The soybean cyst nematode (SCN) is a serious pest, even though soybeans can be produced profitably in infested fields.

Because SCN causes no specific symptoms and its effects are often not dramatic, many farmers don’t know that their fields are infested until a severe problem develops. Meanwhile, up to 30% yield losses can occur without obvious symptoms.

Females are starting to show up on soybean roots, so the time to start scouting for the tiny pests is now, says Greg Tylka, an Iowa State University plant pathologist.

“Identifying it in the field and catching it early is crucial,” Tylka says. “If you catch it early, management is a breeze.”

Management consists of a combination of rotating resistant soybean varieties with non host crops such as corn, oats and alfalfa.

But it all starts with early detection, and that’s why producers need to check fields for soybean cyst nematode, both by digging up roots in July and August, and by testing soil samples in the fall.

“You have to look for it to find it,” Tylka says. “That’s why we emphasize so strongly the two ways to check fields.”

The most obvious spots to scout SCN are areas of fields where soil from other fields could be introduced, such as near gates or fence lines. Also check fields where soybean yields have declined over time for no apparent reason.

Soybean cyst nematode is more common in fields with higher pH soils. Studies have shown a strong relationship between high pH and the prevalence of SCN. That doesn’t mean that low pH soils are immune to nematodes, just that they like high pH.

“It’s very easy to keep low numbers low and very hard to drive high numbers down,” Tylka says, “So successful management really hinges on early detection.”

According to ISU specialists, nematodes have been found in nearly all counties in Iowa this year.

A website with several soybean cyst nematode links