FHB Update from NY, 05/22/20
Winter malting barley in much of New York is emerging from the boot and this is a critical time to consider a fungicide application. The Fusarium Risk Assessment Map (http://www.wheatscab.psu.edu/ ) today indicates a moderate to high risk of Fusarium head blight (FHB) for some areas of New York. Rain showers and thunderstorms are in local forecasts over the next week; duration of leaf/head wetness is more important for FHB development than is the amount of precipitation. Maximal suppression of FHB and grain contamination by deoxynivalenol (DON) mycotoxin results when fully emerged heads of winter malting barley are sprayed with DMI (FRAC Group 3) containing fungicides Caramba, Prosaro, or Miravis Ace (latter includes FRAC Group 7 fungicide). A heads-emerged spray with these fungicides also protects upper leaves against fungal leaf blotches, powdery mildew, and rust. Scald has already been observed on susceptible varieties. Foliar sprays of any of these three products up to seven days after head emergence may still result in significant FHB and DON suppression. Fungicide products containing QoI (FRAC Group 11) fungicides should not be applied to headed wheat or barley as they may result in increased levels of DON in grain.
Winter wheat is generally a week or more behind in development from winter barley planted on the same fall date. Winter wheat in New York varies from stem elongation to flag leaf visible stages. We should reach the critical fungicide application window for winter wheat over the next two weeks. The DMI (FRAC Group 3) containing fungicides Caramba, Prosaro, or Miravis Ace (latter includes a FRAC Group 7 fungicide) are the most effective fungicides for suppression of FHB and DON contamination when applied at flowering (emergence of yellow anthers on heads). A flowering application of these fungicide products should be based on Fusarium head blight (FHB) risk as well as the risks of powdery mildew, rusts, and fungal leaf blotches in the upper canopy based on scouting of individual fields. Stagonospora nodorum blotch and powdery mildew have already been observed. There is an application window of approximately 7 days from the beginning of flowering in which reasonable FHB and DON suppression can be expected. Check the Fusarium Risk Assessment Tool (http://www.wheatscab.psu.edu/ ) and your local weather forecast frequently as your winter wheat crop approaches heading and flowering.
-- Gary Bergstrom, Extension Plant Pathologist, Cornell University
For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu
For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org