Prairie farmers could one day have a natural alternative for controlling sclerotinia in canola and beans.
Researchers with Agriculture Canada are investigating the merits of using a fungus known as Coniothyrium minitans to attack sclerotinia, one of the most serious threats to canola and bean crops in Western Canada.
In field studies done during the past two years, researchers found that C. minitans can control white mould in beans as effectively as a chemical fungicide, said Deb McLaren, a research scientist in crop pathology at Agriculture Canada’s Brandon Research Centre.
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The white mould is caused by Sclerotinia sclerotiorum.
Because of the potential to use C. minitans as an alternative to chemical fungicides, researchers are now doing additional studies that could one day support its registration as a biological control for sclerotinia in western Canadian canola and bean crops. There are no such products now registered in Canada for that purpose.
Field studies using C. minitans to control white mould in beans were done during 2002 and 2003 at Agriculture Canada’s Brandon, Morden and Lethbridge research centres.
In the plots at Brandon in 2003, the seed yield in beans treated with the biocontrol was more than double that of plots that had no treatment against sclerotinia.
Yields were slightly less than in plots treated with the chemical fungicide Ronilan in 2003 and comparable in 2002.
McLaren said the amount of sclerotia found in the seed in 2002 was less in plots treated with C. minitans than in those treated with Ronilan. The reverse was the case in 2003 when the biocontrol agent was used in only a single application and Ronilan was applied in a split application.
However, McLaren said there was evidence that C. minitans reduced the survival of the sclerotia, the overwintering bodies of S. sclerotiorium, meaning that its benefits go beyond controlling the disease in the field.
Public concern about pesticide res-idues in soil and water is heightening the need to find alternatives for controlling sclerotinia, said McLaren.
The study of C. minitans is a collaborative effort between herself and Henry Huang and Robert Conner, other research scientists with Agriculture Canada.
They began field studies this year and will continue over the next two years to further determine the merits of using C. minitans in single or split foliar applications to control sclerotinia in canola and beans.
Those studies will help provide the information needed to get the biocontrol agent approved for use in farmers’ fields.
McLaren said the fungus was found by Agriculture Canada researchers near Morden, Man., in the 1980s, so it is native to the region. It was found while researchers were looking for natural enemies to sclerotinia in sunflower crops, which are also susceptible to the disease.
Much of the emphasis since then has been on the merits of using C. minitans to control sclerotinia wilt in sunflowers. Research into its use on canola and beans began more recently.
C. minitans may not need to be applied every year to provide good control of sclerotinia, McLaren said. As part of Agriculture Canada’s research with sunflowers, the fungus was applied to sunflower plots for two years and then the treatment was skipped for two years.
In the third year, even though no C. minitans was applied, there was still good control of sclerotinia, indicating a carryover effect from the previous two years of treatment.
“There is the possibility this may translate into less inputs for the grower because it has that carryover effect,” McLaren said.
