I have a speckled, dry brown patch on my lawn that won't go away:
I first noticed it a month or so ago while mowing the lawn, when it was isolated to a single area of several square feet. I figured that it might be due to something random like animal urine or a spilled chemical, so I dismissed it.
The next time I mowed (three weeks later), it had grown in size and had taken on a spotted/blotchy appearance. The brown areas are dry, dead, and crumbly - I can clear out the grass and expose the soil pretty easily with my hands.
Adjacent areas of the lawn are still mostly green, but appear to be taking on the same appearance at the base of grass near the soil. Areas farther out still seem to be healthy and unaffected.
Some other info that may help:
- I live in central Texas, where it's very hot and humid.
- We've had drought (often severe) for the past few years, but this season has seen plenty of rain. It rained a lot before this patch appeared, and has rained a bit since it began to spread, though it's been about three weeks since the last rainfall. I haven't noticed the patch spread significantly since then.
- I have awful clay soil that doesn't retain moisture well.
- My "lawn" wasn't seeded or sodded; it's basically whatever will grow in this soil, which is about half grass and half weeds.
- The area of grass that seems to be most - if not entirely - affected by this is pretty lush St. Augustine, at the bottom of a downslope, adjacent to a small creek that keeps the soil moist.
- Kids play in the creek and do all kinds of destructive stuff - burning plastic, pouring out paint cans, and other stuff that bleeds over into my lawn and certainly isn't good for it. I didn't notice anything that would have obviously caused this, though.
More photos in this Flickr gallery.
Can anyone identify this, and recommend how to get rid of it? Please let me know if you have any questions.
A few interesting things to report.
It looks like my memory failed me - the dead grass isn't white or ashy. It's a light straw color, and of a similar tone and appearance to some clippings I left on my driveway that have since dried out. In other words, at a distance, it just looks like normal dried-out grass clippings.
But, on close inspection, I did notice that the dead blades do have some dark speckling that I didn't find on the healthy grass clippings:
The speckles have a sort of faint graphite appearance - medium gray and slightly shiny. They're very small, and vary in density; some leaves have a few, and some leaves are completely covered.
Per @Bamboo's feedback, I looked around for insects, and I did discover numerous big-eyed bugs. I couldn't find any chinch bugs, but per the article that @Bamboo linked to, big-eyed bugs prey on chinch bugs. Maybe that explains why the patch seems to have slowed its growth? Maybe the chinch bugs came first and did their damage to the St. Augustine grass, and now the big-eyed bugs are clearing out the chinch bugs?
Per @ondoteam's feedback, I should also note that I don't have the best lawn care habits; I do mow on a pretty regular schedule, but not as frequently as I should (every 3 weeks during the growing season). I mow very high - about 3.5 to 4 inches, as I understand that improves root growth - but I'm reading now that that's about an inch too high.
I can't control the temperature or humidity, and I can probably only have a limited effect on the poor soil drainage, but it sounds like I need to:
- mow more frequently (weekly, at least during the growth season)
- confirm the ideal grass height
- dethatch (I own a light-duty electric dethatcher, so I'll give that a shot)
- aerate (I can rent a power aerator at Home Depot)
- keep the mower blade sharp (I just sharpened it, but that was the first time in a couple of years)
Anything else I should do? Will the big-eyed bugs serve to limit further damage from the chinch bugs? Should I just let them roam uncontrolled? It seems likely now that the damage was due to chinch bugs, but since the damage has slowed/stopped, and I'm currently seeing only big-eyed bugs, is it safe to assume that I can bypass pesticide treatment for the chinch bugs?
Thanks for all the feedback!