Heads Up, Barley Heads Are Out!

Many barley varieties are heading in the southern parts of Pennsylvania, and others are not far behind. Disease pressure in this region has been low so far due to a lack of moisture, but conditions can change rapidly with lingering rain showers ahead. Much of the barley in the southeast is at a Medium level of risk for infection by Fusarium head blight (a.k.a. head scab) in the last week of April.  If the weather remains rainy, we can expect to see increased levels of common foliar diseases such as powdery mildew and leaf blotches, as well as a greater threat of Fusarium head blight. As many of you know, this is a disease of wheat and barley that can lead to the production of vomitoxin (DON) in grains. 

If you intend to protect your barley from scab using a foliar fungicide, please refresh yourself on the optimal timing, which differs from wheat. Research conducted in North Carolina found that the best spray timing for protecting winter barley from scab is 6 days after 100% heading.  With this newer guidance, we should get better DON reduction in barley than under our previous recommendation, which targeted 50% heading. Current labels state that the last stage of application is mid-flower, and there is a 30-day harvest restriction. Do not use any of the strobilurins (Quadris, Headline), or strobilurin/triazole (Twinline, Quilt, Stratego) combination products at flowering or later. There is evidence that they may increase mycotoxin production.  

Miravis Ace, Prosaro, Prosaro Pro, and Sphaerex all provide very good scab suppression. The Miravis Ace label allows for earlier application than Caramba or Prosaro, but the best results are still achieved when the application is timed after full heading in barley. Spray nozzles should be angled 30° downward from horizontal, toward the grain heads, using forward- and backward-mounted nozzles or two-directional nozzles, such as Twinjet nozzles. Additionally, a fungicide treatment at heading with any of these products will give you excellent control of most leaf diseases.

At this point in the season, the only way to reduce the scab problem is to spray. But in general, do not rely solely on fungicides, as they will provide at most a 50–60% reduction in scab severity and vomitoxin. Start with selecting resistant varieties, and time sprays properly to achieve greater control.

As our season progresses, keeping an eye on the FHB Risk Assessment Tool will become critical for farmers considering whether to spray wheat. The Wheatscab forecasting site is an online model that helps us predict infection risk levels everywhere in the state. It has undergone recent revisions, and you may notice a new look. For local and regional commentary, be sure to click the MidAtlantic region map to learn what is going on in the crops nearest you.

Reference

Christina Cowger, Quentin D. Read, Logan Clark and Yanhong Dong. Optimal timing of fungicide application to manage Fusarium head blight in winter barley. 2023. Plant Disease. 10.1094/PDIS-01-23-0021-RE