You’re admiring your lawn one day when you notice something strange: irregular brown patches, grass that peels up like a cheap rug, and maybe even raccoons or birds clawing at the soil. Chances are, you have a lawn grub infestation.

While a healthy lawn can tolerate a few of these pests, a full-on grub infestation is a force to be reckoned with.

So what are grubs and why are they harmful for your lawn? To help us dig up the facts (pun intended), Family Handyman turned to Valerie Smith, a lawn care expert and Content Strategist at Sod Solutions. We’ll cover everything you need to take your turf back: how to spot the early warning signs and how to get rid of them before your lawn turns into an all-you-can-eat buffet.

What Are Grubs?

Lawn grubs, or grub worms, are the white, c-shaped larvae of several types of beetles that live just beneath your lawn’s surface. They have six legs at the front of their body, brownish heads and range from a quarter-inch to two inches long.

Grubs feed on grass roots, cutting off the plant’s ability to take up water and nutrients. Left unchecked, they can turn lush turf into a brittle, patchy wasteland.

Types of Grub Species in North America

The two main types found in the U.S. are billbug larvae and scarab beetle larvae (commonly called white grubs).

Billbug grubs

Billbug grubs are legless, tan-colored or creamy-white, C-shaped larvae with a reddish-brown or brown head.. Unlike other grubs, they feed inside the grass stems before moving underground to attack roots, which makes early detection tricky. Their damage often gets mistaken for drought or fungal issues. ‘

According to the Entomological Society of America, the most common billbug species found in lawns across the U.S. include:

  • Hunting billbug (Sphenophorus venatus vestitus): A frequent offender in the Southern states and transition zone.
  • Bluegrass billbug (Sphenophorus parvulus): Common across the northern U.S. and southern Canada, especially in cool-season turf.
  • Denver billbug (Sphenophorus cicatristriatus): Targets lawns in the Rocky Mountains and northern Great Plains.
  • Phoenix billbug (Sphenophorus phoeniciensis): Attacks bermudagrass and zoysiagrass in the Southwest.
  • Lesser billbug and Unequal billbug: Found in more localized regions but still damaging when populations surge.

Scarab beetle grubs (white grubs)

These are the classic white, C-shaped grubs most homeowners are familiar with. While there are more than 1,300 scarab beetle species in the U.S., only a handful are true lawn pests. Here are the usual suspects:

  • Japanese beetle (Popillia japonica): invasive and widespread
  • June beetles/May beetles (Phyllophaga spp.): a large group of native species
  • Masked chafer (Cyclocephala borealis)
  • Argentinian scarab (Cyclocephala signaticollis): invasive
  • African black beetle (Heteronychus arator): invasive
  • European chafer (Amphimallon majale): invasive
  • Asiatic garden beetle (Maladera castanea)
  • Oriental beetle (Anomala orientalis)

The Lifecycle of Lawn Grubs

When lawn grubs show up, they don’t make a grand entrance. There’s no dramatic warning, just brown patches, thinning grass, or turf that lifts like a loose rug. By then, the damage is already done underground.

To manage them effectively, it helps to understand how they live, grow, and feed. Most lawn-damaging grubs — whether they’re the C-shaped larvae of scarab beetles or the legless larvae of billbugs — go through four life stages. Knowing this is key to determining when and how to treat lawn grubs effectively.

Egg stage

Grub season begins in summer when adult beetles and billbugs lay their eggs in the soil. Timing depends on the species and location — billbugs start earlier (as early as May), while scarab beetles typically lay eggs from June through August. Moist, healthy turf is ideal for egg-laying, which is why well-kept lawns often become targets.

Within 10 to 14 days, the eggs hatch — and that’s when the real trouble starts.

Larval stage

This is the most destructive stage. Once the eggs hatch, the grubs begin feeding on turf roots.

  • White grubs (from beetles) go through three larval or instar stages, growing larger with each molt. They’re most active near the surface in late summer to early fall.
  • Billbug larvae begin by feeding inside grass stems, working their way down to the crown and root zone. These grubs don’t have legs and tend to damage new lawns, especially those recently sodded.

Because young grubs are smaller and closer to the surface, this stage is the best time to treat with insecticides or biological options. Waiting too long allows them to burrow deeper and cause more damage.

Pupal stage

In the fall, as temperatures cool, mature grubs enter a resting phase called the pupal stage when they form protective cells in the soil and stop feeding. Over the next several weeks or months, they transform from grubs into adult beetles.

At this point, treatments aren’t effective. The grubs are dormant and no longer feeding, so insecticides won’t reach them.

Adult stage

When spring arrives, the cycle starts again. Adult beetles and billbugs emerge from the soil to feed, mate, and lay new eggs.

How Do I Know if My Lawn Has Grubs?

Grub damage isn’t always obvious at first — but if you know what to look for, your lawn will start telling you something’s not right.

“Given the right opportunity and the appropriate amount of time, grub worms have the capability to completely destroy an entire lawn”, says Valerie Smith of Sod Solutions, which provides turfgrass for commercial and residential lawns. Early detection is key — before the damage becomes widespread or irreversible.

Here are the early signs of grubs in grass:

  • Brown patches that feel spongy underfoot: Grub-damaged grass often shows up as irregular brown patches that don’t green up with watering. These areas may feel soft and spongy to walk on due to root loss — almost like stepping on a damp sponge.
  • The tug test: A classic sign of severe infestation is when sod can be rolled back easily, revealing loose, rootless soil and perhaps even a writhing cluster of grubs just below the surface.
  • Wildlife visitors: If you suddenly notice holes in your lawn from birds, skunks or raccoons digging into your lawn, it could mean one thing: a grub buffet is underway. These predators love a grub snack and will tear through turf to get to them.

How to Assess Grub Infestation Levels?

One sure way to tell if you have grubs is to actually see them in your soil. To confirm an infestation, perform the square-foot test:

  • Cut a 1-foot square of turf on three sides.
  • Peel it back and inspect the top few inches of soil.
  • Count the grubs.
  • Repeat this across different sections in your lawn.

What Is the Best Time to Treat Grubs?

  • Late spring to early summer is when the preventive treatments are most effective, just before eggs hatch. Preventive treatments are most effective in late spring to early summer, just before eggs hatch.
  • Late summer is when curative treatments work best because the larvae are actively feeding near the soil’s surface. Curative treatments work best in late summer, when larvae are actively feeding near the soil’s surface.

When Should I Treat Lawn Grubs?

Not every lawn with grubs needs treatment. Finding 0–5 grubs per square foot is usually harmless. But if you find more than five or if your lawn is not very healthy, it’s time for immediate treatment, according to Smith.

How To Treat Lawn Grubs

The best lawn grub treatments depend on when you catch the infestation and how much damage has already been done.

Chemical Treatments For Grub Control

Sod Solutions recommends Dylox 6.2 Granular White Grub Insecticide, which needs to be applied with a broadcast spreader and watered within 24 hours. However, this product is toxic to wildlife, and shouldn’t enter storm drains or drainage ditches.

Grub-killing products can be highly effective — but only when timed correctly.
Apply preventative treatments like chlorantraniliprole in late spring to early summer before eggs hatch. Chlorantraniliprole is considered low-risk to pollinators and pets when used as directed, making it a safer choice for families with kids or animals who use the yard.

For curative treatments, use trichlorfon or carbaryl in late summer when grubs are actively feeding near the surface. These are fast-acting options, but they are highly toxic and may pose risks to bees, aquatic life, and beneficial insects. Always use caution, avoid applying near water bodies, and limit foot traffic until the lawn is dry.

Always follow label instructions, water the treatment in thoroughly and avoid mowing immediately afterward.

Natural And Organic Grub Control Methods

For eco-conscious homeowners, beneficial nematodes and milky spore offer nonchemical options.

Nematodes are microscopic worms that attack and kill grubs. Milky spore is a naturally occurring ‘disease’ that attacks grubs but doesn’t harm other plants or wildlife. The spores must be spread several times over two years, but they  protect your lawn for 10 years or more.

Both methods require consistency and may take longer to show results, but they’re safe for pets, pollinators and the environment.

Environmental Considerations When Choosing Treatments

Chemical pesticides can impact beneficial insects, groundwater and nearby wildlife. Choose selective treatments whenever possible and avoid broad-spectrum insecticides that harm pollinators and other misunderstood insects in your gardens. If you live near water bodies, choose natural methods or consult a professional for eco-safe options.

Professional Treatments vs. DIY

DIY solutions work well for small lawns and minor infestations, but large or recurring grub problems may benefit from a professional lawn care service. Pros will identify species, apply treatments more effectively and even spot underlying soil health issues contributing to the problem.

How to Prevent Lawn Grubs From Coming Back?

Grubs may be out of sight, but they shouldn’t be out of mind. A healthy lawn is the best defense against grubs and beetles.

FAQs About Lawn Grubs

What causes grubs in lawns?

Grubs are caused by beetles laying eggs in your lawn’s soil, usually in midsummer. Moist soil, thatch buildup and lush grass are attractive to egg-laying beetles.

Can grub damage be reversed?

Yes. Once grubs are treated, reseed or sod the affected areas. With proper watering and care, grass can regrow, especially in early fall or spring.

Are grubs harmful to pets?

Grubs themselves are not toxic, but the pesticides used to treat them can be. Always follow label instructions and keep pets off treated areas for the recommended time.

Do grubs come back every year?

They can. Adult beetles often return to favorable lawns to lay eggs. Regular lawn maintenance and monitoring can reduce the chances of reinfestation.

About the Expert

Valerie Smith is a lawn care specialist at  Sod Solutions, a company with more than 25 years of experience in the turfgrass industry. Drawing on her deep understanding of turfgrass health and lawn sustainability, Valerie helps homeowners and professionals make informed decisions about grass care, seasonal maintenance, and pest control.

Sources

Author
Elizabeth Heath
Elizabeth Heath is a travel, lifestyle and home improvement writer based in rural Umbria, Italy. Her work appears in The Washington Post, Travel + Leisure, Reader's Digest, TripSavvy and many other publications, and she is the author of several guidebooks. Liz's husband is a stonemason and together, they are passionate about the great outdoors, end...
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Elizabeth Heath