Glacier FarmMedia — Prairie wheat growers could be getting poor control of fusarium head blight because they’re applying fungicides too early.
Research and field testing in North Dakota has found that the best time to spray for fusarium head blight is when the first flowers appear in the centre of the wheat head.
Once those initial flowers are visible, a farmer has about a week to spray the crop for maximum control of fusarium.
“What we’ve seen from our data across North Dakota, we can spray up to seven days past what we would call ‘early flowering’ in the field,” says Andrew Friskop, a cereal crop plant pathologist with North Dakota State University.
That’s a different recommendation from the early 2010s, when North Dakota growers were told to spray before flowering, when half the head is out of the flag leaf.
“Ten years ago, the recommendation (was) that being too early was better than too late,” said Friskop, who spoke at the CropConnect conference last month in Winnipeg.
“(Now) later is better than being too early.”
Fusarium head blight, also called scab, is a fungal disease that affects yield and grain quality in wheat, barley, oats and barley.
Many wheat growers in North Dakota have followed Friskop’s advice about fungicide timing and are now waiting until flowers appear on wheat heads before spraying.
That’s different from Western Canada, where spraying before flowering is still a recommended practice.
SaskWheat has a webpage on fungicide timing for fusarium that features an illustration telling growers to start spraying when 75 per cent of the heads on main stems are fully emerged and to stop spraying when 50 per cent of the heads on the main stem are in flower .
Those recommendations are likely out of date, says Randy Kutcher, a cereal crop and flax pathologist at the University of Saskatchewan.
In 2021, Kutcher and others published a paper in the journal Plant Disease that looked at fungicide timing for fusarium in durum wheat.
They found that fungicides can be applied at the end of flowering and still be highly effective. The window for spraying begins when flowers first appear, just like Friskop’s message in North Dakota.
“We showed in our work … it’s (when) the first few anthers in the middle of the head open (up),” Kutcher says.
in the late 2010s, Friskop spoke at dozens of meetings across North Dakota, telling growers to change their spray timing and wait longer before applying a fungicide.
“Of the last five years, I think we’ve gained traction. We’ve seen better application timing,” he says.
North of the border, extending that information to growers has been less effective. It could be that recent summers have been dry and fusarium in cereal crops has been less problematic.
“I’ve been talking about it … but growers haven’t been phoning me that much (about fusarium) in the last few years,” Kutcher says.
Proper timing of fungicides does matter because fusarium can be a significant yield robber in cereal crops.
Data from North Dakota shows that wheat growers in the southeastern part of the state are losing 10 to 15 bushels per acre because they’re growing a variety that’s susceptible to fusarium and are not getting good control with a fungicide.
“We’re leaving quite a few bushels on the table,” Friskop says.
In Canada, Kutcher’s research on fungicide timing shows spraying too early provides almost no protection from fusarium in durum.
Spraying too early turned out “pretty much the same as the unsprayed check” in that testing, Kutcher says.
“We didn’t really get any statistical difference…. (Wait) for when the first anthers come out.”
