Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
We finally received some much-needed rain with a lot more in the forecast. While Fusarium Head Blight (FHB) is favored by wet conditions, the dry spring we have had up until now should have kept spores from ramping up in April and we remain at a low risk in the FHB model (Figure 1). I do anticipate that by next week our risk will be a bit more elevated. Most barley is wrapping up heading and will hopefully be in the clear. Over the past few days wheat heads have started to become visible. Depending on the weather, we can usually expect flowers to start showing up on wheat heads 3-5 days after full head emergence. We did have a few cool nights this week that can stretch this process out to 7-10 days. If you are planning a wheat fungicide application, scout frequently and apply when at least 50% of the wheat heads are flowering to 4-6 days after 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 pale white. Additional details on fungicide application can be found in the April 7 article. Data over the past few seasons has shown that it is better to be a little bit after first flowering than to spray too soon, particularly for deoxynivalenol (DON). If you spray too early, heads that have not emerged (secondary tillers) will not be protected by the fungicide application. Although rains have a way of showing up right at peak time for FHB, temperatures will remain a bit below optimum for Fusarium. The rain and temperatures should allow for good grain fill and we will continue to keep a close eye on FHB risk.
Figure 1. FHB Risk Model for April 27, 2023
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).