Fall · Lawn · Updated September 2026
Brown patch in St. Augustine: what cool fall nights do to your lawn
Brown patch shows up in Austin St. Augustine lawns as nights cool. How to spot it, why evening watering makes it worse, and how it's treated.
If your St. Augustine lawn grows brown rings a few feet across in October, it's probably not drought. It's brown patch, also called large patch, a soil fungus that wakes up when nights fall into the 60s and grass stays wet overnight.
How to tell it apart
- Circular brown or yellow patches, often with an orange or smoky edge
- Blades pull easily out of the runner at the base
- Patches grow after cool, wet stretches instead of hot, dry ones
The biggest cause is evening watering
Grass that goes into the night wet stays wet for 10 hours or more, which is exactly what the fungus needs. Move your irrigation to early morning, around 5 AM, so the lawn dries during the day.
How we treat it
A fungicide treatment timed to cool, wet weather stops the spread. We also hold back fall nitrogen on St. Augustine, since heavy fertilizer in the fall feeds the disease. The grass in the patch usually fills back in during spring green-up.
Not sure if it's brown patch, grubs, or chinch bugs? Email a photo and we'll take a look.
