Saturday, December 2, 2023

No quick fix on fruit fly outbreak

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South Australia shares lessons from its belt-and-braces approach.
Eradicating Queensland fruit fly is no quick task, as South Australia’s experience has shown.
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South Australia’s management of a Queensland fruit fly incursion two years ago provides New Zealand growers with insight into just how thorough a response has to be to deal with the pest.

Nick Secomb, director of plant and invasive species biosecurity for South Australia, shared with this year’s Kiwifruit Vine Health biosecurity seminar how his state responded to the event, and the ongoing work to see it to its completion.

The state is about to celebrate 75 years of being fruit fly free. It and Tasmania are the only two in Australia to have the status, with Western Australia still having the Mediterranean fruit fly.

With a budget of $5 million a year, three quarantine border patrols and a desert to the north and west, Secomb said the state also enjoys a high level of community engagement in monitoring the pest, including thousands of backyard sentinel traps.

In late 2020 the fruit fly was discovered in the productive Riverlands area, at the height of covid-19 lockdowns and restrictions.  

Ongoing and widespread outbreaks ensued throughout the year and growers have faced two years of restrictions on orchard access and fruit sale that required fumigation even if selling into the local market.

Secomb said the agency’s response to the outbreak has been prolonged and successful, but it will take another 18 months before the state’s growers can expect things to return to normal. 

Response approaches have included collecting over 500t of fruit for destroying, the release of 20 million sterile male fruit flies, placing 3000 traps in the Riverlands district and visiting over 100,000 properties. Fruit fly detection dogs have also been successfully deployed, and unwanted fruit trees have been cut down.

South Australia has a facility for the controlled irradiation of fruit flies, known as Sterile Insect Technique,  which Secomb said plays a key role in driving numbers down even further and faster. It has proven particularly valuable on backyard populations in residential areas.

Researchers have found that the sterile male flies do not appear to have the same damaging effect on fruit as untreated fruit flies.

“Models have suggested we would be done by the end of the year but that is not going to happen. 

“Our goal is to get to the end of the year with no further detections, then allow 12 months assurance of freedom to our markets, 18 months all up.”

He said South Australia has a good combination of “carrot and stick” incentives and regulation when it came to dealing with the response, and in maintaining a good historic level of biosecurity.

Communications are across as many different media as possible. Dealing with English as a second language has become a challenge more recently, along with “residential fatigue” from householders having staff visit their backyard traps frequently.

Secomb said the state’s action all took place alongside a national committee of fruit fly management, and a challenge at times was dealing with different states’ status on the fly’s infestation.

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