For 17 years a Perth council has been fighting a losing battle against hordes of mosquitoes breeding in urban wetlands.
In an attempt to turn the tide, it has adopted drone technology to combat the insects' relentless sorties against residents of the city's inner north-east.
For 20-year resident David Crispin, it cannot come soon enough.
"Sitting out on the balcony, you'd be swatting them away and they would certainly come in [the house]."
Among Australia's first
In a trial already underway, the City of Bayswater has become one of Australia's first local governments to use drones to spray mosquito larvae in areas that are otherwise difficult for its workers to reach.
Mosquito Control officer Don Sorensen said staff had previously tried to spray mosquito larvae in the Berringa wetlands by foot, "but we just sink in the mud and lose our wellies".
"Sometimes you're up to your waist in mud so it's quite dangerous.
He said the council had also tried using a six-wheeled amphibious vehicle to traverse the wetlands, but it would become bogged in heavy mud.
"We had to leave it for a while — until we started researching the drones," Mr Sorensen said.
Stocked with larvicide
Multiple drones weighing up to 67 kilograms have been fitted with 30-litre tanks of a biological larvicide, which specifically targeted mosquitoes.
The naturally occurring soil bacterium was only toxic to mosquito larvae and did not harm surrounding wildlife or vegetation.
The drones are controlled by certified drone pilots, who are notified by a safety spotter on the nearby Swan River about any changes in weather or if there is a nearby kayaker or fisher.
Mr Sorenson said the wetlands had provided excellent mosquito breeding conditions for the past couple of years.
He said the council planned to treat about six hectares of wetlands using drones over the peak mosquito season from December through to April.
On high alert
But the mosquitoes were more than just annoying pests.
Mr Sorenson said there was an ever-present potential for mosquito-borne diseases like Ross River virus and Barmah Forest virus in the City of Bayswater and surrounding local government areas.
Mosquitoes in Western Australia could also transmit Kunjin virus and the potentially fatal Murray Valley encephalitis virus.
WA Health senior scientific officer Dr Jay Nicholson said data showed the number of Ross River virus cases in the Perth metropolitan area had increased since January, although he did not provide figures.
"This [increase] is consistent with the five-year average," he said.
"Given January-March is peak mosquito season in the metro area, this is not surprising and we would expect the cases to reduce as we move into the cooler months."
WA authorities were also on high alert for any cases of the Japanese encephalitis virus, which had been recorded in Queensland, New South Wales, Victoria and South Australia this year, although there had been no cases recorded in WA.
Strict guidelines in place
Chris Sieber, owner of Omnidrone, the company contracted to carry out Bayswater's mosquito-busting operation, said mosquito mitigation was a "unique" way to use drone technology.
"This technology is still very new in the industry," he said.
"A lot of the capabilities of drones — and also the limitations — are not completely known."
He said it had been two years in the making due to strict regulations involving drones in populated areas.
"We have had to put safety plans together, procedures to fulfil the requirements of the Civil Aviation Safety Authority (CASA)," Mr Sieber said.
City of Bayswater Mayor Filomena Piffaretti said the council also worked with WA's Department of Health and neighbouring local governments to monitor and combat mosquito-borne diseases in the eastern portion of the Swan River.
"We share the responsibility of managing the mosquito issue with other local governments along the Swan River and several other councils have already expressed an interest in our [drone] trial," she said.
