Small Grains Disease and Pest Update 06/24/24

Fusarium Head Blight Risk

Fusarium head blight risk for spring wheat varieties with a rating of 6 or worse will be high across much of the state through the end of the week  (Figure 1). The heart of the Red River Valley is the only area with a low to moderate risk.  A marked difference in the risk of infection exists between highly susceptible and moderately resistant varieties (Figure 2).

Figure 1. Fusarium head blight risk for very susceptible varieties for June 24 through 28. Darker orange indicates moderate risk and red indicates high risk.

Figure 2. Fusarium head blight risk for moderately resistant varieties for June 24 through 28. Darker orange indicates moderate risk and red indicates high risk.

Other Diseases

Last week's scouting reports and my own observations confirmed stripe rust at very low incidence and severity across much of the state (Photo 1).  Likewise, bacterial leaf streak, tan spot, and BYDV can also be found,  but incidence and severity remain low. 

Photo 1. A stripe infection in spring wheat with the tell-tale parallel rows of orange pustules along the leaf blade's veins that are actively sporulating (Photo courtesy of Ryan Casacan).

Insect Pest 

The scouts also continue to find grasshoppers on field edges in nearly every field and aphids in about a quarter of the fields.  The numbers in all cases were below the respective economic thresholds. Cereal leaf beetle (CLB) was found in fields in Red Lake, Norman, and Pennington counties. CLB feeding generally is restricted to the flag leaf once it has emerged. The number of larvae in each field where they were found, exceeded the threshold of one or more eggs and/or larvae per plant. Insecticide applications should be delayed until 25 percent of the eggs have hatched and larvae have emerged because the insecticide is targeted toward the larvae.

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