Reducing Fusarium Head Blight in Winter Barley: The Importance of Timing.

When barley head blight (FHB) threatens winter barley, the best time to apply a fungicide is about six days after the full head of barley emerges, according to a recent study published in the journal plant disease.

FHB, also known as scab, is a fungal disease that attacks young grains, discoloring the heads and contaminating the grains with the mycotoxin deoxynivalinol (DON), a toxic compound also known as vomitotoxin. 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 buyers. Disease in malted barley grains may result in fluxes, or the rapid and uncontrolled foaming of beer, making the crop unusable for beer production.

In a four-year study, researchers from the Agricultural Research Service (ARS) of the United States Department of Agriculture (USDA) and the University of Minnesota evaluated three different fungicides for reducing FHB. The researchers assessed the amount of DON present in heads of mature winter barley after applying a fungicide at one of three growth stages—half head, full head, and six days after emergence of a full head of barley.

“The most recent timing of fungicide application reduced DON significantly more than the earlier timing of all three fungicides tested in the study,” said Christina Kuger, a small grain pathologist at ARS’s Plant Science Research Unit in Raleigh, North Carolina. “Applying fungicides before all heads emerge did not significantly reduce DON in winter barley compared to not spraying at all. If scab is a threat, growers should wait about six days after heads of barley emerge before applying fungicides.”

According to Couger, barley growers in the eastern United States have two main tools for managing FHB—plant varieties with medium resistance and applying fungicides. By understanding the best timing of fungicides to reduce FHB, farmers can manage high FHB epidemic years and maximize profits from malting malt.

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

“Year after year, FHB is considered the disease most threatening to profitable wheat and barley production in the United States,” said Kuger. “Knowing how to get the most out of FHB management tools is key to small grain profitability.”