Friday, March 29, 2024

Dealing the death blow

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A preventative approach to flystrike is far better than waiting for a problem to arise.
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Merial New Zealand product manager Geoff Stephens says blowfly strike is best approached at docking, and product choice and application play crucial roles. 

Ideally, the prevention plan will consider the time until shearing, the chemical class previously used for lice control, regional knowledge about seasonal weather forecasts and patterns, and the relative blowfly challenge. 

Insect growth regulators (IGRs) are the most common chemical family used for flystrike prevention, mainly because of their persistence. The two categories of IGRs are:

Triazine-pyrimidine derivatives – this category is sufficient for fly control only and actives include cyromazine and dicyclanil, and

Benzoyl phenyl urea (BPU) compounds – suitable for fly and lice control and includes the actives diflubenzuron and triflumuron.

Should the need arise to treat blowfly strike Stephens said it was important to look for products that have two actives. Treatment would require one of the above for ongoing strike control and the secondary ensuring rapid knockdown of maggots – for example, Cyrazin KO, containing the IGR cyromazine, in combination with ivermectin. 

Chemical application involves following the label instructions to ensure appropriate coverage of target areas (pour-on and-or spray-on products) or complete coverage and saturation to skin level (dipping products).

When assessing the protection periods of different products (usually stated as “up to” so many number of weeks) it is important to remember actual length of cover will also be determined by the effectiveness of application, fly pressure, environment and other influences. 

If in doubt, talk to your local veterinarian for the best product for your situation. They will be able to advise if sticking with a chemical compound or group previously used will continue to offer long-term protection, or if it is time to change. 

“NZ is still on the front-foot with regards to chemical efficacy with lessons learnt from Australia. However, without responsibly using the currently available chemicals we will risk breakdowns and lack of efficacy,” Stephens said.

Flystrike tips

  • Talk to your local vet about the best product for your situation
  • Act before there is a problem
  • Follow product label guidelines 
  • Use the correct equipment for the product and the job, and
  • Carefully consider (and seek advice if needed) the correct chemical for the job based on your usage pattern and onfarm product history.
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