To examine aspects of disease control in wheat.

 • Reduced sensitivity of the Septoria tritici blotch (STB) pathogen Zymoseptoria tritici to triazole fungicides is likely to be an increasing problem, following the discovery of more resistant biotypes (R8 strain or Isoform 11) on the mainland in 2016.
• The presence of this strain and its proportion in the population will influence disease management strategies differentially.
• In Tasmania, early season disease control in the field with flutriafol (2017 trials) and tebuconazole (2016 trials) has been reduced by the more resistant biotypes of the pathogen, whilst on the mainland trial sites the activity of flutriafol appears to have been maintained in 2017 for the control of STB.
• The performance of a new SDHI based seed treatment and to a lesser extent fluquinconazole (Jockey) has been better than flutriafol in Tasmanian trials.
• Triazole/strobilurin mixtures based on epoxiconazole and azoxystrobin (e.g. Radial, Tazer Xpert), along with new as yet unregistered combinations of triazole & SDHI have given excellent control of STB.
• In 2016 the advantage of these products was evident in disease control and yield response in wheat but in 2017 the yield response to these products was similar to that observed with Opus and Prosaro (registered in wheat but not registered for STB control).
• Single spray timings of foliar fungicide for control of STB made during the tillering phase gave less effective disease control than applications made between GS31 – GS39.
• The most effective control of STB on a canopy leaf layer is achieved by applying fungicide to that leaf shortly after it has fully emerged but before infection becomes established.
• Where more than one fungicide is used in wheat avoid using the same triazole active ingredient twice in a season, irrespective of diseases to be controlled. If it is not possible ensure it is mixed with another mode of action (strobilurin) at one of the timings.
• Since strobilurins are at higher risk of resistance avoid using products containing these active ingredients more than once in a season.