Chinch bugs
Chinch bugs are small sap-feeding true bugs, about 1/5 inch (3–6 mm) long, black with white wings. The bright red or orange nymphs have a white band across the back. They feed in the thatch at the base of the grass, and the lawn turns yellow, then brown, in patches that start in the sunniest, driest spots. In the South the pest is the southern chinch bug on St. Augustinegrass, one of the costliest lawn pests in Florida. In the North it is the hairy chinch bug in fescue, ryegrass, bentgrass and bluegrass. Drought stress looks almost identical, so confirm with a float test first: Penn State puts the point where control may be warranted at 20–30 bugs per square foot, Clemson at 20–25.
Southern chinch bug adults and nymphs in the thatch. Photo: pending.
Identification
Adults are small and slender: about 1/5 inch according to Purdue, 1/6 inch for the hairy chinch bug (Penn State) and up to 1/4 inch (6 mm) for the southern chinch bug (UF/IFAS). The body is black or grey-black and the white wings fold flat over the back, each with a small black triangular spot on the outer edge. Some adults are long-winged and some short-winged. The legs are reddish or orange.
Nymphs look like small wingless adults and are easier to spot because of their colour. The youngest are yellow to bright orange with a white band across the abdomen; they turn brick-red, then grey and finally black as the wing pads grow. An insect easily mistaken for a chinch bug is its main predator, the big-eyed bug. It has a broad head with large bulging eyes; the chinch bug's head is narrower and its eyes are small. Check before spraying: the predator lives in the same thatch.
Easily confused with
- Big-eyed bugsBeneficial — leave itCheck the head: the chinch bug's is small and triangular with small eyes, while the big-eyed bug's is wide and blunt with bulging eyes.
Damage symptoms
Chinch bugs suck sap and inject toxins as they feed, so the grass yellows, turns reddish-brown and dies rather than simply thinning. Damage starts in water-stressed, full-sun areas and spreads outward, and it gets much worse in hot, dry weather. That is also why it is so easy to confuse with drought. UF/IFAS warns that yellow or brown patches can equally come from dry spots, root rot or nematodes, so find the insects before you treat.
- Yellow patches, often roughly circular, that turn brown and die
- Damage that starts in the sunniest, driest parts of the lawn and at water-stressed lawn edges
- Patches that spread outward and merge in hot, dry weeks
- Small black-and-white bugs and red nymphs at the soil line, at the edge between dead and healthy grass
- Dead centres with bare soil in badly hit St. Augustinegrass
Lifecycle & degree days
Adults overwinter in thatch and leaf litter and start laying eggs in spring. The nymphs go through five moults in four to six weeks, so there are usually two generations a year in the North and two or three in South Carolina. In Florida the southern chinch bug typically stays active through the winter (only sometimes going briefly dormant in north Florida), with infestations peaking in early July.
- Generations
- 2 a year (Indiana, Pennsylvania), a partial third in long summers; 2–3 in South Carolina
- Overwinters
- Adults in thatch and leaf litter; mostly active all winter in Florida
- Eggs per female
- Up to 200 (Purdue) to about 300 (Penn State); over 250 for the southern species
- Egg hatch
- 1–2 weeks in summer; a month or more in a Florida winter
- Nymph to adult
- Five instars over 4–6 weeks
- Damage shows
- Early July to late August in the North; peaks in early July in Florida
Host crops
The southern chinch bug is mainly a pest of St. Augustinegrass, and also feeds on zoysiagrass, bermudagrass and centipedegrass. The resistant St. Augustinegrass 'Floratam', released by UF and Texas A&M in 1973, was overcome by Florida populations within twelve years. Clemson notes 'Floratam' and 'Floralawn' as resistant but reports that resistance has broken down in parts of Florida. Further north the hairy chinch bug prefers fine fescues, perennial ryegrass, bentgrass and Kentucky bluegrass. Endophyte-enhanced varieties of perennial ryegrass, tall fescue and fine fescues resist it. Worst-hit lawns are sunny, drought-stressed, thatchy and on sandy soil.
Monitoring & action thresholds
That is roughly 215–320 per m². Sources differ by species and region: Clemson gives 20–25 per ft² for the southern chinch bug, Penn State 20–30 life stages per ft² for the hairy chinch bug, and UMass 30–50 nymphs per ft². UF/IFAS's southern chinch bug fact sheet gives no number, only that the bugs cluster unevenly, so count at several spots.
Look at the margin between yellowing and healthy grass, not in the dead centre: that is where the bugs are feeding. For a float test, cut both ends off a large coffee can or one-gallon can, push it about 3 inches (7–8 cm) into the turf, and fill it with water. UF/IFAS keeps it topped up for five minutes; Penn State fills it three-quarters, stirs the thatch and counts for ten. Repeat at least four times round each damaged patch. A handheld vacuum run over a square foot of turf and emptied onto pale paper also works. Sort the catch before counting: big-eyed bugs live in the same thatch and look similar.
Biological control
The big-eyed bug is the main natural enemy of chinch bugs in both the North and the South. UF/IFAS found Geocoris uliginosus the most numerous predator in Florida St. Augustinegrass, alongside the striped earwig, minute pirate bugs and fire ants. But UF/IFAS also reports that introducing predators on their own did not significantly reduce southern chinch bug numbers. Big-eyed bugs were not in commercial production as of 2011 (Cornell), and they are easily killed by broad-spectrum sprays, so the realistic role for them is background control that you avoid destroying.
Cultural controls
Stressed grass is what chinch bugs exploit, and heavy nitrogen and thick thatch make it worse. UF/IFAS's cultural advice for St. Augustinegrass is to keep it tall, feed it slowly and water only when it needs it.
- Float-test before treating: yellowing from drought alone needs water, not insecticide
- Mow St. Augustinegrass at 3–4 inches (7.5–10 cm), removing no more than a third of the blade, with a sharp blade
- Avoid large doses of fast-release nitrogen; use slow-release or split feeds
- Water when the grass starts to wilt, enough to wet the top 8–12 inches (20–30 cm) of the root zone
- Dethatch by vertical mowing or power raking where thatch has built up
- In the North, overseed or renovate with endophyte-enhanced ryegrass or fescue
Chemical, last resort
Sources
UF/IFAS EDIS EENY-226/IN383, Southern Chinch Bug, Blissus insularis Barber (Woods)
UF/IFAS Gardening Solutions, Chinch Bugs
Clemson HGIC 2487, Chinch Bugs (Gorsuch, 2003)
Penn State Extension, Chinch Bugs in Home Lawns (Heller, 2007, updated 2026)
Purdue Extension E-61-W, Turfgrass Insects
UMass Extension, Turf BMPs Section 11: Insect Management (threshold table)
Cornell, Biological Control guide: Geocoris spp. (Hagler & Sanchez, 2011)
UC IPM, Natural Enemies Gallery: Bigeyed Bugs
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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