Soybean Growers Urged to Spray Before Rust Hits

Experts warn waiting to treat fields until rust appears can lead to significant yield losses.

Apr. 18, 2026 at 6:42am

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A bold, highly structured abstract painting in warm earth tones, featuring sweeping geometric arcs, concentric circular patterns, and precise botanical spirals, conceptually representing the complex spread and impact of the Asian soybean rust fungal disease.An abstract scientific visualization depicts the rapid spread and devastating impact of Asian soybean rust, a fungal disease that can quickly defoliate and destroy soybean crops if not addressed proactively.Greensboro Today

Marty Wiglesworth, a plant pathologist and technical brand manager of fungicides for Syngenta Crop Protection, is advising soybean growers not to wait until they see Asian soybean rust in their fields before spraying fungicides. According to Wiglesworth, Asian rust can quickly defoliate a healthy soybean field in just 4-5 weeks, making it difficult to make up the yield losses by that point. He recommends growers review available fungicide options, including triazole-based and strobilurin-based products, and take preventative action before the disease arrives.

Why it matters

Asian soybean rust is a devastating fungal disease that can rapidly spread and cause major yield losses if not addressed proactively. By the time the disease is visible in a field, it may already be too late to prevent significant damage. Growers need to be vigilant and spray fungicides as a preventative measure to protect their soybean crops.

The details

Wiglesworth, a plant pathologist and technical brand manager of fungicides for Syngenta Crop Protection, is urging soybean growers not to wait until they see Asian soybean rust in their fields before spraying fungicides. He explains that the disease can completely defoliate a healthy soybean field in just 4-5 weeks, making it difficult to make up the yield losses by that point. Wiglesworth recommends that growers review the available fungicide options, including triazole-based products that can be applied curatively to infected plants, as well as strobilurin-based compounds that work preventatively. He says the strongest control is achieved by combining both types of fungicides.

  • Asian soybean rust can hit a healthy soybean field and completely defoliate it in 4 to 5 weeks.

The players

Marty Wiglesworth

A plant pathologist and technical brand manager of fungicides for Syngenta Crop Protection in Greensboro, North Carolina.

Syngenta Crop Protection

A global agrochemical company that produces fungicides and other crop protection products.

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What they’re saying

“I'm really trying to steer people away from waiting until they see rust in their fields, because according to the research we've got, it's difficult to make up the yield you've lost by then.”

— Marty Wiglesworth, Plant Pathologist and Technical Brand Manager, Syngenta Crop Protection

The takeaway

Soybean growers need to be proactive in applying fungicides to protect their crops from the devastating effects of Asian soybean rust. Waiting until the disease is visible in the field can lead to significant and irreversible yield losses, so preventative spraying is crucial.