Chinch bug damage
Two different chinch bugs damage lawns in the United States, with different host preferences and different geographic ranges. The southern chinch bug (Blissus insularis) is the primary pest of St. Augustine grass in the Southeast. The hairy chinch bug (Blissus leucopterus hirtus) damages Kentucky.
Two different chinch bugs damage lawns in the United States, with different host preferences and different geographic ranges. The southern chinch bug (Blissus insularis) is the primary pest of St. Augustine grass in the Southeast. The hairy chinch bug (Blissus leucopterus hirtus) damages Kentucky bluegrass, perennial ryegrass, and fine fescue in the Northeast and Midwest. The damage patterns overlap enough that a single article covering both is practical — but the management details differ.
Southern chinch bug (Blissus insularis)
Host range and distribution
Per UF IFAS Extension, the southern chinch bug is the most damaging insect pest of St. Augustine grass throughout Florida, the Gulf Coast, and into Texas. It also attacks bahia grass and bermuda grass but causes most damage on St. Augustine.
Adults are about 1/5 inch long, black with white wings folded flat on the back. Nymphs (immature stages) are red-orange with a white band across the abdomen.
Symptoms
Per UF IFAS Extension:
- Yellow to brown patches, often in hot, sunny areas near pavement or in the driest parts of the lawn
- Damage initially appears in isolated patches and expands outward
- Grass does not recover when irrigated — the phytotoxic saliva kills plant tissue, not just stresses it
- Misidentified as drought in approximately 30% of cases per extension records
Diagnosis
Float test: Pound both ends off a large coffee can. Push it 3 inches into the soil at the margin between healthy and damaged turf. Fill with water. Chinch bugs float to the surface within 2 minutes. Per UF IFAS Extension, populations above 20—25 bugs per square foot typically cause visible damage and warrant treatment.
Management
Per Texas A&M AgriLife Extension, effective insecticides for southern chinch bug:
- Bifenthrin (liquid or granule) — effective; apply to perimeter of damage and 5 feet into surrounding healthy turf
- Clothianidin or imidacloprid — systemic options
- Repeat application may be needed in 4—6 weeks if populations persist
Insecticide resistance is documented in southern chinch bug populations in Florida. Per UF IFAS Extension, rotate between chemical classes to reduce resistance selection.
Cultural note: Floratam St. Augustine once had resistance to chinch bugs. Per Texas A&M AgriLife Extension, that resistance has broken down as chinch bug biotypes evolved. All St. Augustine cultivars should be treated as susceptible.
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