Army Worms Pest Control and Treatment

Army Worms Pest Control

Army worms are caterpillars that are the larval stage of several moth species. They are notorious agricultural and garden pests, capable of stripping large areas of grass, crops, and pasture in a very short time. Their name comes from their habit of moving in large groups, like an “army,” devouring everything in their path.

In Australia, army worms are a common pest in lawns, sports fields, farms, and pastures. If left untreated, they can cause severe damage to turf and crops, leading to costly repairs and reduced yields.

What Do Army Works Look Like? 

Army worms vary in colour but are typically green, brown, or grey with distinct stripes running along their bodies. They can grow up to 40 mm long and have a smooth, cylindrical shape. The head is usually darker, sometimes with a mottled or patterned appearance.

At night, they are most active, feeding on grasses and crops before hiding in soil or thatch during the day. When mature, they pupate in the soil before emerging as brown moths that continue the breeding cycle.

Where Do Army Worms Live? 

Army worms thrive in warm, moist conditions and are especially common after rain. They prefer grassy areas such as lawns, golf courses, and pastures but also attack cereal crops and vegetables.

They spend the day hidden in soil, thatch, or under leaf litter, emerging at night to feed in groups. Infestations often spread quickly as larvae migrate in large numbers across paddocks and lawns. In favourable conditions, several generations can develop in a single season, leading to repeated outbreaks.

Common Types of Army Worms in Australia

Australia is home to several species of army worms, all of which are destructive pests to lawns, crops, and pastures. These caterpillars feed in large groups, stripping grasses and crops bare almost overnight. Infestations are most common in late summer and autumn, particularly after rainfall when conditions are warm and humid.

Army worms can cause costly damage to turf, sporting fields, and agricultural land, making early detection and treatment essential.

Below are the most common types of army worms found in Australia and why they are a problem.

Common Army Worm (Mythimna convecta)

How they look
Common army worms are green to brown caterpillars with three light-coloured stripes running down their back. They can grow up to 40 mm long.

Where they live
They are widespread across Australia, infesting cereal crops such as wheat, barley, oats, and maize, as well as pastures and lawns.

Why they are a problem
Common army worms are highly destructive to cereal crops. They chew through stems and leaves, causing crops to lodge (fall over), which makes harvesting difficult. They can also devastate lawns and pastures when populations are high.

Fall Army Worm (Spodoptera frugiperda)

How they look
Fall army worms are brownish-green with a distinctive inverted “Y” marking on their head and dark spots on their body. They grow up to 40 mm in length.

Where they live
This invasive species was first detected in northern Queensland in 2020 and has since spread rapidly across parts of Australia. It thrives in tropical and subtropical regions and attacks over 350 plant species, including maize, sorghum, sugarcane, and vegetables.

Why they are a problem
Fall army worms are particularly aggressive feeders and can destroy crops within days. Their rapid spread and resistance to some insecticides make them one of the most concerning agricultural pests in Australia.

Lawn Army Worm (Spodoptera mauritia)

How they look
Lawn army worms are greenish-brown caterpillars with dark stripes running lengthwise along their bodies. Mature larvae reach about 35 mm long.

Where they live
They are commonly found in suburban lawns, golf courses, sports fields, and pastures. They prefer well-watered turf and are especially active in late summer and autumn.

Why they are a problem
These pests can devastate lawns almost overnight, leaving behind bare patches and damaged turf. In severe infestations, entire lawns may need to be reseeded or replaced.

How to Identify Army Worms Infestations 

Rapid Lawn or Crop Damage

One of the clearest signs of an army worm infestation is sudden, large patches of grass or crops stripped bare. These pests feed at night in large groups, and damage often appears almost overnight. In lawns, this looks like brown or scalped patches, while in crops, leaves may be chewed down to the stems.

Presence of Caterpillars

During the day, army worms hide in the soil, thatch, or under leaf litter. In the evening and at night, caterpillars can be seen crawling and feeding in groups. They are usually green, brown, or grey with stripes along their bodies, and may grow up to 40 mm long.

Increased Moth Activity

Adult moths lay the eggs that hatch into army worms. Seeing more moths flying around lawns, gardens, or crop paddocks — particularly at dusk — can be an early warning sign that an infestation is developing.

Frass (Droppings)

Army worms leave behind small, dark pellet-like droppings as they feed. These are often found on soil surfaces, leaves, or around damaged plants. The presence of frass in large amounts usually indicates active feeding nearby.

Spread of Infestations

Army worms move together in groups, which is how they get their name. As food becomes scarce in one area, they march en masse to new feeding grounds. This makes them capable of devastating large areas of turf or crops very quickly.

Property and Environmental Damage

In addition to damaging home lawns and gardens, army worms can devastate sports fields, golf courses, and pastures. In agriculture, they cause severe yield losses in cereal crops, sugarcane, and maize. Repeated infestations can also weaken turf and soil health, making recovery more difficult.

Signs of Heavy Infestation

In severe cases, entire lawns or paddocks may be stripped within days. Bare patches will spread rapidly, frass will be widespread, and caterpillars will be visible in large numbers after dark. Crops may collapse from stem damage, and turf may die back completely.

At this stage, professional pest control or agricultural treatment programs are essential to stop further spread and prevent long-term losses.

How to Prevent Army Worms Infestations

Army worms are one of the most destructive lawn and crop pests in Australia. These caterpillars feed in large groups, stripping grass, turf, and cereal crops almost overnight. Infestations are especially common in late summer and autumn after rainfall, when conditions are warm and humid.

Preventing army worms from taking hold is always easier than trying to restore damaged lawns or crops. By reducing the conditions that attract them and monitoring your property regularly, you can greatly lower the risk of severe outbreaks.

Keep Lawns and Gardens Healthy

Army worms are more likely to infest stressed or weakened turf. Regular mowing, watering, and fertilising help keep grass thick and resilient, making it harder for pests to establish. A dense lawn also reduces bare patches where moths can easily lay eggs.

Minimise Outdoor Lighting at Night

Adult moths, which lay army worm eggs, are attracted to bright lights. Reducing unnecessary outdoor lighting, especially near lawns and crops, can lower the chances of moths settling and starting new infestations.

Monitor Regularly After Rain

Warm, wet weather creates ideal conditions for outbreaks. Check lawns, gardens, and crops frequently during late summer and autumn. Look for chewed leaves, bare patches, or caterpillars hiding in the soil or thatch. Early detection makes treatment much easier.

Reduce Thatched Grass and Debris

Army worms hide during the day in thatch, soil, and leaf litter. Regular dethatching of lawns and clearing away plant debris reduces their shelter and makes infestations less likely to spread.

Watch for Moth Activity

An increase in moths flying around lawns or paddocks at dusk can signal that eggs are being laid. Taking note of this activity allows you to prepare and act quickly before large numbers of caterpillars emerge.

Act Quickly if You Spot Them

Army worms move and feed in groups, often destroying entire areas overnight. If you notice damage or caterpillars, act immediately to prevent the problem from spreading. Avoid waiting until damage becomes severe, as recovery can be costly and time-consuming.

How to Get Rid of Army Worms Infestations

Army worms are among the most destructive lawn and crop pests in Australia. These caterpillars feed in large groups, stripping turf, pastures, and crops almost overnight. Because they move quickly and hide during the day, infestations often go unnoticed until significant damage has already occurred.

Once established, army worms can be difficult to control without quick action. Eradicating them usually requires a combination of household or farm management practices and, in heavy cases, professional pest treatments.

At-Home Actions to Get Rid Of Army Worms

Apply Lawn or Garden Insecticides

Over-the-counter lawn insecticides can help control small infestations. These products should be applied in the late afternoon or evening when army worms emerge to feed. Granular or liquid formulations work best when watered into the soil, targeting larvae hiding in thatch and soil during the day.

Water and Repair Affected Turf

Regular watering and fertilising help grass recover after feeding damage. A healthy lawn is more resilient and can regrow once army worm numbers are reduced. In severe cases, reseeding or patching may be required to restore bare areas.

Encourage Natural Predators

Birds, wasps, and beneficial insects such as ground beetles feed on army worms. Minimising broad-spectrum pesticide use in gardens allows natural predators to thrive, providing long-term biological control.

Monitor Regularly

Because army worms feed in cycles, new outbreaks can occur after initial treatment. Inspect lawns, crops, and gardens daily during warm, wet months. Look for chewed leaves, frass (droppings), or caterpillars hiding in the soil. Early detection makes repeat treatments more effective.

Professional Army Worms Treatments

Targeted Pesticide Applications

Pest control specialists can apply professional-grade insecticides that penetrate soil and turf more effectively than DIY options. These treatments are designed to target active larvae while minimising impact on beneficial species.

Large-Scale Crop Management

For farms and commercial properties, technicians may use broad-acre spraying or baiting programs to suppress infestations. Professional formulations are often stronger and longer-lasting, offering better control of recurring outbreaks.

Integrated Pest Management (IPM)

Professionals often recommend IPM strategies, combining chemical treatments with environmental management to reduce long-term infestations. This may include improving drainage, reducing thatch, and creating conditions less favourable for army worms to thrive.

Follow-Up Inspections

Because multiple generations of army worms can emerge in a single season, follow-up visits are often required. Pest controllers can check for ongoing activity, reapply treatments if needed, and provide tailored advice to prevent reinfestation.

Call a Pest Control Professional

Army worms are not just a nuisance — they can destroy entire lawns, sports fields, and valuable crops in a matter of days. Left untreated, the damage can be costly to repair and may leave outdoor areas unsafe or unusable.

A licensed pest control company can confirm the presence of army worms, identify the species, and apply safe, effective treatments tailored to your property. They can also provide strategies for long-term prevention to stop infestations from returning.

Need help now? Book a professional army worm inspection on 1300 766 614. Our experts will assess your property, explain your treatment options, and create a customised plan to eliminate army worms and protect your lawn or crops from further damage.

Frequently Asked Questions (FAQ)

How to detect army worms in the lawn? 

The first sign is usually rapid brown patches that appear almost overnight as grass blades are chewed down. To check, pour soapy water over a small section of lawn in the evening — if army worms are present, they will quickly wriggle to the surface. You may also spot them hiding in the soil or thatch during the day.

Where do army worms come from? 

Army worms are the caterpillar stage of certain moths. Adult moths lay eggs on grass or crops, and when the eggs hatch, the larvae emerge to feed in large numbers. In Australia, outbreaks are most common in late summer and autumn, especially after rainfall when conditions are warm and humid.

Are army worms harmful to humans? 

Army worms do not bite, sting, or spread disease, so they are not directly harmful to humans or pets. However, their feeding can cause extensive damage to lawns, gardens, and crops, making them a serious pest for households, farms, and businesses.

What do army worms eat? 

Army worms feed mainly on grasses and cereal crops, but they also attack vegetables and pasture plants. In lawns, they eat the green parts of grass blades, leaving behind bare, brown patches. In agriculture, they can devastate crops such as maize, wheat, barley, oats, and sugarcane.