If your lawn is suddenly turning brown, thinning out, or showing unexplained patches of damage, lawn pests could be the culprit. In Australia, some of the most common turf-damaging insects include Black Beetle larvae, Armyworm, and Sod Webworm.

In this guide, we’ll walk through exactly how to perform a soapy water test step-by-step, what results to look for, and how to take action if pests are present.

Why Use a Soapy Water Test?

The soapy water test is a widely used diagnostic method among lawn care professionals and enthusiasts because it:

• Quickly reveals hidden lawn pests

• Helps confirm whether insects are actually causing damage

• Prevents unnecessary pesticide applications

• Takes less than 10 minutes to perform

Many insects hide in the thatch layer or topsoil, making them difficult to detect without this test.

Signs Your Lawn May Have Pests

Before performing a test, look for these common warning signs:

• Irregular brown or dead patches

• Grass that pulls up easily like loose carpet

• Increased bird activity feeding on your lawn

• Chewed or ragged grass blades

• Damage appearing very quickly

These symptoms are commonly associated with pests like black beetle larvae, armyworms, and sod webworms.

How to Do a Soapy Water Test (Step-by-Step)

Step 1: Gather Your Materials

You’ll need:

• 10 litres of water

• Dishwashing liquid

• A bucket
  

Avoid antibacterial or heavily fragranced soaps, as simple dishwashing liquid works best.

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Step 2: Mix the Soapy Water Solution

In a bucket:

1. Fill with 10 litres of water

2. Add a good dose of dishwashing liquid

3. Stir gently to mix

The soap works by irritating insects and disrupting their breathing, forcing them to the surface.

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Step 3: Select a Test Area

Choose an area where you suspect pest damage.

The ideal test patch should be on the edge of the patch that is struggling where it starts going back to healthy.

If your lawn has multiple damaged areas, test several spots to confirm pest activity.

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Step 4: Apply the Soapy Water

Slowly pour the solution over the test area until the soil becomes saturated.

Make sure the water penetrates through the grass canopy and into the thatch + soil layer where insects hide.

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Step 5: Watch for Insects Emerging

Wait 2 - 3 minutes and observe the area closely.

If pests are present, they will begin emerging from the soil.

Common insects you may see include:

Armyworms

• Green or brown caterpillars

• Up to 4cm long

• Often have spots on the back

Sod Webworms

• Smaller caterpillars (10–20mm long)

• Often pale green or beige

• Wiggle rapidly when exposed

Black Beetle

• Black beetles around 10mm in length

• Shiny, smooth black shell
  

Pro Tips for Accurate Results

To improve the reliability of your soapy water test:

✔ Test early morning or late afternoon
✔ Avoid testing during extreme heat
✔ Test multiple areas of the lawn
✔ Repeat the test if damage spreads

These steps help ensure you accurately diagnose the problem before treating the lawn.

Treatment

If you have identified any of the above pests you can use the below products to treat them.

Quarterback - up to 6 months residual protection

Acelepryn - up to 6 months residual protection available in granular form.