Brown patches in a St. George-area lawn do not automatically mean insects. Heat, uneven sprinkler coverage, compacted soil, disease, traffic, and Bermuda dormancy can look similar. Identify the cause before paying for treatment or new sod.
Start with water and site conditions
Run each irrigation zone and compare the damaged patch with a healthy area. Look for blocked heads, poor overlap, runoff, hot reflective edges, compacted soil, and a recent change in watering or mowing. A dry root zone can intensify insect damage too, so more than one cause may be present.
- Check moisture just below the roots in damaged and healthy areas
- Note whether damage follows sprinkler patterns or the hottest exposed edges
- Confirm the grass variety and whether seasonal dormancy is expected
Look for evidence, not just color
Billbug larvae can damage stems and roots of both cool- and warm-season grasses. Affected stems may pull loose at the crown, with hollowed stems or sawdust-like material. White grubs live near roots and are typically C-shaped with legs; damaged grass may lift more easily. These clues guide an inspection but do not prove a diagnosis by themselves.
- Photograph the whole patch and the healthy-to-damaged edge
- Take a close photo of any insect or damaged stem
- Inspect a small soil-and-root sample at the edge of the patch
- Record when the damage began and how it changed
Decide whether treatment is warranted
A confirmed insect and meaningful damage matter more than the presence of one bug. A local lawn-care professional or extension office can help identify a sample and decide whether intervention is warranted. Correcting irrigation and mowing stress may improve tolerance, but it will not replace diagnosis when damage is severe.
- Do not apply a pesticide solely because a patch is brown
- Use only a product labeled for the identified pest and site, following its current label
- Resolve the cause before laying replacement sod so the new grass is not damaged again
These guides offer educational context, not a diagnosis or a one-size-fits-all schedule. Confirm the grass, season, soil, irrigation, product label, and local watering requirements for the actual property.
Extension references: USU Extension: Billbugs in Lawns, USU Extension: Lawn Care and Insect Pest Management.