Most lawn pests in Southeast Queensland announce themselves in summer. The heat, the humidity, the lush growth, it's the conditions that spring to mind when people think about grubs and caterpillars tearing through a backyard. So when winter rolls around and the lawn slows down, it's easy to assume the pests have done the same. Sadly, a couple of them haven't.
Autumn and winter are one of the peak risk windows for armyworm activity in Southeast Queensland, while African Black Beetle and Sod Webworm are both active through the cooler months too, and a dormant or slow-growing lawn has considerably less capacity to recover from a pest hit than one in the middle of its summer growth flush.
Here's what to watch for this winter, how to tell what's causing the damage, and what to do about it.
Armyworm: The Pest That Moves Like Its Name
If you've walked outside on a QLD morning to find your lawn looking like it's been scalped to bare soil overnight, armyworm is almost certainly the culprit. These caterpillars are the larvae of a small, greyish-brown moth, and they earn their name from the way they move: in large groups across the lawn, stripping the grass leaf as they go in a distinctive marching line that leaves a clear, advancing front of damage behind them.
The larvae themselves are brownish-green, dark grey or black, often marked with stripes, and grow up to about three centimetres long. They shelter in the thatch layer during the day and emerge after sunset to feed, which means you'll often find very little sign of them during daylight hours despite significant overnight damage. The moths that produce them are nocturnal too, so if you're noticing small pale-brown moths flying low over the lawn at dusk, or clustering around outdoor lights at night, that's a strong early warning sign that eggs are being laid. 
Armyworm risk in SEQ spikes during autumn and winter, particularly after a period of wet weather following a dry spell. Conditions like this trigger mass hatching events and rapid larval development.
The reassuring news is that Armyworm is a surface feeder. The caterpillars eat the leaf blade, not the root system, which means a lawn that looks completely stripped will still have an intact crown and root system beneath the surface ready to push new growth once the pest is dealt with. Dramatic damage, but survivable if you get on top of it.
Sod Webworm: The Quieter Cousin
Sod Webworm doesn't have the same dramatic, overnight visual impact as armyworm, but it will leave damage if left unmanaged and it’s commonly active through the same cooler months. The larvae are small, light brown caterpillars around 1.5 centimetres long that feed on grass blades in a similar surface-feeding pattern to Armyworm, but they tend to produce a more patchy, irregular damage profile.
Signs of Sod Webworm include small, irregular brown patches that appear and expand over time, a lawn that looks moth-eaten or grazed in scattered spots rather than uniformly, and the presence of fine silken tubes or webbing in the thatch layer when you part the grass. Like Armyworm, the moths are more visible than the larvae, so if you're seeing small moths flushed up from the grass as you walk across the lawn in the evening, Sod Webworm is worth testing for.
African Black Beetle: Damage from Below
While Armyworm and Sod Webworm do their damage above ground, the African Black Beetle operates underground, and that makes it both harder to detect and potentially more damaging in the long term.
The adult beetles are small, shiny black scarabs around 12 to 15 millimetres long. They lay eggs in the soil, and the larvae (white, curl-shaped grubs) feed on grass roots through the cooler months, severing the root system and causing the turf above to die, thin, and lift away from the surface. Unlike Armyworm damage, African Black Beetle damage won't recover once the pest is treated, because the root system itself has been destroyed, meaning the turf in affected areas will need to be re-established. 
Surface signs include irregular brown patches where the turf pulls up easily from the soil with very little root attachment, and the presence of adult beetles on the surface on warm evenings. Birds feeding intensively in one area of your backyard — particularly Australian White Ibis or magpies probing the ground — are a classic indicator of grub activity underground.
How to Test for Lawn Pests: The Soap Drench
Before reaching for an insecticide, it's worth confirming that pests have actually moved in!
The dish soap drench test is simple and reliable. Mix two tablespoons of plain dish soap into ten litres of water and pour it slowly over a one square metre section of the most affected area, and wait a few minutes. If Armyworm or Sod Webworm larvae are present, they'll be irritated by the solution and come to the surface within five to ten minutes, giving you a direct count of what's in the lawn. More than five to ten larvae per square metre in that test is generally considered a threshold worth treating. 
For African Black Beetle grub activity, the test still works but you'll want to go deeper. We suggest pulling back sections of turf in affected areas and checking the top 50 to 75 millimetres of soil for the white curl larvae.
What to Use: Battle Insecticide for Active Infestations
When pests are actively feeding in the lawn and you need them dealt with quickly, Battle Insecticide is Jimboomba's recommendation for fast-acting knockdown. It's effective on surface-feeding larvae and delivers rapid results, so a well-timed application will stop an active armyworm event in its tracks and give the lawn the chance it needs to recover.
Apply Battle in the late afternoon or early evening when larvae are most active and moving toward the surface to feed. Water the lawn lightly before application to encourage grubs upward, and follow with irrigation after treatment to move the product through the thatch layer and into the zone where the larvae are feeding. Avoid mowing for a couple of days after application. After treating, give the lawn a good deep water to help reduce stress and support recovery, and hold off on fertilising until you're satisfied the pest activity has been resolved. Mow on a higher setting while the lawn pushes out new leaf growth. 
For lawns with a history of repeated armyworm or grub infestations, or for homeowners who'd rather not deal with an active event in the first place, Acelepryn GR is the preventative solution worth knowing about.
A single application of Acelepryn GR provides up to six months of protection against a broad spectrum of lawn pests including Armyworm, Sod Webworm and African Black Beetle, and just two applications a year will keep you covered.
Acelepryn is applied as a granular product and watered in after application. It's worth noting that it works best as a preventative measure rather than a cure, so getting it down before an infestation establishes is more effective than applying it to a lawn that's already under active attack. 
Recovery After a Winter Pest Hit
A lawn that has come through an armyworm event in winter has one significant advantage over the same scenario in summer: it doesn't have to perform immediately. With the lawn in its winter rest phase, a good treatment followed by time is often enough. The root system is intact, the crown is alive, and as soon as the soil warms and the weather turns in spring, the lawn will push new growth through the damaged areas.
Support that recovery by avoiding heavy foot traffic on affected areas, keeping the mowing height up while the lawn fills back in, and following up with a fertiliser application once you start to see consistent new growth in spring. Lawns that have had the root system compromised by African Black Beetle grubs will need bare patches repaired with fresh turf once the conditions are right.
Don't Wait Until the Damage Is Done
The thing about lawn pests in winter is that by the time most people notice the problem, it's already had a week or more to establish. A bit of awareness through the cooler months, whether that’s glancing at the lawn on an evening walk, checking for moth activity or keeping an eye on any areas that seem to be thinning unexpectedly, goes a long way toward catching an infestation early when it's easiest and cheapest to deal with.
Battle Insecticide and Acelepryn GR are both available through the Jimboomba Turf online store. If you're not sure what you're dealing with or want advice before you treat, give the team a call. We've been looking after SEQ lawns for more than fifty years, and we've seen pretty much every pest this region can throw at a backyard!
