Kiwi scientists have shown how they can cleverly disrupt the foraging behaviour of a nasty invasive ant, leading it in circles and away from its nest.
A new study by Plant and Food Research, B3 (Better Border Biosecurity) and University of Auckland is the latest example of scientists cunningly seizing on odour to combat invasive pests.
In this case, they're targeting the Argentine ant, considered among the top 100 worst invasive species on the planet and found in most regions of New Zealand.
Along with problems they cause for urban households, the widespread species also poses a risk to agriculture by competing with the food sources of other invertebrate species, such as pollinators.
A previous New Zealand study also showed how they could also act as tiny reservoirs for a pathogen associated with the colony collapse of honey bees.
While the insects are heavily reliant on chemical cues such as odour trails for orientation and retrieving food, the behaviour of outdoor colonies has suggested tactile features in their environment are also used to assist with foraging.
Understanding these physical cues has helped researchers to determine how this ability might undermine pest control methods that involve using pheromones to disrupt the ants' foraging behaviour.
"We've been researching the effects of applying synthetic pheromones to confuse the ants to prevent them from working together in harvesting resources," said Plant and Food Research's science group leader, Professor Max Suckling.
"It's a benign, targeted method for pest management whereby we can get the ants walking in circles instead of making their way back to their nest with your lunch."
To understand the ants' reliance on chemical and physical cues for orientation, the researchers took five Argentine ant colonies into the laboratory and conducted a range of experiments where string was used as a physical cue to determine the trail-following ability of the ants when subjected to different types, amounts and delivery of disruptive pheromones.
"Trail integrity eventually reduced under a continuous oversupply of trail pheromone delivered directly on to the string, but it was clear that the physical cue of the string did improve their trail following," Plant and Food Research Scientist Lloyd Stringer said.
"The ants do not appear to switch from smell to physical cue orientation in the presence of an oversupply of trail disruption pheromones, but they do seem to recover quickly from an oversupply of pheromone when in clean air.
"This information should help with strategies for dealing with them in different environments in the wild."
Now that it was known that odour detection was the primary means for navigation - and as such could be overwhelmed by adding excess trail pheromone - researchers could conduct further experiments to determine if Argentine ants can employ other cues for orientation.
The research, just published in international online journal Scientific Reports, will ultimately contribute to finding long-term, sustainable methods for reducing nest stability.
Other pest-busting work by Landcare Research that has drawn on odour has included a "chemical camouflage" to shield vulnerable and breeding birds from predators, and another study that revealed how ferret stench could be used to lure stoats and other pests into traps.
• Worker ants of the species measure between 2-3mm long and are a uniform honey-brown colour.
• Listed by the World Conservation Union as one of the world's worst invasive species.
• Originally established in Auckland in 1990, and now a problem in an increasing number of towns and cities throughout New Zealand.
• Spread through different areas by hitching rides in freight, potted plants, rubbish, vehicles and other such goods.