Plant Problem Diagnostic
Billbugs in Lawns
The short answer
Billbugs are weevils (long-snouted beetles in the family Curculionidae) whose legless larvae bore inside grass stems and then feed on crowns and roots, producing irregular browning or yellowing patches that peel and pull up easily.
Their damage is very often misidentified as grass that failed to green up, or confused with disease and drought, but the key difference is that billbug-injured areas do not respond to watering.
Confirm billbugs with the tug test: pull on the yellow or brown stems, and if they break off easily at the crown and are packed with fine, whitish, sawdust-like frass, larvae are the cause.
Because adults cannot fly well, you often see the snout beetles crawling on sidewalks and driveways; least-toxic management centers on resistant and endophyte-enhanced grasses, with entomopathogenic (beneficial) nematodes reported to control larvae, though their reliability is considered variable.
What billbug damage looks like
Above ground, billbugs create irregularly shaped or rounded areas of brown or yellowing grass, often appearing in early to midsummer.
As larvae feed, the stems become hollowed out and can sometimes be pulled out by hand, and a sawdust-like material builds up around the feeding area. This frass is the insect's excrement.
This combination of hollow, easily removed stems and fine sawdust-like frass is what separates billbug injury from most other lawn problems.
Why it is mistaken for drought or dormancy
Billbug damage is often misidentified as grass that has failed to green up, and is frequently confused with disease, drought, or even white grub injury.
The distinguishing test is irrigation: yellowish-brown, discolored patches caused by billbugs do not improve with regular watering, whereas truly drought-dormant turf greens back up once moisture returns.
Confirm with the tug test
The tug test is the standard way Extension recommends confirming billbug larvae before treating.
- 1Grab the browning stems — At the edge of a discolored patch, pinch a handful of the yellow or brown grass stems.
- 2Pull upward — Heavily infested stems break away easily at the crown instead of holding fast in the turf.
- 3Inspect the break — Broken stems that are hollow and packed with fine, whitish, sawdust-like frass confirm billbug larvae.
✔ Also watch pavement: because billbug adults cannot fly significantly, the snout beetles are commonly seen crawling on sidewalks and driveways, sometimes infesting where grass meets walkways.
Least-toxic management
The most durable defense is grass genetics: endophyte-infected ryegrass and fescues show resistance to feeding billbugs, and some cultivars (for example the zoysia 'Zeon') have been reported to resist hunting billbug.
Beneficial (entomopathogenic) nematodes including Steinernema carpocapsae, S. feltiae, and Heterorhabditis bacteriophora have been reported to control billbug larvae, though Extension notes their reliability for billbug control is variable. Sound watering, mowing, and thatch management support recovery.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Alabama Cooperative Extension (ACES) — Billbugs in Turf — Billbugs are long-snouted beetles in the weevil family with legless larvae; stems become hollowed out and can be easily pulled out by hand; sawdust-like frass builds up; damage is often confused with disease or drought but these areas will not respond to watering; adults crawl along pavement and infest where grass meets walkways; entomopathogenic nematodes control the larval stage.
- University of Georgia Extension — Hunting Billbug: Biology and Management in Turfgrass (C1173) — In the tug test, heavily infested stems break away easily when pulled and consist of hollow stems packed with sawdust-like frass; damage shows as discolored patches that do not improve with regular irrigation and is misdiagnosed as white grub, nutrient, or drought injury; endophyte-infected ryegrass and fescues resist billbugs and 'Zeon' zoysia shows resistance; Steinernema carpocapsae, S. feltiae, and Heterorhabditis bacteriophora have been reported to control larvae though reliability is questionable.