Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
Across much of the region, barley is approaching or at heading and wheat is ranging from Feekes 7-9. There have been a few reports of scattered powdery mildew, but the warmer weather coming should keep it from spreading as we approach heading. In barley, flowering begins just before the spike emerges from the boot. While florets are not as susceptible, Fusarium can infect the glumes and produce DON. DON accumulation is the primary concern, especially for malting barley acreage. If making a fungicide application to manage FHB in barley, the optimum stage to protect barley glumes is when the spike is fully emerged from the boot and florets are exposed (Figure 1). Work in North Carolina has shown that application up to 6 days after 100% emergence can reduce infected kernels and DON. Disease pressure was very low in our 2021 trial. In our 2020 trial, we saw disease reduction with early, anthesis, and 4 day after anthesis application timings with Miravis Ace, as well as anthesis timings of Prosaro or Caramba (Figure 2). In wheat, ideal application is Feekes 10.5.1 (anthesis), when yellow anthers are visible in the center of the spike. While application of Miravis Ace at 10.3 in wheat can reduce disease, lowest DON has been observed with application at 10.5.1 or up to 4-6 days after 10.5.1. The Fusarium Risk Tool http://www.wheatscab.psu.edu/ has the west part of the state at low risk and a small pocket towards the coast is as medium risk as we look into the weekend (Figure 3).
Figure 1. Stages of barley at or near spike emergence, with the right spikes (100% emergence and 6 days after) at optimum stage for fungicide application.
Figure 2. Summary of 2020 Malting Barley Fungicide Efficacy Trial
Figure 3. Fusarium Risk Tool Prediction for April 21, 2022 (set on the 2 day look forward setting)