Keep ants out of plants at Great Barrier

Great Barrier residents and visitors urged to ‘keep ants out of plants’

26 April 2007

Great Barrier Island residents and visitors are being asked to help prevent the highly invasive Argentine ant reinvading Great Barrier, by ‘bathing’ pot plants before taking them to the island and being vigilant when transporting equipment like camping gear.

The second stage of the ground-breaking Argentine ant eradication programme has now been completed, with further work planned for next summer.

Jack Craw, ARC Biosecurity Manager, says Argentine ants are considered one of the world’s worst invasive pests.

“Left unchecked they reach high densities, form colonies that spread for kilometres and have devastating impacts on horticulture, lifestyle and the environment.”

“Pot plants and soil are a favourite home for ants so we are asking people to ‘keep ants out of plants’ by:

• Buying plants from Great Barrier nurseries where possible, rather than bringing them from the mainland.

• Checking plants, soil and equipment for ants before moving them to or around the island.”

The best way of finding a pot plant ant nest is to dunk the plant container in a water bath until it’s saturated; e.g. in a large bucket or a wheelbarrow. Any ants will immediately abandon the container and can be sprayed. Allow the plant to drain in an ant-free area prior to shipping. Do not ship the plant until you are sure it is ant-free through re-dunking.

If people find small, honey-brown coloured ants, please put them in a secure container, anaesthetise them in the freezer for an hour, and then post to Dr Chris Green, Department of Conservation, Private Bag 68 908, NEWTON, Auckland to be identified. Remember to include your contact details and where you found them.

Camping gear, vehicles and any equipment stored outside should also be checked for ants prior to taking them to the island.

The control programme is being carried out by Great Barrier residents, the ARC and the Department of Conservation (DoC). The programme involves baiting infested areas, and started in February.

A key part of the success of the project has been the hundreds of hours Great Barrier residents have worked as volunteers. Without this level of community support the project could not have got off the ground. The other key player in the project has been DoC entomologist Dr Chris Green. If successful, the Great Barrier programme will be one of the first known Argentine ant eradications in the world.

For more information please call ARC Biosecurity Manager Jack Craw on 366 2000 ext 8771 or Communications Team Leader Glyn Walters on 366 2000 ext 8114.

BACKGROUND NOTES FOR EDITORS

What’s the problem?

Left unchecked, Argentine ants are a major household and garden pest. Their huge numbers mean they will quickly exploit any food source available. Ants have been found in massive numbers in houses, including in refrigerators, microwaves and even down the glass spiral of screw-top jars. In the Mediterranean, a vast interconnected super-colony exists, stretching almost six thousand km from northern Italy to Portugal.

By the time Argentine ants were first discovered in New Zealand in 1990, they had already moved into so many areas it was deemed impossible to eradicate them nationally. Last year they were found on Great Barrier, a large island free of other significant pests.

• Argentine ants threaten native invertebrates and native bird species, either attacking them directly or by competing with them for resources. Argentine ants are aggressive and will eliminate other species of ants, and eat or drive away other insects.

• Argentine ants, like other ants, ’farm’ populations of plant pests like aphid and scale insects, protecting them from predators. This causes serious difficulties for organic growers who rely on biological control of plant pests. Argentine ants overseas are considered one of the worst pests of citrus, viticulture, avocado and tomato.

• In Auckland, they have been seen killing baby birds in their nests, and they will drive nesting birds from their eggs.

• Argentine ants are not poisonous, but they do bite and some people are allergic.

Where are they?

They were first discovered in Auckland in 1990. Although their distribution is still patchy, they are rapidly becoming widespread through out the Auckland urban area – including Waiheke Island. Recently they have been found in Northland, Waikato, Bay of Plenty, Wellington, Nelson and Christchurch. They were also discovered on Tiritiri Matangi, an important conservation island in the Hauraki Gulf, where they have been subsequently controlled.

They were first identified on Great Barrier in February 2006 at Mulberry Grove and subsequently found at five other locations: Mohunga Peninsula, Ocean View Rd, Medlands, another Tryphena site and Puriri Bay. Judging by the area they cover and their density, they appear to have been present for at least two years.

While there are currently no records of Argentine ants being successfully eradicated from anywhere in the world, experts here believe it may be possible within defined areas like islands. New Zealand is a world leader in establishing successful eradication techniques for invasive pest species.

What do they look like?

Argentine ants are small honey-brown ants (workers are only 2-3mm long) so the best way to recognise them is by their trails and their aggressiveness. Argentine ant trails are often five or more ants wide and travel up trees and buildings. If a nest is disturbed, armies of ants will immediately rush out to investigate. They form huge trails on the ground and up trees.

Other identifying features include:

• Small and honey-brown in colour, not black.

• High density of nests

• Active day and night

• Co-operation between nests- very unusual in ants- forming super colonies

• Out-compete other invertebrate species feeding on same food sources

• Very effective chemical defence system to deter other ant species, including much larger species.

How are they spread?

The good news is that Argentine ants cannot spread by flying; they are unusual for an ant species because there is no nuptial flight. They walk to new areas, but left to their own devices do not spread far each year.

The bad news is that they are extremely efficient hitchhikers. Argentine ants have large numbers of highly mobile queens that can invade pot plants, loose earth, freight or vehicles.

ends

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