TIGHTER legislation on fungicide use, better variety selection and ensuring growers have a good understanding of fungicide modes of actions were some of the ideas discussed during a fungicide forum held by the Centre for Crop and Disease Management (CCDM) in Perth last Tuesday.
Speakers expressed concern at the level of fungicide resistance found in a wide range of crops and spoke on developing management tools to reduce reliance on fungicides.
Dr Fran Lopez-Ruiz outlined fungicide resistance cases that have been discovered in WA and the Eastern States.
Confirmed cases of resistance to Demethylation Inhibitor (DMI) fungicides in Australia from 2012-2016 include powdery mildew in barley and wheat (eastern states only), barley net type net blotch (WA only), septoria leaf blotch in wheat (Eastern States only) and blackleg in canola.
There is also resistance to MBC fungicides (carbendazim) to control legume botrytis in the Eastern States.
DMIs are Group 3 fungicides and include popular fungicides such as tebuconazole, propiconazole, epoxiconazole, flutriafol.
"Fungicide resistance is not just concerning the grains industry, it is pretty much concerning all crops," Dr Lopez-Ruiz said.
He said the repeated use of DMI fungicides with the same mode of action, widespread use of susceptible and very susceptible crop varieties, lack of green bridge control and the inadequate use of break crops were creating a "recipe for resistance".
He also warned that the release of off-patent fungicides including strobilurin as the active ingredient, needed to be protected due to the high risk of resistance.
"Strobilurins, which are quinone outside inhibitors (QoI) attack the mitochondria of fungus," Dr Lopez-Ruiz said.
"The problem with stroby compounds is that you only need one mutation and then that population is resistant.
"My concern is how to protect these compounds as we don't have the current tools or legislation to stop their continuous use.
"We will have resistance in the first year is we don't use them properly."
CCDM research agronomist Dr Mike Ashworth said a lot of the tools being used to control herbicide resistance in weeds were also applicable in disease management.
Older practices such as stubble burn, longer rotations into fallow and pasture, wider row spacings and a delay in sowing were some of the practices to help reduce the reliance of fungicides but were no longer popular with growers.
He said the only tools that growers were using to combat fungicide resistance, green bridge management and variety selection, left an over-reliance on fungicides.
"We are currently developing the worst case and becoming incredibly reliant on fungicides," he said.
Dr Ashworth outlined his research into narrow windrow burning as an option to reducing fungal pathogens.
"Instead of allowing all that stubble and disease to be spread out into the paddock, why not sweep it into a windrow and burn it?"
"This practice has an opportunity to control weeds but I think it also has synergies with disease control."
A trial conducted by Dr Ashworth last year in Wubin looked at what temperature and burn duration could help control disease and weeds on narrow windrow and various stubble lengths.
The trial showed that longer burn durations achieved in a narrow windrow burn reduced the severity of disease in the following crop.
"There was a 50 per cent survival rate of disease at 225 degrees Celsius for 20 seconds and even at 300 degrees Celsius there was still an 8pc survival rate," he said.
"However duration is the key with a better kill rate at temperatures of 175 degrees Celsius at 160 seconds."
Samples at Z31 growth stage taken in the following year showed a decrease in disease severity next to the narrow windrow burn," he said.
"Sampling at Z31 on the third leaf down, showed disease on 12pc, however this was a 50pc reduction in disease severity on the low cut and tall cut stubble," he said.
"Some of these tools could be used for some disease but others will still be dependent on fungicide treatments."
This year, Dr Ashworth and honours student Kyran Brooks are looking at how burn temperatures and stubble management can reduce scelrotinia populations.
"Again, long duration of burn can kill scelrotinia at 80 seconds for 125 degrees Celsius, however the problem with burning canola is that is won't burn."
He said some growers were growing a barley crop following canola and then burning the crop, which could help in reducing disease.
"When it comes to disease resistance, if we can remove a lot of the biomass out of the paddock and burning it in windrows, we will take a lot of genetic diversity out of that paddock," he said.
"It is important that we do whatever we can to reduce the population size which then reduces the amount of disease inoculum for the following crop. In a normal dry year, we may not need to do anything but after the bad two years we have had in terms of disease, we need to start thinking about what we do with stubble."
