Lawn Grub Invasion? Fight Back with Beneficial Nematodes!

Is your once-lush lawn starting to resemble a battlefield? Are skunks, raccoons, and other wildlife throwing nightly turf-flipping parties in your yard? If you're seeing dead patches of grass and telltale signs of digging, chances are your lawn has been invaded by grubs—and not the good kind you serve at BBQs.

Let’s break it down: grubs are the larval stage of beetles like Japanese Beetles, European Chafers, and May/June Beetles. These squishy white invaders tunnel through your soil and feast on grassroots like it's an all-you-can-eat buffet. The damage shows up fast—and before you know it, your grass lifts like old carpet and wildlife are crashing your yard like it’s a buffet.

But don't worry. There’s a safe, natural, and incredibly effective solution that doesn’t involve harsh chemicals or a shovel: beneficial nematodes.

 

What Are Beneficial Nematodes?

Beneficial nematodes are microscopic, soil-dwelling worms that love to snack on pests. Think of them as Mother Nature’s secret weapon—tiny, wriggly assassins that seek out and destroy soil-dwelling larvae, especially those pesky grubs lurking under your lawn.

 Unlike chemical grub killers, nematodes don’t nuke your soil’s entire ecosystem. They target specific pests (like grubs), while leaving helpful insects, earthworms, kids, pets, plants, and pollinators completely unharmed. Total win-win.

Meet Lawn Guardian: The Canadian Dream Team

At Georgina Garden Centre, we recommend Lawn Guardian—a mix of two Canadian-isolated strains of nematodes that are specially tuned to the pests living in our zone 5 backyards.

Here’s the nematode lineup:

• Steinernema feltiae (SF) – These shallow hunters work in the top 3" of soil where younger grubs hang out.
• Heterorhabditis bacteriophora (HB) – These deep divers reach 7" below the surface to track down mature grubs. 

Together, they hunt in stereo—taking care of both newly hatched and more established pests, ensuring you don’t just delay grub damage—you stop it.

And unlike imported nematodes, Lawn Guardian nematodes are produced right here in Ontario. That means they’re fresher, local, adapted to our environment, and raised on live hosts (not freeze-dried into dormancy like some imported versions). Translation: they’re alive, alert, and ready to hunt.

 

When to Apply Nematodes

Timing matters if you want results. Here’s when to make your move:

• Spring Application – Once soil temps reach 10°C (50°F) (usually May), and grubs become active again. This stops spring feeding and root damage.
• Fall Application – Late August through September is prime time. The grubs are smaller, closer to the surface, and easier to control. Bonus: this fall treatment sets you up for a grub-freer spring. 

Tip: Fall is often more effective, especially if you can only do one application per year. Try not to skip the spring application though!

How to Apply Beneficial Nematodes (Step-by-Step)

Applying nematodes might sound intimidating, but it’s basically as easy as watering your lawn—with a few key details.

Prep Your Lawn

• Mow your grass to 1–2 inches. This lets the nematodes reach the soil more easily.
• Water the area thoroughly before applying—moist soil is crucial.
• Avoid applying in direct sunlight or during the hottest part of the day—early morning or late afternoon is ideal, on a cloudy day or while it's raining is good too.

Mix It Right

• Nematodes usually come in a sponge or gel that you mix with water.
• Follow the instructions on your package carefully. You’ll typically mix the nematodes with cool, non-chlorinated water (rainwater or dechlorinated tap water).
• Stir gently—these are living creatures, not chocolate milk. 

Your Weapon 

• Hose-end sprayer and hose – Best for easy application. 

Spray Away

• Apply evenly across your lawn (or garden bed—more on that below).
• Keep shaking or stirring your mix every so often to keep nematodes from settling.
• Water immediately after to help wash nematodes down into the soil.

 

Keep It Moist! (Seriously, This Is Important)

Nematodes move through water channels in the soil, so keeping the soil damp after application is crucial. Think of them as little submarines—they need water to move.

Water the area daily for 3–4 days after application, or as needed to keep the soil feeling like a well-wrung-out sponge. Not bone dry. Not muddy. Moist.

Try the Plug Test:

• Dig out a small chunk of soil.
• Squeeze it. If it holds its shape, you’re good. If it crumbles, it’s too dry—time to water.

How Soon Can I Mow?

You can mow as soon as the next day after application—just don’t skip that post-application watering. The nematodes need that moisture to do their job effectively.

 

What Can You Spray Nematodes On?

While they’re commonly associated with turf care, beneficial nematodes aren’t just for lawns! Here’s where you can use them:

Lawn Grubs (obviously)

This is their most popular gig. Apply to the whole lawn or just problem areas.

Garden Beds

Got a veggie garden or perennial bed with root maggots or cutworms? Nematodes can help! Use in moist soil and avoid spraying foliage directly.

Compost Piles or Mulched Areas

If pests like fungus gnat larvae or other soft-bodied invaders are setting up shop in your compost, nematodes can help bring balance.

Container Gardens & Raised Beds

Water soil evenly. Nematodes don’t care about borders—they’ll work wherever there’s dirt and a pest buffet. 

Don’t Spray Them On:

• Dry soil or concrete patios (they’ll dry out and die)
• Hot pavement or walkways
• Leaves or foliage (they’re soil dwellers)

Why Not Use Chemicals Instead?

Chemical grub killers might seem like a quick fix, but they come with a list of downsides:

• Harm beneficial insects
• Leach into groundwater
• Require precise timing and reapplication
• Pose risks to kids, pets, bees, and wildlife 

Beneficial nematodes, on the other hand:

• Work with your soil ecosystem
• Are safe for everything except the pests
• Can actually build healthier soil long-term
• Are fully organic and sustainable

 

Signs They’re Working

You won’t see tiny tombstones in your soil, but you will start to notice:

• Less digging from animals (they’ll move on when the grub buffet closes)
• Greener, more vigorous grass growth
• Fewer brown patches forming
• Better root development overall 

It can take a few weeks for noticeable results, but trust the process—these little worms are working hard underground.

Pro Tips for Success

• Don’t store nematodes in direct sunlight or let them freeze—they’re alive!
• Apply right after purchase for best results.
• Repeat annually—especially in the fall—for long-term protection.
• Combine with good lawn care practices like aeration and overseeding for lush, resilient grass.

 

Ready to Wipe Out Those Grubs Naturally?

So there you have it, Lawn Guardian nematodes are your safe, organic, and effective solution to grub damage—no pesticides, no drama, just results. Whether you're a lawn perfectionist or just want to stop the skunks from turning your yard into a minefield, these little bugs are your new best friends. 

Got questions? Need help figuring out when or how to apply? Come visit us at Georgina Garden Centre, where our team can set you up with everything you need—and maybe even share a dad joke or two while you’re here.

Lawn Guardians: microscopic, mighty, and ready to go to war for your grass. Let nature do the dirty work—so you don’t have to.

 

Happy gardening!

 

Shannon, the Garden Girl

Got dead patches in your lawn or skunks and raccoons digging it up? 🏡🐛 Shannon, the Garden Girl, and Sabrina show you how to apply beneficial nematodes to control white grubs naturally!