Argentine ant: small pest has spread widely in 10 years
February 2001
MAF Biosecurity is coordinating an investigation to assess the distribution and options for management and control of Argentine ant within New Zealand, in response to growing concern over its possible effects.
What is Argentine ant and why the fuss?
Argentine ant (Linepithema humile) is native to Argentina and Brazil. It is an invasive species that has proved to be a serious household, horticultural and conservation pest outside its native range. Over the last 100 years, Argentine ant has spread to North America, Hawaii, South Africa, Europe, Australia and recently to New Zealand.
Argentine ant was first discovered, in New Zealand, in Auckland in 1990. Since its discovery, the ant has spread to other locations including Northland, Bay of Plenty, Christchurch, Wellington and Waikato. Two populations have also established on Tiritiri Matangi, a predator-free island in the Hauraki Gulf.
The severity of the threat from Argentine ant to New Zealand is yet to be established. However, a number of organisations, government agencies and private industries have shown serious concern over the potential economic, social and environmental consequences of allowing this invasive species to establish unchecked. Although natural dispersal rates are slow, other mechanisms (particularly unintentional transport by humans) are facilitating rapid spread over much greater distances.
Why Argentine ant is a pest
In the garden and orchard
Argentine ant in its natural environment feeds predominantly on nectar and honeydew, a substance produced by insects like aphids and leafhoppers. This can create problems for orchardists, particularly organic growers and others who use natural predators to control pests and are limited in the insecticides they can use (Timaru Herald, 31 Oct 2000). They may also injure flowers and various plants while searching for nectar, chew seeds and seedlings, interfere with bees pollinating blossoms in fruit trees, and invade beehives and remove honey. They have also been known to drive laying hens from their nests, kill newly hatched chickens and annoy and attack birds in aviaries and cages (New South Wales Department of Agriculture, 1977).
In the home
In developed areas, Argentine ant will eat virtually anything. They are particularly attracted to sweet foods. They will forage for food in drawers, food cupboards, refrigerators, cake and biscuit tins. They can even squirm under the edge of screw top jars and follow the grooves until they reach the contents! (New South Wales Department of Agriculture, 1977).
On biodiversity
Argentine ant is highly competitive and can displace indigenous ant species and other invertebrates through competition for food and/or predation (Human and Gordon, 1997). They could also threaten other indigenous species, such as the rare stitchbird and bellbird through competition for nectar, or animals that rely on invertebrates for food, such as geckos and skinks.
What is it be done about it?
MAF Biosecurity is coordinating an investigation into Argentine ant. The Government is funding the investigation through its 'green initiatives'. The investigation is to include:
- a national survey of the geographical distribution of the ant
- examination of control and treatment options
- assessment of the effectiveness of a new ant bait that has recently been developed in Australia.
Key stakeholders and scientists met at the end of January to form a technical advisory group (TAG). The TAG will guide the project. The group includes representatives from MAF, the Department of Conservation (DOC), Regional Councils, Forest and Bird, New Zealand Fruitgrowers Federation, Tangata Whenua, Landcare Research and the pest control industry.
In early February, DOC will trial a new Australian ant bait in an eradication attempt on Tiritiri Matangi. The new bait is an exciting development that could significantly improve options for control.
Why has nothing been done until now?
When the ant was discovered in New Zealand 10 years ago, the then Ministry of Agriculture and Fisheries undertook a preliminary survey within and around the Mt Smart area of Auckland, to see how far it had already established. It was decided not to attempt eradication because the ant was by then already well established within several Auckland suburbs. At the time there were no known control methods for Argentine ant and eradication was not a high priority for the Ministry of Agriculture and Fisheries.
Ten years ago MAF Biosecurity did not exist. The Ministry of Agriculture and Fisheries was concerned with protecting and enhancing the productive sector - agriculture, horticulture and fisheries. It did not have a mandate (and was not funded) to deal with incursions of exotic species that affected other interests.
Over the last few years there has been increasing awareness of the importance of biosecurity issues beyond the productive sectors. This awareness has been reflected in the creation by MAF of a separate Biosecurity Authority and by the inclusion of biodiversity in our mission statement.
MAF Biosecurity is committed to responding to incursions of exotic animals. In consultation and collaboration with all interested parties, we will lead the response when multiple government agencies are involved and when other government agencies are unable to take responsibility for dealing with an incursion.
How will the results of distribution survey be used?
The results of this investigation will help decide whether or not Argentine ant should become an unwanted organism under the Biosecurity Act. If this is the case, it will provide the basis for implementing future strategies for management and control and identifying areas where further research is needed. The feasibility for eradication will be investigated. However, these former issues must be resolved before any decisions to eradicate can be made.
Amelia Pascoe,
Programme Coordinator, (Exotic Animal Response),
Animal Biosecurity
References
Human, KG and Gordon, DM (1997) Effects of Argentine Ants on Invertebrate Biodiversity in Northern California. Conservation Biology 11(5): 1242-1248
New South Wales Department of Agriculture (1977) Entomology Branch Insect Pest Bulletin III. Edition 11.
Page last updated: 7 August 2008