Soybean cyst nematode (SCN) is a widespread and serious pest in
Iowa soybean fields. An infestation can reduce yields by 50
percent or more. But surprisingly, fields can be infested with
the nematode for years without noticeable symptoms. Greg Tylka,
Iowa State University nematologist, said the only consistent and
reliable sign of an SCN infestation is the presence of adult SCN
females and cysts (dead females) on the roots of infected
soybean plants. "These adult SCN females and cysts are small,
round, white- to yellow-colored objects that can be seen on
infected soybean roots with the unaided eye. They are about the
size of a period at the end of a sentence," Tylka said. "It
takes four to six weeks for the first SCN females to appear on
the roots of a new soybean crop. We are just now seeing females
on roots of soybeans planted in Ames on May 10," he said. SCN
females and cysts will be on roots of infected plants through
much of the growing season, until late summer or early fall when
the plants begin to mat