By Andi Anderson
White mold, also known as Sclerotinia stem rot, is one of the most damaging diseases affecting soybean production. The disease is caused by the fungus Sclerotinia sclerotiorum and can significantly reduce crop yields when conditions favor its development. Farmers continue to explore different management options, including biological products, to reduce the impact of this persistent disease.
White mold typically infects soybean flowers before spreading through the plant. As the disease develops, white fungal growth appears on stems, and dark structures called sclerotia are formed. These sclerotia can survive in the soil for up to 10 years, making long-term management essential. When conditions are favorable, the sclerotia produce mushroom-like structures known as apothecia, which release spores and start new infection cycles.
Traditional fungicides remain an important management tool when applied at the correct growth stage. These products can help prevent infection of above-ground plant parts. However, fungicides do not eliminate sclerotia already present in the soil and cannot stop infections that have already occurred.
As a result, many growers are evaluating biological products as part of an integrated disease management strategy. Several biological products containing beneficial fungi or bacteria are available commercially. Among the most widely recognized is Contans, currently sold in the United States as LALSTOP Contans WG by Lallemand Plant Care.
Contans contains the naturally occurring fungus Coniothyrium minitans, which attacks and breaks down white mold sclerotia in the soil. By reducing the number of surviving sclerotia, the product may help lower disease pressure in future growing seasons.
Research has shown encouraging results. A Purdue University study conducted by Conrad and Telenko in 2023 reported a 54% reduction in Sclerotinia sclerotiorum growth following application of Coniothyrium minitans under controlled conditions. However, field performance may vary depending on application timing and environmental conditions.
A more recent study by Sharma et al. at the University of Wisconsin-Madison in 2026 found that applications made at planting did not produce significant treatment effects. Researchers suggested that the biological agent needed more time to colonize and attack the sclerotia, indicating that earlier applications may provide better results.
Application rates generally range from 1 to 4 pounds per acre, with many growers choosing 1 to 2 pounds per acre. Higher rates are often recommended in fields with a history of severe white mold or where environmental conditions favor disease development. Applications can be made after harvest, before planting, or in early spring.
For best performance, the product should be incorporated into the top two inches of soil using light tillage or water. Deep tillage should be avoided because it can reduce effectiveness and bring buried sclerotia back to the soil surface.
Farmers should also store the product under cool conditions, avoid mixing it with fungicides during application, and recognize that repeated applications over several years may be necessary in fields with heavy disease pressure.
While biological products are not a complete solution on their own, they can be an effective addition to an integrated white mold management program. Combined with crop rotation, proper field management, and timely fungicide applications, biological treatments offer growers another valuable tool to reduce disease risks and improve soybean health over the long term.
Photo Credit: gettyimages-zoran-zeremski
Categories: Michigan, Crops, Soybeans