By Eliza Carlson, University of MN Extension intern, Stearns, Benton, and Morrison County

White mold or Sclerotinia Stem Rot is a destructive disease that is quite common throughout Minnesota. The occurrence of white mold varies widely from year to year and from location to location depending on weather conditions and past field history.

There are different types of conditions and factors that favor white mold on soybeans.

• Prolonged wet and cool weather
• High Plant Populations
• High Fertility
• Narrow Rows
• Early Planting

There are different symptoms that indicate the presence of white mold. During flowering we look for lesions developing at nodes at the bottom of the plant. After the lesions or markings expand, the tops of the soybean plants become grayish-green and then wilt and die. At this point in the year, stems become soft and mushy and covered with white moldy growth. In some instances, soybean plants can be killed in patches within the field or seen standing upright in affected fields.

There are ways to manage and decrease the chances of white mold on soybeans plants:

• Select white mold resistant soybean varieties
• Lower plant populations
• Plant in wider rows
• Reduce irrigation frequency during flowering
• Planting later
• Proper weed management
• Adding small grains into the crop rotation

Foliar fungicides can also be used but this does depend on the situation. When looking at fungicide applications consider the cost of application, application timing and chemicals used to help maximize the effectiveness and return on investment.

For more information about white mold on soybeans visit www.extension.umn.edu and search white mold. If you have other questions about this or other crops related topics, reach out to your local Extension Educator. Residents in Wright County can call (320) 249-5929.