Wheat School: Flag leaf or head timing — when is a fungicide application warranted?

(Kara Oosterhuis/RealAgriculture)

There are a few different scenarios to look at when it comes to deciding whether or not to spray a fungicide on wheat.

Jeremy Boychyn, agronomy research extension manager with the Alberta Wheat and Barley Commissions, says there are four key times that producers are either already going over the field, or there is potential value for an application: herbicide timing, PGR timing, flag leaf timing, or head timing.

According to research that has been conducted in Western Canada and parts of the Northern Plains in the U.S., in order to get the most out of a fungicide application, PGR timing and herbicide timing is just too early.

Where results have been more positive is when targeting either flag leaf and head timing. With that knowledge in hand, says Boychyn, we can start asking the important questions about what product, when, and if to go in at all. (Story continues below video)

“We’ll go back to the disease triangle,” he explains. “We need the pathogen, we need the environment, and we need the host.” As well, he says, we’ll need to look at field history and rotation, because the tighter the rotation, the higher the chance we see disease development.

There are going to be situations where disease development just likely isn’t favourable, and the parts of the disease triangle don’t all match up, limiting the benefits of a fungicide application and wasting time and resources.

Some producers do ask the question on whether or not applying at both the flag leaf timing and head timing will be beneficial, and although Boychyn says research has shown a bit of a decrease disease-wise, the economic return of a late two-pass system is simply not worth it in Western Canada.

If the field in question is in a high fusarium head blight risk area, a fungicide application is best delayed to target the head, as FHB is just such a huge threat to wheat yield and quality.

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