Australia: Overuse of Fungicides Could Threaten Canola Production
02 September 2025, Sydney: Experts warn that excessive and precautionary use of fungicides in canola could create long-term risks for Australian growers. Researchers say treating fungicides as “cheap insurance” is accelerating the development of resistance, leaving fewer effective options for disease control.
Associate Professor Fran Lopez-Ruiz from the Australian Fungicide Resistance Extension Network (AFREN) explained that repeated applications of the same chemical group—even without proven yield benefits—are driving resistance in fungal populations. Once resistance develops, fungicides lose effectiveness, spores spread quickly, and growers face region-wide problems. Similar scenarios are already seen with barley diseases like net form net blotch, which has evolved triple resistance in some regions.
The threat is now looming for canola. Dr Steve Marcroft of Marcroft Grains Pathology noted reduced sensitivity in blackleg to Group 3 fungicides across multiple states, with early signs of resistance to Group 7 and Group 12 products as well. He cautioned against illegal practices such as double-dosing or off-label applications, stressing that such approaches only worsen resistance.
Research suggests that spraying canola at the four-to-eight leaf stage is a major driver of resistance. Since canola can withstand moderate disease pressure without yield loss, skipping unnecessary early sprays could help delay resistance development. Overuse not only undermines fungicide effectiveness but also risks breaching residue limits when applied late in the season.
Specialists advise growers to apply fungicides strictly according to label directions, only when disease pressure is high, and always in rotation with different fungicide groups. Integrated disease management strategies—such as stubble management, crop rotation, sowing time adjustments, and resistant varieties—remain essential to safeguarding canola yields.
What appears to be cheap protection today, experts warn, may turn into a costly threat for the future of Australia’s canola industry.
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