Challenges ahead for growers without fruit fly 'silver bullet'

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Growers in Western Australia are scrambling to find good alternatives to the fruit fly pesticide fenthion, which will be banned in October.

Fruit growers in Western Australia face a challenging time ahead without access to the 'silver bullet' of fruit fly insecticides. 

Fenthion, or Lebaycid, will be banned after October this year for public health precautions.

Orchardists have spent this growing season trialling alternatives, which include bait sprays and traps.

Some farmers report crop losses without fenthion, while others report success using alternatives for monitoring and controlling the Mediterranean fruit fly (Medfly).

WA grower Garrie Vincenti has not used fenthion for four years and said the level of crop damage today was lower than when the orchard used fenthion.

“We’ve had a fantastic success rate,” Mr Vincenti said.

He said success came after realising the problem with Medfly was on his orchard, not the neighbours’ properties.

“[Medfly] don’t travel at all,” he said. “...We were actually breeding the fruit fly ourselves.”

Medfly was considered a lazy fly, which would not travel much if food was available, WA Department of Agriculture and Food senior entomologist Darryl Hardie said.

“It’ll stay put if it has got host material,” Mr Hardie said.

Since Mr Vincenti’s realisation the Medfly problem was close to home, the orchard has adopted a "systems approach", which involved monitoring all year, baiting and trapping the Medfly at the right time, and using an alternative chemical as a last resort.

Another WA grower, Brett DelSimone, said trailing the alternatives to fenthion had caused significant damage to crops in the Perth Hills region.

He represents the Hills Orchard Improvement Group, who are outspoken about the effects of fenthion's ban.

“We’ve seen high crop losses, as high as up to 50 per cent,” Mr DelSimone said. “It’s going to take some time in the transitional period.”

He said the quality of fruit going to market would not be different.

“The consumer basically will not see a lot of the issues we’re having on orchard.”

Nothing controlled the Medfly like fenthion, Mr DelSimone said.

Vietnam has suspended its imports of Australian fruit, citing concerns about Medfly.

"The [Medfly] is the world's worst economic pest," Mr DelSimone said.

Australia has moved to ensure the Vietnamese the Medfly is not present across all of Australia, although another breed of fruit fly affects crops in the nation’s eastern states.

The Australian Pest and Veterinary Medicines Authority (APVMA) said fenthion would be banned from October this year, after restricting the chemical’s use in 2012.

The APVMA concluded last year: “the use of products containing fenthion may, in most situations, pose undue risks to human health (via dietary and occupational exposure) and the environment.”

The APVMA has said some farmers are using alternatives, but success varied according to how regular and consistently farmers applied the chemicals.

Mr Hardie said farmers no longer have a silver bullet but success can be achieved with a better-coordinated approach.

“It will be more complex for growers to develop these systems,” Mr Hardie said.

A community-based solution in Carnarvon is to flood the Medfly population with sterile males.

“The females might get upset with some of the flies we release,” he said.  

Source SBS

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