How to Stop Billbugs and Weevils Eating Your Grass

Billbugs (a type of weevil) are small beetles that cause big turf problems. The larvae chew through crowns and roots, leaving brown, loose turf that mimics drought stress. The best defense? Know the billbug life cycle, scout early, and use a preventative billbug insecticide like Acelepryn before larvae hatch. If you’ve missed the preventative window and have an active infestation, you’ll need a different approach — more on that below.

What Is a Billbug?

Billbugs are a type of weevil — sometimes called “snout beetles” — belonging to the genus Sphenophorus. At least eight species can damage turfgrass by feeding on crowns and roots. While there are differences in their preferred grasses, the treatment approach is the same.

Common species include:

• Bluegrass billbug (Sphenophorus parvulus)
  

• Hunting billbug (Sphenophorus venatus)
  

• Lesser billbug (Sphenophorus minimus)
  

• Phoenix billbug (Sphenophorus phoeniciensis)
  

• Rocky Mountain billbug (Sphenophorus cicatristriatus)

Fun fact: They’re called “snout beetles” because of their long, curved snout used for chewing.

Billbug Life Cycle (and When They Feed)

Understanding the billbug life cycle isn’t just trivia — it’s the key to knowing when to apply a billbug treatment for maximum impact.

Spring — Adults Active

Adult billbugs emerge from their overwintering hideouts in lawn debris, thatch, or just under the soil surface as soil temperatures warm. They immediately feed on grass blades and stems, creating small notches, holes, or jagged edges on leaves. This adult feeding is primarily cosmetic, but it’s also your first warning sign that the next (and much more destructive) stage is on the way.

Late Spring / Early Summer — Larvae Hatch

Adult females lay eggs inside grass stems. Just a few days later, larvae emerge and begin tunneling into the crowns and roots. This is when the real destruction starts — larvae feed from the inside out, cutting off the plant’s ability to take up water and nutrients. Early on, the damage is hidden underground, but soon it shows as wilting, yellowing, and brown patches.

💡 Timing Tip: This is the critical window for applying a preventative billbug insecticide like Acelepryn SC or Acelepryn G. Once larvae are deep in the crown and root zone, control becomes much harder.

Late Summer — Pupation and New Adults

By late summer, larvae finish feeding and pupate in the soil. A few weeks later, new adults emerge, feed briefly, and then overwinter to start the cycle again the following spring.

Most species — including the common bluegrass and hunting billbugs — produce one generation per year, though hunting billbugs may complete two in warmer climates. Some, like the Rocky Mountain billbug, may even overwinter (the insect version of hibernate) as mature larvae or adults.

Related: Effective Treatment for Armyworms, Grubs, and Billbugs

Billbug Feeding Behavior

Billbugs aren’t picky eaters — but certain species have their favorites.

• Bluegrass billbug: This one’s the cool-season specialist, with Kentucky Bluegrass at the top of the menu. Fescue and Perennial Ryegrass also get hit, making it a headache for northern lawns and golf course fairways.
  
  

• Hunting billbug: This is your main suspect if you have a warm-season lawn. It’s especially fond of Zoysiagrass and Bermudagrass, but centipedegrass and St. Augustinegrass aren’t safe either. In southern states, hunting billbugs can have two generations per year, doubling the trouble.
  
  

• Other species: Lesser, Phoenix, and Rocky Mountain billbugs don’t play favorites — they’ll attack a mix of warm- and cool-season grasses, which is why billbug control is a concern from Florida to Washington state.

While adult billbugs chew notches in grass stems and leaves (you might see jagged edges or small holes), the real lawn-wreckers are the larvae. Once they hatch, they bore into the crown and root zone, feeding from the inside out. This hidden feeding weakens the plant structure, cuts off water and nutrient flow, and eventually causes brown patches and loose turf that looks eerily like drought damage.

💡 Pro Tip: If you see adult feeding damage, that’s your early warning siren — larvae will be right behind them, and that’s when you need to act fast with a preventative billbug treatment.

Billbug Damage: What It Looks Like

Billbug damage can mimic drought, grubs, or poor spring green-up. Signs include:

• Brown, tan, or yellow patches (often near pavement edges).
  

• Grass pulls up easily with no roots — stems are hollow.
  

• Fine, sawdust-like frass (insect excrement) at the base of plants.
  

• Thinning turf in irregular patterns.

Tests to Confirm Billbugs:

• Tug test: Gently pull the grass in a damaged area. If it lifts without roots and you see frass, suspect billbugs.
  

• Dig test: Check 1–2 inches into the soil for small, legless white larvae with brown heads.
  

• Pavement crossing: Watch for adults crossing sidewalks/driveways on warm days in late spring.
  

• Drench test: Mix 2–4 tbsp dish soap per gallon of water, soak 1 sq yd of turf, and count emerging adults.

Billbug Control: Preventative vs Curative

Preventative Treatments (Best Case)

• Apply a systemic insecticide like Acelepryn SC or Acelepryn G in late spring, just before larvae hatch.
  

• These products move into plant tissue, killing larvae as they feed.
  

• Acelepryn is highly effective for billbug control and has a minimal impact on beneficial insects.

Curative Treatments (If You’ve Missed the Window)

If larvae are already large or adults are active, Acelepryn’s effectiveness drops. In that case:

• Use a faster-acting contact insecticide (bifenthrin, carbaryl) for quick knockdown of active pests.
  

• Water granular applications into the soil for the best results.
  

• Repair damage with overseeding or turf renovation, then plan for preventative treatment next year.

Note: Beneficial nematodes (Heterorhabditis, Steinernema spp.) can also target billbug larvae if applied at the right time.

Related: Integrated Pest Management: A Sustainable and Holistic Approach to Lawn Care

How to Recover Your Lawn After a Billbug Infestation

If billbugs have already done their worst, you might be looking at patchy, thin, or dead turf. The good news? Lawns are resilient — with the right approach, you can bring them back stronger than before.

1. Remove Damaged Turf

Start by raking out dead grass in affected areas. Billbug-damaged turf often lifts like loose carpet because the roots are gone. Clearing it out helps prevent disease and makes space for new growth.

2. Encourage Root Regrowth

• Apply a balanced fertilizer or a root-stimulating product like CarbonizPN-G™ to help surviving grass recover.
  

• Keep soil consistently moist (but not soggy) to reduce stress and promote regrowth.
  

• If compaction is an issue, consider core aeration to improve root-zone oxygen and nutrient flow.

Recommended products:

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3. Overseed Bare Spots

If the damage is severe and you’ve lost turf density, overseed with a high-quality seed mix that matches your existing grass type. If billbugs are a recurring problem, consider endophyte-enhanced cultivars (especially in fescues and ryegrass), which naturally deter many lawn pests.

4. Repair with Sod if Needed

For large, heavily damaged areas, sod can restore coverage faster than seed. Just remember to check for pests before installing it, so you don’t reintroduce the problem.

5. Plan for Next Season’s Defense

The best recovery is prevention. Mark your calendar for late spring to apply Acelepryn SC or Acelepryn G before larvae hatch. Healthy, pest-free grass is far easier to maintain than nursing a lawn back from damage.

Related: Aerating and Overseeding: Why These Two Practices Go Hand-in-Hand for Optimal Lawn Health 

The Best Billbug Killer Insecticides

Here are some proven billbug control products from the Golf Course Lawn insecticide collection:

🛡️ Acelepryn SC Insecticide

• Covers: Billbugs, grubs, armyworms, and more
  

• Long residual control: Up to 90 days
  

• Safe for beneficial insects
  

• Apply with a backpack sprayer.
  
  

acelepryn-sc-insecticide-liquid-grub-and-army-worm-control

🛡️ Acelepryn G (Granular)

• All the benefits of Acelepryn SC but in granular form

• Great for broadcast applications on large lawns
  

• Easy to apply with a spreader
  

• Low toxicity, highly effective.
  
  

acelepryn-g-insecticide-grub-and-armyworm-control

🛡️Caravan® G Fungicide & Insecticide

• Combines insect control and disease prevention in one product
  

• Targets grubs, billbugs, and common lawn fungi
  

• Ideal for broadcast application over large areas
  

• Easy to apply with a standard lawn spreader
  

• Long-lasting protection with low toxicity.

caravan-g-insecticide-and-fungicide

💡 Pro Tip: For DIY lawn care heroes, combine Acelepryn SC with a non-ionic surfactant like Hi-Yield Spreader Sticker Non-Ionic Surfactant for better coverage and absorption.

Preventing Billbug Infestations Long-Term

You don’t want to be playing “whack-a-bug” every summer. The goal is to make your lawn a place billbugs don’t want to move into in the first place. Here’s how to keep them from setting up shop year after year:

1. Keep Thatch in Check

Billbugs love thatch — it’s the perfect place to hide, overwinter, and lay eggs. Too much thatch acts like a pest Airbnb, so aim to dethatch or aerate once a year (spring or fall) to keep it under ½ inch thick. Bonus: reducing thatch also improves water and nutrient flow to your grass roots.

2. Don’t Over-Fertilize in Spring

That early-season nitrogen rush might make your lawn greener, faster, but it’s like an all-you-can-eat buffet to a billbug. Push growth too fast in spring and you’ll have soft, tender grass that’s prime for billbug damage. Stick to a balanced fertilization plan, and save your heavier feedings for late spring or early fall when pest pressure is lower.

3. Mow at the Right Height

Stressed turf is more vulnerable to insect damage. Mowing too short weakens the plant, exposes crowns, and gives pests easier access. Follow the “one-third rule” — never cut more than a third of the blade at a time — and keep your grass variety at its optimal height. Healthy, dense turf is much harder for billbugs to chew through.

4. Inspect New Sod Before Installation

If you’re laying new sod, check the crowns, stems, and roots for signs of billbug activity before you buy. There’s nothing worse than importing a pest problem along with your “instant lawn.”

5. Use a Preventative Insecticide in Late Spring

If billbugs are common in your region, a once-a-year application of Acelepryn SC or Acelepryn G in late spring will break the life cycle before the larvae start feeding. Think of it as insurance for your lawn — one treatment can give you season-long peace of mind.

💡 Pro Tip: Combine cultural practices with a preventative application. Healthy, well-maintained grass can withstand more pest pressure, meaning you’ll need fewer chemical treatments over time.

Billbug and Weevil FAQs

Q: Will billbugs kill my whole lawn?

They can — especially if left untreated for multiple seasons. Large infestations can wipe out significant turf areas, requiring reseeding or resodding.

Q: Can billbugs survive the winter?

Yes. Adults (and some species’ mature larvae) overwinter in thatch, debris, or soil, ready to start feeding again in spring.

Q: Are billbugs harmful to pets or people?

No. They don’t bite, sting, or transmit disease to humans or animals. Their only target is turfgrass.

Q: Can I spot-treat billbug damage, or do I need to treat the whole lawn?

Spot treatment can work if the problem is localized and you confirm it through scouting. However, full-lawn treatment is often recommended because adults move to avoid reinfestation.

Q: Do billbugs only attack certain grass types?

Each species has preferred grasses, but together, they can damage both cool- and warm-season lawns, meaning nearly every lawn type is at risk.

Q: What natural predators help control billbugs?

Birds, ground beetles, and parasitic wasps feed on billbugs, but usually not enough to prevent heavy damage without additional control measures.

Q: Can I use beneficial nematodes for billbug control?

Yes — species like Heterorhabditis and Steinernema can target larvae if applied when they’re small. Timing and proper soil moisture are critical for success.

Billbugs Beware: This Lawn Bites Back

Billbugs may be sneaky, but you have what they don’t — knowledge, timing, and a secret weapon in your lawn care arsenal. If you’ve spotted billbugs in your lawn, don’t panic. Follow the game plan, apply the right billbug treatment, and keep your grass thriving.

For the best lawn insect control solutions, check out the full Insecticide Collection. Got questions? Catch Ron on YouTube for more lawn care tips.