Lawn Grubs and European Chafer
White grubs, the European chafer in particular: the signs, the calendar, and the cultural care that matters most.
Lawn grubs and European chafer damage show up as brown patches that lift like a loose carpet, or as turf torn up overnight by skunks, raccoons and crows digging for the grubs underneath. The grubs are the larvae of scarab beetles and they feed on grass roots.
Washington State University describes the European chafer as an invasive turf pest with one generation a year. The University of Massachusetts lists it among the four species causing most grub damage in its region, alongside the Japanese beetle, oriental beetle and Asiatic garden beetle.
Grubs at a glance: Look for brown patches that peel back and animals digging. Check by cutting a square of turf and counting the grubs. Washington State University says a well-maintained lawn can tolerate up to about 20 grubs per square foot. Healthy turf, deep watering and overseeding damaged areas in fall or spring are the first line of defence.
Planning lawn work for the year? See the Lawn Care Calendar for Canada for when each job fits.
The European Chafer Year
| Season | What the chafer is doing |
|---|---|
| Late spring to early summer | Pupating, then adults emerge in June; mating swarms at dusk |
| June to early August | Eggs laid in the lawn |
| Late summer into fall | Young grubs hatch and feed on roots and crowns |
| Winter | Grubs keep feeding |
| April to May | Grubs pupate |
Life cycle from Washington State University. Exact timing varies with local weather.
Signs of Grub Damage
Washington State University describes brown to yellow spots that grow larger over successive years and may die and fill with weeds. In many yards the first sign is animal damage: skunks, raccoons and crows tearing up turf to reach the grubs. The University of Massachusetts notes the grubs damage turf by feeding on the roots, which leaves the grass unable to take up enough water.
Count Before You Act
Washington State University’s method: next to a damaged area where the grass is still intact, cut three sides of a square of turf, roll it back and count the grubs. Sample several spots. It says a well-maintained lawn can tolerate up to about 20 grubs per square foot (about 0.09 m²).
Different grub species behave differently. The University of Massachusetts explains how to tell them apart from the pattern of spines and the shape of the slit at the tail end, which needs a hand lens.
Cultural Care Comes First
Washington State University puts healthy turf first: water deeply, about 2.5 cm (one inch) a week through summer as needed, in applications of at least 6 mm (¼ inch), feed appropriately and mow regularly so the roots can outgrow some feeding. Overseed damaged areas in fall and spring.
Before using any lawn pesticide, check your province’s and municipality’s rules: several provinces restrict cosmetic lawn pesticides. For reseeding, see grass seed for a patchy lawn.
Frequently Asked Questions
What do lawn grubs look like?
C-shaped, cream-white larvae with a brown head and legs near the head, found in the soil just below the turf.
When do European chafer grubs damage lawns?
Washington State University says young grubs hatch in late summer and feed on roots through fall and winter, pupating in April and May.
How many grubs are too many?
Washington State University says a well-maintained lawn can tolerate up to about 20 grubs per square foot.
Why are skunks and raccoons digging my lawn?
They are often feeding on grubs. The digging can do more damage than the grubs themselves.
How do I fix a lawn damaged by grubs?
Rake out dead turf and overseed in fall or spring, then water deeply and mow regularly so the new grass roots well.
Can I use a pesticide for grubs?
Check your province's and municipality's rules first; several provinces restrict cosmetic lawn pesticides.
Sources
- Washington State University Hortsense — Lawn and Turf: European Chafer
- University of Massachusetts Amherst Extension — White Grub Identification