Chinch Bugs in St. Augustine: How to Spot, Test, and Treat Them

What chinch bugs are

The southern chinch bug is the most damaging insect pest of St. Augustine. Adults are only about a sixth of an inch long, black with white wings folded across their backs. Young nymphs are even smaller and reddish-orange with a white band. They live down in the thatch at the base of the grass, which is why most people never see them.

They feed by sucking sap from the runners and leaf sheaths and injecting a toxin that keeps the plant from moving water. That's why damage looks like drought.

What the damage looks like

• Irregular yellowish patches that turn brown and dry, often starting along the driveway, sidewalk, or street.
• Patches that keep growing outward, with yellowing grass at the edges between brown and green.
• Grass that stays brown even after you water.
• Damage that shows up in the hottest, sunniest part of the yard first.

How to check for chinch bugs

Option 1: Part the grass

Go to the edge of the damage, where yellow grass meets green, not the dead center. Get down close, spread the grass apart, and look at the soil surface and base of the runners on a sunny afternoon. Watch for a minute; they'll run for cover.

Option 2: The can test

1. Cut both ends out of a large metal can, like a coffee can.
2. Twist it a couple of inches into the soil at the edge of the damaged area.
3. Fill it with water and keep it topped up for 5 to 10 minutes.
4. Watch the surface. Chinch bugs float up. A handful in one spot is enough to explain the damage.

Option 3: The soap flush test

No can? Mix a couple of tablespoons of dish soap into a gallon of water and pour it slowly over about a square foot at the edge of the damage. The soap irritates the insects and they crawl up onto the grass blades within 5 to 10 minutes, where they're easy to see.

How to treat chinch bugs

If you confirm an active infestation, treat with an insecticide labeled for chinch bugs on St. Augustine lawns. Follow the label for rate and watering in. Treat the damaged area plus a wide buffer around it, since the bugs move out ahead of the visible damage.

If damage keeps spreading after a treatment, test again. Some chinch bug populations have become resistant to certain insecticides, so switching to a product with a different active ingredient can help.

Dead areas won't come back on their own. Once the bugs are under control, fill bare spots with plugs or sod. The runners will spread to close the gap.

How to prevent them

• Preventative insecticide. The Turf Method program applies one in early April, June, and August, ahead of the worst chinch bug months. For those rounds I use Spectracide Triazicide. Check that the label lists chinch bugs and St. Augustine.
• Don't overdo nitrogen in summer. Lush, heavily fed grass attracts more chinch bugs. Stick to the planned feedings.
• Water deeply. Drought-stressed grass takes chinch bug damage much worse. See how to water St. Augustine.
• Walk the hot spots weekly in summer. Catching damage early makes treatment far easier.

Common questions

What do chinch bugs look like in St. Augustine?

Adults are tiny, about a sixth of an inch, black with white wings folded on their backs. Young ones are smaller and reddish. You'll find them at the base of the grass at the edge of yellowing patches, not in the middle of the dead area.

How do I get rid of chinch bugs in St. Augustine grass?

Confirm them first with the can test or a soap flush, then treat the damaged area plus a buffer around it with an insecticide labeled for chinch bugs in St. Augustine, and water as the label directs.