Gary Bergstrom, Extension Plant Pathologist, Cornell University
Most winter malting barley fields in New York have headed out and the remainder will do so this week. Foliar sprays of Caramba or Prosaro up to seven days after head emergence may still result in significant FHB and DON suppression. Fungicide products containing strobilurins should not be applied to headed wheat or barley as they may result in increased levels of DON in grain. A heads emerged spray with these triazole fungicides also helps protect upper leaves against fungal leaf blotches, powdery mildew, and rust. Even though we have had frequent rains, the Fusarium Risk Assessment Map shows mostly low risk of Fusarium infection in New York because temperatures have been considered too low for spore production.
This is a critical week ahead for fungicide spray decisions on winter wheat. Winter wheat in New York varies from boot stage to the initiation of flowering. 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, rusts, and fungal leaf blotches in the upper canopy based on scouting of individual fields. We have observed low levels of powdery mildew and fungal leaf blotches. We confirmed the first stripe rust of the season today on winter wheat in Yates Co.! Foci were fairly large with severe rust in the lower canopy spreading to upper leaves, suggesting a number of rust reproduction cycles in these fields and possible local overwintering of the rust. There is an application window of approximately 7 days from the beginning of flowering in which reasonable FHB 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.
