Question of the Week Number 2: July 13, 2017

“Neil, what is happening to my St. Augustine? Why is it so yellow?”

I had a story on water conservation all written and ready to run in this week’s e-gardens. And then everywhere I turned people started asking about gray leaf spot. On St. Augustine, of course, but even on zoysia (or at least, I think that’s what caused the yellowing in this East Texas lawn).

Photo: JaMur zoysia posted on Facebook from a reader in deep East Texas.

Photo: Closeup of the same JaMur zoysia. I’ve circled what I think is the evidence of gray leaf spot lesions. Click image for larger view.

Photo: Extreme outbreak of gray leaf spot on St. Augustine.

Photo: A more standard level of gray leaf spot infection on St. Augustine. This is enough spots to cause lawn to turn quite yellow.

Continued Below

From a more general perspective…
And here are several other photos of gray leaf spot on St. Augustine lawns as posted on my Facebook page in the past week or two. Notice the way the lawns have “washes” of yellowed blades.


Just the bare facts…
Here are the things you need to remember about this problem.

Gray leaf spot is a fungal disease;
It attacks primarily St. Augustine, but also zoysias;
It appears in sun or shade;
Grass shows characteristic yellowing in washes;
BB-sized, gray-brown lesions will appear on blades, runners;
It is accelerated greatly by nitrogen;
It can do harm, even kill St. Augustine.

And the remedies…
Do not apply nitrogen to St. Augustine between mid-June and early September; and
At least to bring serious outbreaks under control, apply labeled turf fungicide to the entire lawn. Your local independent retail garden center is most likely to offer one.

Posted by Neil Sperry
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