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Issue No. 5, Article 8/April 23, 2004

Fusarium Head Blight (Scab) of Wheat, Part 2: Folicur Fungicide Available in Illinois

In the previous article, general information on Fusarium head blight (FHB) (scab) of wheat was presented. In addition to crop rotation and tolerant varieties for FHB management, the foliar fungicide Folicur 3.6F is available in 2004 for FHB management of wheat in Illinois. The U.S. EPA approved a temporary exemption on April 15, 2004, for the use of Folicur fungicide (tebuconazole), manufactured by Bayer Crop Science, to manage FHB on wheat in Illinois. Folicur has not previously been registered for FHB management in Illinois. This temporary use exception expires on May 31, 2004, and requires that specific guidelines be followed for use of the product.

Results from numerous trials indicate that Folicur can suppress, but does not eliminate, FHB disease and the accumulation of the mycotoxin deoxynivalenol (DON) in wheat. Data from multiple years and multiple states suggest that on average Folicur may suppress FHB severity and DON about 30%. Greater and lesser effects on disease severity and DON concentrations have been reported. A key point is that, based on available data, Folicur can be expected to suppress disease incidence and DON mycotoxin levels, but it will not eliminate the disease or mycotoxin.

Folicur is authorized to be used only when weather conditions are favorable for disease development, and it should be used in combination with other management tactics. Only one application may be made using ground or aerial equipment, at a rate of 4 fluid ounces of formulated product per acre per year. Folicur may be applied up to the beginning of flowering only (Feekes growth stage 10.51). Application may not be made within 30 days of harvest. Those who use the product must have the Section 18 labeling in their possession at the time of pesticide application. The label and more specific guidelines for the use of Folicur are available through Bayer Crop Science representatives.

Application timing is critical for effective use of Folicur to manage FHB. Fields of wheat should be closely monitored for flowers daily, 1 to 3 days after heads begin to emerge, to determine when to apply Folicur. The flowers (anthers) are about 1/8 inch long and pale yellow-green. If weather conditions favor disease development, Folicur should be applied at early flowering, when about 25% of the primary heads have started to flower. Applications will not be legal and will be much less effective if made after 50% flowering.

A forecasting system has been developed for predicting the likelihood of FHB in wheat. The system was just put into place for Illinois by plant pathologists from Pennsylvania State University and Ohio State University. The forecasting system has been tested in other states, and initial results suggest that it can predict the probably of FHB severity greater than 10% with about 80% accuracy. This system may be extremely valuable in helping to determine whether and when Folicur should be applied. However, it is important to emphasize that the forecasting system is still experimental and is being tested for the first time in Illinois this year. The FHB prediction is based on rainfall, temperature, and relative humidity. The system uses NOAA weather data that are collected on a 20-kilometer grid. If you are interested in learning more, feel free to go to http://www.wheatscab.psu.edu and check out the results for your area to compare them to your local weather conditions, especially when the crop is within about 10 days of flowering.

The forecasting system and Folicur together provide producers with a potentially excellent set of tools for management of FHB and should allow producers to make economically sound, data-based management decisions. Combining the information from the forecasting system with the option to spray Folicur when the risk of FHB is high may improve producers' ability to control FHB, thus reducing DON levels in grain and increasing yields to enhance the economic return to producers and the milling industry.--Dean Malvick

Dean Malvick

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