To visualize how the problematic soybean disease white mold spreads, simply picture a pest that everyone is familiar with: the dandelion. This bright yellow flower becomes a fluffy white cloud of seeds that blows in the wind from yard to yard. Similarly, the spores that cause white mold develop in cool, moist soil and infect flowering soybeans.
“This is an important disease of many different agronomic crops throughout the world, and it can also be infect many broadleaf weed hosts as well,” says Damon Smith, Ph.D., assistant professor and extension specialist at the University of Wisconsin-Madison. Smith discussed the disease, along with management options, in a recent Focus on Soybean webinar.
Even after being infected, soybeans typically do not display damage until the R5 or R6 stage. By that time, there is not much you can do to stop it.
In the webinar, Smith explains why management of white mold requires an integrated approach that combines these four strategies:
1. Field mapping – Because spore movement is fairly localized and is usually clustered around where the spores were created, white mold can be managed by scouting fields and employing precision-agriculture techniques. Knowing where the disease occurs this year, can help make site-specific management decisions in future years.
2. Row spacing – Wider row spacing increases air flow and dries out the soil, making it harder for white mold to develop. However, row spacing alone is not enough to combat white mold, and increased spacing may have a negative impact on yield due to decreased plant population in the field.
3. Resistant varieties and crop rotation – Tolerance to white mold is found in certain soybean varieties. And because they are not affected by white mold, rotation to small grains, in conjunction with no-till can trick the disease into developing and releasing spores, thus completing their life cycle without reproducing and allowing for soybeans to be planted the following season.
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