White Mold on Soybeans: Preventable, not Treatable

White Mold

"White mold is terrible," said Bob Marquette, Federated agronomist at the Albertville location, adding, "It's a big problem, and though it depends on the season, Federated saw a lot of it last year."

Unlike many yield-robbing pests and diseases, white mold can't be treated. It must be stopped before it starts. Sclerotinia stem rot - white mold - can affect high-yield-potential soybeans and it thrives under moist conditions and below average temperatures. Several other factors create the ideal environment for white mold to grow:  

  • a dense canopy of soybeans;
  • susceptible soybean varieties (some are more vulnerable than others);
  • a field history of white mold.

While no variety of soybeans is completely tolerant of white mold, the fluffy cottony growth on the outside of pods can be prevented with crop management that includes the following strategies.

  • Consistently rotate between corn and soybeans (but if white mold is present, it is necessary to keep a field out of beans for three to four years, until the sclerotia dies).
  • Avoid dense canopies with wider row spacing ("Lower populations will help," said Marquette).
  • Control weeds; lambsquarter, velvetleaf, ragweed, and Canada thistle, for example, are hosts for white mold.
  • Apply preventive treatments (such as Aproach - see article below); fungicides can be added to many planned herbicide treatments. 

Marquette described sclerotia as small black structures that resemble mouse droppings. "If you slice the stem [of a soybean plant] open, these will be found inside."

It is important to apply fungicides at the right time. Talk to your Federated Agronomist for more info on white mold before it robs yield in your soybean crop.