White Mold is one of those diseases we plan for, but we never really know if we will have it until it’s here. It has been a significant concern for farmers over the years, and rightfully so, because of how devastating it can be to the crop yield. This disease is very different from other vascular and foliar diseases, so it comes with a very different set of considerations to know about.
Let’s dig into the top questions—and answers—about understanding and managing White Mold in soybeans.
When/where is White Mold likely to show up?
White Mold is most likely to occur during seasons with cooler temperatures and high moisture/humidity in a lush soybean canopy during early flowering. Due to delayed planting in some areas, not all fields will have canopy closure before flowering occurs, which will help keep air flowing under the canopy, reducing disease potential during early reproduction. However, soybeans flower for 3-4 weeks, so if you had White Mold problems two years ago in the same field, you should prepare for a resurgence this year.
How is White Mold different from other diseases?
White Mold infects plants earlier than most foliar soybean diseases. White Mold infects through flowers and destroys the vascular tissue of the plant. As a vascular disease (stem rot), White Mold shuts off water and nutrients to the plant, unlike a foliar disease, which infects through the leaf and reduces photosynthesis.
How does White Mold impact plant health and crop yield?
Significant yield loss may occur from White Mold, depending on when it infects the plants and the size of the infected area. Infected plants can be up to 100% yield loss because White Mold typically kills the plant before it starts seed fill, but this may only be in small areas within a field.
What does White Mold look like in the field?
To identify White Mold in your fields, look for fluffy, white growth on the lower stem during mid-to-late reproduction. Plants also begin to wilt and look drought-stressed, with a gray tinge to them from the road. They may also show foliar symptoms similar to Sudden Death Syndrome or Brown Stem Rot, however, the whole plant will eventually turn brown and die. Black sclerotia can also be found inside the stem. Look for little black pellets inside the stem, as the picture below shows.
Photographs courtesy of
Iowa State University and Soybean Research & Information Network
When should I scout for White Mold?
It is difficult to say when to start scouting for White Mold. Typically in late July or early August, if you see heavy fogs in the morning or continued leaf wetness, those are good indications to start to walk fields or call your Liqui-Grow Sales Applicator. At this point, plants are typically in the R3-R4 growth stage and visual symptoms should start to appear.
If you see dull, gray isolated round spots in your field, those could be early signs of White Mold setting in. However, at this point, if you do see White Mold in your fields, it is often too late to save the infected plants. All you can do is make a plan to avoid the disease in your next soybean crop.
Is there any way to treat White Mold once it occurs?
A fungicide at R1 is really the only way to stop or reduce White Mold infection. However, an R3 fungicide application may reduce severity and avoid 100% yield loss from infected plants.
Many fungicides labeled for White Mold recommend an R1 application followed by an R3 pass if expectation for disease is high. Once again, your Liqui-Grow Sales Applicator has been trained and is knowledgeable on the chemistries available to combat and minimize White Mold.
How can I prevent White Mold in my fields?
Managing White Mold is about preventative measures.
- Identify which fields have shown White Mold issues in previous years and let your Liqui-Grow Sales Applicator know as you prepare for the next cropping season.
- Choose soybean varieties with good to excellent White Mold scores. You can also select soybean varieties with tolerance to White Mold and varieties with a “narrow” or less bushy growth habit to help favor airflow under the canopy around flowering. Widening row spacing and/or decreasing planting population also helps increase airflow.
- Be prepared with a labeled fungicide right as the soybeans are beginning to flower (R1). This is one of the ways White Mold is an outlier: R3 is typically the best timing for most other soybean foliar diseases, but it’s too late for White Mold.
- Worst case scenario, stay in a corn-on-corn rotation. Although, that has its own challenges. A corn/corn rotation won’t eliminate white mold issues since sclerotia can survive a long time in the soil.
- Use products like Contans on the field in the fall prior to planting soybeans.
Watch this Liqui-Grow Loop video to learn more about our tips for handling fields with White Mold.
Your Liqui-Grow Sales Applicator and Agronomists are here to help you prevent and treat diseases in your fields. Get in touch with us to help select the right seed varieties and fungicides to protect against harmful diseases like White Mold.
Text us at 564-220-2508 or email questions@liqui-grow.com.
