The immediate weather forecast not only will increase the risk for tan spot but also for Septoria spp. and leaf rust infections. I expect leaf rust to make its way into at least southern Minnesota as severe leaf rust was reported on unsprayed and susceptible winter wheat varieties in eastern Nebraska.
Consider tank mixing half a labeled rate of a registered fungicide with your weed control program to control early season tan spot in spring wheat when tan spot can found in your fields.
Winter wheat is approaching flowering or Feekes 10.51 in the southern half of Minnesota. To date the risk model for FHB has been trending low, largely because of the cooler temperatures rather than the absence of precipitation. The immediate forecast continues to indicate low risk of FHB. However, the application of a fungicide at Feekes 10.51 to suppress FHB is the final opportunity to controls leaf diseases like tan spot, Septoria spp., and leaf rust.
Previous research has shown that control of the leaf diseases usually pays in the case of winter wheat. Therefore, I suggest you scout your winter wheat now and consider a fungicide application if any leaf diseases can be found in the lower canopy.
--Jochum Wiersma, Extension Agronomist, University of Minnesota Crookston
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