Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
Most barley is at the end of anthesis and I am beginning to see wheat heads emerge. Although there was rain this week, our region remains at low risk in the Fusarium Risk Tool (Figure 1). We will continue to keep a watchful eye over the next week or two as wheat flowering occurs across the state.
Figure 1. FHB Risk Model for May 6, 2021
If you are planning for wheat fungicide application, scout frequently looking for yellow anthers in the center of the wheat head to signal that flowering has begun (Feekes 10.5.1). Once around 50% of heads are flowering, fungicides (Caramba, Miravis Ace, Prosaro) are most effective when applied within a 4-5 day window. Anthers can remain attached after flowering, but become a pale white (Figure 2). Fungicide products should be applied at the manufacturers recommended rate with nozzles that are angled 30-45° from horizontal (30 degrees is better than 45). Nozzles angled both forward and backward or twinjet nozzles that spray in two directions give better contact with the head and increase fungicide efficacy. For ground sprays, fungicides should be applied in at least 10-15 gallons of water per acre; aerial applications are recommended at 5 gallons per acre. The North Central Regional Committee on Management of Small Grain Diseases has released their 2021 fungicide efficacy ratings for the most common small grain diseases (Table 1). The full publication can be found at https://cropprotectionnetwork.org/resources/publications/fungicide-efficacy-for-control-of-wheat-diseases
Table 1: Fungicide Efficacy for Control of Wheat Diseases (CPN-3002-W)
Figure 2. (A) Feekes 10.3; (B) anthesis, Feekes 10.5.1 (yellow anthers beginning flowering); (C) 4 days after anthesis (white anthers post flowering).