Red imported fire ant (Solenposis invicta) in Australia

red imported fire ant worker image

Pest Snapshot - Red Imported Fire Ant

  • Scientific name: Solenopsis invicta
  • Identification: Shiny red / brown ant with darker abdomen. Size: 2.0 – 6.0 mm. Create visible nest mounds with no obvious entrance.
  • Health threat: High
  • Bite / sting pain: Very painful sting that get create pustules and potential anaphylatic shock
  • Difficulty to control: Moderate
  • Diet: Oil and protein
  • Nest locations: Outdoors under objectives, next to vertical structures in grassed areas, in pastures and lawns
  • Colony structure: Both single queen, single nest and multi-queen, multi-nest
  • Main pest season: Spring – Autumn
  • Indoor/Outdoor pest: Outdoors

Red imported fire ants are a reportable pest. Although the current area of infestation is in south east Queensland and northern New South Wales, anyone suspecting they have seen a fire ant nest should contact their state Biosecurity department.

Information for Queensland residents:

Early detection is essential to control the spread of fire ants. Under the Biosecurity Act 2014, fire ants are a category 1 restricted pest and you are required to notify Biosecurity Queensland if you think you see them. Phone Biosecurity Queensland on 13 25 23 or complete the online yard check report form. There are a variety of options for fire ant treatment for homeowners. More information on fire ant management in QLD.

Information for NSW Residents:

There are current infestations under management in South Murwillumab and Wardell. All NSW residents and anyone entering NSW from QLD need to be comply with the NSW Biosecurity (Fire Ant) Emergency Order.

More information on the National Fire Ant Eradication Program.

Tend to build nests in disturbed areas, often next to rocks, logs, posts, pavers and paths. Will also build nests in lawns / pasture areas.

Latest information on where fire ants have been found in Australia and New Zealand.

It prefers moist, disturbed habitats – areas around human population are ideal. Typically, it  nests outdoors in soil and under rocks / pavers. Sometimes it will nest indoors in wall cavities and plug sockets.

There are two variants of the red important fire ant:

  • Monogynous colonies: Single queen, single nest variant

Monogyne nests can contain up to 250,000 individuals and produce alates (flying ants) that can disperse over 500 m before mating and setting up new colonies. They will defend their territory aggressively against other ants (including other fire ants).

  • Polygynous colonies: Multiple queen, multi-nest variant

Polygynous colonies can contain hundreds of queens and create new nests through budding – a queen takes a few workers and brood to set up a nest nearby. Through this process the polygynous variant can create super-colonies with a mound density of 220 mounds per hectare containing up to 50 million ants.

Both variants are present in the Queensland incursion.

New research has uncovered how a supergene explains fire ant colony structure.

Colour: Shiny red/brown to dark brown (on the abdomen)
Size: 2.0 – 6.0 mm (workers are of variable size)
Nodes on petiole: 2

Their colour and variable size of worker are key identification features.

Red imported fire ants show a preference for protein / oil, feeding on insects and other animals (alive and dead) and seeds. However, they show a preference for carbohydrate in the cooler months, when presumably they don’t require protein for nest growth. They will tend sap feeding insects to collect honeydew and feed on plant nectaries to get this carbohydrate.

Their nests, once 1-2 years old, become visible as a noticeable mound of dirt which has an open structure with no obvious opening. When the nest is disturbed the ants pour out of the nest in a highly aggressive manner.

  • Red important fire ants have a very painful sting, a bit like a bee sting. Individual ants will sting multiple times and with ants swarming over potential victims, they can receive hundreds of stings
  • Like a bee sting, victims can suffer allergic reactions to the sting with potential anaphylactic shock

The general public can help prevent the spread by remaining vigilant and reporting any suspected infestations.

In addition, the prevention measures legislation by the government restrict the movement of soil and materials from the infestation areas.

  • Little fire ants (Wasmannia auropunctata) are another invasive pest with a couple of areas of incursion in Queensland

Being so small, finding little ant nests if very difficult. The best way is using detection dogs and sausages! Learn more about how to detect little fire ants.

  • The tropical fire ant (Solenopsis germinata) is also an invasive pest but is now considered established in the Northern Territory and it not being treated by the government

A history of red important fire ants, their potential impact and control programs – The fire ant threat in Australia.

The Eradication program is using fire ant detection dogs.

Official information on the National Fire Ant Eradication Program

2022 fire ant program update

Go to the ants page for more species of ants.

How to get rid of fire ants - Fire ant treatment:

All fire ant treatments come under the control of the Biosecurity department of the Queensland Government. Biosecurity have an ongoing baiting program to treat infested areas several times a year. They also have a number of teams to treat new infestations reported by the public.

If a homeowner, business owner or farmer suspects they have fire ants on their property, they should submit a report to Biosecurity. They will send out a team to confirm (or otherwise), collect a sample for identification / genetic analysis and carry out a treatment.

However, it can take several weeks for Biosecurity to complete an assessment. If the property owner cannot or doesn’t want to wait, two self-management options are available:

  • DIY fire ant treatment
  • Engage a professional pest manager (who has completed the Biosecurity fire ant training) to carry out the treatment

DIY Fire Ant Treatment

If you intend to treat the problem yourself, one of the registered fire ant baits should be used. Follow the instructions on the label and apply the bait when the ants are active, making sure the ground is dry and no rain is forecast.

Professional fire ant treatment

By engaging a pest professional it provides the benefit that they should take care of the treatment and all reporting requirements. Professional Pest Managers are also able carry out direct nest injection treatments as well as bait treatments. Direct nest treatments will be more expensive but will eliminate the nest immediately. The other advantages of using a professional is that they will inspect your entire property for fire ant nests you may have missed and will also be able to carry out other pest control services at the same time if you so wish.

Fire ant bait

Fire ant baits are granular baits that contain an attractive food source and slow acting insecticide. The ants take the baits back to the nest where it is feed to other nest members and importantly the queen – kill the queen and you kill the colony.

It can take a couple of weeks to completely eliminate the nest, Using baits are a smart way to control fire ants as you do not have to find every single nest – by spreading bait over the infested area the ants will find the bait taking it back to the nests.

However, it is important to apply enough product for the number of nests / fire ants present (sometimes a second application is necessary). It is also important to make sure the bait is only applied to dry ground and when fire is not forecast for 12 hours or so – fire ants don’t like soggy bait!

Red Imported Fire Ant FAQ

Fire ants are a shiny red / brown ant, typically with a dark brown / black abdomen. The worker ants come in a range of sizes from 2.0 mm long to a large 6.0 mm long worker, with large heads.

red imported fire ant worker
Large fire ant worker

Fire ants start to build an obvious nest mound after only a couple of months. They product a mound of dirt with a crispy outer layer, but will no obvious entrance / exit holes. As the nest matures it can grow to 60 cm or in diameter and 30 cm or more high (although sometimes the next can appear as a flat area of bare ground). The mounds will be built in open pasture / areas of lawn in large infestations, but often they will be built next to hard objects – beside logs and tree stumps, fencing, edge of pavements, etc.

The way to confirm identification of a fire ant nes is to probe the mound with a stick – ants will emerge rapidly in great numbers, attacking the stick aggressively.

fire ant nests The distinctive nest mounds made of dirt, of red imported fire ants

The easiest way to identify fire ants is by spotting their nests. Even after a few months, a nest mount starts to become visible. They produce a mound of dirt, often against a vertical hard objective with no obvious entrance. There are no other ants in Australia that produce nests like this. If you probe the nest with a stick (be careful), the ants will erupt from the nest in an aggressive manner.

As the ants typically forage at ground level amongst the grass, they can be hard to spot… until you get stung! Although it may be diffcult to tell fire ants from some other ant species (to the untrained eye), their aggressive nature and very painful sting is a big giveaway.

Fire ants are an invasive species to Australia. Without any natural predators and their rapid rate of reproduction, they will spread rapidly. The climate of much of Australia, especially the coastal areas, is ideal for fire ants.

If they become established and spread, they will have three big impacts on the Australian way of life:

  1. They will seriously impact the ability of people to enjoy grassed areas. Their stings are very painful and each year it is likely there will be a couple of deaths from anaphylactic shock.  Areas will need to have regular treatment to keep them fire ant free.
  2. Agricultural and farming areas will be serious impacted – crops will be difficult to harvest and livestock will be affected.
  3. Many native wildlife species will be largely eliminated from infested areas – in particular many invertebrates, lizards and ground dwelling birds.

Fire ants can be killed directly with nest injection of insecticide or through the use of fire ant baits, which can be used to treat individual nests or treat large areas of infestation.

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