Research tries to stay ahead of fungicide resistance

Man lightly grasping leafs of a plant in a laboratory

Dr Fran Lopez-Ruiz, based at the GRDC-funded Centre for Crop and Disease Management (CCDM) at Curtin University, says knowledge of fungal disease genomics and evolution are vital to managing the future use of fungicides.

PHOTO: Curtin University

Western Australian cropping systems have the right ingredients for the rapid development of fungicide resistance and strategies to address this will be crucial in coming years.

That is the advice from the Fungicide Resistance Group at the GRDC-funded Centre for Crop and Disease Management (CCDM), based at Curtin University.

Group leader Dr Fran Lopez-Ruiz has been studying fungicide resistance in Europe and Australia for 15 years. He says fundamental knowledge of fungal disease genomics and evolution are vital to managing the future use of fungicides to ensure long-term efficacy.

“Fungicide use is as important to profitable cropping in WA – and Australia – as breeding new crop varieties,” he says.

“To ensure long-term sustainability of fungicides, we need to understand how resistance develops and how we can improve our integrated disease management to reduce the impact of diseases in the field.”

Dr Lopez-Ruiz says the main factors contributing to fungicide resistance are:

  • growing big areas of a susceptible crop (such as Mace in WA);
  • crops being exposed to a rapidly evolving disease (such as powdery mildew and rusts in WA); and
  • over-exposure to the same mode of action (MOA) fungicides.

He says fungicide resistance has already compromised triazole (a Group 3 demethylation-inhibiting fungicide) for control of barley powdery mildew and barley net blotches in disease-prone areas of WA (and some parts of the eastern states).

CCDM research has found that the barley powdery mildew fungus in WA is highly variable and virulence for many resistance genes is present in the mildew population.

Some barley varieties contain various combinations of major resistance genes that have been effective to date.

However, the CCDM warns that, at some stage in the future, more of these varieties could become susceptible to infection if the resistance genes are overcome.

Dr Lopez-Ruiz says the good news is that, across all registered actives, fungicide resistance in WA is at a low level – less than 1 per cent – and there has been no complete loss of any fungicides. Yet.

“There are many management strategies that can be used to slow the development of fungicide resistance and we can learn a lot from research already undertaken in weed herbicide resistance,” he says.

“Top of the list is developing genetic resistance to fungal diseases in our crop varieties and to do this we need fundamental research into disease life cycles – especially for complex pathogens, such as rusts.

“We need diversity in our cropping systems with crop rotations, crop varieties and fungicide MOAs, and we need other non-fungicide disease-control measures.”

Dr Lopez-Ruiz says, unlike weeds, fungal disease control is a ‘social issue’ due to the ability of disease pathogens to multiply quickly during a season and be dispersed across thousands of kilometres – affecting vast tracts of cropping land.

“Also, gene flows are intense – with millions of spores able to be released from stubbles after one rain event, for example,” he says.

“This is difficult to manage and needs many, many growers to be using similar control methods.

“A good lesson from weeds research is that preventative strategies are a lot more effective than curative strategies when it comes to fungal disease management.”

A new GRDC-funded application called Crop Disease Au has been developed by the National Variety Trials program and is now available to growers and advisers.

It provides quick access to disease resistance ratings, disease information and an extensive disease image library. It is available on Apple and Android devices.

More information:

Dr Fran Lopez-Ruiz, CCDM,
08 9266 3061,

End of Ground Cover March-April 2016 (#121)
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