Fall Grub Damage in Ontario Lawns: Skunks, Raccoons and Fixes
If skunks, raccoons or crows are tearing up your lawn in September and October, the culprit is almost always white grubs, the C-shaped larvae of beetles like the European chafer. By fall the grubs are full grown and feeding just under the turf, so animals dig to reach them. Confirm grubs by peeling back a square foot of sod. Fill and rake the holes now, then plan a proper repair and a thicker, healthier lawn to discourage them next year.
Grub damage is one of the most common lawn calls we get in London, Strathroy, Komoka and Ilderton every fall. Here's what's happening and what you can do about it.
What are lawn grubs?
Grubs are the larval stage of several beetles. According to the Ontario government's guide to lawn grubs, the main ones in Ontario are:
European chafer (the most common)
June beetle
Japanese beetle
The grubs are creamy white, C-shaped, with a brown head and six legs near the head. They live in the root zone and eat grass roots.
The grub life cycle and why fall is peak damage
Using the European chafer as the example, the province describes this cycle:
Mid-June to mid-July: adult beetles lay eggs in the lawn.
Late summer: eggs hatch and young grubs start feeding on roots.
End of September: most grubs are full size and feeding heavily just under the turf.
November to December: grubs move deeper into the soil to overwinter.
Spring: they come back up to feed again before turning into beetles.
That fall feeding window is when grubs are biggest and closest to the surface. It's also when skunks and raccoons are fattening up for winter, which is why the digging peaks in September and October.
Signs you have grubs
Look for these clues:
Turf peeled back in strips or chunks, often overnight. This is classic skunk and raccoon damage.
Small cone-shaped holes, usually from skunks.
Flocks of starlings or crows probing the lawn.
Brown, wilted patches that don't green up with watering.
Sod that lifts like a carpet because the roots have been eaten.
A soft, spongy feel underfoot.
How to confirm it
Pick a spot at the edge of a damaged area.
Cut three sides of a 30 cm × 30 cm (1 ft × 1 ft) square with a spade, about 5 cm deep.
Fold the sod back and count the grubs in the soil and roots.
Check two or three spots.
Ontario's guidance says 5 to 10 grubs per 0.1 m² (about one square foot) can cause dead patches. Health Canada puts the damage threshold at 8 to 10 grubs per square foot. If you find only a few, the problem may be something else, such as drought or poor soil.
What Ontario's pesticide rules allow
Ontario banned the cosmetic use of many lawn pesticides in 2009 under O. Reg. 63/09. For cosmetic use on lawns, homeowners can only use products made solely from ingredients on the province's Allowable List. The province's page on pesticides for home lawns and gardens explains what's permitted.
In practice, that means most grub control in Ontario relies on beneficial nematodes and good lawn care rather than chemical insecticides.
Using nematodes
Beneficial nematodes are microscopic worms that infect and kill grubs. Timing and conditions matter:
Health Canada recommends treating grubs just after the larvae hatch, in mid-to-late August or mid-September, when the turf is moist.
Ontario's guidance says to apply nematodes to moist soil in cloudy conditions, water the lawn within 24 hours of application, and apply only when soil temperatures are above 11°C.
By October in southwestern Ontario, soil temperatures may already be dropping toward that limit, so a fall application can be hit or miss. Mark your calendar for late August next year.
Repairing grub damage
Right now (fall)
Rake up loose, torn turf. If roots are gone, it won't reattach.
Fill holes with topsoil so the lawn is safe to walk and mow.
Seed or sod bare areas while the soil is still warm, if conditions allow. Late-season seed may not establish before winter. Sod has a better chance as long as the ground isn't frozen.
Keep the lawn mowed to a normal height until it stops growing.
Next spring
If damage is widespread, patching often leaves a lumpy mess that animals dig up again. A full renovation usually works better:
Strip the damaged turf.
Add quality topsoil to level the area. We deliver screened topsoil across London and area.
Lay fresh sod for an instant, dense lawn.
Follow a proper watering routine. Our new sod care guide covers the first 60 days.
Prevention: make your lawn less inviting
Grubs favour thin, stressed turf. A thick, deep-rooted lawn tolerates more grubs before showing damage.
Mow high, around 7 to 8 cm (3 in). Taller grass shades the soil and makes egg-laying less attractive.
Water deeply but less often in summer so roots grow deep.
Overseed thin areas in late summer or early fall.
Aerate compacted soil, common in London's clay, so roots can spread.
Time nematodes for late August when young grubs are near the surface.
Grub damage checklist
Use this quick checklist when you spot torn-up turf:
Peel back sod in 2 to 3 spots and count grubs.
Note the count against the 5 to 10 per square foot threshold.
Rake up dead turf and fill holes with topsoil.
Decide: patch now or renovate in spring.
Plan nematodes for late August next year.
Improve mowing height, watering and aeration.
A local note
Grub damage shows up all over southwestern Ontario, especially in sunny, sandy or thin lawns and in neighbourhoods with lots of skunks and raccoons. In our experience, older London subdivisions with established trees and wildlife see heavy fall digging, and rural lots near Komoka, Ilderton and Dorchester aren't immune. If your lawn has been patched year after year, a full sod renovation may cost less in the long run than fighting the same patches every fall. See finished lawns in our photo gallery.
FAQ
Why are skunks and raccoons digging up my lawn in the fall?
They're usually hunting white grubs, the larvae of beetles like the European chafer. By late September most chafer grubs are full size and feeding just under the turf, which makes them an easy meal before winter.
How many grubs are too many?
Ontario's guidance says 5 to 10 grubs per 0.1 m² (about 1 square foot) can cause dead patches. Health Canada says 8 to 10 grubs per square foot can damage a lawn. Fewer than that, a healthy lawn can usually tolerate.
Can I use chemical grub killers in Ontario?
Ontario's cosmetic pesticide ban (O. Reg. 63/09) restricts which products can be used on lawns. Only products made solely from ingredients on the province's Allowable List can be used for cosmetic purposes. Read the label and check the province's guidance before buying.
When should I apply nematodes for grubs?
Health Canada advises treating grubs just after the larvae hatch, in mid-to-late August or mid-September, when the turf is moist. Ontario's guidance says to apply nematodes to moist soil in cloudy conditions, when soil temperatures are above 11°C.
Should I repair grub damage now or in spring?
Rake out loose turf and fill holes now so the yard is safe. Early fall can work for seeding or sodding if conditions allow. Otherwise, plan a full repair with topsoil and sod in spring, and consider replacing a thin, grub-prone lawn with a thick new one.
Talk to SPM Landscape & Excavation
If grubs and critters have wrecked your lawn, we can strip the damage, bring in fresh topsoil and lay new sod, so you have a lawn again instead of a patchwork. SPM has served London and southwestern Ontario since 2006, is WSIB covered and carries $1M in liability insurance. Call (519) 474-0008, email spmlandscape@gmail.com, or visit us at 791 Manchester Rd, London, ON.
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