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Midwest agronomists tracking down the cause of yellow soybeans

Multiple reports of increased and rapid yellowing in soybeans are popping up across the Midwest following recent rains.

Illinois Soybean Association Agronomist Stephanie Porter tells Brownfield there could be multiple causes including root rot, phytophthora, nutrient deficiencies, soybean cyst nematode or carryover from herbicides- but the recent drought could be a common theme.

“Whenever we have an extreme drought, then we have lack of oxygen when that heavy rain hits the soil. So did this stress the plant so greatly that now we have some disease?”

She says there are confirmed reports of similar yellowing stretching from northern Missouri into northern and east central Illinois and expanding into Indiana, Ohio and Kentucky. Porter says agronomists across the region are collecting diagnostic samples to determine if there is a broader issue.

 “I talked to an agronomist today and he thinks that we’re having diaporthe issues or stem canker issues. We need to know if this is happening and we have to actually get samples to confirm.”

While collecting samples, Porter says farmers in western Illinois discovered an uncommon pest called Mealybug.

“And that’s not anything that we normally see, but these were yellowing soybeans as well. In Western Illinois, they dug them up and found that that this insect was there and it could be going after some of the more stressed plants as well.”

Porter says they will know more about potential causes and management strategies in the coming weeks as test results come in. She recommends farmers dig up yellow plants to search for root rot or insects and submit samples to a diagnostic lab if the cause is still uncertain.

Audio: Interview with Stephanie Porter, Outreach Agronomist, Illinois Soybean Association