Of the 100 strains examined3,4
- 15 were resistant to cyromazine while 73 were resistant to both dicyclanil and cyromazine.
- Concurrent dicyclanil/cyromazine resistant submissions coming from all of the mainland states (n= 73) which included every strain from NSW (n=55).
- Strains which were found to be dicyclanil resistant were also found to be cyromazine resistant whilst in states other than NSW cyromazine resistance was found to occur independently.
It is important to note that the majority of NSW submitters (70%) declared use of dicyclanil exclusively, or dicyclanil and cyromazine, while 22% failed to provide information on insecticide usage3,4.
To avoid an increase in the level and frequency of dicyclanil/cyromazine resistance, the widespread and exclusive use of dicyclanil should be avoided where possible in all States. In this way it may be possible to maintain the use of the full range of registered products to control flystrike3,4.
Due to the apparent exclusive and widespread use of dicyclanil in NSW, and the subsequent selection of resistance, integrated resistance management (IRM) measures must be adopted1,2.
By adopting IRM measures producers may prevent flystrike and at the same time slow further development of dicyclanil resistance in the NSW blowfly population3,4.
Adoption of an IRM plan in all States is advisable to slow or halt the continued selection of cyromazine and dicyclanil resistance3,4.
By doing this the full arsenal of insecticidal products registered to control flystrike should remain available3,4.
1. Flyboss., (2019) Resistance management strategy for the Australian sheep blowfly Lucilia cuprina (Wiedemann). Accessed: 04/2019. http://www.flyboss.com.au/sheep-goats/files/pages/treatment/insecticide-resistance/resistance-management-strategies/190415-SHEEP-BLOWFLY-RESISTANCE-MANAGEMENT-STRATEGY-FINAL-GD3349.pdf
2. Flyboss., (2019) A fly in the ointment. Accessed 12/2019. http://www.flyboss.com.au/sheep-goats/files/pages/treatment/insecticide-resistance/resistance-management-strategies/A-Fly-in-the-Ointment-Managing-Chemical-Resistance-to-Blowflies-20191129.pdf.
3.Sales, N, Suann, M, Koeford, K, 2020, ‘Dicyclanil resistance in the Australian sheep blowfly, Lucilia cuprina, substantially reduces flystrike protection by dicyclanil and cyromazine based products’, IJP: Drugs and Drug Resistance 14:118-125.
4.Sales, N, 2020, Sheep Ectoparasite Resistance Update 2018-2020, NSW DPI Project no. ON-0049