G’day, Nikolai here from The Lawn Firm. If your lawn has gone from green to patchy in a short time, the African Black Beetle (and its larvae, often called curl grubs) could be the cause. I see this pest across Canberra every year. Below is my clear, step-by-step guide to spot the signs early, stop the damage, and help your turf recover fast.

Quick facts for Canberra

Pest: African Black Beetle (adults) and curl grubs (larvae)
Peak risk in Canberra: Late spring through autumn
Typical symptoms: Sudden yellow/brown patches, spongy feel, turf lifts easily, birds pecking at the lawn
Best defence: Timed preventative treatment in spring, strong lawn health, fast response if you see symptoms

How to identify Black Beetle and grub activity

Above ground (adults):

Adult beetles are shiny, black, and oval. You may see them on warm evenings or under loose debris.

Below ground (larvae/curl grubs):

C-shaped, creamy-white bodies with brown heads.
Live in the root zone and feed on roots, which stops water and nutrient uptake.

Tell-tale lawn signs I look for:

Patch test: Tug gently on the affected patch. If the turf lifts with little resistance, roots have been eaten.
Foot feel: Spongy or hollow underfoot, especially in expanding blotches.
Bird activity: Magpies and Currawongs digging for an easy feed.
Detergent flush check: Mix a few drops of mild dish soap in a watering can and pour over a small patch. Grubs may surface within minutes.

Why damage escalates quickly

Grubs feed on roots. Once the roots are gone, the plant can’t access water, even if you irrigate. In dry, hot spells, this turns minor stress into dead patches fast. Birds then tear up weakened areas while hunting, which makes the lawn look worse in days.

Canberra timing: prevention beats cure

From years on local lawns, this timing works best:

Spring (primary window): Apply a preventative lawn pest treatment before peak egg hatch. This cuts risk through summer.
Late summer to early autumn: If you see active damage, use a knockdown treatment promptly, then plan repairs.

Immediate actions if you suspect Black Beetle

Confirm with a patch test or detergent flush (see above).
Treat quickly if activity is present. A targeted professional treatment saves weeks of decline.
Water deeply (not often) after treatment to support surviving roots.
Plan recovery (see “Repairing the lawn” below).

Important: Don’t overwater or scalp. Both stress the turf and slow recovery.

Strengthen your lawn to resist future attacks

Healthy turf tolerates minor feeding without visible decline. My core program for Canberra includes:

Seasonal fertilising: Balanced in spring; root-strengthening in autumn.
Core aeration (spring or autumn): Opens clay soil, drives deeper roots.
Wetting agent (summer): Helps water reach the root zone in hydrophobic areas.
Consistent mowing heights: Avoid scalping; follow the 1/3 rule.
Weed control: Thick, weed-free turf rebounds faster after pests.

Repairing the lawn after grub damage

Once the pests are controlled, repair is straightforward:

Rake out dead thatch and loosen the surface.
Top dress lightly (5–10 mm) with a fine sandy-loam to re-level.
Overseed thin areas for quick fill-in and better density.
Gentle feed with a slow-release fertiliser to support new roots.
Water to establishment, then shift to deep, less-frequent watering.

Most Canberra lawns show visible improvement in 2–4 weeks with the right sequence.

DIY vs calling The Lawn Firm

You can try DIY checks and minor repairs, but timing and product choice matter. I diagnose on site, confirm activity, and apply the right treatment at the right rate. Then my team stages recovery, top dressing, overseeding, and nutrition, so the lawn bounces back quickly and stays that way.

Leave it to the experts. Let The Lawn Firm represent your lawn.

Book a free consultation today!

FAQs

Often curl grubs from African Black Beetle. Roots are eaten, so grass can’t access water. A quick patch-pull test helps confirm.
Activity varies with season and conditions, but Canberra lawns see regular pressure. A spring preventative cuts most risk.
Birds help a little, but they tear the lawn while feeding. You still need proper treatment and repairs.
With follow-up care, expect 2–4 weeks to see new growth and 6–8 weeks to even out.
No. Without roots, extra water won’t help. Control pests first, then water correctly to support recovery.