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Smith: “Timing is everything” when spraying for soybean white mold

A crop disease expert says timing is everything when it comes to spraying for white mold in soybeans.
Plant pathologist Dr. Damon Smith from the University of Wisconsin-Madison says, “Going between R-1 growth stage and the R-3 growth stage, the start of those pods, that really maximizes the control of those fungicides.”

Smith tells Brownfield controlling the ability of the spores to infect the plant is what matters. “These microscopic spores that infect the plant infect primarily through the flowers and so, once the flowers are gone, the risk of infection goes down substantially, and before those flowers are there, there’s really no risk either, so it’s all about the bloom period.”

Smith says once a field has white mold, it will likely always be there, so farmers should consider changing seed varieties and management practices to minimize losses. “If you’ve got something that gets a little less white mold than another variety, choose that. Then look at row spacing. Going to wider row spacings can be helpful, dropping the planting population down a little bit to open the canopy up. And then, maybe look at some fungicide applications in-season to further reduce the damage.”

Smith says the wider rows reduce humidity under the canopy and it changes the light profile, allowing more ultraviolet rays in and slowing down the development of the little white mold mushrooms.

Work is continuing in Smith’s lab and with seed companies to develop more resistance to white mold, but he says nobody has developed a high level of resistance yet.

Smith spoke to Brownfield at the Wisconsin Agribusiness Classic in Madison, Wisconsin.  You can listen to that interview here:

Dr. Smith can be found online at Badgercropdoc.com and on Twitter @badgercropdoc.