IGR Resistance Development
The Australian blowfly, Lucilia cuprina, has proven over time it can develop widespread resistance to chemicals that are used to control it1. Resistance can either develop through spontaneous mutations (changes) in the parasite’s genetic material or can develop as a result of repeated exposure to the same active, or class of active. Resistance development may be accelerated by the inappropriate use of an active(s) such as underdosing or poor application.

Blowfly resistance to actives within the Insect Growth Regulator (IGR) group of chemicals is now well documented.
Cyromazine resistance and dicyclanil cross-resistance was first reported in the 2010/2011 fly season2
Additional cases of concurrent dicyclanil and cyromazine resistance have been reported since, predominantly in NSW1,3
All larvae samples (n=55) submitted by sheep farmers from NSW in the AWI & NSW DPI research 2018 – 2020 were found to have concurrent cyromazine and dicyclanil resistance3.
With resistance increasingly being reported in key sheep areas, it is timely to consider the appropriate use of actives to prolong the efficacy of all actives currently on the market.
The % of field submissions resistant to dicyclanil and cyromazine, cyromazine only or susceptible to both cyromazine and dicyclanil.4
Total Submissions
(N=100)

NSW
(n=55)

Victoria
(n=11)

SA
(n=12)

WA
(n=21)

Resistant to both dicyclanil and cyromazine
Resistant to cyromazine
Susceptible to dicyclanil & cyromazine
- The trial used a total of 100 maggot submissions from across NSW, VIC, SA and WA.
- 100% of submissions from NSW were both dicyclanil and cyromazine resistant.
- In VIC 82% of submissions were both dicyclanil and cyromazine resistant.
- In WA and SA, concurrent resistance to these two actives was 28% and 25% respectively.
- Higher percentages of cyromazine only resistance were seen in WA (48%) and SA (33%).
Protection Period Evaluation3,4



For the first time, reduced protection periods have been reported to dicyclanil based spray-on products due to
resistance development in the Australian sheep blowfly3.
The protection period of CLiKZiN™ was reduced to less than 3 weeks in a resistant fly population. This equates
to >73% reduction in protection compared to the maximum registered protection period.4 weeks protection (a reduction of 78%) was seen in the resistant population to CLiK™.
Only 9 weeks protection (a reduction of 69%) was seen in the resistant population to CLiK™ EXTRA.
*Graphics adapted from N. Sales et al, IJP: Drugs and Drug Resistance 14:118-125.

No Lice, No Flies, No Worries
AVENGE® + FLY is for the prevention of blowfly strike in sheep in long or short wool plus the control of neonicotinoid susceptible body lice (Bovicola ovis) when used up to 7 days off-shears or on lamb up to 2 months of age.
100% lice knockdown
4 weeks residual lice protection
Fly strike protection – off shears and long wool
*No known published peer reviewed studies demonstrating imidaclopid resistance in Lucilia cuprina.
1.Heath, ACG and Levot, GW, 2015, ‘Parasiticide resistance in flies, lice & ticks in New Zealand and Australia: mechanisms, prevalence & prevention’, NZ Veterinary Journal 63(4):199-210.
2.Levot, GW, 2012, ‘Cyromazine resistance detected in Australian sheep blowfly’, Aust Veterinary Journal, 90(11):433-437.
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-00491
CliKZiN, CLiK and CLiK EXTRA are trademarks of Elanco or affiliates