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Fungicide mixtures: Crop protection elixirs

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Controlling crop fungal disease through the use of mixed fungicides has been confirmed as a successful tactic, by a recent study to reduce fungicide resistance.

Co-author Professor Richard Oliver, Chief Scientist of Curtin’s Centre for Crop and Disease Management (CCDM) – funded by the Grains Research and Development Corporation – said by mixing fungicides with different modes of action, farmers will reduce the rate of fungicide resistance, extending the life of fungicides for future use.

“Crop disease is already costing Australian farmers $50 per hectare per year, and it is critical that the life span of the few working fungicides is extended as long as possible, as new products can never come out quick enough,” Professor Oliver said.

“Already, many fungicides are on the cusp of becoming ineffective, but we have proven that mixing these ‘at-risk’ fungicides with another of a different mode of action reduces the rate of resistance development.”

Professor Oliver said the team developed a simple formula that could predict whether particular resistance management tactics were effective, and used this to explore resistance management using fungicide mixtures.

After comparing the findings to the published experimental evidence, the team could show in nearly all relevant reports, mixing ‘at-risk’ fungicides with another fungicide reduced fungicide resistance, making it a valid resistance management strategy.

CCDM Director, Professor Mark Gibberd highlighted the importance of this research and related studies for both Australian farms and global food security.

“Fungal diseases are evolving in resistance to common modes of fungicide action and this places crop production at risk – both in terms of profitability but, more alarmingly, it raises the possibility of crop failure,” Professor Gibberd said.

“This research by Professor Oliver’s team is an exciting finding, as it will impact the farmers’ bottom line, as well as allow for more sustainable agriculture practices.”

The Curtin team also found that reducing the dose of the ‘at-risk’ fungicide within the mixture did not compromise the disease control, contrary to previous opinion that lowering the dose may cause resistance.

“Furthermore, we have seen evidence from our research that mixing two ‘at-risk’ fungicides (from different modes of action) can also be a useful resistance management technique, however, further studies are needed to confirm this for each mixture,” Professor Oliver said.

He said further research was needed to look at the required doses of each mixing partner, the life span of mixed fungicides, as well as other aspects of mixing fungicides to help farmers combat resistance with mixtures.

The CCDM has compiled a list of all the fungicide active ingredients that are available to Australian farmers, showing which ingredients are now at-risk or compromised for wheat and barley within different modes of action. For a copy of this list, contact the CCDM at

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