Identifying and Controlling Argentine and Darwin's Ants

Argentine and Darwin's ants have only become established within Tasman District within the last two decades but have spread rapidly through urban areas and are starting to spread onto rural land.

Despite an aggressive campaign to contain them within the urban areas, they have continued to spread, and the present tools are not providing effective control. There is concern about their impact on activities in homes and gardens, in resthomes and hospitals, and their potential effect on horticultural crops and on native fauna.

These two species of ant have been included in the Regional Pest Management Strategy because of their potential impact. Occupiers of ant-infested properties are required to control them by baiting. Most householders have found that baiting with Xstinguish has produced very good results that will give up to two years control of Argentine ants and up to four years control of Darwin's ants. The best results are achieved by baiting at a time when ant populations are peaking and food for ants is in short supply and by coordinating with neighbours.

Contact the Biosecurity Team, Tasman District Council

Identifying Argentine and Darwin's Ants

Argentine and Darwin’s ants are a honey brown colour when viewed in sunlight. Most of the more common house ants are black.
Argentine ants are slightly bigger (2.5 – 3mm) than Darwin’s (2.0mm). Darwin’s ants give of a strong odour when crushed.
Both species form multi-queen colonies and will become completely dominant within a couple of years of arrival in an area.
Both species build nests underground, usually within a few metres. Their nests will be distributed throughout a section with a preference for barked areas, shrubberies and compost heaps.
Both species react frantically when their nest is disturbed.
Both species will trail up shrubs and trees to “farm” (tend and protect) scale insects and aphids in return for honeydew.
They forage to seek food and their trails are generally located along edges e.g. curbing, retaining walls, pathways, drives, cracks, garden edging, up shrubs and trees and up your house’s outside foundations or wall to an entry point. They will travel indoors to seek food if outdoor supplies are limited.
Xstinguish is effective because the workers will take back the bait to the queen, larvae and pupae, and kill the whole nest.

Using Xtinguish Bait to Control Argentine and Darwin's Ants

Having identifed Argentine or Darwin’s ants on your property, you can either treat them yourself or get a professional pest control operator to do the job for you.

To achieve better than a 90% control, the whole section should be treated except inside the house and garage.

“Xstinguish” Ant Bait will give a high level of control when applied correctly. Read and follow the directions on the cartridge label regarding Precautions, Disposal, First Aid and Directions for Use. It is available in 125 gm tubes and 325 gm cartridges; the cartridge is dispensed with a caulking gun.

How the Bait Works

Xstinguish bait contains protein, carbohydrates and a slow-acting toxin; workers scavenge for protein when feeding larvae and queens and share carbohydrates amongst themselves. This ensures that the toxin is distributed throughout the nest before it starts to affect the ants and trigger a bait rejection process.

When to Bait

Baiting achieves best results when undertaken during the warmer weather between December and late March. High ground temperatures and warm dry weather ensure a high level of ant activity, maximising uptake before bait rejection occurs.

Bait uptake may be limited if there are planty of other food sources around. It takes 2-3 weeks to achieve the full efect of baiting and the colony enters a state of confusion towards the end of this period when eggs, pupae and larvae are moved around.

Baits are most palatable when moist and this is best achieved by laying bait in the late afternoon or early evening, as ants forage at night during warm weather. If bait is laid earlier and exposed to direct sunlight, it should be covered to slow drying.

Bait Size

Use small blobs of baits (about 1 cm , the size of a small finger nail). If exposed to sunlight, we recommend that the baits are covered to slow the drying process and making them unattractive to the ants. Use small pieces of bark, sticks, a leaf or small pebbles.

Where to Bait

To achieve a 90% + knockdown, use 2 metre spacings in the most situations:

House foundation surround.
Edges along paths and gardens.
Driveway edges.
Driveway cracks or grooving.
Vege gardens (if not being regularly dug or disturbed).
Shrub/ fower gardens.
Lawns.
Street frontage footpath area – both sides.
Street frontage grassed areas.
‘Glass’ house – inside and around outside edge.
Garden sheds – around outside edge.

Closer Spacing Should be Used in the Following Situation:

Barked garden areas – 1 metre spacing.
Compost bins – 1 metre spacing around bins and in the mature mix.
Pot plants – several closely-spaced baits at the base or around the top.
Water toby – several closely-spaced baits inside or around the outside edge.

Helpful Hints for Successful Baiting

A 325g cartridge will cover two small (500 sq. m) sections.
Allow approximately 2 hours to bait an average sized section properly.
If purchasing a caulking gun, we recommend a pressure-release, non-dripping variety.
Use secateurs to cut the end of the bait cartridge, just above the thread and cut the nozzle near the tip – it can always be enlarged if necessary.
Ensure all baits are covered to prevent premature drying.
Don’t mow your lawn the week prior to your control. The longer grass will help shade the bait when you put the bait nozzle in the grass and save a lot of covering.
Don’t water baited areas until at least the following day.
Cover baits in the cracks or grooves of driveways with a small stone or piece of bark to prevent it from being stood on. Keep baits away from the normal vehicle wheel tracks.
When baiting along grass/concrete edges (unless neatly trimmed), scuff the edge of the grass up, lay the bait underneath and gently let the grass back down on the bait.
In bark gardens, the nozzle can be just pushed under the surface bark to cover the bait.
There is no need to bait the surface of large concrete or gravel areas – just along any cracks or grooves and around the outside edge and weedy areas.
We suggest keeping children and dogs out of the baited area for at least 24 hours or until the bait has gone hard.
The bait is toxic to fish and aquatic organisms, so keep all bait out of any channels that drain into your pond and at least 1 metre away from the edge of the pond. Don’t hose bait into the storm water drain.

Further Information

The following are technical reports about Argentine and Darwin's Ants