How do I identify and treat grub damage in a New Brunswick lawn?

Grub damage in New Brunswick lawns typically appears as irregularly-shaped brown patches that feel spongy underfoot and can be peeled back like a carpet, revealing white C-shaped larvae feeding on grass roots just below the surface. The most common culprits in NB are European chafer grubs and June beetle larvae, which are most active from late August through October and again briefly in spring before pupating.

To confirm grub damage, cut a 1-square-foot section of affected turf about 3 inches deep and fold it back. If you count more than 5-8 grubs per square foot, treatment is warranted. Fewer than 5 is generally tolerable and your lawn can recover on its own. You may also notice increased activity from skunks, crows, or raccoons digging in your lawn — these animals feed on grubs and their foraging can cause as much damage as the grubs themselves.

Treatment timing is critical in New Brunswick. The most effective window for grub control is late August through mid-September when grubs are small and feeding near the soil surface. By October, NB grubs move deeper into the soil to overwinter below the frost line (1.2-1.5 metres deep), making them nearly impossible to reach with surface treatments. The biological control nematodes (Heterorhabditis bacteriophora) are the preferred NB option since the province restricts cosmetic pesticide use — apply them in early September when soil temperatures are above 15°C and keep the lawn moist for 2 weeks after application.

For preventive control, consider applying nematodes annually in late August if your neighbourhood has a history of grub problems. A single application costs approximately $50-80 for a typical NB residential lawn (3,000-5,000 square feet) if you do it yourself, or $100-300 for professional treatment. Nematodes must be stored in the refrigerator and applied in the evening or on a cloudy day, as UV light kills them quickly.

To repair grub-damaged areas, rake out the dead grass, loosen the top inch of soil, apply a quality grass seed blend (60% Kentucky Bluegrass, 20% Fine Fescue, 20% Perennial Ryegrass), and keep the area moist until germination — typically 10-21 days in NB's fall conditions. If damage is extensive, professional overseeding at $100-200 per 1,000 square feet may be more efficient than patching by hand.

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