Alyssa Koehler, Extension Field Crops Pathologist; firstname.lastname@example.org
Heading in barley is underway and wheat is entering the boot stage. Overall it has been a dry April which has kept us at low risk in the Fusarium Risk Tool (Figure 1).
Figure 1. FHB Risk Model for April 20, 2023 (wheatscab.psu.edu)
Due to it being so dry, a lot of pivots have been running. It is important to remember that irrigation can impact Fusarium Head Blight risk by creating a humid, warm environment in the canopy to favor development and spread of FHB just like a rainy spring would. While you want to meet the crops water requirements, irrigation timing can be managed by staying aware of when flowering begins and ends. Irrigate to fill the root zone prior to flowering and, if possible, avoid irrigation during flowering. After flowering, irrigation can resume if dry weather persists. Barley starts flowering prior to heading (Figure 2), while wheat usually starts to flower 3-4 days after heading out (Figure 3).
If you are planning for wheat fungicide application, scout frequently and apply when wheat is flowering (Feekes 10.5.1). Weather can impact how many days from when heads become visible until flowering actually begins. If weather continues to be warm, we may have shorter windows this season. Look for yellow anthers in the center of the wheat head to signal the start of flowering (Figure 3). Once wheat is flowering, fungicides are most effective when applied within 4-5 day days. For best mycotoxin (DON) control, it is better to be at flowering or a few days beyond than to spray too early when heads are not out yet. Anthers can remain attached after flowering, but become pale white. Fungicide products should be applied at the manufacturers recommended rate with nozzles 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.
Figure 2. Anthers visible on emerging barley head
Figure 3. Wheat at flowering (Feekes 10.5.1) with yellow anthers visible 3-4 days after heads emerge