Small Grains Disease Update 07/13/20

This past week I found the first Fusarium Head blight (FHB) infected spikelets in my trials near Oklee. This trial was seeded on April 24th and the earliest entries are approaching the soft dough stage. The incidence and severity of the FHB were very low, certainly in comparison to the amount of tan spot and Bacterial Leaf Streak (BLS) present in the canopy. Nonetheless, the presence of infected spikelets confirms that the conditions on the ground were indeed as forecasted by the risk model. The Septoria leaf spotting diseases and leaf rust were still mostly and completely absent, respectively.
The immediate weather forecast calls for rain tonight across much of northwest Minnesota and a period of more moderate temperatures and relative humidities. This bodes well for the grainfill but I doubt that the risk for tan spot, leaf rust, and FHB is going to drop substantially. There is still plenty of soil moisture to create the needed leaf wetness periods to create initial infections for the aforementioned diseases.
It remains therefore imperative to stay vigilant the coming week and apply a fungicide onto the remaining spring wheat acres that have yet to reach the beginning of anthesis (Feekes 10.51). The decision on whether to use tebuconazole or Prosaro/Caramba/Miravis Ace remains difficult. Prosaro/Caramba/Miravis Ace each improve suppression of FHB by about 15% to 20% over tebuconazole.

--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