Southern chinch bug

What is southern chinch bug?

The southern chinch bug is a native true bug that feeds on warm-season lawn grasses, especially St. Augustinegrass. UF/IFAS ranks it the second most expensive plant-feeding pest in Florida, with millions spent each year on control and turf replacement. It is a southern pest; Pennsylvania lawns deal with its cousin, the hairy chinch bug.

Nymphs and adults live in the thatch and suck sap from grass. Their saliva blocks water and nutrient movement, so the grass wilts, yellows and dies. They feed in groups at the base of a sprig until it withers, then move together along the runners to the next one, which makes circular patches that keep growing. Damage often starts in sunny, drought-stressed spots along lawn edges. A population can walk more than 400 feet in under an hour, so infestations spread from yard to yard.

Insecticides remain the main tool, but some populations have become resistant, and the bug adapted to the once-resistant 'Floratam' St. Augustinegrass within about twelve years of its 1973 release. UF/IFAS also lists mowing, watering, fertilizer and thatch habits that make St. Augustinegrass less vulnerable.

Signs and damage

• Roughly circular patches of yellowing, then brown, dead St. Augustinegrass that grow outward.
• Damage that starts in sunny, water-stressed spots, often along lawn edges and on dry, sandy soil.
• Tiny black bugs with white wings, and red or orange nymphs, in the thatch at the edge of the patch.
• Weeds moving into dead areas once sunlight reaches the soil.

Southern chinch bug identification: what to look for

• Adult: Black, oval, about 0.1 to 0.25 inch, with white wings marked by a black triangle or spot on the margin. Long-winged and short-winged forms.
• Larva: Nymphs look like small wingless adults and pass through five stages. First stages are yellow to bright orange with a white abdominal band; later stages turn red, orange-brown or black and grow wing pads.
• Eggs: Small and oval, white turning amber to red before hatching. Laid in leaf sheaths, thatch and soft soil near the soil line, a few a day for weeks, over 250 per female. They hatch in about 6 to 13 days in summer.
• Damage: Circular yellow-to-brown patches in St. Augustinegrass that spread outward from sunny, dry spots.
• Timing: Active year-round in much of the Southeast, slowing in cold weather. Infestations peak in early July. NC State reports 7 to 10 overlapping generations in warm months.

Life cycle

Females lay eggs a few at a time over many weeks in leaf sheaths, thatch and soil near the base of the grass, more than 250 in a lifetime. Eggs hatch in about 6 to 13 days in summer and can take a month or more in winter. Nymphs molt five times before becoming adults. In the Southeast, populations stay active year-round, sheltering at the roots and base of St. Augustinegrass in winter and sometimes going briefly dormant in cold spells. Warm months can produce 7 to 10 overlapping generations, with infestations peaking in early July (UF/IFAS, NC State).

When to look: In southern lawns, check sunny edges from spring through fall, with extra care in early summer when infestations peak.

Southern chinch bug look-alikes

A few things get mixed up with it:

• Big-eyed bugs (Geocoris spp.): Helpful predators named for their large eyes. NC State notes chinch bugs resemble big-eyed bugs but can be told apart by their markings. UF/IFAS names Geocoris uliginosus as the most numerous chinch bug predator in St. Augustinegrass.
• Hairy chinch bug (Blissus leucopterus hirtus): A close relative that attacks cool-season lawns such as Kentucky bluegrass and fescues in the North, including Pennsylvania.
• Drought, frost and disease injury: Dehydration, root rot, nematodes and winter frost can cause similar patches; NC State notes spring frost and drought damage is often mistaken for chinch bugs. Confirm bugs before treating.

How to control southern chinch bug

Cultural control

• Mow St. Augustinegrass at 3 to 4 inches, take off no more than one-third of the blade at a time, and keep the mower blade sharp (UF/IFAS).
• Avoid heavy doses of fast-release nitrogen; use slow-release or split applications instead (UF/IFAS).
• Water only when the grass starts to wilt and the leaf blades fold (UF/IFAS).
• Remove excess thatch by vertical mowing or power raking, since thatch shelters bugs and their eggs.
• Choose resistant grass where pressure is high; NC State says 'Raleigh' St. Augustinegrass is highly susceptible, and 'Floratam' and 'Floralawn' show some resistance but lack cold hardiness.

Biological control

• Big-eyed bugs, the striped earwig and small predatory bugs feed on chinch bugs, and fire ants can also reduce outbreaks, but UF/IFAS says natural enemies alone did not significantly reduce populations.
• Cool, cloudy weather favors fungal diseases that keep chinch bugs low (NC State).

Chemical control

UF/IFAS says insecticides applied to infested areas remain the main control, but isolated populations have developed resistance, so outbreaks may need repeat treatments and repeated use can also kill beneficial insects. NC State uses a treatment threshold of roughly 20 to 25 chinch bugs per square foot and suggests spot-treating off-color areas plus a border around them; its chinch bug table names active ingredients such as bifenthrin, lambda-cyhalothrin, deltamethrin, carbaryl and clothianidin. UF notes the preferred products are not sold over the counter. Use only products labeled for this use; the label is the law.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Follow good St. Augustinegrass care: higher mowing, sharp blades, careful nitrogen and watering only at wilt.
• Keep thatch thin.
• Check the edges of any yellowing patch with a can flotation test before treating.

When to call a pro

Because the preferred products are not sold over the counter and resistance is a concern, UF/IFAS recommends a professional for treatment. Hire a licensed pesticide applicator (see our pesticide applicator license guide) if flotation tests confirm chinch bugs and patches keep spreading.

Related guides: Weed identification guide · All pests and diseases

Questions about southern chinch bug

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