Wisconsin Soybean White Mold Update – August 1, 2019

Damon Smith, Department of Plant Pathology; Shawn Conley, Department of Agronomy; Roger Schmidt, Nutrient and Pest Management Program

Figure 1. Sporecaster predictions for selected non-irrigated locations in Wisconsin for August 1, 2019.

Figure 1 illustrates the calculated risk of white mold for select Wisconsin locations for non-irrigated soybeans, as determined by Sporecaster for August 1, 2019. This means that if soybeans are flowering and the area between rows is filled in more than 50%, risk is mostly low for the presence of apothecia and subsequent white mold development at this point in the season. Figure 2 illustrates calculated risk for the same locations for irrigated soybeans planted to 30-in row spacing. As you can imagine, risk is even higher for irrigated soybeans planted to 15-in rows.

Mild and dry conditions recently have pushed the risk down dramatically in non-irrigated fields. The UW Field Crops Pathology Team continues to scout white mold locations for apothecia. We have only observed apothecia in irrigated fields in the Hancock area.

I’m Ready To Spray, What Should I use?

Figure 2. Sporecaster predictions for selected irrigated locations with soybeans planted to 30″ row-spacing in Wisconsin for August 1, 2019.

If the canopy has met threshold, soybeans are flowering, and your Sporecaster risk is high, then a fungicide might be warranted. If you have decided to spray soybeans for white mold, what are the best products to use? Over the last several years we have run numerous fungicide efficacy trials in Wisconsin and in conjunction with researchers in other states. Applications should be targeted during the R1-R3 growth stages in soybean. Research has shown that applications outside these growth stages, are often less effective. In Wisconsin, we have observed that Endura applied at 8 oz at the R1 growth stage performs well. We have also observed that the fungicide Aproach applied at 9 fl oz at R1 and again at R3 also performs comparably to the Endura treatment. Other fungicide options also include Omega and Proline. You can view results of past fungicide evaluations for Wisconsin by CLICKING HERE. If you would like to run tailored estimations of return on investment for various fungicide programs, you can use another smartphone application called Sporebuster.

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