Wheat School: Flag leaf or heading? Timing fungicides right

It’s time again to get into the best crop — wonderful wheat, as Wheat Pete would say! Kara Oosterhuis was delighted to be back in the field (not in front of the computer screen) with Jeremy Boychyn, agronomy research extension specialist with the Alberta Wheat and Barley Commissions on this episode of the Wheat School.

As we’re heading into herbicide timing in some areas, now’s a great time to start scouting for foliar leaf diseases. Wet conditions because of rain every three to five days in some areas could cause leaf diseases to start progressing. Early scouting and identifying these diseases can be an indicator of what might be coming later if these wet conditions persist.

Multiple passes through the field are necessary. Research has been conducted to determine if plant growth regulator and fungicide timing can coincide but so far, results are fairly confident that the optimal stages for each product are too far apart to combine them.

See this previous Wheat School episode, for more on plant growth regulators.

For fungicides, “the best timing is in that flag-leaf or head timing, that’s when we’re getting the best results, because that’s when we’re protecting that photosynthetic material,” says Boychyn. If you don’t see any disease present heading into that flag-leaf timing— if it’s dry and  there’s not a lot of risk—then waiting for head timing may be more beneficial. It will depend what the disease risk is going into flag-leaf timing, and if fusarium head blight risk is a concern going into head timing.
(More below video)

Is looking at a risk map recommended to figure out if you should wait for head timing, or to determine if you should get out to your wheat field right away?

Boychyn’s answer is that “Each province is going to have their fusarium risk map, and that is not a direct indication of whether you are or aren’t going to get fusarium—it’s a risk potential, it’s based on environmental conditions, you also have to have the inoculum there.”

Watch the province specific fusarium head blight risk maps, which are updated daily in June and July, all the way through to head emergence timing. First, watch for the disease heading into flag-leaf timing, to protect the yield-bearing flag-leaf. Second, ask if you need to check for fusarium head blight risk and applying a fungicide at that time. “If you have the idea that you’re going to spray at head timing, that doesn’t mean you shouldn’t look into see whether there’s issues at flag-leaf timing,” says Boychyn. It’s a year to year situation.

Septoria complex and tan spot will be the most common wheat diseases you should be scouting for, but that depends on diseases you’ve had in the past and the resistance package of the variety you’re growing. However, the management plans are similar for septoria complex and tan spot in terms of fungicide timing.

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