Test for Soybean Cyst Nematode This Fall

National Nematode Day and marks a good time to test fields for soybean cyst nematode (SCN), the No. 1 pathogen of soybean in the United States.

“We anticipate the highest SCN levels to occur at the end of the season. Identifying problematic areas this fall can help with 2024 planting decisions,” said Mandy Bish, University of Missouri Extension plant pathologist and director of the SCN Diagnostics(opens in new window) clinic.

The clinic has partnered with the Missouri Soybean Merchandising Council (opens in new window)to provide Missouri farmers four free SCN egg count tests this fall.

Soybean infected with SCN often appear healthy above the ground because SCN infects the roots of plants. “However, the severe drought during the 2023 season may have unmasked some of our problematic areas,” said Bish. “We have patches of yellow soybean appearing in many fields this year, and there are multiple causes. One contributing factor in some fields may be high SCN levels. A soil test will help determine whether SCN pressure is adding to the problem.”

To determine if SCN is present, collect soil samples in fields:

• Sampled more than three to five years ago.

• With known SCN populations.

• With a history of sudden death syndrome of soybean.

• Where soybeans are not rotated with corn.

Sampling for SCN is a little different than sampling for other purposes, said Bish. Recommended soil cores are 1 inch in diameter by 8 inches deep.

For more than three decades, growers have relied on a soybean line called PI 88788 as the main defense against SCN. More than 95% of commercial varieties grown in Missouri have PI 88788 resistance. Juvenile nematodes feed on roots of PI 88788 plants, which impedes their maturation into adult females, stopping egg production. But recent work by MU soybean researchers found that some juvenile nematodes can feed on PI 88788 soybean and still mature into adult females.