Excess rainfall this year changed more than just farmers’ harvest schedules—soybean cyst nematode, SCN, can move with water. It’ll be important to test field SCN levels because they might have changed drastically since last year.
“With early season flooding, before seed was even in the ground, how did the soil move?” asks Kaitlyn Bissonnette, University of Missouri Extension professor and director of SCN Diagnostics. “Where did that soil deposit? That matters because the soil could contain cysts that float and move with flooded soils.”
However, the window to pull samples is quickly closing as cold weather threatens to freeze soils.
“Even if you tough it out and pull frozen soil samples, with many soils in the Midwest when we thaw those soils and dry them out [in the lab], they turn into concrete,” says Greg Tylka, nematologist at Iowa State University and leader at the SCN Coalition. “[In that instance] we advise people to wait until spring when things warm up and soils drain naturally.”
Knowing where SCN thrives is key to control—and why it’s critical to pull soil samples by management zone. Top of the list are sandy soils, high pH fields and low spots. SCN and sudden death syndrome (SDS) often go hand-in-hand. SCN injures the plant early, which can leave it more susceptible for the Fusarium pathogen in SDS.
SCN tests cost $1 to $2 per acre, but some state soybean checkoff programs offer cost assistance.
“The economics of testing make sense—if it’s $20 for a 20-core sample that represents 20 areas that’s $1 per acre,” Tylka says. “SCN has the potential to take 1 bu. or more per acre, so $1 is a minimal cost.”