Prevention and control | If you don’t need it, don’t use it, says a plant pathologist, who stresses proper crop rotations
A cereal pathologist with the Crop Development Centre in Saskatoon says conditions in Saskatchewan are ideal for cereal diseases this year.
Randy Kutcher said in addition to well-known pathogens, growers should be on the lookout for fusarium and stripe rust, which were not even on the radar for many Saskatchewan producers a few years ago.
He said the emergence of new cereal diseases has created new management challenges, particularly when determining optimal timing of fungicide application.
Farmers might be tempted to tweak applications in hopes of reducing the number of passes required while also achieving control of several diseases.
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In all cases, producers should monitor crops and take an integrated approach to controlling cereal diseases.
During a recent field day at Agriculture Canada’s Melfort Research Farm, Kutcher said fusarium head blight and stripe rust are now established in many parts of Saskatchewan and are expanding to new areas.
“Over the last three, four, five years, we’ve been hearing more and more complaints and concerns from farmers about fusarium,” he said.
Fusarium has historically been a concern for growers in Manitoba, Minnesota and North Dakota, but the disease was evident in every crop district in Saskatchewan last year and has the potential to significantly affect crop values.
Fusarium-related toxins or mycotoxins in harvested grain can have a devastating impact on the value of cereal crops and at certain levels can make the entire crop worthless as either animal feed or food for human consumption.
Ideally, farmers should use a fusarium management strategy that employs good rotational practices, careful varietal selection and responsible fungicide use, Kutcher said.
Although no wheat varieties offer complete resistance to fusarium head blight, varieties such as AC Carberry offer good resistance with little or no yield penalty relative to other popular Canada Western Red Spring wheats.
Resistance ratings for wheat varieties are listed in the provincial seed guide and other seed industry publications.
Fungicides are available for fusarium control, including popular products.
In wheat, fungicides to control fusarium are usually applied when the majority of heads are fully emerged and when 40 to 50 percent are flowering.
Indiscriminate fungicide use can contribute to the development of resistant pathogens, so producers should apply fungicides only if they are assured of an economic benefit.
“Fungicide application is part of the answer for fusarium, but certainly, it’s not the entire answer,” Kutcher said.
“For cereal diseases in general, there are lots of products available but many of them are in the same group or family … the best practice is that if you don’t need it, don’t use it.”
Timing fungicide applications in cereals can be tricky, especially if producers are trying to control more than one disease simultaneously or reduce the number of field passes.
Some producers have tank-mixed herbicides and fungicides and applied it at the seedling stage.
However, assessing the effectiveness of disease control products at that stage can be difficult.
For best results, producers should identify their disease threats and time their applications carefully.
Multiple passes may be required with the emergence of new disease threats.
Stripe rust is another disease that is relatively new to Saskatchewan and can significantly affect yields if environmental conditions are favourable.
Stripe rust generally thrives under damp, cool conditions, and Kutcher is hopeful that warm weather in late July will minimize the disease’s impact.
Last year was probably the worst year on record for stripe rust infection in Western Canada’s grain growing region, he said.
By Aug. 15, the disease had infected wheat fields throughout much of southern Alberta and the entire province of Saskatchewan, except for a small pocket in the province’s southeastern corner.
Last year’s epidemic, combined with unusually high wheat prices this year, prompted many wheat growers to spray for stripe rust even before they saw disease symptoms.
“We need to be concerned about (stripe rust) and certainly a lot of growers were this year,” said Kutcher.
Warm daytime temperatures, in the mid-to-high 20s or low 30s C, could reduce the stripe rust threat this year.
Kutcher said in addition to following disciplined crop rotations, producers should carefully select cereal varieties and rotate fungicides.
Researchers have determined that stripe rust resistance in spring wheat varieties is conferred by two genes: Lr34/Yr18 and Yr36.
Varieties such as CDC Teal, Laura and 5701PR contain the Lr34/Yr18 gene. Lillian, the most widely grown CWRS wheat variety in Western Canada, contains both Lr34/Yr18 and Yr36 and showed the best resistance in varietal trials conducted over the past three years.
