Fusarium head blight commentary, May 16, 2016

Gary Bergstrom, Extension Plant Pathologist, Cornell University

Most winter malting barley fields from Niagara Falls to the Hudson Valley are in the boot to heads fully emerged stages.  Despite the common dogma that anthers begin to be extruded on barley heads before the heads emerge, we are finding that the majority of just emerged winter barley heads in New York aren’t showing anthers until a few days after emergence under our unseasonably cool conditions.  Temperature and varietiy play a more important role in anther development than I previously realized.  Still, based on the preponderance of experimental evidence, the best time to apply triazole fungicides for Fusarium head blight (FHB) and deoxynivalenol (DON) mycotoxin suppression is within a few days after full head emergence.  We have observed low levels of powdery mildew, spot blotch, scald and trace levels of barley leaf rust in New York. This will be a critical week for foliar fungicide application to barley and I urge close observation of crop development and weather forecasts.

Winter wheat in New York is at stem elongation to flag leaf visible stages, so flowering is still about two weeks off.  The triazole products Caramba and Prosaro are the most effective fungicides for suppression of FHB and DON contamination when applied at flowering (emergence of anthers on heads).  A flowering application of triazole fungicide should be based on Fusarium head blight (FHB) risk as well as the risks of powdery mildew, rust, and fungal leaf blotches in the upper canopy based on scouting of individual fields.  We have observed low levels of powdery mildew, Septoria tritici spot, and trace levels of wheat leaf rust in New York.  There is an application window of approximately 6 days from the beginning of flowering in which reasonable FHB suppression can be expected.  Fungicide products containing strobilurins should not be applied to headed wheat or barley as they may result in increased levels of DON in grain. While the current risk of FHB epidemics is low over most of the state, that risk could increase.  Check the Fusarium Risk Assessment Tool (http://www.wheatscab.psu.edu/) and your local weather forecast frequently as your crop approaches heading and flowering.

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I will be providing weekly New York commentaries on FHB risk through June.  You can subscribe to receive FHB Alerts directly to your Cell Phone (http://scabusa.org/fhb_alert.php).  You can select to receive alerts as 1) Text Message Alerts, 2) Email Alerts, or 3) both Text and Email Alerts.  To receive alerts for New York, select the Northern Soft Winter Wheat option which provides alerts for MI, NY, WI and VT.

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