Black Streaks – In Zoysia

Q: I have zoysiagrass. It was beautiful last summer…thick and green. I feel that the lawn maintenance people we have mowing our lawn did not keep the lawn cut low enough. It always seemed too high.

They just started cutting it down a level last week and now this “black” is showing through. Can you help ?

A: The black streaks occur when decomposing fungi feed on dead grass blades or an underlying thatch layer.

Dark streaks seen in zoysiagrass in spring are common and do not require a fungicide. 

Making  a good growing environment for your zoysiagrass is the best prevention. To that end:

1. Fertilize only after May 1, when the grass is almost 100% green.

3. Control moisture – do not irrigate unless the soil is dry and then only 1 inch per week in one application. Irrigation is usually not needed until July.

4. Mow at 1 1/2″  – 2″ every week, even if the grass doesn’t look like it needs it. DO NOT allow it to grow to 3″ and mow it short…this is a great way to cause a thatch layer.

5. Aerate the zoysiagrass thoroughly in May and rake the resulting dirt plugs into the grass. This will inoculate existing thatch with good fungi, which will help reduce the thatch layer.

Zoysiagrass Care Calendar


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