The Argentine ant (Linepithema humile) is recognised worldwide as an invasive ant species. Argentine ants are native to South America but are now present in a number of regions in New Zealand, including Hawke’s Bay.
Argentine ants are a uniform light brown or honey colour as opposed to the dark colours of the more common ants seen. They measure 2-3 mm in length and the workers are all the same size.
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Argentine ant infestations are frequently not detected until they have reached the stage of becoming a human nuisance. By the time they have reached this level, they are well established; impacting on the outdoor lifestyle we are accustomed to here in Hawke’s Bay.
Left unchecked Argentine ants are able to reach very high densities as all Argentine ant colonies within New Zealand are genetically related. With a lack of in-fighting between colonies this species is able to form super-colonies. Therefore, Argentine ants can have a significant impact on the environment, lifestyle and horticulture.
Environmental Impacts
Due to the aggressive nature of Argentine ants and their numerical dominance, their impact on the environment is significant. They will eliminate or exclude other ant species and will severely reduce the number of other insects where they reach high numbers. Argentine ants threaten native insects, lizards and native birds, either attacking them directly or by competing for food resources with them.
Lifestyle Impacts
Left unchecked Argentine ants will become a major household and garden pest. Argentine ants invade houses, often forming trails into kitchens and bathrooms, getting into cupboards and screw top jars, microwaves and fridges, electrical areas, behind walls and in beds. Where Argentine ants are in high numbers some residents are unable to garden, hold outdoor social events, or let their children play in backyards due to aggressive swarming and in some cases being bitten. Argentine ant bites are not poisonous but can be irritating and cause allergic-type reactions in some people.
 | Horticultural Impacts
The main impact on horticulture is the ability of Argentine ants to ‘farm’ sap-sucking aphids and scale insects. This association between Argentine ants and sap-sucking insects often leads to a build-up of sap-sucking insects on plants, with several possible consequences: higher risk of disease transmission, reduction of crop yield and/or quality, disruption of biological control agents and an increase in spray regimes. Argentine ants have also been reported to invade and destroy bee hives. |
Argentine ants invade and colonise new areas in two main ways, through natural spread and human assisted dispersal. Argentine ants can spread naturally up to 150 m per year. The queens do not fly so they form new nests within ant-walking distance. However, the majority of infestations begin with human assisted dispersal; by people inadvertently transporting infested pot plants, firewood, soil, caravans, cars, freight etc.
If your property has Argentine ants or if you have been in an area with Argentine ants there are several simple steps which can reduce the likelihood of you transporting these ants to another area.
- Check potted plants before moving. If a pot plant contains Argentine ants immerse the pot in a solution of water and a synthetic pyrethroid (at label rate), this will kill the ants.
- Check caravans, campervans, cars, etc (particularly if they have been sitting in the same spot for a while) for Argentine ants before moving off site.
- If moving house, check all your pot plants, vehicles, and any outdoor fixtures you are taking to ensure you are not taking the ants with you.
- Before purchasing firewood, compost, mulch or pot plants ensure they are free of Argentine ants so you don’t take this unwanted pest home with you.
| Argentine ant nests found on private land are the landowner’s responsibility. Hawke’s Bay Regional Council does not carry out any ant control operations on private land. However, the Regional Council can provide contact details for contractors who are able to deal with the ants in an appropriate way. If you would like to control Argentine ants yourself see the Best Baiting Guide. If you need assistance identifying Argentine ants please contact Alice at Hawke’s Bay Regional Council (06 833 8083). |  |