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Issue No. 4, Article 8/April 15, 2005

Update on Management of Soybean Rust with Fungicides in Illinois

Fungicide applications are the primary management strategy for soybean rust. Fungicide applications should be considered when soybean rust is first detected in a field, when the disease has been detected in nearby areas, and when disease forecasts and other risk factors suggest that the risk of disease is high. Fungicides must be applied correctly and at the proper time. The list of fungicides with section 3 or section 18 labels for management of soybean rust continues to lengthen as new products are approved for use in Illinois.

Fungicides most effective as preventive products are the contact fungicides such as chlorothalonil and manzozeb, and the systemic strobilurin products such as Quadris, Headline, and trifloxystrobin in Stratego. The other main group of fungicides is the triazole class of compounds, which have curative and preventive activity. A list of fungicide products available for soybean rust management in Illinois as of April 12, 2005, is shown in Table 4. The following EPA Web site is a good place to check for updates on fungicide registration.

Another likely new development in Illinois is that three applications of section 18 compounds may be allowed for soybean rust management in a season. Until the change takes effect, only two applications of section 18 products are allowed collectively. When or if the change is approved in Illinois, then a maximum of three total applications using approved section 18 products collectively may be made under the soybean rust section 18, but no more than two applications may be made with any given active ingredient.

To help with management of soybean rust, a new publication has recently been released. Using Foliar Fungicides to Manage Soybean Rust can be seen in PDF format. Following are some excerpts from the Web site about the book:

"Foliar applications of fungicides to the soybean canopy will be the standard disease management practice to limit yield losses due to soybean rust for the foreseeable future. This book reviews the factors involved in making fungicide spray decisions and basic fungicide information, including mode of action, application, and use strategies.

"Prepared by a group of soybean pathologists working in many regions of North America, this full-color publication contains numerous illustrations, photographs, maps, tables, and charts, as well as a glossary of terms and a list of sources for additional information."

Please watch for reports of new developments related to soybean rust and fungicide options for managing this disease. Information is changing frequently. Additional information on soybean rust can be found on the new and developing Illinois Soybean Rust Web site.--Dean Malvick

Dean Malvick

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