Although Nebraska farmers produced the nation’s highest soybean yields in 2009 averaging more than 54 bushels per acre, their biggest threat to high yields is coming on fast.

The soybean cyst nematode (SCN) the nation’s number one yield robber is now found in nearly all Nebraska’s major soybean producing counties. In 2009, this tiny yield robbing roundworm was discovered in Phelps, Thayer, and Webster counties.

SCN is one of the most costly and damaging pests for soybean growers. It feeds and reproduces on the roots of soybeans and can significantly reduce yields. “The first indication of a problem is when soybean yields are declining,” says Loren Giesler, University of Nebraska-Lincoln extension plant pathologist.

“Soil testing is very important to improve soybean yields,” he continues. Giesler recommends taking samples from a lot of different areas in the field for testing and then to regularly test fields in subsequent years.

“For long term profitability, Nebraska farmers need to determine if they have SCN because many fields are planted to susceptible varieties,” Giesler continues.

“In most SCN-infested fields in Nebraska, females are evident on roots around July 4,” says Giesler. “However, the absence of cysts on the roots does not mean a field is free of SCN.” In fields with a low population, very few cysts may be found on the roots and they may be easy to miss by visual observation.

According to Iowa State University nematologist Greg Tylka, “Low levels of SCN may not produce visible aboveground symptoms, yet yields may be reduced. High SCN levels typically cause plant stunting and yellowing.”

Giesler agrees and states that, “Aboveground symptoms can be confused with damage from compaction, nutrient deficiencies, drought stress, low-lying wet areas, herbicide injury, and other plant diseases.” Circular to oval areas of stunted, yellowed plants can be observed. Areas of SCN injury are typically elongated in the direction of tillage practices, since the cysts are spread by tillage equipment.

As head of a multi-state SCN education project funded by the North Central Soybean Research Program, Giesler and his colleagues are helping soybean farmers around the Midwest diagnose and manage their SCN problems. This group of experts reached out to 11,000 farmers and crop consultants in 2009 delivering the message that SCN is a problem, but it can be managed.

The Nebraska Soybean Board and the University of Nebraska-Lincoln have partnered to help soybean farmers identify fields that have SCN. “It has been estimated that Nebraska farmers are losing $25 million a year due to SCN,” says Giesler. The Nebraska Soybean Board believes that is $25 million too much. The Nebraska Soybean Board has announced that they will pay for the analysis of soil samples to determine the presence of SCN.

Sample bags and analysis of soil samples for the presence of SCN are available to producers at no cost. For free sample bags, contact your local University of Nebraska-Lincoln County Extension office or Loren Giesler, , at .

That’s your soybean checkoff. Delivering results.