MOLD DAMAGE. White mold causes significant stalk damage to developing soybean plants beneath the canopy. Photo by: Michael Wunsch

Precision Fungicide Application Key to Battling White Mold

While no-tillers may have advantages in combatting white mold losses on soybeans, research suggests precise fungicide applications offer profitable control of the disease

THERE’S AN OLD SAYING warning against betting on any proposition with more than one “if” in it, and when soybean producers face seasons with wet, cool conditions during flowering, they face control issues for white mold that present many “ifs.”

North Dakota State University researcher Michael Wunsch has spent years seeking ways to help growers reduce the variables in controlling white mold, a disease that can significantly lower soybean yields through crop-weight reduction and seed loss. 

“White mold needs two things for development: cool, wet conditions and dead blossoms as a target for infection,” Wunsch says. 

Persistent Problem

The Sclerotinia sclerotiorum fungus produces hard, black resting structures called sclerotia that are deposited in the soil behind infected crops and persist for many years. When sclerotia are within the top 1-1.5 inches of soil with sufficient moisture, they germinate to form mushroom-like structures called apothecia.

“Spores released from apothecia infect senesced soybean blossoms when it is cool and moist,” Wunsch says. “Once the pathogen colonizes in dead tissue, it invades adjacent living tissue, causing white mold.”

Wunsch says when daytime highs reach the low to mid 70s F, heavy dew and relatively high humidity are sufficient to allow spores to infect and cause disease. As the mercury climbs into the 80s, recurrent rainfall or overhead irrigation are generally needed to cause significant infection. When daytime temperatures reach the 90s, white mold is much less likely to develop, regardless of field history.

But moist, cool field conditions provide only a couple of…

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Dan crummett 0618

Dan Crummett

Dan Crummett has more than 35 years in regional and national agricultural journalism including editing state farm magazines, web-based machinery reporting and has an interest in no-till and conservation tillage. He holds B.S. and M.S. degrees from Oklahoma State Univ.

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