Garry Webb of Sumitomo Chemical outlines the threat posed by invasive ant species.

Australia is an ideal environment for the introduction and establishment of invasive animals and plants. As an isolated island continent, Australia abounds in ecological niches that invasive species can take advantage of – look no further than feral rabbits, cats, foxes, pigs, deer, camels and even the iconic brumby. But these are the big ticket species. Think a little smaller and we have just as many problems from invasive agricultural pests to something of interest for professional pest managers. We don’t think twice about it but most of the common pests we deal with, such as American and German cockroaches, cat fleas and a range of other species are invasive insects – they don’t originate here in Australia. The good old coastal brown ant (aka African big-headed ant) has been here for over 100 years and we call it our own.

There are five ant species on the world’s most invasive species list1 and Australia is home to all five of them – Argentine ant, African big-headed ant, yellow crazy ant, little fire ant (electric ant) and red imported fire ant (RIFA). Along with these we have the tropical fire ant, which is widespread in northern Australia, and very recent introductions of the browsing ant Lepisiota frauenfeldii at Perth Airport, Darwin and now at the port of Brisbane. There is also a range of ant species of cosmopolitan but uncertain origin including pavement ant (Tetramorium), white-footed house ant (Technomyrmex), ghost ant (Tapinoma), black crazy ant (Paratrechina) and various species of Monomorium, some which are invasive (e.g. Singapore ant and pharaoh ant) and others that are also very likely to be invasive species. Only two of these species are now considered to be of national significance – RIFA in Brisbane and electric ant in Cairns. The status of yellow crazy ant, Anoplolepis gracilipes (main picture, above) has been downgraded from federal to state and now local significance because it is no longer considered to be eradicable. The rest are the forgotten invasives that attract little or no attention at any level of government.

The black crazy ant, Paratrechina longicornis

An endless stream of container ships arrive at Australian ports from all over the world and we will continue to be challenged in the ght against establishment of invasive species. Luckily we caught the incursion of RIFA into port Botany in Sydney in 2013 and it is now eradicated. The recent port of Brisbane incursion of browsing ant will require a variation on theme because standard bait products are not effective. There is no silver bullet for invasive ant species; they all have different nest biology, reproductive potential and food requirements. A very recent study by James Cook University2 has highlighted some of the problems associated with baiting yellow crazy ant – today’s food preference is a reflection of food availability in the past. Following a diet of predominantly protein, they prefer sugar. So standard bait products may not always be effective.

The browsing ant, Lepisiota frauenfeldi, was first detected in Perth in 2013 (photo credit: Eli Sarnat/ CC)

Red imported fire ant (RIFA) was discovered in Brisbane in 2001 and since then the joint federal and state task force has spent in excess of $350M in attempting to eradicate it. To a large extent the endeavour has been successful, with RIFA eliminated from the core areas of infestation, but has been less successful in limiting its outward expansion and re-infestation of past infested areas due to operational difficulties in limiting the movement of soil, plants, building material and earthmoving equipment. Nevertheless, the Brisbane program has been the most successful eradication program worldwide, with the exception of the elimination of a small infestation in New Zealand and recently the port of Botany infestation.

RIFA is the big ticket item in the invasive ant world, largely because of its human health impacts and its potential to affect agricultural, urban and natural environments. However, the impacts of other invasive ant species should not be ignored. Their impacts are largely ecological but some still do impact people and agriculture directly. The sting of tropical fire ant is no less painful than red imported fire ant but its distribution (northern Australia) overlaps less with human occupation. Hence it receives less attention from biosecurity authorities. Yellow crazy ant is now much more widespread and has become a more significant pest of urban areas, particularly in northern Queensland. The ants’ ability to spray formic acid onto sensitive skin causing painful ‘burns’ and into the eyes of pets and livestock sometimes causing blindness is of concern. Singapore ant is not of medical concern but it is another invasive species that seems to be on the move, spreading to new areas in Queensland. As they spread, some of these invasive ants are becoming urban pests and entering the orbit of the pest management profession. These new invasive species complicate the process of selecting appropriate treatments.

Synergy Pro was developed primarily for the control of invasive ants with the aim of being a broader spectrum bait. Synergy Pro combines the effects of the ATP inhibitor hydramethylnon with the IGR pyriproxyfen to target all life stages and deliver complete colony control. With many of the invasive ant species being oil/protein feeders, the two different food granules (one protein, one oil), make Synergy Pro ideally suited for targeting these ants. As invasive ants are primarily outdoor species, the granule format also makes it easy to treat large, infested areas.

However, as with all ant management programs, in many cases a combination of products should be used. Certainly when dealing with invasive ants the use of non-repellent sprays in combination with Synergy Pro should be considered, especially in situations where there are large numbers of invasive ants. Sprays can be very useful to reduce population numbers and protect buildings while Synergy Pro can deliver the colony control.

Garry Webb, Sumitomo Chemical Australia

1 Lowe S.J., Brown M. and Boudjelas S. (2001). 100 of the world’s worst invasive alien species. Aliens: The Invasive Species Bulletin 12: 1-14.

2 Lach L., Volp T.M. and Wilder S.M. (2019). Previous diet affects the amount but not the type of bait consumed by an invasive ant. Pest Management Science, https://doi. org/10.1002/ps.5365.