The summers of 2006 & 2009 were particularly stressful for some sheep farmers.  In 2006 we had the first national case of Aussie green blowfly resistance to the commonly used Insect Growth Regulator (IGR) triflumuron (Zapp).  This meant treated sheep were getting flystruck after only two weeks when in the past it had lasted at least ten weeks.  Since then the areas involved has enlarged to areas of the Waikato river and even over to Waerenga.

In February of 2009 we had a repeat of the humid still weather and resistance to the related chemical diflubenzuron (Zenith) was also detected.  This was not unexpected as the resistance to these two chemicals was found to be genetically similar to Organophosphate (OP) resistance found in resistant flies in Australia.  Therefore we do not advise using these products in future in these areas.  Outside these areas use it at your own risk.  The Aussie green blowfly lays live maggots and resistance to OP;s came with it's introduction from Australia, reducing it's effectiveness to only 2-3 weeks of protection.

Like all pour-on lice products, treating straight after shearing is ideal.  Contact our rural sales managers for advice on which products to use.