Imported Fire Ants, Solenopsis invicta, are one of the most serious ant pests in
the world and have recently been found in Brisbane, Queensland. A survey to detect any
that may have established in Western Australia is being conducted by Agriculture Western
Australia. The public is asked to assist by submitting specimens of any suspect Red
Imported Fire Ants (RIFA), as detailed below.
The amount of money spent on controlling RIFA is estimated to be
$900 million in the USA annually. If at all possible, the plan is to eradicate RIFA in
Australia, and prevent the need for a similar annual cost to Australians.
WHAT DO RIFA LOOK LIKE?
The Red Imported Fire Ants are small ants, varying in size from
2mm to 6mm. They are golden to reddish-brown in colour (see photo 1) and look like many
common native ants found around homes and in gardens. As their name suggests, RIFA have a
fiery sting, which is unusual in that blisters and then pustules develop at the sites of
the stings (Photo 2). Native ant stings dont develop these symptoms.
RIFA build characteristic mounds (Photo 3) that are low and squat,
up to 40cm high and half to three quarters of a metre in diameter. The mounds are built in
open areas, such as lawns, sporting grounds, golf courses and pasture paddocks and may
number in excess of 100 per hectare. They are different from the native stick-nest ant,
which builds mounds in bush areas in the south-west of Western Australia. Another feature
of RIFA mounds is that they often have grass and other vegetation growing through them
(Photo 4). RIFA require ready access to water and prefer lowland areas and situations next
to streams, ponds and lakes.
WHY ARE THEY PESTS?
RIFA are primarily an urban and human health pest, but also have a
significant impact on agriculture and the environment. In the USA, where this exotic
species is widely established, RIFA is estimated to cause losses of more than $3 billion
dollars annually, in terms of damage done and cost of control.
As an urban pest, RIFA thrive in backyards, school grounds, golf
courses and street verges and, as a consequence of their aggressive stinging behaviour,
deter outdoor activities. They commonly invade indoors and can injure pets if these are
tied, penned or caged and unable to escape.
RIFA chew electrical insulation and cause extensive damage to
electrical motors, air conditioners, pumps, transformers, telephone exchanges, signal
boxes and other devices. In the process of nest and mound building, they can excavate so
much soil that structural problems can result under paving, driveways, and retaining
In the USA, it is estimated that 33,000 people a year seek medical
attention for RIFA stings. Some severe cases require hospitalisation, and allergic
reactions can result in death, although this is rare. The cost to the community is
significant especially when workers compensation is included. Permanent scarring can
occur from RIFA stings.
In agriculture, RIFA have been recorded directly damaging many
species of cultivated plants from potato tubers to young citrus trees killed by ants
girdling the stems. They collect seeds, feed on germinating seeds and seedlings, and on
developing fruits and buds. Scale insects and aphids are tended and protected by RIFA,
resulting in severe infestations requiring the application of insecticides. The ants
frequently cause problems in reticulation systems and their activity in horticultural
paddocks can deter workers from harvesting fruits and vegetables. Numerous ant mounds,
commonly at 100 per hectare but sometimes exceeding 400 per hectare, can interfere with
hay cutting and can make the simple act of driving across farm paddocks difficult.
Livestock can be deterred from feeding and the area occupied by
mounds can reduce available pasture significantly. Animals in pens, feedlots or
high-intensity production systems can be attacked.
RIFA are omnivores, feeding on a wide range of plant and animal
material. They are aggressive predators and have a major negative effect on ground active
and nesting animals, from insects to frogs, reptiles, birds and mammals. Populations of
mice, snakes, turtles and other vertebrates have shown a two-fold reduction as a result of
RIFA infestation of an area. The native flora of an area can be adversely affected by the
ants feeding on plant seeds..
SURVEY FOR RIFA HOW YOU CAN HELP:
A nation-wide survey is underway to detect any RIFA that may be
present. This survey will help determine if eradication of the currently known RIFA
infestations in Queensland is viable. As there are over 2,000 species of native ants we
can only positively identify suspect RIFA from specimens. You can assist by submitting
suspect RIFA specimens. [CAUTION: Collect specimens away from the nest to reduce the risk
of being stung.]
Ants can be easily submitted by sticking about a
dozen suspect ants to clear sticky tape and sticking that to a piece of paper with the
collectors contact details. The specimens can then be posted to:
Fire Ant Survey
Locked Bag No.4
Bentley Delivery Centre WA 6983.
Suspect RIFA are:
- Small, golden to reddish brown ants 2-6mm long.
- Multiple ant mounds in urban or developed areas
- Pustule formation at sting sites.
Acknowledgements: Much of the information used in this
Factsheet has been obtained from various web sites based in the USA. Photographs 1& 3
are courtesy of Texas A&M University, Photo 2 from Tim Lockleys Fire Ant site
and Photo 4 is courtesy of Bill Crowe, QDPI.
|Photo 1: Red Imported Fire Ants (2-6mm in
||Photo 2: Pustule formation as a result of multiple Red
Imported Fire Ant stings.
||Photo 3: Red Imported Fire Ant mounds in paddock.
||Photo 4: Red Imported Fire Ant mound note
vegetation growing through it.