Brown patches in your Florida lawn: chinch bugs, fungus or drought?
, By Galapagos Lawncare Team · · Lawn care tips
Three different problems make a St. Augustine lawn turn yellow and brown. Here is how to tell them apart before you spend money on the wrong fix.
Brown patches in a Central Florida lawn usually come from chinch bugs, a fungus called large patch, or plain drought stress. They look alike from the sidewalk, but each needs a different response, and treating the wrong one wastes money and can make things worse. Look at the shape, the season and the edge of the damage.
How do I tell chinch bugs, fungus and drought apart?
The diagram above sums it up. Here are the details behind each column.
What do chinch bugs look like in a lawn?
Chinch bugs are a major pest of St. Augustine grass and also attack Zoysia. They leave yellow-to-brown patches with dead centers, and the damage usually starts in hot, dry, full-sun spots, often next to pavement. UF/IFAS says mowing too short, too much nitrogen, poor sprinkler coverage and thick thatch make them worse. Watch for them from May and again in September.
If the patch grows outward week after week in a sunny strip, suspect bugs. The UF/IFAS chinch bug page shows how to check for the insects themselves; do it before you spray.
What is large patch, and when does it show up?
Large patch is a fungus (Rhizoctonia solani) that is active in cooler weather, below about 80°F, from roughly November through May. It makes round patches with darker or orange borders. It is often called brown patch, but UF/IFAS reserves “brown patch” for a separate summer disease, so a round patch in December is large patch.
The fix is mostly habit: water only in the morning and only when the lawn needs it, and go easy on nitrogen with slow-release products. The Florida lawn calendar lists November and December as the months to watch.
How do I know it is drought stress?
A thirsty lawn gives warnings before it browns: blades fold in half, the grass takes on a bluish cast, and footprints stay pressed into it. If you see those signs, check your sprinkler zones for broken heads or poor coverage, and check that your schedule matches your watering days. A broken rain sensor or a clogged head can leave a stripe dry while the rest of the lawn is fine.
What should I do first?
- Look at the pattern: a straight strip beside pavement points to bugs or an irrigation gap; round rings point to fungus.
- Check the season: November to May favors large patch, hot dry spells favor chinch bugs.
- Run the sprinklers by zone and look for dry spots, broken heads and overlap.
- Raise the mower to the recommended height (3.5 to 4 inches for standard St. Augustine) until the lawn recovers.
- Send us a photo before you treat anything.
When should I call someone?
If you cannot tell which problem you have, or the patches keep spreading after a week of corrected watering and mowing, we can look at it. Our lawn maintenance service covers lawn health checks, and fertilization is timed to the local rules. Send photos with a free quote request or call (407) 577-6400.
Questions on this topic
Is brown patch the same as large patch?
No. UF/IFAS uses “brown patch” for a separate summer disease. The round patches that show up from November to May in St. Augustine are large patch.
Will fertilizer fix brown patches?
Not by itself, and extra nitrogen can feed both chinch bugs and large patch. Identify the cause first, then fertilize on the UF/IFAS schedule and your county’s rules.
Why is the grass next to my driveway dying first?
Pavement radiates heat and dries the edge, which is where chinch bugs and drought stress usually start. Check sprinkler coverage along the strip first.
Can I just re-sod the patch?
Only after you know the cause. New sod placed beside active chinch bugs or fungus can fail too. Once the cause is under control, patching with sod works.