Fungicide application in growing season depends on small grain type

Date:03-18-2022

By Andrea Johnson

If you haven’t raised spring wheat, barley, or oats in a while, there are some good reasons to include them in a crop rotation.

Small grains are planted early and harvested in mid-summer. Prices are excellent for small grains, and soil moisture levels have an opportunity to get recharged because small grains only need about 12-15 inches of moisture from germination to maturity. That benefits heavier water users the next year.

Inputs should include fungicides and fungicide applications.

During the recent University of Minnesota Strategic Farming webinar, small grain specialist Jochum Wiersma was asked about the use of fungicides in small grains.

Jochum Wiersma, University of Minnesota Small Grain Specialist

As with all crop production, best management practices warrant scouting ahead of fungicides applications.

“Fungicides, we know that is a multi-pronged discussion of ‘when’ and it varies a little by what small grain we’re talking about,” Wiersma said. “Scouting is still key here regardless of what your end-use is, because disease can be a problem.”

He gave the following recommendations for small grains:

Oats

Wiersma said fungicides may need to be applied twice during the growing season. The first fungicide application may occur at the flag leaf fully extended stage or Feekes 9. The second fungicide application may be needed at fully headed oats or Feekes 10.5.

“If I see crown rust in the bottom of the oat canopy, I probably want to do an application at flag leaf already,” he said. “If I don’t see any crown rust, I automatically move the application to full-headed oats and use it then.”

Barley

If raising NDSU’s Pinnacle two-rowed barley, then net blotch is a significant risk. ND Genesis two-rowed barley is also susceptible to net blotch.

For Pinnacle, look for net blotch in the bottom of the canopy. Spray at flag leaf fully extended, if needed. If not, automatically spray at fully headed Pinnacle barley, he said.

For barley varieties that are less susceptible to net blotch, be aware of Fusarium headblight (FHB) that can produce deoxynivalenol (DON).

“DON is a very large disrupter in the malting and brewing industry,” he said. “You use a fungicide application at fully headed barley, Feekes 10.5.”

Fungicides include Prosaro, Caramba, and Miravis Ace, he said.

Wheat

Applying a fungicide at Feekes 5 or jointing stage has become commonplace. Wiersma said he doesn’t favor making an application without scouting for tan spot. Tan spot is the “canary in the coal mine,” that indicates leaf diseases are present.

“We don’t want to use these very cheap chemistries that still have efficacy and lose the efficacy because we are starting to select for resistance,” he said.

In Europe, the tan spot fungus has developed resistance to commonly used Group 3 and Group 11 fungicides.

If you don’t see tan spot, he said, don’t spray a fungicide. If you see stripe rust or leaf rust in the bottom of the canopy, there could be a need to apply a fungicide at Feekes 9, which is flag leaf fully extended. In most years, it won’t be necessary to spray that early. A fungicide application can be delayed to Feekes 10.5.1 or the beginning of anthesis, the optimum timing to reduce the incidence and severity of FHB in wheat.

Because of improved genetics in spring wheat, it is not a foregone conclusion that fungicides will be needed. In 2021, conditions were dry enough that disease wasn’t a problem, but in some cases, an insecticide application was still needed for aphid control.

Winter wheat

Watch for tan spot at Feekes 5 – most winter wheat varieties are susceptible to the leaf disease and a fungicide application may be required. There could also be powdery mildew.

A fungicide application at Feekes 9 may be needed to fight leaf rust or stripe rust.

Winter wheat may also require a heading application to fight against FHB, using products like Caramba or Miravis Ace, he added.

One caveat about the use of fungicides and/or herbicides was raised by University of Wisconsin Monroe County Extension agent Bill Halfman. If small grains are going to be harvested for forage, it’s imperative to read the labels to follow preharvest intervals. Labels have the information for correct chemical application.