Fungicide tolerance found in blackleg populations
With the support of the Grains Research and Development Corporation (GRDC), the National Canola Pathology Program has this year tested 200 canola crops from across Australia to determine if the blackleg fungus has developed tolerance to the fungicide fluquinconazole (such as Jockey®). Of the 200 samples, 62% showed no tolerance, 23% showed low tolerance and 15% showed tolerance.
Samples of canola stubble from 2014 crops were collected by growers and agronomists, incubated to induce spore production and then used to infect fluquinconazole-treated seedlings. If significant disease occurred on the fluquinconazole-treated seedling the sample was reported as fungicide tolerant. In the southern cropping region, 94 crops were screened for tolerance to fluquinconazole in blackleg fungal strains. Of the 50 samples submitted from Victoria, 60% showed no tolerance, 26% showed low tolerance and 14% showed tolerance. Of the 44 South Australian samples screened, 61% had no tolerance, 23% showed low tolerance and 16% showed tolerance.
University of Melbourne researcher Dr Angela Van de Wouw, who has been involved in the screening program, says no correlation was found between tolerance and fungicide practice (seed applied, fertiliser applied or foliar use), variety or location. She also pointed out that researchers have identified tolerance, not resistance. “This is an important distinction – resistance means that the fungicide is no longer effective, whereas tolerance means that the fungicide has lost some of its efficacy but still has some control over the disease,” Dr Van de Wouw said. “As this was the first ever survey for fungicide tolerance in Australian blackleg populations, we do not know if the level of tolerance has increased over time. It is also unknown whether this tolerance is specific to fluquinconazole or will affect other fungicides.”
Growers and advisers who submitted stubble samples for screening have been provided with the results. “We are very grateful that so many growers took the time and effort to send in samples to assist us with our survey work,” Dr Van de Wouw said.
For those growers where high tolerance was observed it is recommended that growers read the GRDC’s current Blackleg Management Guide and follow the management steps to reduce the effect of blackleg, such as choosing resistant cultivars, avoiding previous year’s stubble and rotating cultivars to a different resistance group.
Angela Van de Wouw, University of Melbourne
0439 900 919
Sharon Watt, Porter Novelli
Caption: A map of the Victorian and SA results of the National Canola Pathology Program’s screening for fluquinconazole tolerance, undertaken with the support of the GRDC.