Question of the week: What is up with all of this white mold on soybeans?

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

Damage from white mold in a soybean field under irrigation.

Damage from white mold in a soybean field under irrigation.

I have been getting a lot of questions this week about the perceived large amount of white mold in soybeans in Wisconsin. There is more white mold out there than we predicted. However, there is also some confusion out there on how all this white mold got there and how to interpret the amount of white mold as it relates to yield loss. Below is a great question I received today and will try to answer below.

Question

What is up with all this white mold? Here is my interpretation of what is going on, correct me if I’m wrong. White mold infection happens at R1, way back in June, but disease symptoms (flagging plants) show up in late July and August, correct?  While the plant got infected in June, the weather needs to be right for the disease to grow – cool nights, warm days and wet conditions. As we go into August these conditions are more common and the disease appears to be spreading when actually it was already there it just needed the right weather to explode? Also I think we often over estimate the amount of infection, it just looks bad, but infection rates are not as high as we think.  If we lose 2 to 5 bushels for every 10% increase by R7, that means if we have a 10% infection rate, we may lose a very small amount 2 bushel or more, maybe 5  bushels.   Assuming 130,000 plants per acre, that would require 13,000 plants per acre to be infected, correct?.

Answer

I’ll answer the easier part of the question first.

  1. Yes, everyone over-rates severity of white mold.  Because it makes those bleached stems that look horrible, everyone estimates it much higher than it is. I had a person tell me that he had a field that was 60-70% white mold. I asked him, “you mean to tell me there are 6-7 plants out of every ten plants in that field infected?” He stopped a minute and then thought about his answer again. Our field crew has rated about 20 fields around the state, in addition to our research plots. In production fields incidence ranges from 0-30% with most in the 10% range. We make 25 stops in a field. We rate the plants in 1 meter for two rows at that stop. We count all the plants in that one meter to establish the stand number, and then count infected plants. We then take a severity index rating too. I try to encourage people to make random stops and count the stand and then infected plants and not try to visually estimate. As humans, we make everything worse – its habit. So yes, at 10% and a stand of 130,000 plants you would need to have 13,000 plants per acre showing symptoms before you can detect reliable yield loss. Sure, you might have sections and pockets where you will have white mold and high yield loss, while other sections of the field yield really well, offsetting that loss. So you need to look across the whole acre to get a good estimate.
  2. Now for the hard part. The data, ours included, show that you have to have apothecia during bloom for infections.  Yes, some plant-plant touching can spread the pathogen, but our data suggest that this method is infrequent. In 2016, the weather during the major part of bloom was really too warm and our models suggested this. However, here is what I’m thinking happened based on our observations and what we know about the white mold fungus biology. First, we had above average rain. Frequent rains can cool the plant canopy and offset the ambient temperature. This fungus is super sensitive to temperature. More so than moisture. Our lab and other labs have done a lot of work on this and it always comes back to temperature that is most important for the white mold fungus. Also, because we had good growing conditions, rows closed quickly this year, giving us thick canopy even at R1; bloom often started early this year. A lot of our soybean varieties are indeterminate and can have an extended flowering period. This also doesn’t help our case. The longer that bloom lasts or flowers are present, the longer the crop is at risk for white mold.  The weather has continued to be conducive now for apothecia.  We continue to find apothecia right now (Mid-August) in our plots and my student is still trapping white mold fungus spores.  This is unusual, but given that the canopy is thick and the weather is mild, not entirely surprising. If there are blooms out there, these spores are infecting. There is about a 10-14 day incubation period in the field. So fresh infections you are seeing now happened in early August. All of this just depends on when the crop bloomed and how long it bloomed for. So, late-planted soybeans with extended bloom periods probably got hit pretty hard. White mold is definitely heavier north of Arlington, Wisconsin.  So I think having a slightly later planting and bloom period coincided with conducive temperature.

Summary

There is a lot of white mold out there. Be diligent in trying to assess the damage. Don’t just visually estimate incidence. Actually make 10-20 stop per acre and count plants with white mold and also total stand at that stop. Convert the white mold numbers to percentage based on the stand count. The rule of thumb is that for every 10% increase in white mold incidence yield loss with range between 2 and 5 bushels.

 

White Mold Showing Up in Wisconsin

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

Wilting and plant death as a result of Sclerotinia stem rot. Photo Credit: Craig Grau.

Wilting and plant death as a result of Sclerotinia stem rot. Photo Credit: Craig Grau.

The UW Fields Crops Pathology team has begun to scout for white mold symptoms in soybean fields around the state. Generally white mold incidence has been relatively light in fields we have visited in the southern half of the state. Some pockets of higher incidence do exist, but pressure has been generally low.

Incidence in the northern half of the state is higher. We have visited fields as far north as Bloomer, Wisconsin and have observed incidence ranging from 3% to 20% of plants infected. Reports from areas in the northwest and northeast also confirm similar findings. Most of the soybean crop is at the R5 growth stage, with some earlier maturing fields approaching R6. Questions have arisen about spraying fungicide now to reduce the damage caused by white mold and preserve yield. The short answer is NOThe reason is that the primary means of infection by the white mold fungus is through soybean flowers. These infections happened several weeks ago. Therefore, the optimal time to spray would be when flowers were out. A low level of plant-to-plant transmission can occur late in the season in soybeans. However, this rate is low enough, that spraying to prevent it does not produce favorable results.

Figure 1. White mold severity index ratings for soybeans treated with or without fungicide at the R5 growth stage.

Figure 1. White mold severity index ratings for soybeans treated with or without fungicide at the R5 growth stage.

In 2014 we conducted a trial where we applied the fungicide Aproach and Endura to soybeans already showing symptoms of white mold and compared these treatments to a non-treated check. These were plots in a production field. We rated them for severity at the time of application and then again 2 weeks later. We also collected yield data.

Aproach and Endura both have good efficacy on white mold when they are applied at the right time. However when applied late (R5 growth stage), like we did in this trial, we noticed no ability of these products to reduce disease advancement. Figure 1 shows the disease severity index ratings of the two treatments compared to the non-treated check. On the left are the pre-spray ratings and on the right are the post-application ratings. All treatments resulted in basically an equal increase in disease. Figure 2 shows the average yield for each treatment. You will notice that there is no statistical separation in yield, with only about a 2 bushel difference among treatments. In fact the yield for all treatments was equally low. There was no response out of these fungicides at this late application timing. Had the timing been appropriate (R1 to R3 growth stages) then we might expect a greater than 10 bushel response out of Aproach and Endura.

Figure 2. Yield of white mold-symptomatic soybeans treated with fungicide at the R5 growth stage or not treated.

Figure 2. Yield of white mold-symptomatic soybeans treated with fungicide at the R5 growth stage or not treated.

How much soybean yield might I lose from white mold?

Research has demonstrated that for every 10% increase in the number of plants that are infected with white mold at the R7 growth stage, you can expect between 2 to 5 bushels of yield loss. Thus, the fields I mentioned earlier will likely range from little detectable yield loss (3% incidence) to as high as 10 bushels lost (20% incidence).

What should I do if I see white mold in my soybean field now?

Get out and survey your fields for white mold. It is a good idea to determine how much white mold you have in your fields, so you can make some educated harvest decisions. One way to move white mold from one field to the next is via combines. You could clean your combine between each field, but this can be time consuming. So my determining which fields have no white mold and which fields have the most white mold, you can develop a logical harvest order by beginning your harvest on fields with no white mold and working your way to the heavily infested fields. This will help reduce spread of the white mold fungus to fields that aren’t infested. You can also make some decisions on your rotation plan and future soybean variety choices based on these late season observations.

If you would like to learn more about white mold and management of this disease, CLICK HERE to download a fact sheet from the crop protection network. You can also watch a short video about white mold by CLICKING HERE.

Wisconsin White Mold Risk Map – July 27, 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 risk has declined to the point that most of Wisconsin has no risk or low risk. Hot weather has continued to push the risk lower. The UW Field Crops Pathology crew has continued to scout production fields and has not found many fields with any apothecia. It is possible to find more apothecia in some irrigated fields. The window of opportunity to apply fungicides to control white mold in soybean is nearly over (Fungicides are not recommended after the R3 growth stage). Focus for our team will shift to looking for the disease next week in research plots and production fields.

White Mold Risk Map - July 27, 2016

White Mold Risk Map – July 27, 2016

 

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.

Wisconsin White Mold Risk Map – July 22, 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 risk has declined over the last week across the state of Wisconsin. Hot weather has reduced this risk substantially. Three-day forecasts show continued stability of low risk throughout much of the state. The UW Field Crops Pathology crew has scouted 10 production fields in southern and south-central Wisconsin over the last week. These activities have yielded very low numbers of apothecia in naturally infested, dry-land fields. This is consistent with the low predictions by the model. Risk for white mold in irrigated fields can be elevated above that predicted by this model. 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. The window of opportunity to apply fungicide to control white mold in soybean is rapidly closing. In another 7-10 days optimal timing of fungicide application will have passed for much of the soybean production area in the state. Be sure to consult the how-to guide for assistance in interpreting this map if you are considering spraying fungicide to control white mold.

White Mold Risk - July 22, 2016

White Mold Risk – July 22, 2016


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.

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.

White Mold Risk - July 15, 2016

White Mold Risk – July 15, 2016


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.

Wisconsin White Mold Risk Map – July 11, 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 continued to decrease slightly for southern and south-central Wisconsin compared to the last model run (see map below). Three-day forecasts continue to show slight decreases in risk due to forecasted hot and dry weather for later this week. The UW Field Crops Pathology crew has been scouting for apothecia and setting traps for spores of the white mold fungus in fields in the soybean growing areas of south and central Wisconsin and HAVE NOT found any apothecia or captured spores. This confirms the generally low risk currently being predicted by the model. Growers near higher risk pockets should monitor the soybean crop for closing canopy and flowering growth stages that may lead to increased risk of white mold in these pockets. Be sure to consult the how-to guide for assistance in interpreting this map if you are considering spraying fungicide to control white mold.

White Mold Risk Map - July 11, 2016

White Mold Risk Map – July 11, 2016


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.

Wisconsin White Mold Risk Map – July 8, 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 decreased a bit for most of Wisconsin compared to the last model run (see map below). The UW Field Crops Pathology crew has been scouting for apothecia and setting traps for spores of the white mold fungus in fields in the soybean growing areas of south and central Wisconsin and HAVE NOT found any apothecia or spores. This confirms the generally low risk currently being predicted by the model. Growers near higher risk pockets in Dodge, Walworth, and Waukesha Counties should monitor the soybean crop for closing canopy and flowering growth stages that may lead to increased risk of white mold in these pockets. We have seen numerous fields this week in the R1-R2 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.

White Mold Risk - July 8, 2016

White Mold Risk – July 8, 2016

 


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 apothecia. This model predicts when apothecia will be present in the field using 30-day averages of maximum temperature, relative humidity, and 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.

Wisconsin White Mold Risk Map – July 5, 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**

Wisconsin White Mold Risk in Soybean - July 5, 2016

Wisconsin White Mold Risk in Soybean – July 5, 2016

Risk of apothecial presence and subsequent white mold development remains generally low for most of Wisconsin today. Risk has increased slightly across the state over the holiday weekend with some isolated pockets in the northern and south-central areas of the state. The UW Field Crops Pathology crew has been scouting for apothecia in fields in the soybean growing areas of south and central Wisconsin and HAVE NOT found any apothecia. This confirms the generally low risk currently being predicted by the model. Growers near higher risk pockets should monitor the soybean crop for closing canopy and flowering growth stages that may lead to increased risk of white mold. We have seen numerous fields this week already in the R1 growth stage. Be sure to consult the how-to guide for assistance in interpreting this map if you are considering spraying fungicide to control white mold.


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 apothecia. This model predicts when apothecia will be present in the field using 30-day averages of maximum temperature, relative humidity, and 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.

Wisconsin White Mold Risk Map – July 1, 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**

White Mold Risk - July 1, 2016

White Mold Risk – July 1, 2016

Risk of apothecial presence and subsequent white mold development is generally low for most of Wisconsin today. A few isolated pockets of moderate or higher risk are located around Shawano Co. and north of Barron Co. Soybeans in this area are likely not at the susceptible growth stage. A high-risk pocket is also present in the southeast in western Waukesha Co. Growers near this pocket should monitor the soybean crop for closing canopy and flowering growth stages that may lead to increased risk of white mold. Be sure to consult the how-to guide for assistance in interpreting this map.


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 apothecia. This model predicts when apothecia will be present in the field using 30-day averages of maximum temperature, relative humidity, and 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.

Time to Start Watching for White Mold in Soybeans

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

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

Figure 1. Severe white mold in a soybean field.

Figure 1. Severe white mold in a soybean field.

The warm weather over the last several weeks has pushed the Wisconsin soybean crop quickly toward the reproductive growth stages. By the end of the week, most early-planted soybean fields in the southern portion of Wisconsin will begin flowering (R1 growth stage). This growth stage is a critical time to make a fungicide application decision for white mold (Fig. 1; also called Sclerotinia stem rot). Fungicide decisions should be made for this disease between the R1 and the R3 (pods beginning to form on upper nodes) growth stages. After the R4 growth stage control of white mold using fungicides quickly declines. The decision to apply fungicide during this time should be made based on the weather. As discussed in this FACT SHEET and VIDEO, cool (less than 80F) and wet and/or humid conditions during the R1-R3 growth stages can lead to increased risk of white mold later in the season.

Figure 2 illustrates the white mold cycle. Small hardened black structures called sclerotia survive many years in the soil (Fig. 2A). When conditions are cool and wet during the bloom period small mushroom-like structures called apothecia germinate from the sclerotia (Fig. 2B). The apothecia release spores that land on flower petals and germinate (Fig. 2C) allowing the fungus to infect and colonize the soybean plant. As the fungus continues to colonize the inside of the plant, symptoms will begin to develop around the R5 or R6 soybean growth stages. These include wilting plants and paper bag-brown lesions on stems. Eventually new sclerotia of the fungus begin to develop on the plant (Fig. 2D). These sclerotia become the source for future white mold epidemics. Because the white mold fungus needs the open flowers to infect and colonize soybean, it is important to apply a fungicide during this time to protect the plants from infection IF the weather is conducive for the white mold fungus. It can be difficult to determine what “conducive weather” is and if you need to spray.

In an effort to help define these “conducive” conditions, a 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 apothecia. This model predicts when apothecia will be present in the field using 30-day averages of maximum temperature, relative humidity, and wind speed. Using virtually available weather data, predictions can be made in most soybean growing regions. Based on these predictions, a map is generated (Fig. 3) to indicate 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, the soybeans are flowering, and the canopy is somewhat closed, then the white mold risk is elevated. If your fields are at-risk, we recommend to consult your local extension personnel or resources for the best in-season management options for your area. To view and download a handy user guide for the model, CLICK HERE.

For Wisconsin soybean growers, regular updates and commentary regarding risk of white mold can be found on this blog. Color coded, state-wide maps will be posted and our recommendations will accompany these posts. So be sure to check back regularly or subscribe to the blog to receive an automatic e-mail update when a new post has been added. You can subscribe via the window immediately to the right of this window. The inaugural post for 2016 can be viewed by clicking here. 

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. Fungicides that have performed well in multi-state studies can be found in the Soybean Fungicide Efficacy Table. 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 by CLICKING HERE.

For even more detailed information about white mold you can visit the Crop Protection Network page on white mold . You can also find more information about white mold by clicking here and scrolling down to the white mold section.

To vist other posts on this blog about white mold, click below:

2015 Blog Post

2014 Blog Post