Wheat School: Hot weather narrows the FHB treatment window


Wheat has been progressing rapidly thanks to seasonally high temperatures in many areas over the past few weeks, quickly moving into and through the early flowering stage. Early flower is when a fungicide application to prevent fusarium head blight (FHB) is recommended.

“Typically we’d expect flowering to start three days after head emergence, and flowering to last three to five days, but in a hot, dry year it can speed through those grow stages and the flowering period can be shortened,” notes Anne Kirk, cereal specialist with Manitoba Agriculture, in this Wheat School video.

With early dry conditions resulting in uneven or stagy wheat, spraying should be timed to hit as many heads as possible, focusing on main stems instead of tillers, especially in situations where the tillers are already suffering from drought stress, she explains.

Wheat School: Tips for fungicide decisions in a dry year

To gauge how far along a wheat field is in flowering, Kirk suggests scouting early in the morning.

“Look at where the anthers are emerging from the head. The best time of day to check is early in the morning, because the wheat is flowering in the morning. Later in the day you’ll see the dried up anthers, but it’s hard to know if those were today’s anthers or from two days ago. So check early in the morning, and keep in mind the flowers emerge from the middle of the spike first. When it’s emerging from the top and bottom, that would be a couple of days into flowering,” she says.

What if the early flowering window has passed and rain suddenly appears in the forecast, raising the risk of FHB infection? Is there any benefit to a late fungicide application?

The effect of a fungicide application closer to the end of flowering is not well understand, says Kirk, noting Manitoba Agriculture and the Manitoba Wheat and Barley Growers Association are conducting on-farm trials this summer looking at the impact of a fungicide application four days after the recommended early flowering stage.

Check out this Wheat School episode with Anne Kirk for more on fusarium fungicide timing:

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