Scout now for fusarium

Conditions could be ripe for fusarium head blight across large swathes of Manitoba and Sask­atchewan.

Recent rain, high humidity and warm daytime temperatures may have increased the risk of the disease in many fields of winter and spring wheat.

It’s also a combination of high levels of inoculums carried over from last year in relation to temperature and relative humidity, say provincial pathologists.

“Last year with high levels of fusarium across the province there’s inoculums definitely present in the environment,” said Barb Ziesman, Saskatchewan Agriculture’s provincial specialist for plant disease.

“The other factor we’re looking at is the environment, and that’s really going to push the disease and that’s really giving us that annual variation,” she said.

The latest risk assessment maps, which are updated daily using data collected from weather stations across each province, show much of Manitoba in the medium zone with scattered pockets of high risk for the fungal disease.

Saskatchewan generally remains at low risk, except a broad strip classified as moderate that travels from the southeast region up to the northeast where the risk is high.

However, it remains somewhat early to know for sure because flowering dates are generally still a week or two away for winter and spring wheat crops in many areas.

“Watch and wait and be prepared,” said Holly Derksen of Manitoba Agriculture.

“Our risk maps are really just a guide. You still need to go out there and scout your individual fields to know, are you at the right stage for a fungicide application, is the risk matching up with what you’re seeing in your own field?”

Derksen said large portions of winter wheat in southeastern Manitoba died during the winter, forcing producers to replant to another crop.

“Most of our winter wheat acres are in western Manitoba this year.”

While she cautioned against overuse of fungicide, she expected that many producers may spray regardless of the risk factor.

“We’ve been dealing with fusarium for a number of years so a lot of guys here will be planning to spray a fungicide regardless of what our maps show,” she said.

“I think they’ve been hit enough times by fusarium that even in years when risk is low they know that it pays off for those other years, so they just pencil it in right from the beginning.”

Randy Kutcher of the University of Saskatchewan’s Crop Development Centre said growers are using fungicides as insurance.

“It’s hard to predict exactly what the risk is going to be and so I think a lot of growers are becoming, unfortunately I would say from an integrated pest management point of view, using routine applications rather than looking at the tools we have like the maps, getting to understand the disease, looking at their crop rotation, looking at their variety — all the things that you could factor into trying to decide, do you really need to spray this year,” he said.

Added Ziesman: “They’re (fungicides) not going to give us complete control. With a lot of diseases, fungicide applications can give fairly good control. Fusarium head blight is one disease that an integrated approach is very important.”

It has been an excessively breezy spring, which has kept many spraying operations grounded or confined to working early mornings and late evenings. However, it’s not known how the wind has affected risk levels for the pathogen.

“If the spores are in the environment, it can carry them from field to field, but there’s no exact information on how far the spores can be carried,” said Ziesman.

Added Kutcher: “On the other hand, it might reduce the relative humidity within the crop canopy (and lower the fusarium risk).

Ziesman said the most important thing that producers can do is take the time to check the stages in their fields because the risk assessment maps are going to be effective only if used for the heading date of a specific crop.

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