Preventing Fungicide Resistance in Corn and Soybeans

Diseased soybean leaf

University researchers and fungicide providers have identified five fungicide best management practices to ensure long-term fungicide effectiveness in corn and soybeans.

“By implementing multiple best management practices, growers can preserve the long-term effectiveness and viability of fungicides,” said Thorsten Schwindt, product manager for Bayer.

  1. Choose a Resistant Hybrid/Variety. Carl Bradley, Ph.D., plant pathologist for the University of Illinois, said this is the most important decision growers can make in managing disease. Seed companies often provide disease ratings for their seed products. Growers should also factor in field history when selecting a disease-resistant seed.

  2. Scout Fields Regularly. Growers should keep records over several years, as diseases can reappear after an absence of some seasons when the conditions are favorable for development.

  3. Implement Crop Rotation. Growers know the risk of disease increases in non-rotated fields. Using a regionally appropriate crop rotation can reduce this risk. When planting a continuous crop, growers should alternate disease-resistant hybrids/varieties and monitor fields closely.

  4. Mix and Rotate Fungicide Classes. Applying fungicides with a single active ingredient can create a high risk for resistance. Using fungicides or tankmixes with multiple modes of action is advised. A fungicide such as Stratego YLD® fungicide has two modes of action. It provides both preventive and curative activities and systemic movement to provide broad-spectrum, long-lasting disease control and higher yield potential. The Fungicide Resistance Action Committee (FRAC) provides a fungicide modes of action list.

  5. Follow Label Recommendations. Timing, plant size and target disease may dictate the use rate and spray interval. Growers should check the label for size-appropriate rates. Using lower-than-labeled fungicide rates could cause resistance to develop sooner. Fungicide labels include FRAC modes of action and the number of fungicide applications permitted per season. “Growers should apply fungicides proactively or early in the disease cycle and also when a disease threat is looming,” Schwindt said.

Additional fungicide management practices include maintaining proper soil fertility, use of integrated pest management practices and improving surface and subsurface drainage.

The Plant Management Network and Integrated Pest Management – Pest Information Platform for Extension and Education also have additional fungicide resistance management information for growers.

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