Control of Argentine Ants
New Ant Bait Approved by ERMA
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A new bait to control and, in some situations, eradicate Argentine ants is now commercially available. Xstinguish Argentine Ant Bait was developed by Western Australia Department of Agriculture and modified by Landcare Research for New Zealand conditions. |
Xstinguish Argentine Ant Bait has been approved by ERMA (Environmental Risk Management Authority), the New Zealand Agency responsible for preventing or managing risk to people and the environment, and has been registered in New Zealand by Landcare Research. The bait is manufactured and distributed by:
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PO Box303-439, North Harbour, Auckland, New Zealand Ph 09 444 0350 or 027 444 4005. Email: info@baittechnology.co.nz |
Xstinguish Argentine Ant Bait is highly attractive to Argentine ants and our product testing has shown that even after one treatment with Xstinguish Argentine Ant Bait there is a dramatic reduction in ant numbers.The bait has also been shown to be particularly attractive to several other pest ant species (Pheidole rugosula, Darwin’s ant Doleromyrma darwiniana, Paratrechina vaga, Monomorium antipodum), all pests of urban environments.
Directions for use
Xstinguish Argentine Ant Bait is supplied in a cartridge and dispensed using a caulking gun. Cut the tip of the cartridge and apply a small amounts of bait (<2 g, about the amount of toothpaste you would use with a manual toothbrush) every few metres in the infected area. Place bait in a grid pattern in vegetated areas or in built up areas, where there is concrete or asphalt, in cracks, around vegetation and in the path of ant foraging trials. It is recommended that bait be placed under leaves or in crevices to reduce dehydration. Bait is applied at the rate of 3 kg/ha (i.e. 0.3 grams of fipronil per hectare) in urban areas, and at up to 6 kg/ha in areas of continuous vegetated habitat (up to 0.6 g a.i./ha). If you need to treat ant infestations inside your home place the bait in a bait station.
When large areas or discrete ant populations are treated, one treatment annually is sufficient to reduce ants to very low levels. Any pockets that have survived the initial operation are then retreated in subsequent years. When treating urban properties, because of continued reinvasion from neighbouring populations another treatment may be necessary to maintain low ant populations.
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| Putting out ant bait at Tiritiri Matangi, an offshore island nature reserve. |
Why baits?
Designing a control strategy for Argentine ants is challenging. At any one time only a small percentage (~2%) of ants are foraging (Davis & Van Schagen 1993). Many insecticides are repellent, and unaffected ants stay inside the nest until insecticide residues fall to low levels. Direct sprays have little effect unless every colony is exposed and treated. If using bait, it needs to be sufficiently attractive, and the toxin must consist of very small particles or they will not be imbibed (J. Van Schagen pers. comm.), and if workers feel affected by poison they refuse to feed nest mates (Davis & Van Schagen 1993).
Toxic baiting is probably the most effective control method available today (Davis et al. 1993). Ideal baits for ants are non-repellent, have a delayed action to allow spread throughout the colony, and are effective over a large range of concentrations (to counter dilution through food exchange) (Stringer et al. 1964).
Liquid sucrose has been shown to be the most attractive non-toxic bait to Argentine ants (Baker et al. 1985). Sucrose solutions containing boric acid are effective at controlling workers in both the laboratory and the field, but only if the boric acid is no greater than 1% (Hooper-Bui & Rust 2000; Klotz et al. 2000a). Control may take some time – only partial control of queens was achieved in laboratory conditions when bait was available for 24 hours - so bait should be left out until no more ants are seen collecting it. Attractive protein bait is an alternative as queens are fed protein for egg development, and a protein bait will therefore specifically target them and have the greatest effect on the colony.
If baiting is not an option, Argentine ants can be chemically excluded from specific sites (e.g., tree trunks) for 2–3 months using cotton twine permeated with farnesol and stickem (Shorey et al. 1996).
Background Research
To determine effectiveness of Xstinguish Ant Bait, and how it can best be used, we conducted efficacy trails on Tiritiri Matangi (an offshore island of important conservation value), Nelson and Mt Maunganui (both busy ports), and in urban Auckland. In a single application at each site, bait was laid (every 2 m along lines 3 m apart, an application rate of 3–6 kg/ha).
Whole colonies, including queens, were destroyed across much of the treated area, but some colonies survived. This indicates the bait is highly effective at killing colonies but that not all colonies are getting sufficient bait.
Reduction in the number of Argentine ant foragers on non-toxic baits after one treatment with toxic baits. Mean ± SE ants per bait. |
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| Pre treatment | Post treatment | |
| Non-Treatment | 181.8 ± 49.5 | 113.3 ± 50.5 |
| Mt Maunganui | 226.2 ± 30.0 | 1.9 ± 1.9 |
| Port Nelson | 319.3 ± 43.1 | 0.0 ± 0.0 |
| Tiritiri Matangi | 294.7 ± 56.6 | 0.0 ± 0.0 |
After one treatment there was a dramatic reduction in ant numbers. This technique is highly effective at reducing populations to low levels, and numbers will take several seasons to build up again. If only treating a small area within a larger infestation there will be reinvasion from surrounding untreated areas, so re-baiting will be required more often. To succeed in eradicating Argentine ants from the treated area every last queen needs to be killed. Further trials are planned to develop more sensitive monitoring techniques to locate surviving colonies and determine the best follow-up treatment method.
Biological control
Biological control of Argentine ants has not been attempted in any of the countries that the Argentien ant has spread to. Phorid flies, Pseudacteon spp. (Diptera: Phoridae), attack Argentine ants in Brazil and deter ants foraging during the flies’ activity period (Orr & Seike 1998). In the US, phorid flies of the same genus (Pseudacteon spp.) are being considered for release against the red imported fire ant Solenopsis invicta (Porter & Alonso 1999). Pathogens have also been trialled against S. invicta (Stimac et al. 1990), but the ants, like other social insects, have very efficient hygienic behaviour that inhibits the spread of pathogens that appear in the nest. This behaviour has so far prevented the use of pathogens for biological control of many social insects (Harris et al. 2000).
An alternative approach to biological control would be to increase the genetic diversity through the importation of queens or males from South America. The aim would be to reproduce the situation in their native range where intra-specific differences are recognised and there is, as a consequence, wider territorial spacing of colonies and significantly lower ant densities (Tsutsui et al. 2000). However, such an approach has not been tried and would reqiure careful risk assessment.
A novel control technique being used by a student at the University of California, Davis, to control Argentine ants was "baiting" with a haybale (B. Inouye pers. comm.). The ants moved their nests out of wetter or less sheltered areas and into the hay, which was then burnt or frozen.
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