)

What I was considering:
- Spreading Disarm G (granular) in the fall when it appeared the disease was active. I'm not quite sure what this looks like, but the internet tells me the diseased region of grass at the margin of the patch will turn orange when the fungus is active, or that the leaf sheaths may show lesions or discoloration

After reading this forum, I also see some other folks are advocates of organic methods to attract beneficial fungi, such as spreading 20 lbs corn mean / 1000 sq ft. I am willing to try this as well, as even though I have purchased the fungicide I would prefer to not use it than need it.

Thanks for your thoughts and guidance!

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

    Bookmark   August 1, 2014 at 8:39AM
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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.

    Bookmark   August 1, 2014 at 8:43AM
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botanicalbill(9b SWFlorida)

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.

    Bookmark   August 6, 2014 at 12:37AM
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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.

    Bookmark   August 6, 2014 at 7:35AM
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Is this evidence of large patch infection?

    Bookmark   October 26, 2014 at 11:52AM
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dchall_san_antonio(8 San Antonio)

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.

    Bookmark   October 26, 2014 at 12:44PM
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