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Select the Proper Fungicide for Soybeans

Select the Proper Fungicide for Soybeans
Which fungicide you use matters, especially for the future.

More and more farmers indicate fungicide applications on soybeans will pay, as long as you spray an appropriate fungicide for the situation and apply it properly. Usually that means early in the reproductive stage, often from R2 to R4. Consult the fungicide label for exact instructions.

Kiersten Wise, Purdue University Extension specialist, says it's not enough anymore to know which herbicide by brand or family name you're spraying. You need to know mode of action as well.

Keep healthy: A scout would need to determine if these beans are right to spray for fungicide. Timing around critical growth stages is crucial if you want to see a benefit.

Two scientific groups, the North Central Regional Committee on Soybean Diseases and the Regional Committee for Soybean Rust Pathology, have developed information about the efficacy, or ability of fungicides to control various diseases.

Efficacy refers to how well the fungicide performs when there is sufficient disease pressure and the fungicide is applied properly. Ratings are developed based on multiple years of testing at multiple locations. Also, Wise notes that just because a product helps wipe out a disease, there is no guarantee that the product will boost yield enough to make a profit.

Part of the goal of determining the efficacy comparisons is to get people to think in terms of mode of action and not just product names of fungicides.

In 2011, resistance to fungicides that controlled frogeye leaf spot was confirmed. It was confirmed again in 2012 and 2013. No other resistance to soybean diseases for control by fungi are known at this time, she says.

Scientists know fungicide resistance could develop. They are hoping that if people use various modes of action, it will slow down the movement toward development of resistance of other fungi to other fungicide resistance scenarios. You can learn more about fungicide efficacy in soybeans and how to limit its development by contacting Wise or someone at Purdue. Your county Extension educator should be able to guide you to BP-161-Wk, 5h3 handout on fungicides and soybean efficacy. You can also call 1-800-EXT-INFO or visit

TAGS: Soybeans
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