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Issue No. 5, Article 8/April 27, 2007

Using the Fusarium Head Blight Risk Assessment Tool to Help Make Fungicide Application Decisions for Wheat

Fusarium head blight of wheat (also known as "scab") is caused by the fungus Fusarium graminearum. Another form of the same fungus can cause Gibberella stalk and ear rot of corn. Wheat heads are most susceptible to infection by spores of the scab fungus during the flowering stage. Symptoms of scab on wheat appear as white heads or heads that are half white and half green. Scab can reduce both yield and quality of winter wheat. Infected wheat kernels may be lightweight, shriveled, and chalky in appearance. Also, the fungus can produce toxins that may be found within infected kernels. The most common toxin produced by the scab fungus is deoxynivalenol (DON), also known as vomitoxin.

Symptoms of Fusarium head blight (scab) on a wheat head (Photo courtesy M. McMullen, North Dakota State University).

Management of scab includes several strategies, including crop rotation, planting partially resistant (or tolerant) varieties, and spraying a fungicide. A Fusarium head blight risk assessment tool, developed by a team of researchers from several universities with the help of funding from the U.S. Wheat and Barley Scab Initiative, assists producers with the decision of whether to spray a fungicide for scab control. The risk assessment tool uses weather data to estimate the risk of scab development. While not 100% accurate, the models used to develop the risk assessment have been shown to have nearly 80% accuracy.

The Fusarium head blight risk assessment tool provides information on the risk of scab for different areas of Illinois and the U.S.

The fungicides Folicur (Bayer CropScience), Orius (Makhteshim Agan), and Proline (Bayer CropScience) are available to Illinois wheat growers this year for management of scab. In addition to providing disease control, these fungicides have been shown to reduce the level of DON in the grain produced by the scab fungus. Both Folicur and Orius contain the active ingredient tebuconazole and have section 18 emergency exemptions for use in the 2007 season; the use rate for Folicur and Orius is 4 fl oz/A. Proline, which contains prothioconazole, recently received a full section 3 registration for use on wheat; its use rate is 4.3 to 5.7 fl oz/A. For best results, these products should be applied at early flowering (Feekes 10.51). Seven to ten days before flowering, check the risk assessment tool to help with a decision on fungicide application.--Carl A. Bradley

Carl A. Bradley

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