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Did Freddie Mercury predict today’s fungicide resistance?

Another one bites the dust (barley powdery mildew)
Another one bites the dust (wheat powdery mildew)
And another one gone (canola blackleg), and another one gone (legume botrytis)
Another one bites the dust (wheat septoria leaf blotch)
Hey, I’m gonna get you, too
Another one bites the dust
(barley net-form of net blotch)

Could it be possible that Queen was singing about fungicide resistance in broadacre cropping systems, forecasting the situation for 2016?

Well, surely stranger things have occurred, and as it happens, we’ve just discovered the sixth case of fungicide resistance in broadacre cropping (ninth when you count horticulture crops) – it’s the sixth time a fungicide bites the dust instead of killing the pathogen – nice one Freddie!

NTNB LR
Barley net-form of net blotch

Our Fungicide Resistance Group has just confirmed net-form of net blotch’s (NFNB) resistance to tebuconazole and a lower reduction in sensitivity to other DMI fungicides such as epoxiconazole, prothioconazole and propiconazole from Western Australian barley samples.

“Interestingly, straight tebuconazole is not registered for the control of NFNB, however growers should be mindful that NFNB may be present when applying tebuconazole to control other barley diseases, which may contribute to NFNB issues in subsequent seasons,” Dr Fran Lopez-Ruiz, leader of CCDM’s Fungicide Resistance Group, said.

“We’re asking growers from across Australia to monitor the level of disease control they receive when using fungicides, and if there are problems with control, please send us a sample to diagnose resistance.”

The sword and the dagger – NFNB evolves two weapons to fight fungicide

When fellow researchers Dr Weiwei Deng and Wesley Mair investigated the resistant NFNB pathogen, they discovered the fungicide target enzyme was present in much higher amounts. This means there are more fungicide targets, so more fungicide molecules are required to control the disease.

Furthermore, they also found a new mutation within the NFNB pathogen that changed the shape of the target enzyme. This makes the fungicide less effective at binding to the enzyme (see diagram).

“It’s as if NFNB is armed with a sword and a dagger by working against fungicides in two key ways – by producing more fungicide targets, and changing the shape of those targets,” Wesley said.

Evolution

Where were the samples from?

So far, five locations across WA have tested positive to the resistant strain of net form net blotch, including Kojonup, Beverley, Bakers Hill, West Arthur and Dandaragan.

A small number of NFNB samples were tested from across the eastern states of Australia, and so far all samples tested negative for signs of resistance. A large scale analysis is required to determine whether NFNB resistance has developed outside of WA.

Map

Don’t get blotched out! 5 ways to avoid NFNB resistance

  1. Only use fungicides registered for NFNB control
    Applying a fungicide that is not registered for the control of NFNB can be a waste of time and money, and is against Australian regulation. The fungicides you use to control NFNB should be used within a rotation of fungicides and applied at label recommended rates.
  1. Select fungicide mixtures with different modes of action
    Some fungicides registered for NFNB are mixtures, however not all mixtures contain active compounds from different modes of action (for example, Group 3 and Group 11). Using fungicide mixtures containing different modes of action is the best anti-resistance strategy in disease control and a good way to control tebuconazole resistant NFNB.
  1. Minimise tebuconazole fungicides
    When applying tebuconazole fungicide for the control of barley diseases, be mindful that tebuconazole will apply selection pressure for tebuconazole resistant NFNB strains if they are present. Fungicides containing tebuconazole should only be used within a robust anti-resistance disease control strategy.
  1. Scout your field after a fungicide spray
    Tebuconazole resistant NFNB showed a reduced sensitivity to triazole fungicides epoxiconazole, prothioconazole and propiconazole – which are all registered for the control of NFNB. Scout your field after a fungicide spray and remember disease control failure does not always mean fungicide failure as there are many different factors that can influence the level of control you receive. If you aren’t receiving the level of disease control you hoped for talk to your local pathologist or send in samples of disease to the Fungicide Resistance Group for fungicide resistance testing.
  1. Plan ahead for next season
    If disease pressure was high during the growing season, you can minimise disease infection in the following season by rotating crops, managing infected stubble and planting resistant crop varieties. Seed treatments or in-furrow fungicides can act as a great preventative measure for disease hot spots. A new SDHI fungicide (group 7) is now available as a seed treatment for NFNB control.

If you think you have resistant NFNB – send us a sample!

The Fungicide Resistance Group is looking to test NFNB samples from all growing regions across Australia.

If you think you may have a case of fungicide resistance, please contact the group for a sampling kit by email frg@cutin.edu.au or phone 08 9226 1204.

The Paper

This research was recently published in Frontiers in Microbiology, and can be found here: http://journal.frontiersin.org/article/10.3389/fmicb.2016.01279/abstract

About Fran Lopez-Ruiz, Weiwei Deng and Wesley Mair

Fran Weiwei Wes
Fran Lopez Ruiz, Weiwei Deng and Wesley Mair

Fran, Wesley and Weiwei carry out research on fungicide resistance in pathogens.

Since joining Curtin University in 2012, Fran has led the Fungicide Resistance Group which works towards understanding how fungi are able to develop fungicide resistance and how management of diseases in the field can be improved to reduce losses.

Wesley joined the Fungicide Resistance Group in 2011 with a main role to carry out ongoing fungicide resistance analysis, to keep track of which chemicals are still effective and the genetic changes responsible for fungicide resistance.

Weiwei is a newer addition to the group, recently moving from CSIRO, Canberra in 2015. Her main role is to investigate epigenetic and molecular mechanisms of fungicide resistance and the further application into new fungicide development.

 

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