Apothecia that produce the spores that cause white mold infection observed in a soybean field in Pennsylvania (Credit: Adriana Murillo Williams, Penn State).

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Over the past several years, we have tested and validated the Sporecaster scouting app for white mold in soybeans. The app has now been integrated into the Crop Protection Network under the "Crop Disease Forecasting" tools. A helpful (and concise) tutorial explains how to use the forecasting tool.

Last week, we received our first questions about the risk of white mold in 2025 due to the heavy rainfall since early May. We understand that predicting the risk of white mold will be more challenging and occur over a longer period in 2025, given the delayed planting in many areas.

For white mold monitoring in 2025, we will provide weekly and biweekly updates using different locations throughout Pennsylvania. Based on our earlier findings, we will continue to apply a 50% threshold (i.e., a predicted risk of greater than 50% is required to consider a fungicide application) to provide management recommendations for 2025. Model specifics are available in Willbur et al. (2018, "Weather-based models for assessing the risk of Sclerotinia sclerotiorum apothecial presence in soybean (Glycine max) fields").

The "Fungicide Efficacy for Control of Soybean Foliar Diseases" lists fungicides currently available for white mold. Understanding the meaning of the R1 to R3 growth stages is crucial for the decision-making process in managing white mold (Table 1).

Table 1. Description of the R1 to R3 growth stages in soybean (adapted from A Visual Guide to Soybean Growth Stages)
Soybean Growth Stage	Description
R1	One open flower at any node on the main stem (Figure 1)
R2	Open flower at one of the two uppermost nodes on the main stem with a fully developed leaf
R3	Pod is 3/16 inch long at one of the four uppermost nodes on the main stem with a fully developed leaf

Two images showing soybean at R1 and R3 — Figure 1. (Left) Soybean plant at the R1 growth stage (initial flowering). (Credit: Tyler McFeaters, Penn State);
(Right) Soybean plant at R3 growth stage (one pod 3/16 inches long at any of the top four nodes with a fully expanded leaf). (Credit: Adriana Murillo-Williams, Penn State.)

Table 2. What is the current risk of white mold at selected locations in Pennsylvania? As of July 7, 2025
County*	Risk on 07/07	Future risk (6 days)	Interpretation
Cambria	20% (low risk)	Low to very slight increase	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.
Centre	15% (low risk)	Remains low	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.
Huntington	19% (low risk)	Remains low	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.
Indiana	20% (low risk)	Low to very slight increase	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.
Lawrence	19% (low risk)	Remains low	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.
Lebanon	15% (low risk)	Remains low	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.
Northhampton	10% (low risk)	Remains low	With the hot temperatures, the risk of white mold has dropped. Continue to monitor crop growth stages to identify flowering and canopy development. Fungicides for white mold are not recommended at this time.

*Additional counties will be added as the season progresses.

Table 3. What is the current risk of white mold at selected locations in Pennsylvania? as of June 21, 2025
County*	Risk on 06/21	Future risk (6 days)	Interpretation
Cambria	55% (high risk)	Trending lower	If soybean is flowering, it is advised to consider a fungicide application. Nonetheless, the 6-day forecast shows a lowered risk due to hot conditions that do not favor white mold.
Centre	54% (high risk)	Trending lower	If soybean is flowering, it is advised to consider a fungicide application. Nonetheless, the 6-day forecast is for lowered risk due to hot conditions that do not favor white mold.
Huntingdon	57% (high risk)	Trending lower	If soybean is flowering, it is advised to consider a fungicide application. Nonetheless, the 6-day forecast is for lowered risk due to hot conditions that do not favor white mold.
Lawrence	59% (high risk)	Trending lower	If soybean is flowering, it is advised to consider a fungicide application. Nonetheless, the 6-day forecast is for lowered risk due to hot conditions that do not favor white mold.
Lebanon	45% (moderate risk)	Trending lower	Given future conditions, the risk of white mold is decreasing to a moderate level. Continue to monitor the risk map for your specific field situation.

*Additional counties will be added as the season progresses.

Check back next week for the updated white mold risk in your area. If you have questions about the prediction or white mold management, please get in touch with your local extension educator or one of our white mold team members: