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What Can I Do To Prevent Frogeye Leaf Spot?

Jun 20, 2011

Question:I had a problem with frogeye leaf spot in soybeans last year and want to be proactive this season to prevent it.   What would you advise?

Answer:Cool, wet conditions and early planting can set the stage for seedling diseases and for frogeye leaf spot. Fortunately, it’s becoming less of a threat in the Midwest as growers adopt resistant varieties, and hopefully that’s what you’ve done this year. Carl Bradley at the University of Illinois has detected fungicide-resistant strains of Cercospora sojina, the causal agent of frogeye leaf spot, which suggests the disease should not be taken for granted. Bradley found the strobilurin fungicide–resistant strains in plant samples from a Tennessee soybean field. The active ingredient strobilurin is used in several popular fungicide products. So far, the fungicide-resistant strains have not been found to be widespread. But their existence reaffirms the importance of planting varieties resistant to frogeye leaf spot. If you planted a susceptible variety and are considering applying a fungicide, choose a triazole fungicide rather than a strobilurin product. If you need to spray a strobilurin fungicide for other foliar diseases as well as frogeye leaf spot, apply a product or a tank mix containing both classes of fungicides.
Know what conditions can foster each disease, select resistant or tolerant varieties and be prepared to apply a fungicide if necessary.
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