WINNIPEG — Wheat growers in North Dakota have altered how they use fungicides to control fusarium head blight.
Many farmers now apply fungicides later, after flowers first appear on wheat heads, to cut the risk of fusarium damaged kernels (FDK) and reduce levels of deoxynivalenol (DON) in cereals.
Western Canadian farmers should make a similar switch, says a plant pathologist with Agriculture Canada in Alberta.
Right now, some agronomists and grower groups say the ideal fungicide timing starts when 75 per cent of wheat heads are fully emerged.
Research from North Dakota and the Prairies has shown that the 75 per cent timing is too early, says Kelly Turkington, who works for Agriculture Canada in Lacombe, Alta.
“You need to get fungicide directly onto the plant tissues you want to protect. If those tissues (heads) haven’t emerged or have only partially emerged, then they are either not protected at all or are only partially protected,” he said.
If a grower sprays a fungicide when 75 per cent of wheat heads have fully emerged, that potentially means that “25 percent of the heads don’t receive any fungicide at all,” Turkington added.
Instead, farmers should be spraying when the first flowers appear on the middle of the wheat heads.
“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,” said Andrew Friskop, a cereal crop plant pathologist with North Dakota State University.
“Ten years ago, the recommendation (was) that being too early was better than too late…. (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 other crops.
Many wheat growers in North Dakota have followed Friskop’s advice about fungicide timing.
That shift hasn’t happened in Canada, yet.
However, Turkington and others are trying to deliver the “later is better” message to cereal growers.
“It (FHB) is a challenging disease to manage,” he said.
“My focus is, how do we tweak things? How do we improve a grower’s ability to suppress FDK and DON?”
Some herbicides, such as glyphosate, are systemic, meaning they are absorbed and translocate throughout the plant.
Fungicides can also move within plant tissues, but not much.
Farmers might hear that a certain fungicide is “systemic” and assume that the product moves into cereal heads from other parts of the plant.
“That’s not the case. With fungicides … if they’re systemic, they are locally systemic,” Turkington said.
That’s why it’s critical to get the fungicide on the cereal head, where the disease does its damage.
Randy Kutcher, a cereal crop and flax pathologist at the University of Saskatchewan, has published a paper on fungicide timing for fusarium in durum .
He 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 from North Dakota.
“We showed in our work … it’s (when) the first few anthers in the middle of the head open (up),” Kutcher said.
Research indicates that fusarium-damaged kernels are more likely when the infection happens at flowering, but mycotoxins in the head will develop later.
“In wheat, the most damaging symptoms and potential for downgrading (for FDK) … occurs if you have infection around anthesis,” Turkington said.
“If that infection occurs later on, during the grain filling period, your severity of FDK may be very lower, but you may have potential for DON contamination.”
Research on fungicide timing and DON control from North Dakota shows that spraying later is definitely better:
When applied at 50 per cent full head emergence, fungicides provided 20 to 30 per cent control.
At early flowering or five to seven days after early flowering, DON control was closer to 50 per cent.
Managing DON levels is critical in cereals, especially for crops such as malt barley, where tolerances for mycotoxins are very low.
“(Fungicides) are active for about two weeks, maybe three,” Turkington said.
“The longer you can protect that cereal head during the grain filling period, the less potential you have for DON contamination.”
Contact robert.arnason@producer.com
Robert Arnason is a reporter with The Western Producer.