What’s up with Wheat – Diseases

May 24, 2021

With warmer temperatures wheat has really progressed across the province. Fields in southern Ontario are beginning to head out while fields further east and north are at or approaching flag leaf emergence. That being said, all herbicide applications should be wrapped up in those fields that are at or approaching flag leaf. Disease should be monitored for movement up the canopy until fusarium head blight (FHB) fungicide applications (T3) begin.

Given the warm temperatures are forecasted to stay into early next week, helping the wheat progress quickly, it is important to stay on top of staging to avoid missing the window for T3 applications. By adding up the average daily temperature, weekly Growing Degree Day (GDD) accumulations can be determined to help estimate when wheat may begin anthesis. Once the flag leaf has emerged and the flag leaf collar is visible, it takes about 250-270 GDDs to reach the beginning of anthesis. If the flag leaf has fully emerged today and there is an accumulation of about 20-25 GDDs per day, the wheat is expected to begin anthesis in about 10-14 days.

Winter wheat is most susceptible to FHB infection during anthesis. Spores are carried from infected crop residue by wind or rain and splash onto the wheat head. Rainfall or heavy dew during this period then causes the spores to germinate and infect florets on the wheat head. Wheat fields planted after corn or wheat or those planted to a susceptible variety are at most risk. To determine the susceptibility of a variety please visit www.GoCereals.ca under the performance tab.

Looking at the DONcast model, fields heading out in some areas the week of May 24th are at low risk while fields in other areas are showing moderate to high risk for DON accumulation. If the model suggests the risk for DON accumulation is medium to high and you are growing a susceptible or moderately susceptible variety a fungicide application is warranted. If the risk is low and you are growing a moderately resistant variety a fungicide application may not be necessary if persistent dry weather continues.

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