Armyworm Treatment for Lawns in Australia | How to Kill Armyworm

How to Treat Armyworm in Lawns (Australia)

Armyworm is one of the most destructive lawn pests in Australia. If your lawn has turned brown or patchy almost overnight, armyworms may already be feeding beneath the surface.

In this guide, we explain how to identify armyworm, the most effective armyworm treatments for Australian lawns, and how to prevent future outbreaks.

What Is Armyworm and Why Is It a Problem in Australia?

Armyworms are caterpillars that hatch from moth eggs laid in lawns during warm, humid conditions. They feed aggressively on grass, often moving quickly across lawns in large numbers.

Armyworm activity is most common in:

  • Late spring

  • Summer

  • Early autumn

How to Identify Armyworm in Your Lawn

Armyworm damage appears suddenly and is often mistaken for heat stress or lawn disease.

Common signs include:

  • Rapid browning or thinning of grass

  • Chewed or ragged grass blades

  • Scalped patches of turf

  • Increased bird activity

  • Moths flying up when walking across the lawn

Armyworms feed mainly at night, which is why damage can appear overnight.

How to Confirm an Armyworm Infestation

To confirm armyworm:

  1. Mix water with a small amount of dishwashing liquid

  2. Pour it over the affected area

  3. Watch for caterpillars emerging within 2–5 minutes

If caterpillars surface, immediate treatment is recommended.

Best Armyworm Treatment for Lawns in Australia

The most effective way to kill armyworm is with a targeted lawn insecticide designed for caterpillars.

Look for products containing:

These products provide up to 6 months residual protection.

💡 Tip: Always choose products labelled for use on Australian lawns and follow label directions.

When and How to Apply Armyworm Treatment

For best results:

  • Apply in the late afternoon or early evening

  • Treat the entire lawn, not just damaged areas

  • Avoid mowing 2–3 days before and after treatment

  • Lightly water in 24 hours after application.

How to Prevent Armyworm in Lawns

Regular applications of Quarterback or Acelepryn are effective at preventing armyworm as they offer 6 months residual coverage.

If prevention was not possible, early detection and treatment is key to minimising damage.

Is Armyworm Treatment Safe for Pets and Children?

Armyworms themselves are harmless, but some insecticides require care.

Fortunately Quarterback and Acelepryn have very low toxicity to non-target organisms and require no specific PPE when being applied. Keep away from waterways as it is toxic to aquatic life.

Always follow label safety instructions.

If unsure, consult a lawn care professional.

Recommended Products: 

Liquid - Quarterback

Granular - Acelepryn

Frequently Asked Questions About Armyworm

How fast does armyworm destroy a lawn?
Armyworm can cause visible damage in 24–72 hours if left untreated.

Will armyworm go away on its own?
No. Without treatment, damage usually worsens.

Can armyworm come back?
Yes. Follow-up treatments and lawn health management reduce recurrence.

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