Argentine Ant survey completed

5 September 2001

The national survey to ascertain the spread of the Argentine Ant (Linepithema humile) in New Zealand has been completed.

The latest distribution survey has found the ant has moved to two new locations in Kaitaia and Hamilton. Other North Island centres where the ant has been identified are Auckland, Dargaville, Hastings, Morrinsville, Mt Maunganui, Warkwarth, Whangaparoa and Whangarei. The ant appears to be largely absent from the South Island although small populations have been identified in Nelson and Christchurch.

The survey was based around urban centres. Main habitats where the ants have been found include transport depots, residential areas and ports. This distribution highlights the risk of spread by people. The climate through much of New Zealand is cooler than the ant's native environment. However temperature modelling suggests that Argentine ants could eventually spread throughout most of New Zealand.

The Argentine Ant was first found in Mt Smart in Auckland in 1990. Eradication was not attempted at that time because the ant was found to be widespread in several Auckland suburbs and because there was no known control method. Natural dispersal of the ant is slow, but unintentional transport by humans facilitates rapid spread over much greater distances.

Bait recently developed in Australia has raised expectations that control of the ant may be possible.

The Government has funded a MAF co-ordinated investigation into the ant. This has included a national geographic distribution survey, conducted by HortResearch and AgriQuality, which got underway earlier this year, as well as an investigation into control and treatment options and an assessment of the effectiveness of the new bait developed in Australia. The research will be used to produce a range of recommended options for management of Argentine ants in New Zealand.

Eradication trials are currently underway in Mt Maunganui (Environment Bay of Plenty), on Tiritiri Matangi Island, Hauraki Gulf (Department of Conservation), and in Nelson (Port Nelson and Landcare Research) with promising initial results.

Further research will continue this summer.

Technical and policy advisory groups met last week to review the results of the recent research initiatives and to advise MAF on further research needs.

The advisory groups were set up to help guide MAF on technical issues and to assist MAF during the development of policy including recommendations to Cabinet for management options for Argentine ants.

These groups include representatives from MAF, Department of Conservation, Regional Councils, Landcare Research, Flybusters pest control company, Ministry of Health, Ministry for the Environment, New Zealand Fruit Growers Federation, and Forest and Bird.

Argentine Ants will bite, but they are not poisonous. They are capable of completely eliminating other types of ant colonies and many other insect groups suffer significant decline. They develop large multi-nest colonies with large numbers of workers that can monopolise food sources effectively. Argentine Ants will eat virtually anything although they are particularly attracted to sweet food.

Argentine ants are serious household pests. Being attracted to sweet foods they will forage heavily around rubbish bins containing sweet food remains, and have even been known to find their way into microwaves, refrigerators and screw top jars.

Argentine Ants 'farm' populations of aphids, scale insects and other insects that produce honeydew. The ant will protect these insects from predators and may move them to new plants or parts o the plant.

The best way to tell Argentine Ants from other ants is by their trails, which are often five or more ants wide and will travel up trees and buildings. This is uncommon in other ant species. The wingless worker ant (most commonly seen) is light to dark honey brown, and 2-3mm long. The most common household ant in New Zealand is black.

If people outside urban centres where Argentine ants are established suspect they have ants on their property, they can send samples in a film canister or similar container to Landcare Research (Private Bag 6, Nelson).

Specimens should be killed using fly spray or by placing them in the freezer. Information of where the ants were found and contact details of the sender (name, address and phone number) should be included with all samples.

For further information contact:

Amelia Pascoe, Programme Co-ordinator, Exotic Animal Biosecurity or
Gita Parsot, Senior Communications Adviser

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