Plant Problem Diagnostic
Chinch Bugs in Lawns
The short answer
Chinch bugs suck sap from grass and inject a toxin (salivary secretion) that interferes with water movement, turning turf yellow and then brown; in the South the southern chinch bug is a major pest of St. Augustinegrass, while in the North the hairy chinch bug attacks cool-season lawns including Kentucky bluegrass and fescues.
Damage shows up as irregular yellow-to-brown patches concentrated in hot, dry, sunny areas, often near driveways, sidewalks, and roadways, that expand over time.
The critical diagnostic is that drought-stressed turf greens back up when watered, whereas grass killed by chinch bug feeding does not recover with irrigation.
Confirm with the float (flotation) test before treating, and favor least-toxic management first: resistant St. Augustine cultivars such as Floratam, Floralawn, and FX-10, adequate moisture to raise tolerance, and targeted, monitored control rather than blanket spraying.
How chinch bugs damage a lawn
Both adults and nymphs feed by sucking sap; as they feed a toxin is injected into the grass that causes it to turn yellow and eventually die.
Infestations are worst on thick, thatchy turf in sunny, open areas, and damage appears fastest where grass is already under heat or drought stress, such as near roadways, driveways, and sidewalks.
In the Southeast the southern chinch bug is the common turf pest and hits St. Augustinegrass hardest; in northern lawns the hairy chinch bug prefers Kentucky bluegrass, fine and red fescues, perennial ryegrass, and bentgrass, with damage typically from early July through late August.
Chinch bugs vs. drought and dormancy
Because the symptoms overlap, chinch bug patches are easily mistaken for drought or heat stress, and conversely winter frost or drought damage in spring is sometimes misdiagnosed as chinch bug feeding.
The deciding test is watering: drought-stressed turf that turns brown regrows fresh foliage as it recovers with irrigation, whereas grass does not recover once it has turned brown from chinch bug damage.
✔ Chinch bug injury clusters in the hottest, sunniest, driest spots and keeps expanding despite watering. If a browning patch bounces back a few days after irrigation, suspect drought, not chinch bugs.
Confirm with the float test
The float (flotation) test is the standard Extension method to verify chinch bugs and gauge numbers before any treatment.
- 1Make a bottomless cylinder — Cut both ends out of a large metal can (a coffee can works) and push it a couple of inches into the turf at the edge of a damaged patch, where dying grass meets green grass.
- 2Fill with water — Fill the can with clear water and skim off floating debris; keep it topped up if it drains.
- 3Wait and count — Within about 5 to 10 minutes, chinch bugs float to the surface where you can count them.
Least-toxic management
For St. Augustinegrass, planting resistant varieties such as Floralawn, Floratam, or FX-10 is a core preventive tactic, while the 'Raleigh' cultivar is highly susceptible.
Maintaining adequate soil moisture increases the turf's tolerance to chinch bug feeding and promotes beneficial fungi that attack chinch bugs; reducing thatch and avoiding over-fertilization also help.
Because healthy turf tolerates low numbers, monitor with the float test and reserve targeted control for confirmed infestations that exceed Extension thresholds rather than spraying the whole lawn.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Clemson HGIC — Chinch Bugs — Adult and immature chinch bugs suck sap and inject a toxin causing grass to yellow and die; the southern chinch bug is a major pest of St. Augustinegrass; damage is more severe near roadways, driveways, and sidewalks; confirm with a bottomless one-gallon can filled with water, watching for bugs to float up within about five minutes; resistant cultivars include 'Floratam' and 'Floralawn'.
- UC IPM — Southern Chinch Bug (Turfgrass) — Southern chinch bugs suck sap producing yellowish to brownish patches, most active in full sun above 90F; monitor with a 6-inch coffee can set 2-3 inches into turf, filled with water, waiting 5 to 10 minutes for bugs to float up; select resistant varieties such as Floralawn, Floratam, or FX-10; adequate moisture increases tolerance and promotes beneficial fungi that attack chinch bugs.
- University of Minnesota Extension — Chinch Bugs — Hairy chinch bugs prefer red fescues, perennial ryegrass, bentgrass, and Kentucky bluegrass; irregular yellow patches turning brown occur in thick-thatch turf in full sun during hot dry weather, early July through late August; float bugs up with a bottomless can of water in 5-10 minutes; drought-stressed turf regrows with irrigation whereas chinch-bug-killed grass does not recover once brown.