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How to combat white mould

How to combat white mould

OMAFRA soybean specialist shares a comprehensive strategy to address the disease

By Evan Karigianis Writer
Ontario producers need to use a multipronged approach to deal with the threat of white mould in soybeans, said Horst Bohner at Bayer CropScience’s Dead Weeds Tour.
The fungus thrives during cold, rainy seasons (under 30° C), and will deposit sclerotia during harvest. The sclerotia are the hardened reproductive bodies of white mould and they can remain infective for over three years.
“White mould is a big problem and is pretty consistent across Eastern Canada,” said Bohner, the soybean specialist for OMAFRA, in an interview with “It is very difficult to prevent” the disease from becoming established in fields, as “sclerotia move with the equipment and dirty seeds.”
Horst Bohner, Soybean Specialist for OMAFRA, discussing white mould at Bayer's 2018 Dead Weeds Tour.
The first step to dealing with white mould is understanding the different soybean varieties available. Some varieties can be very susceptible to the disease, while others have a high tolerance, Bohner said.
In addition to variety selection, crop rotation can have a significant impact on the sclerotia counts in the top soil. Fields with a history of white mould should not be in two or three-year rotations with broadleaf crops, he noted.
Tillage can also affect the spread of the disease. Farmers using both no till strategies and deep tillage have had varying success in reducing the appearance of white mould. Deep tillage can reduce the amount of sclerotia found in the topsoil but further tillage can bring it up again. No-till practices leave the sclerotia in the upper soil profile, which allows it to rot and cycle out of the field.
Foliar fungicides are another important part of the toolkit.
“When I started this job, there were essentially no foliar fungicides in soybeans,” Bohner said. “Today, that’s changed. We do have products that offer pretty reasonable suppression. It’s not full control but it will help if it’s part of a strategy.”
Finally, producers are gaining access to newer tools and practices, such as variable rate seeding, to help fight this disease.
“It’s a very innovative approach, so I can see some potential,” said Bohner.
Producers can selectively limit populations in trouble areas. Indeed, farmers could cut seeding rates in these sections in half, he said. The result is a more controlled canopy density.


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