Fighting White Mold in Soybeans: What Farmers Need to Know
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Information provided by Mark Jeschke, Ph.D., Agronomy Manager
Information provided by Mark Jeschke, Ph.D., Agronomy Manager
White mold, also known as Sclerotinia stem rot, has become an increasing concern for soybean growers across the Northern U.S. and Canada. Once a sporadic issue, it's now a frequent yield-limiting disease. Managing it requires foresight, an understanding of environmental triggers and a balanced agronomic strategy. Here's what you need to know to protect your fields.
White mold thrives in high-yield soybean environments. Ironically, practices that push for better yields—like early planting, narrow rows and dense canopies—also create ideal conditions for the disease. These setups trap moisture and shade beneath the canopy, fostering mold development.
White mold is a one-cycle-per-season disease, starting from sclerotia—dark, seed-like structures that can survive in soil for years. These germinate in cool, wet conditions and produce mushroom-like apothecia, which release millions of spores.
However, spores can’t invade healthy tissue directly. Instead, they colonize senescing (dying) flowers, often lodged in leaf axils or pods. From there, the infection spreads, forming white, cottony growths on stems and eventually causing plants to wilt and die.
White mold thrives when all the following align:
Early canopy closure—a yield-boosting goal—also increases the risk of mold outbreaks.
Some risk indicators to watch:
There's no silver bullet for white mold. The best approach layers multiple tactics.
Weeds like pigweed, ragweed and velvetleaf can also host white mold. Good weed control isn’t just for yield—it reduces mold pressure too.
Chemical control is a tool—but not a cure. Fungicides must be applied before symptoms appear, ideally at the R1–R2 growth stage (first bloom). Later applications are less effective due to reduced canopy penetration.
University and on-farm trials show sequential applications at R1 and R3 yield the best results—up to 13 bu/acre advantage over untreated soybeans.
White mold is most damaging in your highest-yielding environments. That’s why it’s critical to balance practices that push yield with those that protect it. Evaluate your fields annually and adapt your strategy based on risk levels.
Need help selecting the right varieties or adjusting your management plan? Contact your local Hoegemeyer rep—we're Right Here to help.