Sheep blowflies (Lucilia cuprina) costs the Australian sheep industry $323.7M p.a. (Priority list of endemic diseases for the red meat industries, MLA B.AHE.0327, Shephard et al., 2022).  It causes a 10 -20% mortality rate in fly struck sheep, requiring chemical use to both treat and prevent.

Resistance to the most commonly used and long-lasting preventative chemicals, cyromazine (e.g. Vetrazin) and dicyclanil (e.g. Clik), has emerged. This compromises control by other classes of chemicals and adds to the entrenched resistance to organophosphates.. Further, fine wool Merino genetics are currently missing the diversity required to be able to select rams with smooth/strike resistant breeches, resulting in the continuation of mulesing.

Sheep blowflies occur at low population densities and the females need only to mate once. This makes them very vulnerable to population control by the Sterile Insect Technique (SIT). Work conducted by CSIRO in the 1970s and 80s, using a genetic translocation induced by radiation, showed efficacy of the concept in Australia. After 6 months they achieved an 87% reduction in flies on Flinders Island. However, the prior paradigm was directed at eradication that is technically difficult in Australia. This is because of its size and lack of geographical features that allow an eradication program to be rolled out like a carpet across the blowflies’ range.

This NSW DPI funded project completed extensive laboratory experiments, developed Lucilia cuprina specific parameters to determine fitness and conducted sheep trials using infertile male blowflies. Trials were initially conducted in insect proof sheep pen facilities to determine the efficacy of the sterilisation process and the success of infertile males to compete with wild type males in mating with wild type females. Trials were also conducted on release and control sheep properties. Firstly, mid blowfly season at CSIRO’s Chiswick Research Station and lastly in the Yass Valley, prior to emergence of the overwintered population, to prevent or suppress the spring flystrike season. Flystrike was successfully prevented on the Yass Valley release property across the spring and early summer flystrike season, ending just prior to shearing.

This project has proven that the release of infertile male sheep blowflies (L. cuprina) can be used as part of an integrated pest management approach to prevent flystrike at a property level.

There is scope for  future collaboration with Macquarie University, who have skills and expertise with diets for Fruit flies and SARDI, who are currently building a blowfly manufacturing facility on Kangaroo Island and plan an eradication program on that island. This NSW DPI study and our expertise is providing valuable information to SARDI Kangaroo Island eradication program.

This approach would be clean, green and sustainable, and has the potential for significant reputational and financial benefits for the Australian sheep-meat and wool sectors. As a result of this project, NSW DPI has contributed to alternative pest control methods globally.

Project value: $300,000