Experimental treatments

Experimental treatments are just as the name suggests - people are always researching new treatments to find the best options, and this requires experiments. The approaches outlined here are part of on-going research work. This research involves finding out if the treatment works on the target ants, but also identifies potential non-target effects.

These are not commercial products and are not licensed for public use. They have not yet had the type of testing required of commercially available pesticides, and their effect on other non-target species and the environment is not yet widely known. We provide this information to allow people to understand some of the potential future approaches, but we advise caution when considering whether to use these approaches.

Polyacrylamide hydrogel bait carriers

Experimental use of these approaches will identify and study potential non-target effects, in a similar way to the approach used with hydrogel crystals as an insecticide carrier in the Channel Islands, which assessed potential impacts on native foxes. Hydrogel crystals consist of polyacrylamide, which easily absorbs water and chemicals that dissolve in water (such as toxins and sugar), making them ideal carriers for insecticides. However, polyacrylamide slowly breaks down into acrylamide, a toxin, when left in the environment. So far there has been no research into what impact the persistence of acrylamide in the environment may have. An alternative, non-toxic seaweed-based, hydrogel has been developed, but is not yet available for sale.

At present it is known that hydrogel baits infused with various insecticides kill ants effectively. Often this is indiscriminate - that means all ant species are killed, even those that are not harmful. In addition the hydrogels are used with commercial insecticides that can affect other animals that we value.

In the examples below, fipronil is the active ingredient, and is incorporated into the hydrogel crystals using the Termidor commercial product*, and a sugar solution. Fipronil kills bees, and some studies have found a link between insecticides such as fipronil and the decline of pollinators such as honeybees. For these reasons, commercial treatment products to treat ants, and other social insects, avoid combining fipronil-based products with sugar as an attractant, as pollinators are attracted to the bait and are killed. 

Because of this we do not recommend choosing such a treatment option, unless the use is experimental, or the circumstances are exceptional, and there is no risk of honey bees or other native bees being affected, such as Johnston atoll, which has no native ants or bees.

*Termidor, used in the example below, is a commercial product often used to kill termites. However, mixing it in hydrogel crystals and broadcasting these across the landscape is not a use the manufacturers intended / tested and this use is not included on the label. Scientists have special permits to conduct this research in a highly controlled manner. 

CSIRO hydrogel bait experiments

The same product is used for treating both yellow crazy ants and Argentine ants: Termidor (fipronil, 100 g/L) diluted to 0.000064% in hydrogel crystals mixed with a 30% sucrose solution. The treatment is applied at a rate of 50-80 kg/ha. To make up the desired concentration, the hydrogel crystals are added to a mixture of 500 L 30% sucrose solution and 32 ml Termidor. Irregular-shaped hydrogel crystals have been found to work better than the round crystals, as they absorb the solution better and provide more surface area for the ants to feed on.

Yellow crazy ants in Northeast Arnhem Land, Australia

Goal: Control of overall infestation, eradication of selected individual infestations.

Size: individual infestations <1 ha - 200 ha

Manager: Ben Hoffmann (ben.hoffmann@csiro.au), CSIRO

Hydrogel crystals and solution are brewed in the big plastic tubs then transferred to plastic buckets to load into the helicopter dispersal system (© Ben Hoffmann, CSIRO)
 

Loading hydrogel crystals into a side-mounted helicopter dispersal system (© Ben Hoffmann, CSIRO)

In 2016, CSIRO changed it's yellow crazy ant control regime in Arnhem Land to using Termidor (a fipronil product) diluted in a 30% sucrose solution and absorbed into hydrogel crystals. This product was cheaper than commercially-made products. Each infestation is treated three times at rates between 50-80 kg/ha. All rates have been found to induce dramatic declines in yellow crazy ant abundance. It is yet to be determined if there are seasonality issues with the treatment timing affecting eradication success.

Although treatments are not desirable in wet weather, the technique has been found to produce great ant control even in very wet weather (the bait is not destroyed by rain).

It should be noted that this technique has large non-target impacts on other ant species compared to the formerly used granular baits. Research into minimizing these impacts is ongoing.

Argentine ants on Norfolk Island, Australia

Goal: Control of overall infestation, eradication of selected individual infestations.

Size: individual infestations <1 ha - 200 ha

Manager: Ben Hoffmann (ben.hoffmann@csiro.au), CSIRO

In 2016, CSIRO commenced treatments of Argentine ants on Norfolk Island with Termidor (a fipronil product) diluted in a 30% surcose solution and absorbed into hydrogel crystals. Treatments can be conducted weekly, and the number of treatments required to eradicate Argentine ants appears to be dependent upon ant population density and season. Best results appear to be achieved immediately after winter when ant populations are at their lowest. A minimum of four treatments is probably required to achieve eradication. Many more treatments are required if the treatment regime commences in summer when ant populations are greatest. Treatments have been conducted at rates up to 80 kg/ha, and the higher rates appear to give best results.

The relative non-target impacts of this technique compared to other treatments against Argentine ant are yet to be fully quantified.

More research on hydrogel baits

Further information about using hydrogel baits for ant control can be found in the following papers

Boser, Hanna, Faulkner, Cory, Randall, Morrison. 2014. Argentine ant management in conservation areas: results of a pilot study (download 2 MB). Monographs of the Western North American Naturalist 7: 518-530

Boser, Hanna, Holway, Faulkner, Naughton, Merrill, Randall, Cory, Choe, Morrison. 2017. Protocols for Argentine ant eradication in conservation areas. Journal of Applied Entomology DOI: 10.1111/jen.12372

Buczkowski, Roper, Chin. 2014a. Polyacrylamide hydrogels: an effective tool for delivering liquid baits to pest ants (Hymenoptera: Formicidae). Journal of Economic Entomology 107(2): 748-757

Buczkowski, Roper, Chin, Mothapo, Wossler. 2014b. Hydrogel baits with low-dose thiamethoxam for sustainable Argentine ant management in commercial orchards. Entomologia Experimentalis et Applicata 153: 183-190

Rust, Soeprono, Wright, Greenberg, Choe, Boser, Cory, Hanna. 2015. Laboratory and field evaluations of polyacrylamide hydrogel baits against Argentine ants (Hymenoptera: Formicidae). Journal of Economic Entomology 108(3): 1228-1236

Tay, Hoddle, Mulchandani, Choe. 2017. Development of an alginate hydrogel to deliver aqueous bait for pest ant management. Pest Management Science DOI: 10.1002/ps.4616