Understanding the Saskatchewan and Manitoba Fusarium Head Blight Risk Maps
Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba
Both Saskatchewan and Manitoba publish Fusarium Head Blight (FHB) risk maps. At a glance, on a given day the maps may appear to indicate a different risk for growers in each province, which can be concerning for farms along the Manitoba-Saskatchewan border. However, closer examination will reveal minor differences in the models and maps useful for considering FHB risk.
In Saskatchewan, maps are created with models (depending on spring or winter wheat) using temperature and/or relative humidity in the previous five days, plus four days forecast. While in Manitoba, maps are created with a model that uses the hours of precipitation and the hours with temperatures between 15°C and 30°C during the previous seven days. Each province then has its own categorization based on slightly different threshold values – low, moderate, high (and extreme in Manitoba) – based on the output from their respective models.
Models are also constantly validated and fine-tuned for the region where it is relevant. The model that is best for the Fusarium population and conditions in individual provinces in western Canada, or even across the border in the USA, might not be the same. However, crop scientists and pathologists continue to work together to determine how FHB risk maps can be most valuable to all farmers, including those along the border! Producers along the border may have a potential advantage in assessing risk, by using both maps and interpreting which one is most relevant for their farm. And keep in mind risk maps may not perfectly represent a producer’s individual field(s).
Regardless of the model used, no FHB risk map can be taken as a stand-alone tool to make management decisions about FHB as it only takes into account environment. The existence of disease requires three factors: the interaction of a susceptible host, a virulent pathogen, and an environment favourable for disease development. So although a risk map in Saskatchewan or Manitoba may show High risk due to environment, disease risk may be low if the wheat crop is not at the proper stage for infection.
We strongly encourage referring to additional information and consultation with local extension specialists and agrologists to determine if fungicide applications are needed to suppress FHB in your area.
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