A plan to rid Kangaroo Island of sheep flies within five years could be a precursor to a wider program in Australia.
Research and Development Institute of South Australia researcher Maarten van Helden said the world’s first dedicated sterile fly breeding facility on the island would be expanded over the next 12 months.
The brownfield will become a state-of-the-art insect breeding center on the island, where up to 50 million flies a week will be bred and irradiated to make them sterile before release.
The facility will be built from shipping containers located at the Kangaroo Island Resource Recovery Center and will be operational by mid-2023. It will and will be in place for up to five years, after which it can be deployed elsewhere within South Australia to continue the program.
Dr van Helden said by releasing sterile flies to compete with their naturally fertile counterparts, the fly – Lucilia cuprina – could be eradicated from the island within 3-4 years.
The results of the $3.45 million Kangaroo Island project will then be used to expand operations nationally.
“Yes, that’s the idea of continuing on the mainland – of course you can’t really eradicate it on the mainland because there will always be flies coming from areas you don’t treat.”
There have been some experimental releases of sterile flies with larger releases over larger areas in the spring of 2024 to collect data on fly longevity and migration.
Kangaroo Island’s isolation makes destruction possible
Dr van Helden said the KI work would answer questions such as how quickly flies can be eradicated from an area, how long it takes for fertile flies to repopulate a treated area and when the treated area should be withdrawn.
“Such questions are scientific questions that do not yet have answers.”
Dr van Helden said the same technique that would be used on Kangaroo Island was the same method that protected South Australia from fruit flies.
“We think Kangaroo Island is far enough from the mainland that the flies can’t get in on their own, so we think we can eradicate them.”
Dr van Helden said it would be impossible to cover Australia with sterile flies in a year’s time.
“It should be territorial.”
Work has been done in the southern United States and Mexico to eradicate the screwworm fly and push it south into Panama, releasing billions of sterile flies, he said. Dr van Helden said CSIRO had also tested sterile fly releases in Australia, but these were not strong enough to compete with flies in the field.
He is confident that SARDI can now breed a more powerful fly at a lower cost.
“We’ve actually gone back to basics, we’re usually a sterilized wild breed of fly that needs to be well adapted.
“We’re not trying to create infertility in the wild population, we’re just going to mate our sterile males with wild females.”
This results in the female flies being unable to lay eggs. Adult flies can live for several months. Dr van Helden said regular releases would increase the number of sterile flies over time and increase their effectiveness.
“Maybe leave up to 10 times in the spring.”
Dr van Helden said expanding the program beyond Kangaroo Island would depend on KI results, industry and government and available funding. Potential areas could be areas with high concentrations of sheep, including southeastern South Australia, Yorke Peninsula, Tasmania or Western Australia.
A report published for Meat and Livestock Australia in 2021 found that Australia has the capacity to mass-reare sterile males within 1-2 years using existing knowledge and capacity for areas of 2000-5000km2. Kangaroo Island. The report notes that once established, the sheep fly can be eradicated within 3-4 years at an estimated cost of $5-6 million, including the creation of a facility that can be repurposed later.
The sterile insect technique is also being used successfully against the sheep fly in Bangladesh, the report said. Flystrike infestations can cost the industry $173 million a year in storage loss, yield loss and control measures. These losses can potentially be reduced by reducing sheep fly populations through SIT, the report says.