Fire Ants – Still Here

Fire Ants first were first reported in Brisbane in 2001 and since then been under an eradication plan by Biosecurity Queensland. More than $275 million has been spent on the eradication programme. But a recent report has indicated that the area infested by Fire Ants has increased to 342,000 ha in December 2011. So, is it a battle that can we won?


The Red Imported Fire Ant (RIFA) is a significant turf pest in the temperate and tropical areas of the USA. In 2005 I was stationed at the Envu Research Station in North Carolina for a few months and one of the projects we worked on was fire ant control. RIFA (Solenopsis invicta) is a relatively small red-brown ant which grows up to 6mm in size. Their nests can be mounds or flat areas of loose soil. There is no obvious entrance as occur with other ant nests. The nest has a honeycomb structure of tunnels which then can lead to multiple openings at the soil surface.



What makes them such a problem is their aggressive nature, especially when nests are disturbed. A nest can contain several hundred thousand ants and the number of ants per hectare can be in the order of several hundred. The sting of the RIFA is very painful and because the ants swarm together you can get stinging from a large number of ants at the same time. When we worked in areas with RIFA we would wear gum boots which were treated with a band of insect repellant to ensure you didn’t end up with a painful surprise. In the USA insecticide treatment is an absolute must on many golf courses, sportsfields and domestic lawns, otherwise the use of these areas turf area is nearly impossible.

In Australia RIFA have been declared a notifiable pest under the Plant Protection Act 1989 and suspected sightings must be reported to Biosecurity Queensland (phone: 13 25 23) or heavy fines could be imposed. To date surveillance of the infested area has been by ground-based surveys. These are time consuming and expensive, so the latest development has been to take to the air.

Currently remote sensing technology is being trialed to see if it can successfully detect Fire Ant infestations which can then be confirmed and treated by ground crews.

Remote sensing is done by specially mounted cameras on helicopters which fly at a height of 150m and capture images at three different frequencies (visible, near infra-red and thermal). In the right conditions RIFA nests are 10oC warmer than the surrounding soil and image analysis technology developed by the University of Sydney is then used to detect nests. The estimated cost of this technology is $72 per hectare and 750 hectares could be covered in one day. This would save $24 million a year compared to ground-based surveillance. The remote sensing is being conducted in areas into which it is expected the RIFAs have expanded based on modeling done by Monash University. The remote sensing trial found a success rate of 75% in detecting nests and five false positives per hectare. False positives are cases where the image analysis predicted a nest, but field confirmation actually found it to be something else rather than a RIFA nest. Refining of the technology is likely to improve the success rate and decrease the false positives.


So can the battle be won? When the RIFA was first detected in Australia I asked some turf entomologist in the USA what hope they thought we had of eradicating the pest from Australia. They felt that there was no chance of this occurring. Some still believe that eradication could be achieved. Even if this is not possible to limit the impact, reducing the spread of RIFA is very important in the future.

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