Managing soilborne diseases
Are white mold and other soilborne diseases affecting your soybeans? Camilo Parada-Rojas, Ph.D., field crop pathologist with Cornell University, presented “Soybean Soilborne Disease Management and Research Priorities for Field Crops Pathology in New York” at the recent Soybeans & Small Grains Congress, hosted by CCE’s Northwest New York Dairy, Livestock & Field Crops Program.
“White mold can be a big issue with soybeans,” Parada-Rojas said. “It’s a disease spreading throughout the Northeast.”
Since 2014, $3 billion worth of soybean yields were lost to the disease. In 2024, it caused 0.25% of soybean market loss. The next highest causes of disease-related loss were soybean cyst nematode and sudden death syndrome (each at 0.5%) and purple seed stain (0.3%).
“The white mold cycle is crucial to manage this disease in the field,” Parada-Rojas said.
A dense canopy paired with wet, dewy and foggy mornings create a perfect environment for white mold to develop. Once a field becomes infected, the disease colonizes.
“The fungus has become so smart that it infects the flowers, followed by the stems and pods,” Parada-Rojas said. “Look for flagging or wilting as the first symptoms at the beginning pod (R3) to full seed (R6). There’s bleaching of the stem with fluffy growth.”
White mold is devastating because the plant’s vascular system can’t move water, so the plants wilt. By the time farmers notice, it’s often too late to effectively curb the infestation.
White mold overwinters on residue in the field. “It looks like rat droppings,” Parada-Rojas noted.
Severe cases of white mold can cause yield losses up to 20 bushels/acre. Interestingly, the disease affects only some of the branches of the same plant, which can help hide the extent of infestation.
Parada-Rojas said prevention, prediction and response are ways to mitigate the effects of white mold.
“Be diligent if you know you have white mold with cleaning the combine,” he said. “Harvest the affected fields last. If you harvest first, you are spreading white mold around your farm. White mold likes wet, humid weather. Keep an eye on the weather as well.”
He added that if you plant 30 inches apart, you have less white mold in fields that are heavily infested. An open canopy creates a less-than-ideal environment for mold development, so wider rows and using herbicide to reduce weed pressure can help. Parada-Rojas also noted that seed density can be adjusted to improve airflow and control white mold.
In studies in 2017 and 2018 across Wisconsin, Michigan and Iowa, maintaining a seeding rate of 80,000 to 110,000/acre provided the best chance for low disease severity.
“Cultivars are being released with improved resistance,” Parada-Rojas said. He encouraged attendees to check with their seed representative for resistant varieties that would perform well in their area.
For organic farmers, Parada-Rojas said growing and roller crimping rye in winter can reduce instances of white mold in no-till beans.
It may help farmers to use the Network for Environment & Weather Applications (NEWA) tool to assess white mold risk for their soybean crops. Drop a pin on the map and the app asks questions to make recommendations regarding white mold.
Fungicide trials in 2025 for controlling white mold found that in order of effectiveness (most to least effective), Endura® 70 WDG (very good), Propulse® 3.34 SC (good), Aproach® 2.08 SC (good) and Omega® 500 DF (good) all provided control of the disease. Endura is approved for use in New York without restrictions. Propulse is allowed in some counties; the other two are restricted to a 100-foot limit near bodies of water.
“The label is the law,” Parada-Rojas said. “Read the labels and understand what it is telling you.”
He plans to conduct his own white mold chemical control trials with Cornell to establish on-farm sampling, screen varieties and look at fungicide efficacy. He’s also interested in early detection using robots in soybean fields to detect white mold.
Sudden death syndrome is another soilborne disease affecting soybeans. The fungus grows in root tissues and toxins produced there spread upwards towards leaves. The leaves may eventually drop and petioles remain attached to the stem. Inoculum survives in soybean and corn residue as well as in the soil. The early season infection of soybean roots continues the cycle.
“Sudden death syndrome, caused by Fusarium virguliforme, survives in soil, infects roots and hurts the plant by entering the vascular tissue and infecting it with pathogens,” Parada-Rojas said.
Scouting for brown splotches on leaves can help farmers get a jump on sudden death syndrome, as can using treated seeds on farms that have experienced the disease. Parada-Rojas recommended seeds treated with fungicides like cyclobutrifluram, fluopyram and pydiflumentofen, as these have shown efficacious against sudden death syndrome.
Parada-Rojas said this pathogen likes compaction and wet soil. Using tillage and drainage can reduce the severity of sudden death syndrome.
“Think about planting later,” he said. “Leave those fields with history last for planting. Warmer, drier soils reduce favorable conditions for the fungus.”
