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Lawn Pests

Caterpillars and beetle larvae that eat grass leaves or roots, leaving brown, dying patches. Armyworm and curl grubs cause most lawn damage in eastern Australia, especially in warm, humid months.

Written by PestMan Editorial TeamTechnical review pendingPublished Updated
Main pests
Armyworm, curl grubs
Peak
Late summer and autumn
Quick test
Soapy water flush
Sign
Birds feeding on the lawn
Risk level
Low (turf damage only)

Lawn pest identification

How to recognise lawn pests

  • Armyworm: caterpillars up to about 40 mm, green to brown with stripes along the body, curling up when disturbed; active at night.
  • Curl grubs: C-shaped, creamy-white larvae with a brown head and three pairs of legs, found in the soil under damaged turf.
  • Adult beetles: African black beetles are shiny black, about 12–15 mm; other scarab beetles are brown and fly to lights in late spring and summer.

Common species in Australia

Lawn Armyworm

Spodoptera mauritia

A moth caterpillar that feeds on grass at night and can turn lawns brown within days, especially in Queensland and northern NSW in late summer and autumn.

Curl Grubs

Scarab beetle larvae (Scarabaeidae)

C-shaped, creamy-white beetle larvae that live in soil and eat grass roots, causing patches of turf that die and lift away like loose carpet.

African Black Beetle

Heteronychus arator

An introduced, shiny black scarab beetle whose larvae are a common type of curl grub. Adults also chew grass at the base and are drawn to lights.

Lawn pest overview

Lawn pests are a common reason for brown patches in otherwise healthy turf, particularly in Queensland and northern NSW. The two main culprits work in different ways. Lawn armyworm caterpillars eat grass blades, usually at night, and can strip a lawn within days. Curl grubs, the larvae of several beetles, live in the soil and eat the roots.

Telling them apart matters because the signs, timing and treatment differ. Not every brown patch is a pest problem, though. Dry weather, poor drainage, shade, fungal disease and dog urine all cause similar symptoms. See why is my lawn dying in patches.

Behaviour

  • Armyworm caterpillars hide in the thatch by day and feed at night, moving across a lawn as a front.
  • Curl grubs feed on roots below the surface; damaged turf lifts easily, like loose carpet.
  • Birds, ibis and bandicoots digging or pecking at a lawn often mean grubs or caterpillars are present.

Habitat

  • Warm-season lawns such as couch, kikuyu, buffalo and zoysia.
  • Sunny, well-watered lawns after rain (armyworm).
  • Soil under turf, especially sandy soils (curl grubs).

Lifecycle

  • Armyworm: moths lay eggs in batches; caterpillars feed for a few weeks, then pupate in the soil. Several generations a year in warm regions.
  • Curl grubs: beetles lay eggs in soil in late spring and summer; grubs feed through summer and autumn, then pupate.

Food sources

  • Grass leaves and stems (armyworm).
  • Grass roots and organic matter in soil (curl grubs).

Entry points

  • Moths and beetles fly in from surrounding areas; pests are not "brought in" except occasionally with new turf.

Infestation signs

  • Brown or straw-coloured patches that spread quickly (armyworm).
  • Chewed, ragged grass blades and caterpillar droppings in the thatch.
  • Turf that lifts easily, with grubs underneath (curl grubs).
  • Birds feeding intensively on the lawn, or animals digging.

Health implications

  • Lawn pests are not a health risk; the damage is to turf and gardens.

Prevention

  • Keep turf healthy with appropriate mowing height, watering and fertilising, which helps it recover.
  • Check the lawn regularly in late summer and autumn, especially after rain.
  • Do a soapy-water test on suspect patches early, before damage spreads.

Treatment overview

  • Confirm the pest before treating: a soapy-water flush brings armyworm to the surface, and lifting a section of turf reveals curl grubs.
  • Registered lawn insecticides are available for both; choose one labelled for the pest and turf type, and follow the label, including watering-in and keeping pets and children off as directed.
  • Avoid spraying when bees are foraging on flowering weeds in the lawn, and keep products away from waterways and ponds.
Product safety

If you use any pest product, read the label first and follow it exactly — it is a legal requirement in Australia. Keep products away from children, pets and food areas as the label directs.

Questions about lawn pests

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Sources & further reading

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