Soybean Cyst Nematode Now Appearing on Bean Roots

SCN doesn't always cause obvious, above-ground symptoms so you have to check the roots to see if plants are infested.

Many Iowa soybean fields may be infested with soybean cyst nematode. But you may not know your fields are infested because SCN doesn't always cause obvious aboveground symptoms. "In fact, yield loss of up to 40% has been documented without aboveground symptoms occurring," says Greg Tylka.

Tylka is an Iowa State University Extension plant pathologist who specializes in nematode management. He says an easy, free and reliable way to check fields for the presence of SCN is to dig roots of susceptible soybean varieties. Carefully crumble away much of the soil from the roots, and look for the adult SCN females on the roots. The females appear as small, round, white object on the roots and are about the size of a period at the end of a sentence.

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"We recently observed adult SCN females on soybean roots in research plots in central Iowa," says Tylka. "The beans were planted in late May. SCN females will be apparent on young roots of susceptible soybean plants in Iowa through July and August and probably early September this year - since the soybean crop is delayed in development. Roots should be checked for SCN females no earlier than four or five weeks after planting."

Soybean cyst nematode is the No. 1 soybean pest in Iowa in terms of yield loss. SCN can be controlled by planting SCN-resistant bean varieties. Additional information about the biology, sampling and management of SCN can be found on ISU's soybean cyst nematode site www.plantpath.iastate.edu/soybeancyst.

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