Invasive ant species tend to be multi-nest, multi-queen species. This makes them very difficult, if not impossible to eliminate, even using a combination of products. Here are 4 of the top invasive ant species in Australia than every pest manager should know…



To successfully deal with ant infestations and keep your customers happy, it is important to understand the species of ant you are dealing with.

Different ant species have different behaviours, which can impact the level of control you will achieve. Colony structure is a key factor that influences both treatment techniques and the level of control than can be achieved. For example, some ant species live in colonies that are supported by a single queen, whilst others are supported by multiple queens (polygynous). Single queen colonies are often easy to control, but polygynous species will often dominate an area with numerous nests over a large area. Even if nests around a building are controlled, such species can quickly re-invade. In such situations, total long-term control will not be possible. You will need to advise your customer that regular re-treatments are required to ensure their homes have minimal interruption from ants.

The common, most destructive, global invasive ants species all have this polydomous (multi-nest), polygynous (multi-queen) colony structure. Their biology allows them to quickly dominant local environments where conditions are suitable. Although red imported fire ants are perhaps the invasive ant with the highest media profile, there are some more common invasive ants that pest managers will come across on a daily basis. Here are four of the most common…

Argentine Ant (Linepithema humile)

Argentine ant


  • Distribution: Southern Australia (NSW, VIC, SA, WA, TAS), approximately as high as Sydney on east coast and Perth on the west coast.
  • Colour: Light to dark brown.
  • Size: Workers are about 2.5mm long.
  • Single, flat raised petiole

Key behaviours:

  • Argentine ants bite instead of sting, and drive other ant species out of the area.
  • Young are produced in spring and increase in numbers up until autumn.
  • They follow food trails for long distances on wide, slow moving trails.
  • Alates (reproductive kings and queens) are produced in early spring before the workers. They mature within three months and mate soon afterwards, mating in their nests, so no swarming is seen.

Food preferences:

  • Prefer sweet foods but will also eat live and dead insects, meats, cereals and damaged fruit, with higher protein requirements during egg production in the warmer months.

Coastal Brown Ant (Pheidole megacephala)

Coastal brown ant


  • Distribution: Eastern seaboard, Darwin, Perth and some inland towns.
  • Colour: Yellow brown to brown.
  • Size: Minor workers are 1.5-3.0mm long, major workers 3.5-4.5mm.
  • Dual node petiole.

Key behaviours:

  • Nest in soil along pathways around the house, including gardens and walls.
  • Excavate soil, leaving unsightly mounds along footpaths and other paved areas.

Food preferences:

  • Will eat a wide range of foods but show a preference for oily foods and protein.

Pharaoh ant (Monomorium pharaonis)

Pharaoh antIdentification:

  • Distribution: Australia wide, more common in warmer areas
  • Colour: Yellow brown with brown abdomen. Black eyes.
  • Size: Workers are 1.5-2.0mm long
  • Dual node petiole

Key behaviours:

  • Colonies proliferate by budding – a number of queens, workers and brood leave the main colony to set up a new nest.
  • New colonies are often formed through fragmenting, which occurs when nests have been disturbed, for example, as a result of insecticide spray treatments.
  • Lays well–defined trails, often associated with heating systems.
  • Will often nest indoors, especially in heated buildings, with nests located in wall cavities. They are often found in hospitals and places associated with humid conditions.
  • Individual nests may consist of a few thousand workers, but colonies can include up to 300,000 individuals.

Food preferences:

  • Preference for high protein foods such as meat, blood and dead insects, and some fats.

White footed Ant (Technomyrmex difficilis)

White-footed house antIdentification:

  • Distribution: East coast of Australia, including Tasmania.
  • Colour: Dark brownish and black colour with yellow-white feet.
  • Size: Workers are 2.5-3.0mm long.
  • Single node petiole.

Key behaviours:

  • Very difficult to eradicate – a colony has huge reproductive capabilities and can contain up to a million ants.
  • Tend to spread out into satellite nest in nearby locations.
  • Baits often ineffective – the nest includes large number of intercastes (reproductive females) and the level of trophallaxis is unclear. They use trophic eggs as a food supplement.
  • Ideal nesting locations include in trees, under loose bark or plant debris, nearer the home in attics, under roof shingles, in wall voids, along fences and in outdoor furniture.
  • Often seen foraging for food in large numbers, usually at night in warmer weather.

Food preferences:

  • Primarily sugar feeders, attracted to sweet substances such as plant nectars, flowers, sweet human foods, aphids and mealy bugs that secrete honeydew.

Tips for effective treatment

Once you’ve identified the ant species, locating the entry points is key to choosing the right treatment program for your customer’s ant problem. Other than obvious entry points such as windows and doors, the building construction method can provide ants with numerous ingress points, such as wall voids, pipe entry points, slab joins and conduits. Ants are also generally attracted to moisture, which means you are likely to find the source of the ants – that is, nests and ants runs – located near plumbing or garden beds.

So, once you’ve identified your species and located the ingress points, what products will produce the most effective result? This will depend on the species and location of application. To get you started, here are some options for common treatments.

Indoor treatment

If strong trails are present, the placement of baits can be a good option. For ants with a sugar preference, Optigard or Advion ant gels are a good option. Baits can also be used in cracks and crevices where ants are present or have recently been seen. Trails and their surrounding areas can be spot-treated with a non-repellent insecticide such as Arilon.

Sometimes, it may be necessary to treat entry points to deter ants from entering the building. Obvious entry points include around doors and windows frames, weep holes or even in subfloors and under the eaves and awnings. The use of non-repellents is less essential in these areas and a quality pyrethroid product such as Demand can be an ideal choice.

Outdoor baiting and spot treatments

To get on top of infestations, when the nest cannot be located, bait provides the best option. The choice of bait will depend on the species and time of the year, but a good starting point is to try either Advion or Optigard gel. Even for ants foraging on protein or oils, a sugar based bait can be readily accepted as an alternative and different food source. Place baits adjacent to strong foraging trails outside the building. Ants will ingest the liquid component of the gel, or physically take the solid component back into the nest for further feeding (and insecticide transfer) to nest mates.

For direct nest treatments, use a general purpose insecticide such as Demand to liberally treat nest areas and inject directly into the colony. For areas of sparse ant activities that may be linked to the problem, treating soil surfaces can be treated with an non-repellent spray such as Arilon.

Inspect garden beds, landscape ornamentals and plants – such as palms and succulents – that are close to the home, as sources for water and food. Items such as fertiliser, manure, flowers or plants with naturally occurring sticky sap can also be a commonly overlooked as a source of sustenance for ants. If ants are active in these areas, treat with an appropriate spray, normally a non-repellent labeled for such areas (eg. Arilon).

Caution should be taken with native and non-native pollinators, for example, wasps, butterflies and bees. Other pests such as honeydew-producing insects, can also attract and encourage ant populations. These tertiary insects may need a differing treatment approach, so be sure to consult the product label or a local horticulturalist.

Perimeter application

Perimeter treatments to control and exclude ants need to be comprehensive. Demand insecticide can be very effective as perimeter treatment, especially when ants are trailing from adjacent properties or structures. The high tech formulation leaves a high density of microcapsules sitting on the treated surface, which rupture when contacted by ants. Being non-repellent, Arilon provides a very different alternative to Demand and can be very effective when used in combination with baits.

Whereas these treatments can provide permanent solutions to ant problems cause by single queen colonies, for the invasive ant species, with their multi-nest, multi-queen colony structure, not only should combinations of products be used, but regular re-treatments will be required to keep the ants at bay and excluded from the building.

Click for more information on Syngenta ant solutions

Mike De Luca, Technical Manager – Lawn & Garden, Professional Pest Management