With many regions facing a warm, wet summer, sheep producers are being warned that forward planning and chemical rotation are vital for managing flystrike season.
An Australia wide study published by Australian Wool Innovation and the NSW Department of Primary Industries showed increasing dicylanil resistance as well as some resistance to cyromazine.
In NSW, where the most tests were done, 100 per cent of submissions showed resistance to both chemicals.
Troy Animal Health marketing manager Craig Lyons said resistance management is critical to ensuring effective fly control options are safeguarded.
"Studies like this one by AWI & NSW DPI are important to keep farmers informed of how the effectiveness of flystrike control products are changing over time and the importance of integrated pest control," Mr Lyons said.
"Findings from this study demonstrate that dicyclanil resistance is a major concern for the Australian sheep industry.
"The research showed that with a resistant fly population, a significant reduction in protection period from dicyclanil based spray-on products, compared to their registered claims, can occur.
"We've seen widespread resistance develop to valuable chemicals, and this reminds us of the importance of rotating chemical groups used for fly prevention, and ensuring producers are familiar with the different treatments for flystrike.
"Reductions in length of protection periods mean it's critical farmers are planning their flystrike management, keeping up to date with latest information and products, such as AVENGE + FLY, and incorporating chemical rotation into their management program."
For Victorian producer Julie McClelland, the issue is front of mind.
Along with her family, Mc McClelland runs 'Windarra' in the Mallee around Birchip, with 3,500 merino ewes, 1,500 prime lambs and a mixed cropping operation.
"Blow flies continue to be an issue for us on farm year after year, and we are gearing up for a bad flystrike season as the conditions have been highly favourable for flies this year," Ms McClelland said.
Understanding the importance of minimising chemical resistance, she started rotating the fly and lice management chemicals used in her operation a few years ago following a conversation with the local reseller.
"Chemical resistance around certain fly products is starting to filter through talks with our resellers and vets," she said.
"I'd strongly recommend that producers reach out to their local experts to ensure that they are protecting their valuable livestock and mitigating resistance risk on farm.
"It's important that industry is staying ahead of flystrike by using chemicals that work in rotation to minimise productivity impacts and resistance before they become serious issues."
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