Fly fight proving fruitful

Primary Industries Minister David Basham said while the contaminated fruit thought to have caused the outbreak had come from interstate, seasonal conditions had exacerbated SA's worst fruit fly outbreak in history.

"Last year, we had a mild winter and summer, which gave us no check within the natural cycle," he said.

"We also had a warm, early spring, which allowed the fruit fly to breed up. So when we didn't have extreme summer temperatures, it was really hard to keep on top of populations."

Last week, there was another outbreak in Marleston, taking the tally to 10 Mediterranean fruit fly outbreaks and one Qld fruit fly outbreak in metropolitan Adelaide, affecting up to 310 suburbs, while the Riverland has three Qfly outbreak zones in Monash, Renmark West and Cooltong.

Qfly is endemic in the eastern states, while the Medfly is endemic in WA.

"What exacerbates the Adelaide scenario is that because we have had so many outbreaks over a period of time, we haven't been able to remove any zones from suspension, even if they have had no further detections," he said.

"If they fit within the over-arching circles of the new outbreak zones, they stay in under the rules."

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Restrictions will now remain in place across metropolitan Adelaide until December 4.

The gravity of the situation was also highlighted late last month when Mr Basham said Qfly larvae was detected seven times in SA supermarkets across 10 days.

"We normally average three to four larvae detections in supermarkets each year - so something went drastically wrong," he said.

Mr Basham said the fruit had come from the Sunraysia region in Vic and the participating properties were "suspended".

"The frequency stopped pretty quickly, so it appears that issue in the chain has been rectified," he said.

"But PIRSA is working with the Vic Department of Ag to better understand how it happened."

Mr Basham said it was pleasing to see there had been no crossover of fruit fly outbreaks between Adelaide and the Riverland, highlighting that people within SA understood the importance of minimising fruit movement.

He said there had also been a noticeable decrease in fines being handed out at the Yamba quarantine station, which showed the zero tolerance message was getting through.

"Yes, there has been less people coming over the border because of COVID-19, but on a percentage, there has been a significant drop in people bringing fruit to the border," he said.

From January to March last year, 1851 expiation notices were issued at Yamba, while only 397 have been issued so far this year.

Mr Basham said they were considering releasing sterile fruit flies along the border as a natural barrier.

"It is something we will consider in the winter months, when we hope to be not so intensively managing the outbreaks," he said.

Mr Basham said sterile fruit flies had been used "significantly" since April 2020, with more than 176 million sterile flies released in the metro area and 21m released in the Riverland.

"We use them in the clean up phase, after the first eight weeks of baiting, trapping and spraying," he said.

"But there are strict protocols when we use the flies to appease our trading partners, as they don't recognise the difference between the two flies."

Mr Basham said sterile flies were currently being used at Monash, which was nearing the end of its quarantine on March 22.

"Unfortunately there is larvae still being detected in backyard trees at Renmark West and Cooltong, so eradication dates have been extended to October," he said.

"These detections have unfortunately triggered the 'overwinter period' - a time when it's possible for Qfly to survive through winter."

Mr Basham stressed the importance of backyard fruit tree management, particularly removing fallen fruit.

"Removing host fruit reduces the options for fruit fly to lay their eggs. We want to upset the cycle," he said.

Fruit removal was the target of a recent eradication program in the two "hotspot" Adelaide suburbs of Prospect and Stepney, where there had been a significant number of larvae detections.

Mr Basham said that removal program was considered a success as there had been zero detections reported in those suburbs this week.

"PIRSA officers stripped nearly 8500 tonnes of fruit from backyard trees in those two zones over two days," he said.

"We were very grateful people were happy for us to come in and do it. We are still seeing a few fly detections around those suburbs, which is not ideal, but is not as bad as finding larvae."

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Last week, opposition primary industries spokesperson Clare Scriven criticised Mr Basham for not meeting with the State Fruit Fly Committee enough to get the outbreaks under control.

"This fruit fly crisis has been an issue well beyond the Riverland for more than nine months, yet he has not acted to bring them together," she said.

"SA is at risk of permanently losing its fruit fly-free status amid conflicting communication and a lack of leadership from the minister."

In response, Mr Basham said the state committee last met on February 22 to talk about both outbreak regions.

"The state committee generally meets on an annual basis at a minimum, but will also come together when it feels it's necessary to do so," he said.

"But there is also a great crossover of membership between the state committee and the Riverland fruit fly committee that meets on a weekly basis.

"The Riverland committee is a much more operational, engaging committee as that's where industry is. They still give advice to PIRSA about the metro area, as it is all about protecting the commercial growers.

"My information comes through PIRSA or industry members on that committee about where things are at and how to respond. There is an enormous amount of communication going on to get on top of this."

Mr Basham said the state government had spent about $17m so far on the eradication program.

"We expect that figure to surpass $20m when we hope to have this under control by Christmas," he said.

"But we also have to see what weather arises to assist us - we really need a cold winter and a hot summer."