Practical Research Drives Profitable Performance

Managing White Mold

White mold infecting a soybean plant. (Progressive Farmer image by Beck's Hybrids)

This advertorial series highlights Beck's Practical Farm Research and agronomy conducted over multiple states to help farmers improve profitability.

There's good news and bad news when it comes to white mold in soybeans. The bad news is once the fungus is in your soil, you'll probably never get totally rid of it.


The good news is seed treatments are coming on the scene to help control the yield-robbing disease. The other good news is white mold is not everywhere--at least not yet. Currently, it's fairly concentrated in the upper Great Lakes region where it thrives in prolonged cool, humid, wet conditions.


White mold can move easily between fields via tillage and harvest equipment on contaminated soil or soybean stover. And, once in a field the fungus persists in the soil, waiting for the "right" conditions and a host plant -- such as the sunflower, dry bean and soybean -- to strike.


"The growing number of soybean acres in the upper Midwest, and the move to continuous corn/soybean rotation, are what's really making this disease spread," says Ben Puestow, Beck's Hybrids area agronomist in Wisconsin.


Fortunately, corn is not a host crop. "But, the white mold fungus survives well," he continues, "and can easily remain in the soil until the rotation comes back to soybeans. In fact, the fungus can survive in the soil up to 10-plus years."

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IDENTIFYING WHITE MOLD


White mold is caused by the pathogen Sclerotinia sclerotiorum. The fungal spores enter the soybean plant through the early flowers.


The infection of the disease typically occurs at the R1 and R2 growth stage. However, visual symptoms may not appear until four to six weeks later and are usually in circular pockets across the most productive area of a soybean field where plant canopy is the thickest. Infected and uninfected areas can be very close. "Soybeans may yield zero in a white mold hot spot," Puestow says, "and produce normal yields just 100 feet away."


When scouting, he advises to walk into an infected area and look under the canopy 4 to 6 inches off the ground. "If you see a white fungus infecting the stem, that's white mold--it's very visible. Unfortunately, by the time you see white mold, it's too late. There's nothing you can do to help the crop."


DISEASE MANAGEMENT


Managing white mold involves using multiple practices. Puestow recommends the following in fields where the disease has been seen:


> Varietal selection. Plant a soybean variety tolerant to white mold. "There's no variety 100 percent tolerant," says Puestow, "but there are tolerant varieties that can reduce yield loss by about 50 percent." Beck's offers white mold-tolerant varieties across its entire maturity platform.


> Use a seed treatment. "Seed treatments are a fairly new tool in the toolbox to help fight white mold," says Puestow. He notes that Beck's will be offering a seed treatment for 2020 to suppress white mold. "Escalate®, Nemasect™ and SDS+ work together to drive performance. The combination of a hard chemistry, a biofungicide and a biostimulant will provide a well-balanced white mold management system."


> Plant population and row spacing: White mold thrives in cool, humid, stagnant air under the soybean canopy. Seeding a thinner plant population allows better air movement through the stand, says Puestow, producing conditions less favorable for infection. He points out reducing the seeding rate doesn't necessarily mean less profit. Beck's Practical Farm Research (PFR) shows that soybean seeding rates in the 100,000 to 125,000 seeds/A range typically gives growers the best return on investment.


> Apply a fungicide: Be sure the fungicide is rated for white mold suppression. "The application needs to be made when soybeans are flowering, between the R1 and R3 growth stages," says Puestow. He recommends watching the weather forecast and "if you see cool, humid, wet conditions coming in the next 2 to 3 weeks, and your plants are headed into the R1 to R3 flowering stages, then make a fungicide application."

Summing up, Puestow stresses the disease requires diligence to stay on top of it. "One silver bullet does not exist in white mold management."

PODCAST:

You can hear more about white mold by listening to the Practical Research Drives Profitable Performance podcast at: https://spotlights.dtnpf.com/…

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