Yellow crazy ant case studies

Northeast Arnhem Land, Australia : Christmas Island, Indian Ocean : Atafu, Tokelau : Kiritimati, Kiribati : Tepuka, Tuvalu :Johnston Atoll, Hawaii : Kaneohe Bay, Hawaii : Wet Tropics, Australia

Location: Northeast Arnhem Land, Australia

Justification: Containment

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

Size: individual infestations <1 ha-82 ha (total of 4000 ha)

Products: Three treatments via aerial baiting by helicopter of some combination of AntOff (fipronil 0.01 g/kg; fish meal matrix; 10 kg/ha) and Campaign (hydramethylnon 7.3 g/kg; corn grit matrix; 5 kg/ha) or Distance plus (pyriproxyfen 5 g/kg; corn grit matrix; 4 kg/ha).

The combination of products does not matter so long as a total of three treatments are applied and in the months specified.

Time of year: The first treatment must be done in December, after the ants have finished producing new queens (if it is done earlier then the new queens will still be in the pupal stage and will not eat the bait and the treatment will not work).

The second treatment is in March or April, and the third in July or August.

Outcome: Between 2003 and 2009, 246 ha of infestation was eradicated

Programme cost: not available

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

 
Helicopter returning to refill bait basket during baiting operations (© Meghan Cooling)

Buckets of AntOff® awaiting application (© Meghan Cooling)

In northern Australia, the yellow crazy ant (Anoplolepis gracilipes) has infested undisturbed savanna woodland (an open canopy forest made up mostly by Eucalyptus and Acacia trees) where it is patchily distributed across more than 16 000 km2.

Australia’s federal science agency (CSIRO) began their control programme for yellow crazy ants in 2003, dispersing bait aerially by helicopter.

The helicopter drops the bait over the known area of infestation as well as over a 100 m buffer zone around the infestation.

Bait is only dropped in the early morning (6 am-10 am) and late afternoon (3 pm-6 pm) because this is when the ants are the most active (because the temperature is cooler) and most likely to pick up the bait.

As rain reduces ant worker foraging and dissolves the bait pellets, the bait is not dispersed less than four hours before forecast rain, or less than 24 hours after rain.

Between 2003 and 2009 twenty-one individual infestations were successfully eradicated, covering a total of 246 ha (the outcome of treatments done since that time is not yet known).

In areas where an infestation occurs within 20 m of open water, the same amount of bait is applied as above (i.e. 10 kg/ha for AntOff) but using manual spreaders.

Information source

Further information was provided by Ben Hoffmann, CSIRO Land and Water Flagship, ben.hoffmann@csiro.au

Lach, Barker. 2013. Assessing the effectiveness of tramp ant projects to reduce impacts on biodiversity. A report prepared for the Australian Government Department of Sustainability, Environment, Water, Population, and Communities

case study reviewed by Ben Hoffmann, CSIRO Australia, September 2016

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Location: Christmas Island, Indian Ocean

Justification: Conservation

Goal: Control

Size: 2509 ha scattered across 13 500 ha

Products: AntOff (fipronil 0.01 g/kg; fish meal matrix; 4 kg/ha); Distance (80-200 m away from waterways; pyriproxyfen 5 g/kg; fish meal matrix; 4 kg/ha); Engage (20-80 m from waterways; S-methoprene 5 g/kg; fish meal matrix; 4 kg/ha)

Time of year: September (end of dry season) for three reasons: 1) rain can interfere with bait delivery and uptake by the ants 2) robber crab activity, a species highly susceptible to the bait, is very low at the end of the dry season, thus minimizing the risk of non-target effects 3) the rainforest canopy is the most open, allowing more bait to fall to the forest floor.

Outcome: 99.4% reduction in ant abundance after 20 weeks

Programme cost: approximately 1.2 million AUD for each year of with aerial treatment

Manager: Dion Maple (dion.maple@environment.gov.au), Christmas Island National Park

The goal of the control programme on Christmas Island is now suppression of yellow crazy ant numbers, not eradication. The goal is to keep yellow crazy ant abundances below that at which they kill the endemic red land crab and impact heavily upon other species.

Helicopters are used to disperse bait because there are many isolated, difficult to access infestations spread across the entire 13 500 ha island, including inaccessible cliff faces.

Aerial baiting by helicopter took place in 2002, 2009 and 2012. All three helicopter-baiting programmes treated each infestation a single time and used AntOff (fipronil) in a fishmeal matrix spread at 4 kg/ha and other baits in lesser quantities.

However, the first programme in 2002 used a higher concentration of fipronil, 0.1 g/kg, instead of using 0.01 g/kg as was done in the 2009 and 2012 baiting programmes.

The 2002 programme baited over 2509 ha of infestation, and reduced ant abundances by 99.4% in four weeks.  The 2009 and 2012 programmes achieved similar successes using AntOff with a lower concentration of fipronil, with 99.4% fewer ants seen in 20 weeks. These two programmes baited 785 ha and 1062 ha, respectively.

Between 2000 and 2011, ~200 ha of infestations were also baited by hand each year AntOff (0.1 g/kg; fish meal matrix; 4-6 kg/ha). However, this method was inefficient at controlling large and remote areas of ants, and was not enough to prevent the ant populations from expanding substantially during this time.

In 2012, areas that were 80-200 m away from waterways were baited with Distance, and Engage was spread in areas 20-80 m from waterways. Both these baits were spread by helicopter. These two insect growth regulators both only had limited success in controlling ant populations mostly because of a single application. However, the only other option was not to bait areas within 200 m of water.

Likewise, trials testing hydramethylnon and indoxacarb showed these chemicals to be ineffective compared to fipronil at controlling yellow crazy ants on Christmas Island.

Indirect biological control of yellow crazy ants by targeting the scale insects they farm is the programme's new direction.

 
Bait being prepared for distribution (© Director of National Parks)

 

Helicopter with a full basket of AntOff® to be distributed (© Director of National Parks)

View from helicopter dropping bait over the infested areas (© Director of National Parks)

Information sources

Boland, Smith, Maple, Tiernan, Barr, Reeves, Napier. 2011. Heli-baiting using low concentration fipronil to control invasive yellow crazy ant supercolonies on Christmas Island, Indian Ocean. In: Island invasives: eradication and management (eds Veitch, Clout, Towns), pp 152-156. Gland, IUCN

Lach, Barker. 2013. Assessing the effectiveness of tramp ant projects to reduce impacts on biodiversity. A report prepared for the Australian Government Department of Sustainability, Environment, Water, Population, and Communities

Further information was provided by Dion Maple, Natural Resource Manager- Invasive Species, Christmas Island National Park, dion.maple@environment.gov.au

case study reviewed by Dion Maple, Parks Australia, August 2016

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Location: Atafu, Tokelau

Justification: Social, conservation

Goal: Suppression to harmless levels

Size: ~67 ha

Products: Antoff (fipronil 0.01 g/kg; 10 kg/ha); Vanquish Pro (fipronil 0.1 g/kg; spot treatments); ATTRATHOR (fipronil 0.26 g/L; spot treatments)

Time of year: June/ July

Outcome: >90% reduction in numbers, patches where the ant is absent 

Programme cost: 250 000 USD to date

Manager: Allan Burne (allan.burne@vuw.ac.nz), Monica Gruber (monica.gruber@vuw.ac.nz) and Rafael Barbieri (2015), Pacific Biosecurity. Field Manager 2015 Vivian van Dyke (viv@flybusters.co.nz), Flybusters

Atafu is the northernmost of the three coral atolls of Tokelau. Yellow crazy ants were first recorded in Tokelau in 1934, but were not observed on Atafu until 2008.

From their first detection yellow crazy ants spread rapidly and were distributed throughout most of the inhabited islet of Atafu at high abundance by 2012, where they were reported to kill birds, poultry, coconut and hermit crabs as well as causing a general nuisance to the atoll’s residents. For these reasons it was decided to reduce the ants’ numbers to harmless levels.

Spreading granular bait using hand spreaders (© Alex Cook, Flybusters Antiants Consulting)
 
Petrol driven blower for applying bait in dense areas of bush (© Alex Cook, Flybusters Antiants Consulting)

AntOff granular bait was distributed in 2015 using a combination of manual "Scott" spreaders in easily accessible areas and petrol driven blowers in areas of dense bush.  A 5 m buffer zone, where no bait was spread, was enforced near all open water.

Conical tree mounted bait stations filled with 15 g of AntOff bait and set at a minimum of 1.5 m above ground level were initially used in areas where children or stock might have been able to access broadcast bait granules on the ground (i.e pig sty). However recruitment to these stations was found to be poor. Instead Vanquish Pro paste bait or ATTRATHOR targeted insecticide was used in these situations – applied at approximately 3 m intervals 1.5 m above ground level.

The single application indicate a >90% reduction in yellow crazy ants across the islet, and many areas where the ant is now absent.

In 2016 one ha was treated with AntOff where the ant remained in moderate abundance. Spot treatments were also undertaken with Vanquish Pro and ATTRATHOR. Monitoring continues until 2019.

Information sources

Burne, Barbieri, Gruber. 2015-2019. Management Plan Atafu, Tokelau (download 9 MB). Pacific Biosecurity Management Plan

Craddock. 2015. Yellow crazy ant treatment on Atafu Atoll, Tokelau (download 2.8 MB). FBA consulting client report for Pacific Biosecurity

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Location: Kiritimati, Kiribati

Justification: Conservation

Goal: Eradication

Size: 1.85 ha

Products: AntOff (fipronil 0.01 g/kg; fish meal matrix; 10 kg/ha); Vanquish Pro (fipronil 0.1 g/kg; spot treatments); ATTRATHOR (fipronil 0.26 g/L; spot treatments)

Time of year: August to October

Outcome: Eradicated after 5 treatments over 2 years

Programme cost: 68 000 NZD to date

Manager: Monica Gruber (monica.gruber@vuw.ac.nz) Pacific Biosecurity. Field Manager Allan Burne (allan.burne@vuw.ac.nz) Pacific Biosecurity

 

Placing bait stations (© Allan Burne, Pacific Biosecurity)

Kiritimati is a raised coral atoll that is part of the Line Islands group. Yellow crazy ants were first recorded in Kiritimati in the village of Ronton (London) on the western side of the atoll in 2013. The ants appear to have remained contained in this area.

Ronton is in close proximity to Motu Tabu, a significant sea bird breeding sanctuary. Because of the threat posed to seabird breeding by YCA, and because of the comparatively small extent of the infestation it was decided to attempt eradication.

An initial round of baiting using AntOff granular bait was attempted in April 2015, but wet weather prevented the bait from being broadcast. Attempts were made to distribute bait in B&G ground bait stations spaced at 10 m intervals within the infested area, but no recruitment to the bait was observed. A warehouse containing copra was found to be infested with YCA. Movement controls were put in place to prevent the ants’ spreading from the warehouse with movements of copra.

During a subsequent visit in August 2015, AntOff bait was successfully distributed throughout the infested area using manual “Scott’s” spreaders.  No bait was spread within 5 m of all open water.

Broadcast baiting was supplemented with Vanquish Pro paste bait or ATTRATHOR targeted insecticide in building interiors and other sites where broadcast bait was not considered appropriate because of possible access by children or stock animals. In these situations both ATTRATHOR and Vanquish Pro were applied at approximately 3 m intervals no less than 1.5 m above ground level.

Follow up monitoring in October 2015 indicated a shift from continuous distribution of YCA throughout the infested area to pockets of patchily distributed ants foraging at low abundance. These patchy areas were spot treated with a combination of ATTRATHOR and Vanquish Pro, plus Antoff granules distributed at the equivalent of 10 kg /ha in 2015 and 2016.

No ans were detected in surveys in 2017. Monitoring will continue through to 2019.

Information source

Burne, Gruber. 2015-2019. Management Plan Kiritimati, Kiribati (download 4.4 MB). Pacific Biosecurity Management Plan

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Location: Tepuka, Tuvalu

Justification: Conservation

Goal: Suppression to harmless levels

Size: 8 ha

Products: AntOff (fipronil 0.01 g/kg; fish meal matrix; 10 kg/ha)

Time of year: April

Outcome: >96% reduction in numbers

Programme cost: 26 000 NZD to date

Manager: Monica Gruber (monica.gruber@vuw.ac.nz) Pacific Biosecurity. Field Manager Matio Lonalona MNRL Agriculture Tuvalu (matiolnln@gmail.com)

In 2014 SPC carried out surveys for yellow crazy ants (YCA) on Funafuti and Nukulaelae atolls and Niulakita Island at the request of the Tuvaluan government.  

Due to concerns about the extremely high numbers of ants present on some of these atolls, a control programme was proposed with the goal of reducing the number of ants to harmless levels. In April 2017 a control programme was begun. Pre-monitoring surveys were done on Fualopa and Tepuka islets. It was found on Fualopa that YCA abundances had declined on their own, and card counts revealed their numbers were less than the threshold of 37 ants recommended to justify treatment. However, Tepuka card counts were an astounding 420 ants!

Preparing to take the management gear to the motu (© Monica Gruber, Pacific Biosecurity) 
 

The management team approaching Tepuka (© Monica Gruber, Pacific Biosecurity)

A single application of AntOff was applied to Tepuka using manual spreaders. Due to concerns about fipronil getting into the marine environment, the first 20-30 m within the vegetated area of the motu was NOT treated. Post-monitoring surveys three days later showed YCA abundances had dropped more than 96%.  Tepuka motu was declared off-limits for three months by the Funafuti village council. This was broadcast on Tuvalu’s National Radio, as well as clearly signposted around Tepuka motu. Monitoring will continue for two years to see if YCA numbers increase.

Information sources

Burne, Gruber. 2016-2019. Management Plan Tuvalu (download 10 MB). Pacific Biosecurity Management Plan

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Location: Johnston Atoll, USA

Justification: Conservation

Goal: Eradication

Size: 52 ha

Products: Safari 20SG Insecticide (dinotefuran; 200 g/kg) mixed at 0.05% by weight with cat food for protein (25%), dark karo (corn) syrup for carbohydrates (25%), water (~50%) and a small amount of xanthan gum, a thickening agent. This bait was applied with squirt guns (27 kg/ha).

Time of year: January

Outcome: More than 99% reduction in ant numbers; however, eradication was not achieved

Programme cost: approximately 345 000 USD (an underestimate)

Manager: Stefan Kropidlowski (stefan_kropidlowski@fws.gov), U.S. Fish and Wildlife Service

Yellow crazy ants threaten seabird colonies on Johnston Atoll in the Pacific.

The first eradication attempts on Johnston Atoll, a former naval base, took place between 2010 and 2012 and experimented with a number of different methods.

 
Members of the 2012 Crazy Ant Strike Team with squirt guns full of cat food ant bait (© Stefan Kropidlowski-USFWS)

Bait stations containing Maxforce Quantum, and manually broadcasting Maxforce Complete and Provaunt all failed to control yellow crazy ants.

Control was successfully achieved when customized bait was developed by the team working on the eradication. They used Safari 20SG Insecticide mixed with catfood, corn syrup and xanthan gum and applied with squirt guns.

As the bait dried out very quickly, it was only applied a maximum of two hours before sunset (as the ants are active at night was well as the coolest parts of the day).

Treating the 52.16 ha infestation took 16 days, or 140 person hours (the bait preparation took 280 person hours).

This custom bait reduced ant populations by more than 99%; however it failed to eradicate the ants.

It should be noted that though Maxforce Complete and Maxforce Quantum did not affect yellow crazy ant numbers on Johnston Atoll, both these products used the same way reduced yellow crazy ant numbers by more than 90% after a single application in Kaneohe Bay, Hawai'i.

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Location: Johnston Atoll, Hawai'i

Time of year: March to May

Justification: Conservation

Goal: Eradication

Size: tested on 0.25 ha plots

Products: Safari 20SG Insecticide (dinotefuran; 200 g/kg; 6 L/0.25 ha) at 0.05% by weight in hydrogel crystals was applied three times every 10 days.

Outcome: 99% reduction in yellow crazy ant numbers after the third treatment

Programme cost: approximately 345 000 USD (an underestimate)

Manager: Stefan Kropidlowski (stefan_kropidlowski@fws.gov), U.S. Fish and Wildlife Service. Advisor Robert Peck (bwpeck@usgs.gov), University of Hawai'i at Hilo

Since 2012 additional research has been done on Johnston Atoll to try and find a technique that completely eradicates the ants.

The most promising technique so far is the application of 0.05% by weight Safari 20SG Insecticide in hydrogel beads. Hydrogel beads consist of polyacrylamide, which easily absorbs water and chemicals that dissolve in water (such as toxins and sugar), making them ideal bait carriers. Multiple 0.25 ha plots infested with yellow crazy ants were used to test the efficacy of this bait.

Applying 6 L/0.25 ha of bait by hand three times over a 30 day period (one application every 10 days) resulted in a greater than 99% reduction in yellow crazy ant numbers. Similar results were obtained using Safari 20SG Insecticide at 0.05% by weight in a cat food matrix and a textured vegetable protein matrix (applied at 6 L/0.25 ha).

 
Yellow crazy ants feeding on hydrogel crystals laced with insecticide (© Robert Peck-UHH)

Yellow crazy ant taking a hydrogel bead back to the nest (© Robert Peck-UHH)

Trials testing the efficacy of 0.01% by weight Optigard Flex (thiamethoxam) in a hydrogel matrix were conducted, but Optigard Flex failed to adequately control yellow crazy ants, with abundances being reduced by only 71% after two applications of the bait.

As hydrogel is quickly dried out by sun and wind, the matrix is applied a few hours before sunset on days with a low chance of rain.

Further Johnston Atoll work

Time of year: July - October; April - May

Justification: Conservation

Goal: Eradication

Size: 57 ha

Products: Safari 20SG Insecticide (dinotefuran; 200 g/kg) mixed at 0.05% by weight with either cat food for protein (25%), dark karo (corn) syrup for carbohydrates (25%), water (~50%) and a small amount of xanthan gum, a thickening agent (this mix applied at a rate of 24.1 kg/ha with squirt guns) or 20% sucrose solution in hydrogel crystals (60.8 kg/ha; applied manually).

Outcome: 99% reduction in yellow crazy ant numbers after the third treatment

Programme cost: for the hydrogel treatment alone approximately 60 USD/ha (treatment material costs only)

Manager: Laura Beauregard (Laura_Beauregard@fws.gov), U.S. Fish and Wildlife Service

Work to eradicate the remaining yellow crazy ant infestation on Johnston Atoll continues. Between July and October 2015 the entire formerly infested area was treated by hand with Safari 20SG Insecticide in two different matrices. Half the infestation was treated with the cat food mixture and the other half with the hydrogel crystals. The 2nd treatment was done 2 weeks after the first, some areas alternated between cat food and hydrogel crystals and others received only hydrogel crystals.

In April - May 2016 the infestation was retreated with Safari 20SG Insecticide in hydrogel crystals at a rate of 30.4 kg/ha, except where yellow crazy ants had been detected in the previous 4 weeks in which case 60.8 kg/ha were applied.

From June - December 2016 only areas where yellow crazy ants were found during monitoring surveys were treated. Monitoring was conducted within 7-10 days after treatment, and the area was re-treated, with hydrogel crystals or catfood bait, if yellow crazy ants were still present. The ants were considered eliminated if they were not detected during four biweekly monitoring session in a row. 85% of areas required 1-3 treatments, and a few needed 4-7 treatments before the ants could be considered eliminated.

Yellow crazy ants have now been reduced by 99% and are becoming increasingly difficult to find. Eradication is now considered possible.

Information sources

Kropidlowski, Woodward, Plentovich. 2012. Successful control of yellow crazy ants at Johnston Atoll NWR. 20th Annual Hawai’i Conservation Conference (Talk) https://vimeo.com/56951285

Peck, Banko, Donmoyer, Kropidlowski, Pollock. 2015. Efforts to eradicate yellow crazy ants on Johnston Atoll: results from crazy ant strike team IX, December 2014-June 2015. Hawai'i Cooperative Studies Unit HCSU-067. DOI: http://hdl.handle.net/10790/2586

Peck, Banko, Donmoyer, Scheiner, Karmi, Kropidlowski. 2017. Efforts to eradicate yellow crazy ants on Johnston Atoll: results from crazy ant strike teams X, XI and XII (June 2015-December 2016). Hawai'i Cooperative Studies Unit HCSU-081. DOI: http://hdl.handle.net/10790/3205. Creative Commons License

White. 2011. Eradication of yellow crazy ants on Johnston Island. Region 1 FY 2011 Invasive Species Control Program Proposal

Further information was provided by Kevin Donmoyer Field Operations Coordinator for CAST, US FWS, kevin_donmoyer@fws.gov

Further information was provided by Stefan Kropidlowski, Refuge Manager, Palmyra Atoll and Kingman Reef National Wildlife Refuges, US FWS, stefan_kropidlowski@fws.gov

case study reviewed by Kevin Donmoyer, US Fish and Wildlife Service, June 2017

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Location: Kaneohe Bay, Hawai'i, USA

Justification: Conservation

Goal: Suppression of numbers

Size: unknown

Products: Maxforce Complete (hydramethylnon 10 g/kg; granular matrix (unknown composition); 1.7 kg/ha); Safari 20SG Insecticide (dinotefuran 200 g/kg; 27 kg/ha); Maxforce Quantum; (imidicloprid 0.3 g/kg; liquid gel; unknown rate)

Time of year: unknown

Outcome: More than 90% reduction in yellow crazy ant numbers after a single application of each of these products. However, the area was always reinvaded from the surrounding untreated area.

Programme cost: not available

Manager: Sheldon Plentovich (sheldon_plentovich@fws.gov), U.S. Fish and Wildlife Service

Kaneohe Bay is home to a seabird colony. When part of this colony was invaded by yellow crazy ants the decision was made to attempt to reduce the ant numbers (eradication was not considered possible due to the large area the ants had already invaded outside of the seabird colony).

Three different treatments were tried in six-week pulses. Maxforce Complete was applied using hand-spreaders. Safari 20SG Insecticide mixed at 0.05% by weight with cat food for protein (25%), dark karo syrup for carbohydrates (25%), water (~50%) and a small amount of xanthan gum, a thickening agent to form a thick paste, was applied with squirt guns. Maxforce Quantum was distributed in Ant Café bait stations.

All of these treatments resulted in a more than 90% reduction in yellow crazy ant numbers after a single application. However, numbers rebounded after 3 months, partially due to reinvasion of yellow crazy ants from the surrounding area.

It should be noted that though Maxforce Complete and Maxforce Quantum reduced yellow crazy ant numbers in Kaneohe Bay, they failed to do so on Johnston Atoll.

Information sources

Plentovich, Russell, Camacho. 2012 The effects of yellow crazy ant (Anoplolepis gracilipes) invasion and subsequent control on burrow-nesting seabirds in the Hawai'ian archipelago. 20th Annual Hawai’i Conservation Conference (Talk) https://vimeo.com/56951284

Further information was provided by Sheldon Plentovich, Pacific Islands Coastal Programme Coordinator, US FWS, sheldon_plentovich@fws.gov

case study reviewed by Sheldon Plentovich February 2017

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Location: Wet Tropics, Queensland, Australia

Justification: Conservation, containment, economic

Goal: Eradication

Size: 880 ha spread across Wet Tropics World Heritage Area, sugarcane fields and residential areas (includes a 100 m buffer zone outside the infestation area to allow for foraging ants)

Products: Engage P (S-methoprene 5 g/kg; 5 kg/ha); AntOff (fipronil 0.01 g/kg; 5 kg/ha). The bait is currently applied to infested areas three times a year, for three years.

Time of year: Ideally, March, July and September. Starting in 2017, treatments will begin in the dry season in May and finish with the Engage P by September.

Outcome: Eradication attempts are ongoing; however, the infestation has been contained and its spread limited.

Programme cost: 2 million AUD to date. An additional 10.5 million AUD over three years has been granted by Australian federal and Queensland state governments to continue the eradication activities to clear YCA from in and around the Wet Tropics World Heritage Areas. This is the initial funding granted for a 10 year proposal put forward to the respective governments in 2015.

Manager: Lucy Karger (lucy.karger@wtma.qld.gov.au), Wet Tropics Management Authority

When the yellow crazy ant was first discovered near the Wet Tropics World Heritage Area, the infestation covered around 300 ha. However, due to a slow management response, lack of funding and and improved surveillance techniques, the infestation now covers about 880 ha (including a 100 m buffer zone), spread across World Heritage Area (61 ha), sugarcane fields (500 ha), residential areas (91 ha), riparian areas (20 ha) and other forested areas (208 ha).

The Wet Tropics Management Authority launched an eradication programme in 2014, whereby Engage P is applied aerially during wet season months (September-April) over the World Heritage area and sugarcane fields where possible. It is applied using hand spreaders in riparian areas and within 5 m of waterways and drains.

AntOff is applied aerially during the dry season (May-August) as per permit conditions for the use of this product. Fipronil is applied using hand spreaders in residential areas and riparian areas where aerial treatment does not reach (except within 5 m of waterways and drains where Engage P is used).

Infested areas are currently treated three times a year, for three years. The first round of three treatments was done in May, August and November 2014 (delayed due to wet weather).

 

Aerial baiting operations July 2016 (© Bill Carrodus)

Spreading bait over the cane fields using hand spreaders 2015 (© Gareth Humphreys)

The 2015 rounds were done in March, July and September and the 2016 treatments were done in April and July with the third treatment planned for September. Starting in 2017, treatments will begin in the dry season in May and finish with the Engage P by September. These months were selected to take advantage of the colony life cycle and make sure that there were no queens in the pupal stage.

The eradication attempts are ongoing with only 7 of 9 planned treatments done so far through the first round of funding (2014-16). Now that additional funding has been granted triple annual treatments will continue until 2019 (if required). However, the infestation has been contained and its spread limited.

In three sites no YCA activity has been observed after fewer than five treatments and are currently undergoing proof of freedom post treatment surveillance (two years of fine scale luring surveillance, deemed as internationally recognised best practice). In other areas there was a 70-99.9% reduction in worker numbers observed 6 months after the fifth treatment. However, numbers increased to a pre-fifth treatment quantity by April 2016, though through increased monitoring and research more effective baiting treatments are consistently being applied.

Information sources

Lach, Hoskin. 2015. Too much to lose: yellow crazy ants in the Wet Tropics. Wildlife Australia Spring 2015: 37-41

Further information was provided by Lucy Karger, Yellow Crazy Ant Eradication Programme Coordinator, Wet Tropics Management Authority, lucy.karger@wtma.qld.gov.au

Further information was provided by Chris Clerc, Yellow Crazy Ant Eradication Programme Technical Officer, Wet Tropics Management Authority, chris.clerc@wtma.qld.gov.au

case study reviewed by Chris Clerc, Wet Tropics Management Authority, August 2016