Tasmanians Are On The Frontline Of Fungicide Resistance – What Options Are Available To ‘Slow The Train’?

GRDC - Nick Poole, Tracey Wylie and Katherine Fuhrmann (FAR Australia)

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

The authors of this paper note in the conclusion: "In many cases the full label rate is the most appropriate rate for control. However, for some diseases, the lower rate from the label range of a fungicide can be used in conjunction with a crop variety that has a good disease resistance rating because disease pressure will be lower. Contrary to what might be the case with other agrichemicals, there is evidence that by using a higher rate than necessary this increases the risk of resistance, as removing all of the sensitive individuals provides more opportunity for resistant individuals to dominate the population and hence be the strain colonising the plant. This is particularly the case with Group 11 QoIs and Group 7 SDHIs fungicides." Please access the full paper via the link below if this research interests you.

The take home messages from this GRDC funded research are below. Please access the full paper via the link below for methodology, references, acknowledgements and discussion.

Take home messages from the paper include:

  • Tasmanian growers are on the frontline of fungicide resistance issues in Australia as a result of a growing season that is typically longer, wetter and more disease prone than the mainland.
  • The typically longer growing season confers large benefits in terms of productivity however this means Tasmanian crops require more fungicide applications to control disease compared to mainland Australia.
  • The number of fungicide applications over time is a key driver fuelling the shift (the selection of more resistant strains) in pathogen populations towards fungicide resistance.
  • Reduced sensitivity of the Septoria tritici blotch (STB) pathogen, Zymoseptoria tritici, to Group 3 DeMethylation Inhibitors (DMI) fungicides (e.g. triazoles – Folicur®, Tilt®) is already evident in the field in Tasmania, following the discovery of more resistant strains (R8 strain or Isoform 11) back in 2016.
  • In addition, wheat powdery mildew (WPM) strains resistant to strobilurin fungicides are widespread in Tasmania, Victoria and SA following their discovery in 2017.
  • Other disease pathogens are known to be at high risk of resistance developing in the future, particularly in the Tasmanian environment, for example, STB pathogen resistance to strobilurins, which is common in Europe and New Zealand.
  • The Net blotch pathogens, Pyrenophora teres f. maculata and P. teres f. teres in barley have shown reductions in sensitivity and increases in field resistance to Group 3 DMIs in SA and WA.
  • For the first time in 2019 resistance to Group 7 Succinate Dehydrogenase Inhibitors (SDHI) fungicides on the Yorke Peninsula in SA.
  • Ramularia in barley overseas has overcome all three fungicide groups; Group 3 DMIs, Group 7 SDHIs e.g. fluxapyroxad (Systiva®)and Group 11 Quinone outside Inhibitors (QoIs) e.g. azoxystrobin (Amistar®), but there is no evidence of this in Tasmania at this stage.
  • The presence of resistant pathogen strains and their proportion in the population will increasingly influence our ability to control disease in Tasmanian crops, making it imperative that we adopt disease management strategies that will slow down resistance development.
  • To ‘slow the train’, growers and advisers need to adopt anti resistance measures when using fungicides that avoid repeating the same active ingredients, and wherever possible, in an integrated disease management (IDM) approach.

2020 - Australia - GRDC - Nick Poole, Tracey Wylie and Katherine Fuhrmann (FAR Australia)
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