Lawn armyworm
Spodoptera mauritia
Caterpillars that feed at night and strip grass leaves down to the crown. Damage can spread across a lawn in days, then the lawn usually recovers once they're gone.
Also called: Armyworm, Army worm
Short answer
Armyworm are caterpillars that feed at night and strip grass leaves down to the crown, so damage can spread across a lawn in days. Look for chewed leaves and an advancing brown edge, and check at dusk or after dark with a torch. Lawns usually recover once the caterpillars are gone; treat only with a product whose label lists armyworm.
Overview
Lawn armyworm caterpillars feed on most lawn grasses, mostly at night. Large numbers can strip a lawn in days, which is why the damage seems to appear overnight.
The good news is that they eat leaves rather than roots, so lawns usually recover. Queensland’s guidance suggests treating lawns when you see rapidly expanding areas with more than 60% leaf loss, and helping recovery with water and fertiliser.
The months shown are a general guide: several generations can occur through spring and summer, and an industry guide notes outbreaks in late summer.
Signs of damage
- Patches that look grazed or mown very short, spreading quickly over days
- Ragged, chewed leaf edges; in heavy feeding only the midrib is left
- Striped caterpillars up to about 40 mm long, most active late in the day and at night
- Moths around lights in the evening
How to check
Check the lawn at dusk or after dark with a torch, when caterpillars feed.
Part the grass at the edge of a damaged area and look for caterpillars and droppings.
When it's active
| Zone | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tropical | ● | ● | ● | ● | ● | |||||||
| Subtropical | ● | ● | ● | ● | ● | |||||||
| Warm temperate | ● | ● | ● | ● |
What favours it
- Warm months; several generations can occur in spring and summer
Control without chemicals first
Help the lawn recover with water and a feed once caterpillars are no longer active.
Treatment options
| Timing | Active ingredient | What it does | Grass types |
|---|---|---|---|
| curative | See product label | Insecticides registered for armyworm in lawns, applied late in the afternoon when caterpillars are active. Check the label lists armyworm and follow its bee and waterway warnings. | Check the label |
In the Lawn Calendar
Armyworm caterpillars feed at night and can strip a lawn in days. If you see chewed leaves or a spreading brown patch, check the lawn at dusk or after dark with a torch.
January, February, March, November, December · Tropical, Subtropical
Armyworm caterpillars feed at night and can strip a lawn in days. If you see chewed leaves or a spreading brown patch, check the lawn at dusk or after dark with a torch.
January, February, March, December · Warm temperate
Popular questions about lawn armyworm
Guides
Common questions
Will my lawn recover from armyworm?
Usually, because the caterpillars eat leaves rather than roots. Water and feed the lawn to help it regrow.
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Sources
- Native armyworm (including lawn armyworm, Spodoptera mauritia), Business Queensland, Queensland GovernmentAppearance, hosts, life cycle, the lawn threshold and recovery with fertiliser and water. Accessed 4 October 2026.
- Turf weed, pest and disease identification guide (poster), Bayer Environmental Science, hosted by Turf AustraliaArmyworm occurs in late summer, feeding at night and eating leaves down to the crown. Accessed 3 October 2026.