Getting Rid of Lawn Grubs Naturally: A Practical Guide

• Give A Shit About Nature
• May 3, 2026
• Backyard Habitat
• 0 Comments

Lawn grubs, those fat, C-shaped larvae of beetles like Japanese beetles, June bugs, and European chafers, feed on grass roots through summer and fall, and a heavy infestation can turn sections of lawn spongy, brown, and peelable. The damage is real. The chemical aisle at the garden center is well-stocked with solutions. And yet, a significant portion of grub treatments get applied to lawns that don’t actually have a damaging grub population, based on brown patches that turn out to be drought stress or fungal disease.

The first thing to do before buying anything is check whether you actually have a grub problem.

Confirm You Have a Grub Problem First

Cut a one-square-foot section of sod, peel it back, and count the grubs at a depth of one to two inches. Do this in several spots across the affected area. Extension guidance from Cornell says that most lawns can tolerate a low grub population without significant damage. The threshold where treatment becomes warranted is generally around six to ten grubs per square foot, depending on grass type, soil conditions, and how irrigated and healthy the lawn is. A healthy, well-watered lawn can sustain more grubs than a stressed one without showing damage.

If you find fewer than six per square foot and the lawn is otherwise healthy, you may not need to treat at all. If you’re clearly above that threshold, or if you’re peeling up sod and finding the roots significantly chewed through, treatment makes sense.

One more variable: the species of grub matters for which treatment you choose. Japanese beetle larvae have a distinctive V-shaped raster pattern (a set of spines on the underside of the last abdominal segment) that distinguishes them from other white grubs. Identification matters because the most common biological controls work differently depending on grub species.

Beneficial Nematodes: The Most Flexible Option

Beneficial nematodes are microscopic roundworms that actively hunt soil-dwelling insects, enter their hosts through natural openings, and release bacteria that kill the grub within a couple of days. They’re harmless to humans, pets, earthworms, and beneficial insects, and they don’t persist in ways that create ecological problems.

UMass Extension’s research confirms that Heterorhabditis bacteriophora (Hb nematodes) can suppress common turf grubs including Japanese beetle larvae, with results described as erratic in some field studies but effective when conditions are right. The University of Missouri’s IPM program describes Hb nematodes as active hunters that swim through soil water films in search of hosts, which distinguishes them from other nematode species less suited to grub control. When buying nematodes, look specifically for Heterorhabditis bacteriophora, since other nematode species commonly sold at garden centers are less effective against white grubs specifically.

Timing is critical. Nematodes work best on young grubs that are close to the soil surface, which typically means late July through August in most parts of the country. Application should happen in the evening or under overcast conditions, since nematodes are killed by UV light. The lawn needs to be irrigated immediately before and after application, within 15 to 20 minutes, to keep the nematodes viable in the soil. Soil temperature should be above 50°F. These aren’t difficult requirements, but skipping any of them significantly reduces effectiveness.

Nematode products need to be kept refrigerated before use and applied soon after purchase. Maine’s Department of Agriculture notes that shelf life drops quickly at high temperatures, which is one reason results can vary between batches.

Milky Spore: Long-Term Control, Japanese Beetles Only

Milky spore (Paenibacillus popilliae) is a naturally occurring bacterium that has been used against Japanese beetle grubs since the 1940s. When grubs ingest the spores while feeding, they develop a fatal infection. As the grub dies and decomposes, it releases billions of new spores back into the soil, building up the bacteria’s presence over time.

The appeal is the longevity. Ecological Landscape Alliance suggests that milky spore’s effects can last fifteen years or more once established, making it a long-term rather than seasonal investment. It’s species-specific, posing no harm to other insects, animals, or plants.

The significant constraint is that milky spore only works on Japanese beetle larvae. It has no effect on European chafers, masked chafers, June beetles, or other white grub species. This is where identifying your grub species matters most. Fairfax Master Gardeners have raised concern about recent field trials showing disappointing results in some states, though it remains a commonly recommended tool where Japanese beetles are confirmed. In colder climates, it may take two to four years for the bacteria to fully establish in the soil before providing consistent control.

For heavy infestations, one option is combining milky spore with nematodes: the nematodes provide faster knockdown while milky spore builds up in the soil for long-term suppression.

Making the Lawn Less Attractive to Grubs

Chemical-free grub management isn’t only about what you apply. Beetle adults lay eggs in moist, recently watered soil in summer, so reducing irrigation in late June and July, when adult beetles are laying eggs, can make your lawn less hospitable to the next generation of grubs. A lawn in stress from drought may show damage at lower grub numbers, but the eggs themselves are less likely to survive in drier soil.

Letting grass grow a bit taller (three to four inches) also helps. Taller grass shades the soil surface and creates less attractive conditions for egg-laying adults. This is the kind of low-effort environmental modification that doesn’t solve a serious infestation but can meaningfully reduce future pressure.

Reducing the chemical pesticide use that kills ground beetles and other natural predators of grubs also helps over time. Predatory beetles, birds, and skunks all consume grubs, and a yard that supports diverse wildlife naturally has more natural grub pressure than one maintained with broad-spectrum pesticides.

Birds like robins and starlings actively probe lawns for grubs after rain softens the soil. Attracting birds to your yard and supporting ground-foraging species has real pest control value, even if it’s not measurable on a per-square-foot basis. The same logic applies to supporting native plantings that bring insect-hunting wildlife into the yard naturally.

What Doesn’t Work

A few common recommendations don’t hold up under scrutiny. Dish soap drenches are frequently suggested as a way to bring grubs to the surface, but there’s limited evidence that this works reliably and it can harm earthworms and soil biology. Diatomaceous earth is ineffective against grubs because it works through desiccation on the soil surface, not in moist soil where grubs live. Fake owl decoys don’t address the underground problem.

The actual choices that work are the two biological agents above, applied at the right time to a confirmed infestation.

FAQ

When is the best time to apply nematodes for grub control? Late July through August is the recommended window in most of the country, when young grubs are near the soil surface and actively feeding. Apply in the evening or on an overcast day, water the lawn first, and water again immediately after. Soil temperature should be above 50°F.

Can I use milky spore and nematodes at the same time? Yes, and for heavy infestations it’s a reasonable approach. Nematodes provide faster control while milky spore establishes in the soil for longer-term suppression of Japanese beetle larvae.

My lawn has brown patches. How do I know if it’s grubs? Peel back a section of turf in the affected area. If roots are intact and the patch lifts cleanly but the soil is dry, drought or fungal disease is more likely. If you find roots chewed through and white grubs present in numbers above six per square foot, grubs are a likely cause. Checking multiple spots gives a more reliable picture.

Do I need to treat every year? Nematodes don’t persist in the soil year over year at significant levels, so annual application is needed if grub pressure continues. Milky spore builds up over time and can provide multi-year control for Japanese beetle grubs without reapplication.

Do birds eating grubs cause lawn damage? Skunks and raccoons digging for grubs can cause visible surface damage, and starlings probing for grubs sometimes leave scattered holes. This digging is actually a sign of a real grub problem underneath. Addressing the grubs removes the incentive for digging.