Head Scab Prevention in Wheat

Fusarium head blight (FHB), also called head scab, is a fungal disease that infects wheat during flowering, which typically occurs between mid-May to early June in this area. This year, early maturity varieties and earlier planted winter wheat fields started heading on May 15 and likely will be flowering by May 21. Over the past 15 years widespread FHB epidemics occurred in Nebraska in 2007, 2008, 2015, and 2019. Southeast Nebraska is particularly prone to FHB issues. In addition to yield loss as high as 50%, FHB reduces grain quality and the received price at the elevator due to damaged kernels or presence of a mycotoxin.

The pathogens causing FHB are always present in the area as it survives on corn and wheat residue. In May, excessive and frequent rainfall two weeks prior to flowering and during flowering creates a potential high FHB risk. The frequent rainfall events so far in May in southeast Nebraska have set the stage for a potential 2022 outbreak. Other factors will increase risk of FHB including planting a susceptible variety, planting after corn or wheat, no-till, and recent irrigation. At this point, the weather and these production practices are set. What can we do to protect the wheat from FHB?

Fungicides can significantly suppress FHB by 70%, but not completely control it. There are six fungicides recommended and labelled to suppress FHB including Caramba, Sphaerex, Miravis Ace, Proline, Prosaro, and Prosaro Pro. Large ground sprayers (>90 ft boom width) are very effective due to high volume application capability (>10 gpa), reduced tire damage to spray area ratio, and by using recommended nozzles (front & back angled nozzles). Aerial application is often chosen since ground sprayers are tied up with corn and soybean herbicide spraying or because wet weather limits field traffic. The effectiveness of aerial applications to suppress FHB can be improved if the volume is increased to 4 to 5 gallons per acre. 

Target fungicide application during early flowering (Feekes 10.5.1) when yellow anthers become visible. Miravis Ace and Prosaro Pro is labeled for suppression of FBH prior to flowering during heading, but it is still less effective than use during early flowering. From early flowering, applications can still be made 7 days later with very good suppression of FHB. Applications at the end of flowering lose effectiveness and can become off-label applications due to a 30 to 32-day preharvest interval or a growth stage restriction at the watery-ripe stage (Feekes 10.5.4). It is preferred that it does not rain 2 to 4 hours following the fungicide application.

Additionally, the six fungicides mentioned are labeled to effectively control stripe and leaf rust while providing 2 to 3 weeks of residual activity during the early grain fill period for rusts. However, there are no reports of leaf or stripe rust in the region, which is good. For more information about these and other agronomic issues, contact me at nathan.mueller@unl.edu  or 402-821-1722. Know your crop, know your tech, know your bottom line at croptechcafe.org.

Nathan Mueller
Extension Educator
Saline, Jefferson, Gage Counties
May 2022