Pest

White grubs in lawns

C-shaped beetle larvae that eat grass roots, leaving brown patches that peel up like a loose carpet.

What you'll see

• Irregular brown patches in late summer or autumn that feel spongy underfoot.
• The turf lifts or rolls back like a rug, with fat, white, C-shaped grubs in the soil below.
• Birds, skunks, raccoons or other animals tearing up the turf to eat the grubs.

Why it happens

Japanese beetles, chafers and June beetles lay eggs in lawns in summer. The grubs feed on grass roots from late summer into autumn, and again in spring.

How to fix it

1. Lift a square foot (30 by 30 cm) of turf in a few damaged spots and count the grubs.
2. Fewer than about 6 to 10 grubs per square foot rarely need treatment; a healthy lawn copes.
3. If counts are high, water in insect-killing nematodes sold for grubs in late summer, while grubs are young, as the label says.
4. Water the lawn in dry spells so the grass can regrow lost roots.

Keep it from coming back

• Mow high and feed moderately so the lawn grows deep, strong roots.
• Don't water heavily in midsummer droughts; beetles prefer moist lawns for laying eggs.
• Check for grubs each late summer where damage happened before.

Sources

• UC IPM: Masked chafers (white grubs)
• University of Maryland Extension: White grubs in lawn and garden soil
• RHS: Chafer grubs in lawns

General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.