Watch soybean fields now to detect symptoms of soybean cyst nematodes (SCN), South Dakota State University scientists say.

Nematologist Jim Smolik of the SDSU Plant Science Department says knowing there's a soybean cyst nematode infestation can help producers prepare for subsequent years.

"It's manageable by using SCN-resistant soybean varieties and crop rotations," Smolik says.

Smolik says SCN damage is currently very apparent in SDSU test plots in southeastern South Dakota.

"Mainly what we're seeing is stunting, uneven growth and the failure of plants to close the rows," Smolik says. "A ragged appearance of the field is also a symptom."

SDSU Extension Plant Pathologist Marty Draper adds that yellowing of soybean plants can also be a symptom of soybean cyst nematodes, but he cautions that other problems such as iron deficiency chlorosis are also quite common. Draper says the pattern of yellowing is different for those two problems, with SCN typically causing a marginal yellowing around the edges of the leaves. Iron chlorosis, in contrast, causes yellowing between the veins of the leaves.

Smolik's ongoing research with SCN is supported by the South Dakota Soybean Research & Promotion Council. Smolik says South Dakota test plots have shown yield increases of approximately 30% through the use of SCN-resistant varieties in infested fields.

The soybean cyst nematode is believed by many researchers to have been introduced from Japan, where it was reported more than 75 years ago. In the U.S. it was first detected in North Carolina in 1954 and has since spread to at least 28 states. It is estimated to cause more than $1 billion in crop losses annually nationwide.