Army Worms

Army Worms Each summer, a troop of hungry caterpillars invade Australian lawns, advancing in plague numbers and leaving damage in their wake.

Aptly named army worms, these destructive pests pose a threat to all lawn types, feeding on healthy lawns at night.

In fact, army worms are so aggressive, they are said to be able to eat through an average lawn in two nights.

What Are Army Worms?

Army worms, also known as lawn army worms, are the larvae of the army worm moth (Spodoptera mauritia). They are a major pest of turf and pastures and are particularly problematic in tropical, subtropical, and warmer coastal areas of Australia.

Army worms typically target healthy pastures, including Couch, Buffalo, and Kikuyu, among others. Army worms will infest the best looking turf in the neighbourhood and feed on it, before moving on to a nearby lawn.

Army worm moths lay clusters of hundreds of eggs in areas adjacent to lawns, including nearby plants, walls, fences, or buildings. When these eggs hatch, young larvae descend onto the lawn on fine silk threads.

Army worm larvae start out green but become brown with lighter stripes as they mature. The lifecycle of the army worm, from egg to adult, lasts approximately six weeks, with the larvae pupating in the soil before emerging as fully grown moths.

Army worm infestations are most prevalent through the warmer months, from late spring to early autumn.

Damages from Army Worms

Lawn Damage Caused by Army Worms

Army worm larvae are renowned for eating through lawns at a rapid rate. Working as a colony, the larvae are most active at night, when they strip the grass leaves, leaving unsightly bare patches across a previously healthy lawn.

Damage caused by army worms is mostly seen in spring and summer, although it may extend into autumn if the warm season is extended. Army worms damage typically appears as a small patch of light-brown, straw-like grass, often along the outer edge of the lawn. However, thanks to their army-like strength, this damage will rapidly expand radially across the lawn, with the complete decimation of the lawn in a matter of nights. 

Larvae tend to hide in the lawn thatch during the day and will curl up and lie still if disturbed. 

Army worms may also attack other types of plants and vegetables.

Detecting Army Worms in Your Lawn

Lawn Worms in Grass

As army worms are dormant at the soil level during the day, it can be hard to detect these pests before damage has already been done.

Signs that you may have army worms include evidence of skeletonised leaves, chewed leaf tips, scalloping of grass leaves along the margins, or complete defoliation of the plant.

Larvae faeces, known as frass, is also a sign of army worm infestation. These may look like tiny green-yellow pellets within the lawn.


Testing Methods to Check for Army Worms

There are several ways to determine whether you have army worms on your lawn.

One method is to pour a mixture of water with detergent over a small area of the lawn. You should then monitor the area for 10-15 minutes for the appearance of caterpillars on the surface of the lawn.

Alternatively, you can go hunting for army worms at night. Armed with a good lawn, you should survey the lawn at ground level for signs of active caterpillars. Begin the search at the damaged area of turf, and spread outwards from there.

Army Worm Moths

Another sign of possible caterpillar infestation is the presence of adult moths at night. Adult army worm moths will lay their eggs at night, so a large population of moths seen flying around your garden at night may be an indication of an army worm invasion.

If you are unsure whether you have found army worms on your lawn, you may find it useful to gather some caterpillars in a container and take them to your local garden centre for positive identification. Your garden centre expert will also be able to advise on the best insecticide for your lawn.

Early Monitoring

The key to controlling army worms is to act early before damage is done to your lawn.

If you are concerned about army worm infestation, it is advisable that monitoring and detection activities start with the onset of warm weather.

Birds can be reliable indicators of pest infestations. If you have noticed many birds pecking through your lawn, they may be feeding on army worm larvae.

How to Kill Army Worms

Once army worms have been identified, they should be treated with a lawn insecticide which is available for purchase from online garden stores and nurseries.

Acelepryn is an effective insecticide that can be purchased through our myhomeTURF online store.

The insecticide is mixed up and applied to the lawn just before dusk. Ensure to allow yourself enough time to finish the entire lawn treatment before dark. The treatment is then lightly watered into the lawn so it can reach down to the base of the thatch layer. The poison is then ingested by the Army Worms as they are feeding on the lawn. Be careful not to overwater, this will simply wash the poison away, and it will not be ingested by the caterpillars.

A spray kit is a fast and effective way to apply all your liquid lawn care products; an easy-to-use option is the Solo 7L Manual Sprayer that comes with a quality pressure sprayer. Spray indicators such as Blazon allow you to clearly identify where you have applied the spray. myhomeTURF also recommends a surfactant such as the Wetter 600 to increase the activity and efficiency of liquid chemicals.

Recommended Products

Acelepryn GR

Acelepryn GR 10kg Bag is a superior granular formulation that is unmatched in controlling season long grub and caterpillar control in one single application. Acelepryn GR 10kg is suitable for ZoysiaKikuyuCouch and Buffalo grasses. Always read the safety directions and instructions on the product label before use.


Indigo Rumbler 100SC 5L

Indigo Rumbler 100SC 5L is an effective broad-spectrum insecticide in a suspension concentrate formulation which contains the active ingredient Bifenthrin (100g/L). Indigo Rumbler 100SC is suitable for use on Zoysia, Kikuyu, Couch and Buffalo grasses. Always read the safety directions and instructions on the product label before use.


Repairing Damage from Army Worms

The life cycle of the army worm, and its moth parent, is very rapid, and as such, it is possible that multiple infestations can occur over the warmer months of the year. Ongoing monitoring is recommended from spring through autumn, and any infestations should be treated as soon as army worm is confirmed.

Despite doing extensive damage to the leaves of the lawn, army worms typically do not cause damage to the grass roots. Water and fertilise your lawn appropriately to help with lawn recovery.

Army worms are a significant pest of Australian lawns, often doing the most damage during warm summer nights. These ravenous pests will quickly destroy an entire lawn if not intercepted, so early detection is key. If you suspect army worms in your lawn, you should confirm with monitoring, and treat your lawn with an appropriate insecticide. Once you have treated the infestation, help to restore your lush lawn with watering and feeding.

For more information on leading pesticide treatments for your home lawn, visit myhomeTURF’s online store.

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