LawnSuite guide: Lawn armyworm: how to spot it and check before you treat
Use this LawnSuite guide to recognise the problem before deciding what to do. Armyworm are caterpillars that eat the grass leaf, mostly at night. Damage can appear almost overnight and spread across the lawn in a moving front, so it pays to confirm quickly.
How to spot it
Look for chewed leaf tips, ragged brown patches that appear fast, and damage that spreads across the lawn in a moving front. Birds suddenly taking a serious interest in your lawn is another hint.
Check for caterpillars at home
Wet-towel test: lay a soaked towel or hessian bag on the edge of the damage in the evening and lift it in the morning. Caterpillars will be underneath. Or pour a bucket of soapy water on a suspect patch; armyworm and other caterpillars come up within about ten minutes. You can also check with a torch about 30 minutes after sunset, down at soil level. These checks bring up surface caterpillars in general, not only armyworm, so identify what you find before you treat.
When to watch
Keep watch from spring. The highest risk is in late summer and autumn.
Your grass type
Armyworm can strip zoysia fast. Kikuyu grows quickly, so it usually regrows well once an outbreak is over. Buffalo and couch lawns get armyworm too.
Not the same as grubs
The long-lasting preventive protection some lawn-grub products give is for beetle larvae. Don't count on it to stop armyworm. Watch for caterpillars. If you treat, do it while caterpillars are present and feeding, with a product whose current label lists armyworm and your grass, and follow the label.
If you use a product
Confirm the pest first. Then use an insecticide whose label lists armyworm and your turf type, and follow the label.
Keep reading
Not sure it's armyworm?
Create a free LawnSuite account in your browser and photograph the patch. Photo diagnosis uses Google Gemini vision to identify the likely weed, pest or disease and shows a confidence score for each result, so you can match it to the signs on this page before you treat.