Grass grub in Christchurch lawns: the signs, and what to do about it

Canterbury's number-one lawn wrecker

If a Christchurch lawn suddenly develops dead brown patches in late summer or autumn, the odds-on culprit isn't drought. It's grass grub. The larvae of a native beetle, they live just under the surface and chew through grass roots, and Canterbury's light, free-draining soils are exactly what they love. A healthy-looking lawn can go patchy in a matter of weeks.

The tell-tale signs

• Brown, dead patches that spread through late summer and autumn.
• Turf that lifts like carpet: roots gone, so the grass peels back with a gentle tug. This is the definitive test.
• Birds ripping up the lawn: starlings and magpies tearing at the turf are hunting grubs, and they're rarely wrong.
• Spongy ground underfoot where roots have been eaten away.

Treat in autumn, while grubs are young

Timing beats product choice. Grass grub is easiest to knock down in late summer to autumn (roughly February–April), when the new season's grubs are small and feeding near the surface. Treat then, with granules or liquid watered in properly and applied to the label, and you break the cycle before winter. Wait until spring and the grubs are big, deep and far harder to reach.

Helping the lawn come back

Once the grubs are dealt with, recovery is straightforward: rake out the dead material, overseed the bare patches in spring, and mow a little higher while new grass establishes. Taller grass grows deeper roots, which makes the lawn more grub-resistant next season. A regular mowing round at the right height does more for grub resilience than most people expect. Severely hammered lawns might want a full tidy-up and reseed.

Lawn looking patchy and you're not sure why? Andy sees grass grub damage every autumn. Lawn care in Christchurch: free assessments with any quote. Call or text 027 787 3246.