WHERE DO FLIES GO AT THIS TIME OF YEAR?

The Australian sheep blowfly Lucilia cuprina is the primary fly species responsible for flystrike.

In cooler conditions at the end of the fly season, any further development of Lucilia cuprina from its larval or ‘maggot’ stage is inhibited or “arrested” at the prepupae stage. This lifecycle stage is away from the sheep – usually in the top 3-4cm of soil.  This allows survival of Lucilia cuprina through winter, with development not resumed until conditions are again suitable.

It is then the increase in soil temperature in spring in south-eastern Australia that has been shown to trigger synchronous emergence of the first generation of flies for the new season¹, regardless of exactly when the larvae were deposited.

Given that this species of blowfly is largely dependent on sheep as a breeding resource², fly numbers can build up very rapidly under suitable environmental conditions, assuming susceptible sheep are available.

The seasonal nature of fly activity actually provides a unique opportunity to plan ahead.

Strategically treating sheep early in the season with an effective and long-lasting chemical prevents fly numbers from building up by removing the host environment required for flies to reproduce. This can significantly reduce subsequent fly pressure and the risk of flystrike in the season ahead.

If chemical treatment is applied to sheep before flies emerge at the start of the fly season, sheep are essentially removed as a resource for the propagation of the fly population when the first generation appear. As emergence is relatively synchronous and the first generation is typically small, this can have a significant effect in reducing fly numbers and the risk of flystrike for the rest of the fly season.

Optimum fly control will also depend on farm management practices. Integrating early season treatment with strategically-timed shearing or crutching will further reduce susceptibility to flystrike and contribute to reducing fly numbers³ – remembering to be conscious of wool withholding periods.

Elanco Brand Manager Kathryn Humphries recommends the use of CLiK™ Extra for early season treatment.  CLiK™ Extra contains dicyclanil, a potent insect growth regulator (IGR). Dicyclanil products provide long lasting protection from flystrike and break the lifecycle – ideal for strategic control.

On-farm research into early season treatment identified that chemicals used for this purpose have to be relatively long acting to suitably cover the full period of spring emergence¹. The availability and ease of application of insect growth regulators to protect sheep for extended periods makes them ideal for this purpose^3,4.

CLiK™ Extra contains 30% more dicyclanil than CLiK™ and sets the benchmark in flystrike prevention. CLiK™ Extra has a registered protection period of up to 29 weeks, ideal for early season treatment – even in years with a late or delayed start to the fly season.

CLiK Extra is indicated for use on sheep either off-shears or with any length wool, with a meat withholding period of 21 days, wool withholding period of 3 months and ESI of 63 days.

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

1. DeCat, S. et al. (2012). Survival over winter and spring emergence of Lucilia cuprina (Diptera Calliphoridae) in south-eastern Australia. Aus J of Entomology 51:1–11.

2. McKenzie, J.A. & Anderson, N. (1990). Insecticidal control of Lucilia cuprina: strategic timing of treatment. Aus Vet J 67(10):385–386.

3. Larsen, J.W.A. et al. (2012). Prevalence of breech-strike in mulesed, clipped and unmulesed Merino hoggets in south-eastern Australia. Aus Vet J 90(5):158–166.

4. Bowen, F.L. et al. (1999). H.R.: Long-lasting prevention against blowfly strike using the insect growth regulator dicyclanil. Aus Vet J 77:454–460.