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ABC RURAL

Moroccan fly could help keep pest pointed snails under control

SA Country Hour / 

By Lucas ForbesPosted 2ddays ago

A fly emerges from the shell of a pointed snail.
This particular strain of Moroccan fly parasitises pointed snails.(Supplied: Yassine Fendane)

  • Scientists have imported a Moroccan fly to Australia to test if it can be used to kill introduced pest snails.

Key points:

  • Scientists are looking to introduce a Moroccan fly to Australia so it can kill pest pointed snails
  • Pest snails are a major issue for farmers, particularly in wetter areas
  • Scientists are studying the fly under quarantine in Australia, to see if it will damage the environment if released

Pest snails eat Australian crops and can get caught in machinery during harvest, costing Australian farmers dearly — especially those in high rainfall areas.

However, the CSIRO is studying a strain of a parasitic fly under quarantine that could help get pointed snail numbers under control if it can be safely released into Australia’s environment.

CSIRO researcher Valerie Caron said, unlike other pest control methods, using flies as a biocontrol agent required little action from humans once they were released.

“They lay the larvae on the shell, and that little larvae will go inside the snail, it will kill it and eat it and the only thing that comes out of the shell after that is another fly later that can also mate and reproduce and kill more snails,” Dr Caron said.

Before that though, scientists need to be sure that this fly will not kill native snails as well.

A black fly on a branch with several snails with pointed shells.
A parasitic Moroccan fly looking for its host in the field.(Supplied: Yassine Fendane)

Perhaps the most infamous example of a biocontrol agent gone wrong is the cane toad.

Cane toads were brought into Australia in 1935 to control cane beetles in the sugar cane industry, but quickly spread throughout the country becoming a pest and outcompeting native wildlife.

However, Dr Caron said Australia’s biosecurity practices had changed to prevent another cane toad situation.

good generic pic of cane toad
Cane toads were originally introduced to keep other pests from getting out of control.(ABC)

“The CSIRO, SARDI, and me as a researcher, there’s no way we want to have our names associated with a pest, or with a biocontrol agent that becomes a pest,” she said.

“We’ve come a long way since the cane toad and that’s why we have good biosecurity regulation, and we also have our ethics — making sure that we wouldn’t do anything harmful.”

‘No silver bullet’ for pests

The Moroccan fly, which scientists are studying, has been imported into Australia before.

A strain of the same species based in France was released on South Australia’s Yorke Peninsula in the early 2000s.

However, Dr Caron said that fly did not work as well as they wanted, possibly because of where it was from.

Scientist Dr Valerie Caron
The CSIRO’s Dr Valerie Caron says scientists need to be sure that this fly won’t damage the environment before it can be released into the wild.(Supplied: CSIRO)

“We really hope that it is going to help with controlling the pointed snail. But further research down the line showed that, first, it didn’t spread very much and second, it really didn’t suppress population like we were hoping,” she said.

“More research showed that, when we look at the genetics of the snails, the ones introduced to Australia don’t come from France at all, they come from Morocco, Portugal, Spain. So then, where we got the fly from is not where our invasive snails are from.

“We thought that maybe if we really look at where the snails come from, maybe we can find something that is more efficient.”

However, Dr Caron said the flies would not fix pointed snail populations by themselves.

“I call snails super organisms, they’re extremely hard to control and I think any producer with snails will agree with me — they’re very difficult to control,” she said.

“So I would say to everyone, it’s not going to be a silver bullet against snails. They’re extremely adaptable.”

Biocontrol agents at work in Australia

Perhaps one of the most famous biocontrol agents to be used in Australia was Myxoma virus, which causes myxomatosis in rabbits.

In the 1950s, Australia’s rabbit population numbered around 600 million, eroding soil and competing with livestock for pasture so much so that farms were abandoned.

Myxomatosis reduced rabbit numbers and, while they would eventually recover, they still have not reached the same numbers they did in the 1950s.

Two rabbits in a field
Myxomatosis is perhaps the most famous case of a biocontrol agent at work in Australia.(ABC News)

Prickly pear was another pest that was successfully suppressed with biocontrol agents.

The cactus was introduced to Australia in 1840 and by 1930 it had infested 30 million hectares around Brisbane.

However, the cactus moth helped turn the tide with trillions of the moth’s larvae consuming an estimated 1.5 billion tonnes of prickly pear in less than a decade after its introduction in 1926.

More recently the Federal Government provided funding for scientists to import a South African weevil that could be used to control fireweed, a yellow weed that can poison livestock.
Posted 2ddays agoShare

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