Fungicide Resistance
Herbicide resistance is a real-time issue affecting most farm operations across Western Canada. Fungicide resistance has not yet reached the same level of alarm; however, it does exist and we can stop the issue from growing with proper management.
There are important differences in the development of herbicide resistance to the development of fungicide resistance. For example, weeds are generally an annual issue with one generation per year managed by one herbicide application. Conversely, disease pathogens can reproduce new spores within two weeks under ideal conditions. Herbicides are also used more commonly and vastly across Canada. Almost every crop will have a herbicide application every year, whereas you might not apply fungicide every year, therefore the speed at which resistance is developing is much slower.
That being said, the speed at which a disease can spread and, therefore, the resistance can develop and spread, is faster than weeds. For example, it was discovered that in most areas of the U.S. where soybeans are grown, frogeye leaf spot was resistance to strobilurins. Researchers discovered it only took two years of using the fungicide for the resistance to develop, when, according to Dr. Carl Bradley from the University of Illinois, they would have expected eight or nine years of use.
There has been an increase in fungicide use in the Prairie provinces due to higher precipitation levels which cause high disease severity, but also the increase in intensification of cropping systems (including two-year rotations, large field sizes, and high yield expectations) is an even greater factor for favouring fungicide use. These factors can allow pathogen inoculum to build up quickly and spread easily.
Currently, the diseases that have shown insensitivity in Western Canada are:
Net blotch (net form) in barley – insensitivity to propiconazole (Group 3) and pyraclostrobin (Group 11)
Mycosphaerella blight in peas – insensitivity to pyraclostrobin and strobilurins (Group 11)
Anthracnose in lentils – insensitivity to strobilurin (Group 11)
Ascochyta blight in chickpeas – insensitivity to pyraclostrobin and strobilurins (Group 11), mancozeb (Group M 3), pyraclostrobin (Group 11)
As with herbicide use for resistance management, it has been found that mixing and alternating effective modes of action are effective strategies, as well as the general rule of diversity as effective stewardship: diversity of crops, diversity of genetics, diversity of agronomic practices, and diversity of crop protection active ingredients.
The Miravis® line-up of fungicides from Syngenta offers a range of active ingredients with new modes of action providing new tools for disease control that can work toward fungicide resistance management.
Ask your AgResource territory manager about the Miravis fungicides available for your area.