Weather canopy and farming practices increase white mold risk in soybeans
As soybean yields increase, the risk of white mold is also rising. This fungal disease develops under specific field conditions and can significantly damage crops if not managed properly.
White mold thrives in cool and wet weather, especially when soybean plants grow densely and create high humidity during flowering. Areas with poor drainage, tree lines, and limited airflow often become high-risk zones for infection.
The disease spreads through infected seeds, contaminated soil, and airborne spores. The fungus forms structures called sclerotia, which can survive in soil for many years. Once conditions are favorable, they release spores that infect plants from beneath the canopy.
White mold usually starts by infecting dead plant parts, such as old flowers. It then spreads into the plant, causing water-soaked spots that soon develop into mold. Infected plants wilt, weaken, and eventually die, allowing the disease to spread further through plant contact.
Managing white mold requires an integrated approach. Farmers are advised to select resistant varieties, rotate crops, control weeds, and adopt no-till practices. These methods help reduce the presence and spread of the pathogen.
Crop rotation with non-host plants like small grains helps limit the disease cycle. However, certain weeds can carry the disease and must be controlled carefully. No-till farming can also reduce disease pressure by keeping fungal structures on the soil surface.
Fungicides play an important role in controlling white mold, especially in high-risk fields. Applications should begin early flowering before symptoms appear. Since soybean flowering can last several weeks and fungicides remain active for a shorter period, a second application may be needed.
“Many studies year over year say the same thing, two different fungicides applications is the best way to prevent white mold from affecting your yield,” said Eric Rice, Pioneer field agronomist. “I’d apply my fungicide any time I start seeing flowers. I would follow that up about 10 to 14 days later, just systematically, with the second application, and that is the best way to do it to get a full season of protection against white mold.”
Experts suggest applying fungicide when flowering begins and repeating the application after 10 to 14 days. This approach provides better seasonal protection and helps minimize yield loss due to white mold.
Photo Credit: istock-sandramatic