Brisbane lawns face a particular grub problem in summer. The warm, humid conditions between October and April create ideal conditions for the larvae of several moth species that feed on grass leaves and stems. An untreated infestation can strip an entire lawn in three to five days. The first sign most homeowners notice is a cluster of birds working over the same patch of lawn — by that point, the damage is already underway.
The most common lawn grubs in Brisbane
Armyworm (Spodoptera mauritia) is the most destructive and common lawn pest in south-east Queensland. The larvae are grey-brown caterpillars up to 35mm long that feed primarily at night. They move in waves across a lawn, which is where the name comes from. A heavy infestation can remove all visible green leaf growth overnight, leaving a lawn that looks like it's been hit with herbicide.
Webworm (Herpetogramma licarsisalis) is a smaller caterpillar that builds a silky web mat through the thatch of the lawn as it feeds. Damage appears as brown patches with a mat of dead material that can be peeled back to reveal the grubs underneath.
Sod webworm and lawn armyworm are sometimes used interchangeably in Brisbane, though they're different species. The treatment for both is similar.
How to tell if your lawn has grubs
The clearest signs are:
Birds feeding intensely on one area of the lawn — magpies, ibis and starlings dig for grubs and are often the first indicator.
Patches of brown or dead grass appearing rapidly — not the gradual browning of drought stress, but fast-appearing areas of stripped lawn.
Grass pulling up easily — armyworm severs the leaf at the base; affected turf can be lifted like a mat with almost no roots holding it down.
Visible larvae at dusk or when you peel back a section of damaged turf — grey-brown caterpillars of varying sizes curled in the thatch layer.
To confirm, try the soap test: mix a tablespoon of dishwashing liquid with 4 litres of water and pour it over a square metre of affected lawn. Grubs will surface within a few minutes if present.
Treatment options
Once confirmed, treat immediately — do not wait to see how bad it gets. Options include:
Bifenthrin-based insecticides (e.g. Acelepryn, Bifen) — effective, widely available, and appropriate for most residential lawns. Apply in the late afternoon when grubs are most active and water in lightly after application.
Chlorantraniliprole (Acelepryn) — lower toxicity to beneficial insects and considered the premium residential option. Also provides preventive protection when applied in advance of grub season (September–October).
Bacillus thuringiensis (Dipel) — biological option, effective against young larvae but slower-acting. More appropriate for mild infestations or as part of an integrated pest management approach.
After treatment: lawn recovery
If caught early, a treated lawn will typically recover on its own with regular watering and appropriate fertilising. The surviving grass will spread back into bare patches over two to six weeks depending on the time of year. Recovery is fastest in spring and early summer when growth is active.
If damage is severe — entire sections stripped to bare soil — you may need to oversow with appropriate grass seed or lay fresh turf in the worst areas once the infestation is resolved.
Prevention
The most effective prevention is a pre-season treatment applied in September to October before the first moth flights. A single application of a preventive insecticide can protect a lawn for the entire summer season. Given how quickly an untreated infestation can destroy a lawn, the cost of prevention is almost always less than the cost of recovery.