Lawn grubs in Ontario: signs, skunk and raccoon damage, and what you can legally use

Lawn grubs are beetle larvae that eat grass roots. In southern Ontario the usual one is the European chafer, and its grubs do most of their damage from late September into November. The grass wilts, turns brown and lifts off the soil like a loose rug.

Skunks and raccoons then rip it up to get at them.

Ontario’s cosmetic pesticide ban rules out the usual chemical grub killers on home lawns. You can still use beneficial nematodes or a bacterial grub product, and grow a thicker lawn.

Then there’s the repair. If whole sections have been rolled back, new sod is quicker than seed. That’s what our sod installation and lawn repair service covers in Markham and nearby.

How do you check for lawn grubs?

Lift the turf and count them. Cut three sides of a square about 30 cm (1 foot) across in a brown patch, fold it back and look through the top 10 cm or so of soil.

Repeat in a few spots, including the green edge of the damage.

Grubs are white and C-shaped with a tan or brown head and six legs. OMAFRA says they’re 3 to 4 mm long when they hatch and up to 2 to 4 cm when grown, depending on the species.

How many is too many:

A watered, actively growing lawn has more roots, so it can lose more of them before it shows.

OMAFRA lists two other signs: flocks of starlings or blackbirds feeding on the lawn, and skunks digging it up in spring and fall.

Is it grubs, chinch bugs or a dry spell?

Pull on the dead grass. If it comes up with no roots, it’s grubs. If it stays put, think chinch bugs or drought.

OMAFRA notes that both pests get mistaken for drought, and the timing helps tell them apart.

Hairy chinch bugs suck sap from the grass at the crown instead of eating roots. OMAFRA says they do less harm on watered lawns, and endophyte-enhanced ryegrass and fescue resist them.

Our Ontario lawn care calendar shows when each pest turns up through the year.

Why are skunks and raccoons digging up my lawn?

They’re eating the grubs. The City of Toronto says skunks dig small round holes and roll up large chunks of sod to reach them, especially after rain, when the grubs sit close to the surface.

OMAFRA lists raccoons and starlings feeding on grubs as well.

OMAFRA’s factsheet points out that the digging usually does more harm than the grubs themselves, and it treats skunk damage as a sign of a grub infestation.

Trapping one skunk doesn’t fix much while the grubs are still there for the next animal. Toronto suggests soap flakes watered into the lawn and lighting the problem area, with natural lawn care to deal with the grubs.

What is the European chafer life cycle in Ontario?

It takes one year, and the grubs feed in fall and again in spring. This is the timeline OMAFRA gives:

1. Mid-June to mid-July: adult beetles come out of the lawn at dusk and swarm around trees to mate. This happens about when catalpas and hybrid tea roses are in full bloom.
2. Late June and July: females lay eggs in the soil, which hatch in about two weeks. A dry July and August can kill the eggs, because they need soil moisture to hatch.
3. August: young grubs feed near the surface. This is the window for nematodes.
4. End of September: most grubs are full size, and damage gets serious.
5. October to November: feeding carries on until frost drives them down in November or December.
6. Spring: they come back up as soon as the frost leaves, even before the snow is gone, and feed until mid to late May, then pupate.

June beetle grubs take three years, but OMAFRA calls the European chafer the most common lawn grub in southern Ontario.

How do you get rid of grubs in your lawn legally in Ontario?

Use beneficial nematodes or a Bt galleriae grub product, plus good lawn care.

Under the Pesticides Act and Ontario Regulation 63/09, you can only use a pesticide on a lawn if its active ingredients are on the province’s Allowable List. There are a few health and safety exceptions (wasps, for example).

The current list is version 5, effective November 28, 2022. Chemical grub insecticide ingredients, such as chlorantraniliprole and imidacloprid, aren’t on it.

OMAFRA’s turf publication notes that nematodes, as living organisms, aren’t regulated by the Pesticides Act or Regulation 63/09. Landscape Ontario says garden centres sell them.

Maine’s state guidance says the species Heterorhabditis bacteriophora works best on European chafer and Japanese beetle grubs, because it moves down through the soil looking for them.

Health Canada registered Bacillus thuringiensis galleriae, strain SDS-502, in 2019. Products made with it are sold in Canada and labelled for European chafer and Japanese beetle grubs. Follow the label for rate and timing.

When should you apply nematodes for grubs?

Mid to late August, and no later than early September. That’s the window Pam Charbonneau, OMAFRA’s turf specialist at the time, gave in a 2009 Landscape Ontario column.

Grubs that hatched in mid to late July are still young then and feeding near the surface.

On spring treatment with nematodes she was blunt: don’t bother. OMAFRA’s turf publication notes the grubs spend the winter full grown and feed only briefly in spring before they pupate.

To give the nematodes a fair chance:

1. Buy them close to the day you’ll use them and keep them in the fridge. Maine’s guidance says they last 2 to 3 weeks there.
2. Water the lawn first. If the soil is dry, Maine suggests at least 13 mm (0.5 inch) of water beforehand.
3. Apply at dusk, on a heavily overcast day or while it’s raining.
4. Mix and spray as the package says, keep the mix stirred, and take any fine screens out of the sprayer.
5. Water again right after, about 6 mm (0.25 inch), to wash them off the blades and into the soil.
6. Keep the soil moist for at least two weeks.

Count again in late September to see whether it worked.

Can a lawn recover from grubs, or should you resod?

Grass that’s thin but still rooted can come back. Turf that lifts like a carpet won’t, because the roots are gone.

OMAFRA says a grub-damaged lawn can be reseeded or resodded, and the best time is spring, after most of the feeding is done.

To lay sod, rake out the dead turf and loosen and level the soil so the new sod sits flush with the old lawn. Lay it and keep it wet until it roots.

Our guides on the best time to lay sod in Ontario and watering new sod cover the timing and aftercare.

If the damage showed up this fall, fall lawn care in Ontario explains what’s still worth doing before winter.

How do you make a lawn less attractive to grubs?

Grow thicker grass with deeper roots. Health Canada suggests mowing at 6 to 8 cm (2.5 to 3 inches) in summer, because beetles prefer to lay eggs in short lawns.

It also recommends watering no more than once a week, deeply enough to put down at least 2 cm, and leaving clippings on the lawn. OMAFRA adds aeration and balanced feeding.

When you reseed, Health Canada suggests fescues and ryegrasses that carry endophytes, a fungus that lives inside the grass and makes it less appealing to some insects.

Common mistakes

• Putting nematodes down in spring or October, outside the mid-August to early September window.
• Applying nematodes on a sunny afternoon or to dry soil, then not watering after.
• Laying new sod over a patch without counting grubs first. Check the soil before you replace anything.
• Treating a lawn that has two or three grubs per square foot. That’s normal.
• Calling dead grass grub damage without the pull test. Chinch bugs and drought need a different fix.

When it’s worth calling someone

Counting grubs and putting down nematodes is a fair job to do yourself. Get help when large parts of the lawn are dead or the animals have left the ground lumpy.

Those lawns usually need the dead turf cut out, the soil levelled and new sod laid. That’s what our lawn repair and sod installation service covers. For mowing and care through the season, see our lawn care service.

Call (437) 684-2535 or text us a couple of photos of the damage and we’ll come by for a free quote.