Alyssa K. Betts, Extension Field Crops Pathologist; akoehler@udel.edu
The temperatures have been a bit of a roller coaster this week, but hopefully after this week we are done with the cold nights. Most barley is wrapping up heading. Over the past few days wheat heads have started to become visible. Depending on the weather, flowers will start to show up on wheat heads 3-5 days after full head emergence, this could be stretched to 7-10 days under cool weather conditions. With hot temperatures in the forecast this weekend, it seems we will be likely to have a shorter period from head emergence to flowering this year. Currently we are at low risk in the FHB Risk Model (Figure 1), dry conditions have this low risk maintained over the 6-day outlook. If you are planning a wheat fungicide application, scout frequently and wait to apply when at least 50% of the wheat heads are flowering. You will be looking for bright yellow anthers in the center of the wheat head to signal the start of flowering (Figure 2). Anthers can remain attached after flowering, but become a pale white. Additional details on fungicide application can be found in the April 5 article. Data over the past few seasons have supported that it is better to be a little bit after first flowering (4-6 days) than to spray too soon, particularly for the mycotoxin deoxynivalenol (DON). If you spray too early, heads that have not emerged (secondary tillers) will not be protected by the fungicide application. The goal is to try to make application when the highest percent of the field is at or just past flowering.
Figure 1. FHB Risk Model for April 25, 2024 (wheatscab.psu.edu)
Figure 2. From left to right Feekes 10.3, Anthesis, Feekes 10.5.1 (yellow anthers beginning flowering), 4 days after anthesis (white anthers post flowering).