Residents of Paekākāriki have recently confirmed the presence of Argentine ants in the village and they may have been here, spreading, for several years already.
Argentine ants are an invasive species from, you guessed it, South America. They got to New Zealand from Australia via an unknown pathway in 1990. They are one of the world’s top 10 invasive species and have never been eradicated anywhere in the world. Their nests contain multiple queens. Most concerningly, the invasive populations lack the genetic diversity of their homeland ancestors so when new populations encounter existing ones, they recognise each other as kin and form super colonies. This is what we want to avoid in Paekākāriki.
Argentine ants can build up to huge numbers because of the multiple queens and they are an extreme nuisance in domestic situations. For example, they are a pest within houses, getting into cupboards, sealed jars and electrical areas. Other examples include people being unable to garden or hold social events because of aggressive swarming. These ants will give you a nip that you will definitely feel.
Argentine ants are competitors for resources in the environment. They outcompete local ants and dominate the ecology of the gardens they invade. They collect large amounts of nectar from flowering plants and trees, reducing its availability for bees, butterflies and birds. They are known to reduce the invertebrate fauna in your garden or lawn so your friendly blackbird will find feeding there more difficult. They are a direct threat to the lizard populations that cling on in the village. A resident with a known infestation on Wellington Road no longer has a single worm in his compost bin thanks to these invasive pests.
Argentine ants will spread naturally about 150m a year, but this can be rapidly increased when they are spread by people via movement of potted plants, mulch, old stacked timber, and such like. So far in Paekākāriki we know they are on Wellington and Tilley Roads, between Cecil and Ocean Roads. They’re on Paneta Street and, possibly, on Haumia Street as well.
We want to slow their uncontrolled spread and prevent them from establishing in high-risk locations like the Paekākāriki School nursery. Greater Wellington Regional Council has told the Friends of Queen Elizabeth Park that if the ants infest their nursery in the Park, it will need to be shut down. We don’t want to risk that for our school’s biggest fundraiser.
We are a community full of gardeners and conservationists. These pests pose a threat to the environment we value. We do not want them getting on to the Paekākāriki escarpment, nor out to Kāpiti Island.
Until now, we had no idea they were here. Now we know, so it is up to us to ensure our special places are protected and that these pests don’t proliferate and become a super colony.
Greater Wellington does not fund control on private land. It has, however, offered the following advice:
The current recommendation is to carry out ant control twice per year (Spring and Autumn) and ideally coordinate the timing of this with neighbours to minimise reinvasion. Control should involve putting bait at intervals of one to two metres everywhere that ant trails are found. This needs to be done when the weather forecast allows enough dry weather for the bait to be consumed (at least a couple of fine days) and ideally put the bait where it won’t be taken by blackbirds or pet dogs before the ants get to eat it.
Biosecurity is now a top priority for the village. However, there is no absolute feature that can solely identify Argentine ants in the field. If you think you have them, the below features are helpful to look out for:
- Workers are about 2–3 mm long and a uniform light-brown colour (compared with the common black species found foraging in urban areas in New Zealand).
- The ants move quite fast (not ponderous).
- They walk in defined continuous trails (not erratic ‘crazy’ behaviour of running about in circles)
- They have only a slight greasy odour when crushed, as opposed to the strong formic acid smell of some ant species.
Landcare Research has a very helpful website with lots of options for control and bait. If you think you have an infestation, please get in touch. Predator Free Paekākāriki is offering a central point of contact to help respond to this pest. Populations quieten down over winter so we need to be ready to strike in Spring.
