Fusarium Head Blight (Wheat Scab)

As wheat in Missouri approaches flowering, fungicide applications for Fusarium Head Blight (FHB) will begin soon. FHB can reduce yield, grain weight, and seed quality. Fusarium graminearum, the pathogen that causes Fusarium Head Blight (FHB), typically infects wheat heads at anthesis (Figure 1), prefers warm, wet conditions, and can produce the mycotoxin deoxynivalenol (DON).

Variety selection plays an important role in FHB management. A moderately resistant or resistant variety can help manage FHB even in the absence of a fungicide application. More information can be found in the following article.

For fungicide applications, monitoring the Fusarium Risk Tool and current and forecasted weather can help you determine whether a fungicide application is warranted.

The most effective timing for a fungicide application targeting FHB is at early anthesis (Feekes 10.5.1), when approximately 50% of primary tillers are flowering (Figure 1). Research by multiple groups has demonstrated that applications prior to anthesis or after anthesis can reduce FHB, DON accumulation, and yield loss but are generally less effective than an application made at early anthesis. For more information on application timing, please see the following article.

Figure 1 Anthers with yellow pollen begin to emerge from the middle of the head (Feekes 10.5.1).

In 2024 and 2025, we continued our small plot research trials to evaluate application timing and various fungicide products at Bradford Research Farm and Lee Greenley Jr. Memorial Farm. In both years, disease severity and DON levels were low, and yields were statistically similar across all treatments (Figures 2 and 3).

Figure 2 2024 yield data from Bradford and Lee Greenley Research Farms. Treatments applied at 10.5.1 unless otherwise noted. Disease severity was low and yields were statistically similar across treatments.

Figure 3 2025 yield data from Lee Greenley Research Farm. Treatments applied at anthesis (Feekes 10.5.1) unless otherwise noted. Disease severity was low and yields were statistically similar across treatments.

In 2025, we began evaluating whether drone applications can manage FHB as well as a tractor applications given the potential utility of a drone application under wet conditions. Each system was operated using standard commercial parameters: the ground rig applied 15 GPA with the boom 24" above the canopy, while the drone applied 3 GPA at a height of 9.8'. Both methods utilized coarse droplets (~350 microns). The ground rig application provided better coverage (Figure 4); however, disease severity, DON levels, and yield were similar between both application methods under the low disease pressure observed in 2025. This may vary under high disease pressure, and we are set to repeat this trial in 2026.

Figure 4 Spray card coverage following applications. (A) Spray cards were wrapped around individual wheat heads and clipped at the base. (B) Spray card coverage following the ground rig application at a standard rate of 15 GPA and (C) Spray card coverage following the drone application at 3 GPA.

Leaf Rust vs Stripe Rust

Low incidences of leaf and stripe rust have been reported in neighboring and southern states. While wheat is most vulnerable during the flag leaf stage, stripe rust's aggressive nature may justify a later fungicide application if the crop remains susceptible to yield loss. Stripe rust can progress rapidly and early intervention is key.

Fungicides for stripe rust are most effective as soon as the threat has been identified and before disease reaches 5% severity or incidence in the field and while weather conditions remain favorable for spread. The Crop Protection Network has a table that summarizes symptoms of stripe, leaf, and stem rusts.

Viruses

Viruses continue to be observed annually across wheat production fields in the Midwest and great plains. Although there are not good in-season management options, identifying the virus is valuable for future seed selection and for targeting the virus's vector (the insect or mite carrier).

Because many viruses cause similar symptoms, visual differentiation is difficult. We encourage farmers to submit symptomatic wheat samples to the MU Plant Diagnostic Clinic for analysis. Additionally, we highly recommend that farmers focus on removing the "green bridge" risk by removing all volunteer wheat and grassy weeds at least two weeks prior to drilling in the fall. This can reduce vector populations before the next crop emerges.