Wisconsin White Mold Risk Map – July 15, 2016

Damon L. Smith, Extension Field Crops Pathologist, University of Wisconsin-Madison

Jaime Willbur, Graduate Research Assistant, University of Wisconsin-Madison

Sclero-cast: A Soybean White Mold Prediction Model

**This tool is for guidance only and should be used with other sources of information and professional advice when determining risk of white mold development. We encourage you to read the model how-to guide which can be downloaded by clicking here**

Risk of apothecial presence and subsequent white mold development has increased slightly in the south central portion of Wisconsin since the last posting on July 11 (see map below). Three-day forecasts show continued increase in the south and central portion of the state. While the risk may increase slightly, the risk is low to moderate. The UW Field Crops Pathology crew has been scouting for apothecia and has observed low numbers of apothecia in naturally infested, dry-land fields in Columbia Co. The prediction model forecasted this event earlier last week in this location. In irrigated fields around Hancock, larger numbers of apothecia have been observed. Risk in this portion of the state has been shown to be low (blue color), however, irrigation modifies this risk to a more moderate level. Growers who irrigate or are near moderate- or high-risk pockets should be considering their fungicide application options now.  The window of opportunity to apply fungicide to control white mold in soybean is between the R1 and R3 growth stages. Be sure to consult the how-to guide for assistance in interpreting this map if you are considering spraying fungicide to control white mold.

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This model was developed at the University of Wisconsin-Madison in conjunction with Michigan State University to identify at-risk regions which have been experiencing weather favorable for the development of white mold fungus apothecia. Weather information and maps are provided by the Soybean Integrated Pest Information Platform for Extension and Education (iPIPE), which is managed by ZedX, Inc. This model predicts when apothecia will be present in the field using 30-day averages of maximum temperature, maximum relative humidity, and maximum wind speed. Using virtually available weather data, predictions can be made in most soybean growing regions. Based on these predictions, this map is generated and indicates areas at no (white), low (blue), medium (yellow), and high (red) risk levels. Fields in yellow or red areas have >40% chance of having apothecia present and may be at risk of white mold developing later in the season. Model predictions must be combined with soybean growth stage and canopy characteristics to aid in timing of fungicide sprays. If the model is predicting medium to high risk in your area, soybeans are flowering, and the canopy is somewhat closed, then the white mold risk is elevated. For further information on how to use and interpret this risk map, CLICK HERE to download a how-to guide.