Environmental and social impact considerations

Before planning an ant management programme (or even deciding which pesticides to use around your home), you must have a good understanding of the pesticides available, the considerations associated with their use and their potential non-target effects. We provide information on appropriate treatment options for the most problematic ants in various environments.

It is also important to consider whether legislation exists that either permits or forbids the use of a particular pesticide or group of pesticides either in a specific environment (e.g. conservation areas) or altogether. Some of the more potent insecticides may only be available to and used by trained and certified "approved handlers". This legislation will likely be the result of an assessment of the toxicity, persistence and potential non-target effects of the pesticide, undertaken by a country's Environmental Protection Agency (EPA) or equivalent.

At scales larger than domestic use, pesticide use should be accompanied by a monitoring programme that assesses its success in achieving its management goals and identifying any non-target effects or impacts on human or environmental health.

Where proposed management of an invasive ant incursion is to be undertaken using insecticide, an Environmental Impact Assessment (EIA) or Environmental and Social Impact Assessments (ESIA) is required to weigh the possible human and environmental consequences of pesticide use against alternative management options and to ensure that every effort has been made to minimise those consequences. Typically, EIAs / ESIAs for pesticide are required as part of the management process under a country’s Hazardous Substances and New Organisms (HSNO), Conservation, Environmental Protection, Resource Management or Biosecurity Act or equivalent(s) depending where the pesticide is to be used.

The EIA / ESIA should also include the outcomes of consultations with affected stakeholders. These stakeholders might be residents or business owners in the treatment area, or other parties potentially affected by either the ants (e.g. exporters) or their treatment (e.g. organic growers).

An Environmental Impact Assessment should include the following information:

  • What is being proposed, which species is the target, how much area does it cover, why is it a problem etc.
  • Objective (e.g. eradication)
  • Methods (including pesticide type and means of application if applicable)
  • Potential environmental impacts, health risks and benefits of pesticide use
  • Proposed means of reducing impacts
  • Comparison between proposed means and available alternatives
  • Consultation (who will be affected and what do they think?)
  • What measures will be put in place to minimise risks
  • A design of the monitoring for non-target effects

On Christmas Island, Indian Ocean, an independent consulting company was hired to assess the impact of fipronil, used to treat yellow crazy ants, on other invertebrates and the environment. Surveys investigating the potential impact of the fipronil treatment program on invertebrate communities in three different environments were done at three separate times, right before treatment, immediately after treatment, and 6 months after treatment. Ground-dwelling invertebrates were assessed using pitfall traps; sticky traps were used to collect invertebrates living in the canopy; and aquatic invertebrates were surveyed in freshwater/sediments. To determine if the toxin was accumulating in the environment, soil, water and sediment samples were collected and analysed using liquid chromatography mass spectrometry for the presence of fipronil and its three main toxic degradates (the main toxic compounds fipronil breaks down into: fipronil sulfide, fipronil sulfone and fipronil desulinyl). Details of the survey methods used can be found in this report.

Advice on producing Environmental Impact Assessments is available from the Environmental Monitoring and Governance division of SPREP.

The rest of this section should provide all the information needed for understanding the effects of pesticide use, to refer to when conducting an ESIA / EIA for a project.

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Pesticides

For invasive ants there are basically three groups of pesticides: neurotoxins, stomach poisons and insect growth regulators.

This pesticide summary (Excel spreadsheet) describes the known environmental fate of the active ingredients in several commonly used ant control products along with details of toxicant concentrations, application rates, manufacturers and invasive ant species they are known to be effective on.

You can use the pesticide summary to find the brand name of the pesticide you want ot use, find out the active ingredient, and then use the following sections to find out how the toxin works, ant the effects (and non-target effects).

1. Neurotoxins

Neurotoxins typically contain fipronil (eg: Xstinguish, Vanquish Pro, ATTRATHOR, AntOff), indoxacarb (e.g. Carbodox, Arilon, Advion, Provaunt), synthetic pyrethroids (eg: Delta Force, Permex Dust) or neonicotinoids (e.g. Safari, Maxforce Quantum, PROTHOR). Neurotoxins disrupt insect central nervous systems by blocking neuron receptors. The poisons are comparatively fast acting, with results visible within a few days. Because of this rapid action, doses should be low to ensure that workers collecting bait survive long enough to transfer the toxin to the queen, larvae and other workers in the nest. More detailed information is available here.

2. Stomach poisons

Stomach poisons include hydramethylnon (eg: Maxforce or Amdro), sulfuramid and sodium tetraborate decahydrate (eg: Borax, Exterminant). Stomach poisons act on a variety of metabolic pathways and are lethal to both workers and reproductives (queens and males). Like neurotoxins they are comparatively fast acting, so doses should be low. More detailed information is available here.

3. Insect growth regulators

Insect growth regulators (IGRs) include compounds such as fenoxycarb, S-methoprene (eg: Tango, Engage and Engage P) or pyriproxyfen (eg: Esteem, Distance). Growth regulators may disrupt development of the queens' ovarian tissue, prevent eggs from hatching or disrupt larval development so that reproductive adults do not form. These effects result in sterilization of the colony, but do not affect surviving workers, which may persist for several months after the application of the toxicant. For this reason IGRs are often used in conjunction with either neurotoxins or stomach poisons. More detailed information is available here.

Toxicity

Note: toxicity is based on the available information for the pure toxicant and toxicity categories are based on those specified by the United States Environmental Protection Agency presented in the table below.

Please read the Safety Data Sheets (SDS) and label or brochure for the product.

US EPA Toxicity Categories

High Toxicity (Danger)

Moderate Toxicity (Warning)

Low Toxicity (Caution)

Very Low Toxicity (Caution)

Oral
LD50
Less than 50 mg/kg 50 - 500 mg/kg 500 - 5000 mg/kg Greater than 5000 mg/kg
Dermal LD50 Less than 200 mg/kg 200 - 2000 mg/kg 2000 - 5000 mg/kg Greater than 5000 mg/kg
Inhalation LC50 - 4hr Less than 0.05 mg/L 0.05 - 0.5 mg/l 0.5 - 2 mg/L Greater than 2 mg/L
Eye Effects Corrosive Irritation persisting for 7 days Irritation reversible within 7 days Minimal effects, gone within 24 hrs
Skin Effects Corrosive Severe irritation at 72 hours Moderate irritation at 72 hours Mild or slight irritation

Further information

Gruber. 2014. Environmental and Social Impact Assessment (ESIA) for Outputs 4 & 5 (management of yellow crazy ant incursions in Tokelau and Kiribati). New Zealand Ministry of Foreign Affairs and Trade

Stork, Kitching, Davis, Abbott. 2014. The impact of aerial baiting for control of the yellow crazy ant, Anoplolepis gracilipes, on canopy-dwelling arthropods and selected vertebrates on Christmas Island (Indian Ocean). Raffles Bulletin of Zoology 30: 81-92

Weeks, McColl. 2011. Monitoring of the 2009 aerial baiting of yellow crazy ants (Anoplolepis gracilipes) on non-target invertebrate fauna on Christmas Island. Prepared for the Director of National Parks by CESAR Consultants Pty Ltd

Osenberg, Bolker, White, St Mary, Shima. 2006. Statistical issues and study design in ecological restorations : lessons learned from marine reserves. Restoration Ecology in Context. Foundations of restoration ecology. Island Press, Washington, DC, USA

Osenberg, Schmitt, Holbrook, Abu-Saba, Flegal. 1994. Detection of environmental impacts: natural variability, effect size, and power analysis. Ecological Applications 4: 16–30.

Thault, Kernaléguen, Osenberg, Claudet. 2017. Progressive-Change BACIPS: a flexible approach for environmental impact assessment. Methods in Ecology and Evolution 8:288-296

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