Exotic ants

Exotic ants in NT

Many exotic ants are accidentally introduced to Australia in pot plants, soil or in nests in wood products and other small spaces.

Some exotic ants have characteristics that make them especially invasive in Australia.

These include any of the following:

  • small size
  • large colony sizes, allowing them to swarm around native ants
  • aggressive towards other ants, insects and even small animals - exotic ants will often attack and force out other animals from their territory
  • choose to live near people, where they are provided with food, moisture and shelter.

There are three exotic ants in the Northern Territory (NT).

Yellow crazy ant

The yellow crazy ant is an aggressive ant that has caused declines in invertebrates and vertebrates through competition and predation.

It eats plant seeds so it affects the germination rate of plants.

Yellow crazy ants have been seen removing nectar from plants, making it unavailable for native species.

Read more on yellow crazy ants.

Big-headed ant

The big-headed ant competes with and preys on native vertebrates and invertebrates.

It also eats the seeds of plants.

Read more on big-headed ants.

Ginger ant

Ginger ants prey on native invertebrates and young birds and reptiles.

They affect plants by eating seeds, which damages the seed and affects germination.

A single ginger ant can sting many times, even after its venom sac is empty. In some people, the sting may cause a severe allergic reaction.


Impact of exotic ants

Exotic ants are a major problem around the world as they compete with native ants for food and habitat. 

They prey on other native invertebrates such as grasshoppers, butterflies, beetles and bugs. Some ants will prey on young native vertebrates such as young birds in nests or reptiles.

Exotic ants often have a vicious sting. 

In many places, exotic ants have displaced the native ants, which can affect the balance of ecosystems.


Management of exotic ants

It is difficult to manage exotic ants once they are in an area. 

The best way to control them is through prevention.

To stop the spread of exotic ants, you should do all of the following:

  • always have your luggage and goods checked by customs when you return from overseas travel
  • do not move soils and pot plants to other areas, as the soil may contain ant nests
  • clean machinery before moving it long distances - dried soil can contain ant colonies.

Yellow crazy ant

Yellow crazy ant

In the Northern Territory (NT), yellow crazy ants have been found in Darwin and Arnhem Land.

Yellow crazy ants are yellow-brown and around 4mm long. They have long legs and antennae.

Yellow crazy ants spray formic acid on their competitors or prey, which causes agitation or blindness in the animal. The ants will then swarm over the animal or insect. This acid doesn't affect people.

Yellow crazy ants are successful at invading and surviving new territory due to all of the following:

  • large population sizes - this helps to swarm native insects and other animals such as birds and lizards
  • they have many queens in their nest - all queens must be killed for the colony to be destroyed
  • they eat a wide range of food
  • they are able to find and move to food and water quickly, often before other insects and animals
  • they are aggressive to native invertebrates and vertebrates
  • they will prey mostly on insects, but also on slow moving crabs, snails, small reptiles and birds that can't fly out of the nest
  • they are not territorial to other yellow ant colonies - they will join colonies to form super colonies
  • they are very territorial and will fight with any insect that enters their territory.

Impact

Yellow crazy ants have caused declines in native invertebrates and vertebrates numbers. These declines are usually from competition or predation.

They are fast at finding food and will swarm over native animals to move them out of an area.

These ants also cause the following:

  • decline in the spread of seeds
  • increase sooty mould on trees and plants, which affects plant growth
  • reduce nutrient recycling.

Report yellow crazy ants

If you think that you have yellow crazy ants at your home, contact the Wildlife Use and Pest Animal Unit:

Phone: 08 8999 2258
Email: wildlife.use@nt.gov.au


Big-headed ant

The big-headed or coastal brown ant has spread worldwide and caused a lot of damage in new areas.

The big-headed ant is light yellow or ginger to a dark reddish brown. 

The worker ants come in two sizes. 

The smaller worker is 2mm to 3mm long, while the larger workers are 3mm to 4mm and have big heads that are out of proportion with their bodies.

In the Top End, big-headed ants prefer cooler temperatures with higher humidity. They are commonly found in urban areas, including Darwin, Katherine and Alice Springs.

Impact

Big-headed ants are aggressive and will kill native insects. By reducing insect numbers they compete with other native species that eat those insects.

They are badly affecting ant diversity through direct predation and by competing with them for food sources.

Reducing native ant numbers can have a major impact on the ecological balance. 

Native ants provide aeration and the addition of nutrients to the soil, pollination, spreading seeds and pest control.

In the Top End, big-headed ants threaten rainforests. 

At Howard Springs Nature Park the big-headed ant has eliminated 40 native ant species and reduced numbers of insects, snails, spiders and centipedes by around 85%.

Big-headed ants invade houses and can damage electrical wiring and the grouting between tiles and pavers.

In the Top End, their nest entrances are usually at the base of trees and shrubs. 

Their nests disturb root systems, dry out the soil and can lead to the death of trees and shrubs. 

When nests are in brick paving they can cause soil disturbance that can destabilise pathways.

Management

The best way to stop the spread of ants is to check items before moving them away from your home.

Amdro ant bait

Nests can be treated with the ant bait Amdro. 

Wide spreading or broadcasting of ant bait has been the best way to remove ant nests in gardens, around buildings, in plant nurseries and in non-crop farmland.

You must consider all of the following before using Amdro:

  • don't heap ant bait on the ant nest - this risks non-target animals and insects taking bait
  • when used as directed on packaging, this bait is not harmful for pets, livestock or children, but keep the bait out of reach of these when not in use
  • don't use ant bait inside bird cages, near water or in areas where it can be washed into waterways
  • don't use bait on wet ground or in the Wet Season
  • turn off sprinklers a day before using bait and don't use for a day after
  • you should use bait in the late afternoon or at night to avoid direct sunlight
  • treatment may take four to six weeks before the ants are gone
  • you will need to use bait every two to three months until ants are gone.

Coopex Residual Insecticide

Coopex Residual Insecticide is a safe pesticide to use inside homes or on areas around the home that are protected from water. 

You will need to use this pesticide every 12 weeks or until the ants are gone.

Don't disturb ants before using insecticide or pesticide. If you do the colony will likely move the queen to safety.

Pest control companies can also treat nests. You should try and treat ants with neighbours to stop ants returning.


Browsing ant

Browsing ants (Lepisiota frauenfeldi) are an exotic invasive ant species of national significance and a serious environmental pest.

They have not established in Australia but there have been several small infestations detected in the Northern Territory (NT), Western Australia and Queensland.

They are commonly found in South East Asia, including Timor-Leste.

Browsing ants are omnivorous. They are often found on the ground as well as in trees, leaf litter and infrastructure, including electrical boxes.

A distinct behavioural trait is that when undisturbed, they generally move around very slowly. When disturbed, they run around in a haphazard way.

Current situation in the NT

Browsing ants were identified in the Darwin Port region on 6 August 2015 by Australian Government biosecurity officers.

Since then, 23 infected locations have been detected. Initially, known infestations were limited to Berrimah, East Arm, Frances Bay and Wickham Point.

In September 2020, there was a detection near Kakadu which was a direct trace from the most recent detection in Darwin.

Only one infected location remains active, the other 22 have been resolved.

Treatment and surveillance

Treatment is underway at this most recent infestation and surveillance is being carried out to confirm that it has not spread into surrounding areas.

To eradicate this latest detection and show proof of freedom, funding for the National Browsing Ant Eradication Program (NBAEP) NT has been extended until December 2025.

As a result of NBAEP NT’s activities, 22 of the locations initially detected have been resolved. The remaining location is expected to be resolved by December 2025.

The Department of Industry, Tourism and Trade (DITT) has carried out extensive surveillance with help from Aboriginal ranger groups at remote sites across the NT, with no further detections.

Browsing ants

The browsing ant has all of the following features:

  • slender
  • shiny dark-brown colour
  • 3 to 4 mm long
  • long antennae
  • long legs.

Invasive ant species are considered some of the most serious global pests.

They pose a significant environmental and economic threat as they can:

  • cause native species decline
  • alter ecosystem function
  • minimise agriculture outputs
  • impact national and international market access.

Impact on industry

They can also indirectly impact any industry that relies on transporting goods or services. This includes tourism, transport, logistics, construction and mining. This is because invasive ant species can easily spread undetected through shipping containers, vehicles, equipment and other goods.

Environmental impact

Browsing ants are ideally suited to Australian conditions. They form multi-queened super colonies that can reach very large numbers and displace or overwhelm native ants and invertebrates.

This means they will outcompete local ants and insects, strip native vegetation and disrupt ecosystems.

Browsing ants also threaten the NT environment, and agriculture and horticulture industry by farming and protecting damaging pests such as aphids, mealybugs and scale insects. These insects reduce plant health and can spread serious disease. They are not harmful to humans or animals.

Browsing ants and other exotic invasive ant species can be transported through various pathways and materials.

They can travel via:

  • planes
  • trains
  • marine vessels
  • vehicles in freight
  • shipping containers
  • various equipment and heavy machinery
  • luggage
  • plant and soil matter.

NBAEP NT uses several techniques for successful surveillance and control of browsing ants.

This includes luring, observation and odour detection dogs. Using different techniques increases the chance of detection and gives greater confidence in eradication efforts.

Treatment includes a combination of granulated bait specifically for nuisance ants and a spray treatment where browsing ant activity has been detected.

Afterwards, an intensive post-treatment surveillance program is carried out. Eradication can be declared once 2 years of surveillance is carried out indicating no presence of ants.

Biosecurity is everyone’s responsibility. To help protect the NT, you should do the following:

  • Comply with movement restrictions on infested sites to prevent transport and spread of browsing ants.
  • Check vehicle and goods when leaving any site where ants may be present.
  • Check vehicles and property before moving to a new location, especially interstate.
  • Avoid transporting plant or soil matter between states or territories.
  • Watch out for exotic pests when dealing with imported goods and mail from overseas.

If you think you have seen browsing ants or exotic invasive ant species, call the exotic plant pest hotline on 1800 084 881.

You can also call the NBAEP NT program manager on 08 8999 2247 or email christopher.collins@nt.gov.au.