Western Crop and Pest Management

Producers listen to fungicide trials at the Western Crop and Pest Management School as Brian Jenks, NDSU weed specialist, helps with weed identification.

Many producers experienced high risk for Fusarium head blight (FHB) in their spring wheat, winter wheat, durum or barley in North Dakota last summer during periods of high humidity.

It was a cool, wet growing season, with high dew points beginning around June 27 and continuing into the first week in July.

At the Western Crop and Pest Management School, Dr. Audrey Kalil, NDSU pathologist at Williston Research Extension Center, presented U.S. Wheat and Barley Scab Initiative Trials on fungicide applications on all classes of wheat.

“These studies looked at (fungicide) applications from early to late,” Kalil said. Application timing was based on growth stages of main tillers.

The studies found that applying Prosaro or Caramba to wheat from early flowering or within seven days post-flowering provided “significantly more disease suppression” than applications made at head emergence.

In barley, it is different.

Scientists found fungicides applied at head emergence or seven days post-head emergence provided “significantly more suppression than fungicides applied prior to full-head (early).

FHB is caused by a fungal pathogen that produces a toxin called DON (deoxynivalenol), and levels can rise during infection and contaminate grain.

“These studies found there was significantly less DON suppression when a fungicide was applied too early,” she said.

In recent years, USWBSI FHB management fungicide trials have included a new fungicide product, Miravis Ace, which was released by Syngenta last year.

Miravis Ace is a suspoemulsion (SE) formulation and contains pydiflumetofen and propiconazole.

“Twenty-four studies were conducted across the U.S. to help producers understand application timing for Miravis Ace,” Kalil said.

In these studies, scientists compared Miravis Ace, Prosaro, and Caramba at different timings on all classes of wheat.

These were compared with plots where no fungicide was applied.

“In these studies, researchers found that Miravis Ace applied at Feekes 10.3 (or half-head emergence) had less DON suppression when compared to Feekes 10.51 and seven days post flowering,” she said.

Feekes are growth stages of the wheat.

The research trial also evaluated a double fungicide application where Miravis Ace applied at early flowering was followed by Caramba or Prosaro 4-6 days later.

“They found that there was only a slight gain in DON suppression,” Kalil said. “It is likely that this would not provide enough control for this strategy to be economical.”

Kalil also presented results from their six 2018-19 Integrated Management Trials on susceptible and moderately susceptible varieties of durum across the different fungicide treatments under low and high disease pressure.

At the low disease pressure site, the untreated check had DON levels at 2.2 parts per million (ppm).

“Under low disease pressure, Miravis Ace, applied at head half-emergence, achieved similar DON suppression to Prosaro applied at Feekes 10.51,” she said.

However, DON levels were slightly lower when Miravis Ace was applied at Feekes 10.51, or seven days post early flower.

At the high disease site (Fargo 2019), DON levels in the untreated check were greater than 30 ppm.

At this site, Miravis Ace applied at half-head emergence had DON levels similar to the untreated check.

Miravis Ace and Prosaro applied at early flowering or seven days post flowering resulted in a 10-15 ppm reduction in DON.

“The timing recommendation for Miravis Ace based on the data from these trials will be consistent with what is recommended for Prosaro and Caramba,” she said.

Fungicide applications, when timed appropriately, provide 40-50 percent DON suppression.

“For hard red spring wheat, it is also recommended that producers plant a variety that provides some resistance to FHB,” Kalil said. “Some durum varieties are slightly less susceptible to FHB, however resistance is not comparable to hard red spring wheat.”