Blowfly strike is estimated to cost the industry almost $324 million each year, with $227 million of this due to production losses.

Flystrike is primarily caused by the Australian sheep blowfly, Lucilia cuprina.

Adult female blowflies lay their eggs in the moist wool of susceptible sheep.

After hatching, maggots progress through three larval stages before dropping from the sheep to pupate in the soil.

Depending on seasonal conditions, the entire lifecycle can be completed in just two to three weeks, meaning blowfly numbers can increase rapidly if susceptible sheep are available.

The onset of cooler conditions at the end of the fly season prevents the development of pupae, which are inhibited (or ‘arrested’) at the prepupae stage.

Elanco sheep brand manager David Rathbone says pupal development recommences once soil temperature begins to rise in spring.

“In south-eastern Australia, the first generation of flies tends to emerge at the same time, regardless of when the larvae were deposited,” he says.

“Fly numbers can build up rapidly under suitable environmental conditions if susceptible sheep are available.”

Treatment with an effective chemical early in the season can reduce the build-up of the blowfly population and the risk of blowfly strike later in the season.

“Applying a chemical treatment before blowflies emerge removes sheep as a breeding resource for the first generation of flies,” David adds.

“Strategically timed shearing or crutching will further reduce the susceptibility of sheep to flystrike.”

Most sheep and wool producers apply a preventative treatment at the same time each year, typically using a spray-on treatment, such as CLiK Extra.

Applied to sheep off-shears or with any length wool, CLiK Extra protects against blowfly strike for up to 29 weeks.

It can also be applied to protect mulesing and marking wounds against blowfly strike.

CLiK Extra contains 65 g/L dicyclanil, the same proven active ingredient in CLiK Spray-On.

Dicyclanil is a powerful insect growth regulator which breaks the life cycle of blowflies by preventing first stage larvae from developing into damaging second-stage maggots.

“CLiK Extra contains 30 per cent more dicyclanil than CLiK and provides up to five weeks’ longer protection against blowfly strike,” David says.

“Its two-band application technique for sheep weighing more than 30 kg provides extra protection against breech strike8,9 the most common site of blowfly strike in typical years.”

CLiK Extra provides extra protection against development of resistance where it remains above the minimum effective concentration (MEC) throughout the entire season and until flies are no longer active.

This will also reduce the need for re-treatment within the same fly season.

“All told, CLiK Extra provides extra peace of mind, knowing your sheep are protected against blowfly strike for up to 29 weeks,” David explains.

“That gives you the option to treat early whilst still providing season-long protection.”

Dicyclanil was discovered in the 1980s by Ciba-Geigy, which later became Novartis Animal Health.

Elanco acquired Novartis in 2015.

In-vitro and in-vivo tests indicated this molecule was significantly more potent than cyromazine, the active ingredient in Vetrazin, and provided significantly longer protection against blowfly strike.

Research continued throughout the 1990s and CLiK was registered for use in Australia in 1998, followed by CLiKZiN (12.5 g/L dicyclanil) in 2009 and CLiK Extra in 2017.

David says Elanco is continuing to develop new solutions to prevent and control blowfly strike at its Yarrandoo research facility in western Sydney.

“Yarrandoo is the only private-sector animal health R&D facility in Australia,” he says.

“It has played key role in the development of the CLiK portfolio and more recently, the development of Zolvix Plus broad spectrum drench for sheep and cattle.

“Elanco is committed to developing new solutions which improve the health and wellbeing of animals – and helping our customers to get the best results from their investment in quality animal health solutions.

“Our team of regionally-based representatives and technical advisors provide a range of practical, on-farm advice and support, including best practice guidelines, application training, applicator servicing and diagnostic services.”

Always read and follow the label directions. Good agricultural practice is essential for optimal blowfly strike prevention.