Timing matters when reducing fusarium head blight in winter barley

Date:05-16-2023

When Fusarium head blight (FHB) threatens winter barley, the best time to apply a fungicide is about six days after full barley head emergence, according to a recent study published in Plant Disease.

FHB, also known as scab, is a fungal disease that attacks small grains, discoloring the heads and contaminating the grain with the mycotoxin deoxynivalenol (DON), a toxic compound also known as vomitoxin. For barley, the most common grain used to make malt for beer and spirits, even a small amount of DON can cause crops to be rejected by purchasers. The disease in malted barley kernels may lead to gushing, or the rapid and uncontrolled foaming of beer, making the crop unusable for beer production.

In a four-year study, researchers with the U.S. Department of Agriculture (USDA)'s Agricultural Research Service (ARS) and the University of Minnesota assessed three different fungicides for FHB reduction. The researchers evaluated the amount of DON present in mature winter barley heads following a fungicide application at one of three growth stages — half heading, full heading, and six days after full barley head emergence. 

Healthy resistant barley (right) and susceptible barley shows symptoms of Fusarium head blight (left). (Photo by Brian Steffenson, University of Minnesota)

"The latest timing of fungicide application reduced DON significantly more than the early timing for all three fungicides tested in the study,"said Christina Cowger, small grains pathologist at ARS's Plant Science Research Unit in Raleigh, North Carolina. "Applying fungicide before all heads were emerged did not significantly reduce DON in winter barley as compared to not spraying at all. If scab is threatening, growers should wait about six days after barley heads have all appeared before applying fungicide."

According to Cowger, eastern U.S. barley growers have two main tools for FHB management —plant moderately resistant varieties and apply a fungicide. By understanding the best timing for fungicide to minimize FHB, growers can manage high-FHB epidemic years and maximize profits from malting barley.

FHB is one of the factors limiting the global production of barley since it can result in yield loss and economic damage. According to the American Phytopathological Society, the disease has cost U.S. wheat and barley farmers more than $3 billion since 1990.

"Year in and year out, FHB is the disease that most threatens profitable wheat and barley production in the U.S.," Cowger said. "Knowing how to get the most out of our FHB management tools is key to small grain profitability."