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National nematode day test for SCN
Missouri Ag Connection - 09/22/2023

National Nematode Day on Oct. 2 serves as a reminder to test fields for soybean cyst nematode (SCN), the leading soybean pathogen in the United States.

Mandy Bish, University of Missouri Extension plant pathologist and director of the SCN Diagnostics clinic, emphasizes the importance of identifying problematic areas this fall to aid in planting decisions for 2024. To assist Missouri farmers, the clinic has partnered with the Missouri Soybean Merchandising Council to offer four free SCN egg count tests this autumn.

While soybean plants infected with SCN might appear healthy above ground, the nematode targets their roots. The 2023 season's severe drought may have exposed certain problematic areas. Mandy Bish explains, "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 ascertain SCN presence, soil samples should be collected in fields sampled over three to five years ago, with known SCN populations, with a history of sudden death syndrome in soybean, and where soybeans are not rotated with corn. SCN soil sampling involves using 1-inch diameter by 8-inch-deep soil cores.

For over 30 years, growers have relied on the soybean line PI 88788 as their primary SCN defense. Over 95% of commercial varieties in Missouri feature PI 88788 resistance. However, recent research by MU soybean researchers has shown that some juvenile nematodes can still mature into adult females after feeding on PI 88788 soybean.

The SCN Coalition recommends four strategies for managing SCN:

• Test fields to understand nematode numbers.

• Rotate to resistant soybean varieties.

• Rotate to nonhost crops.

• Consider using a nematode-protectant seed treatment.

Sampling for SCN can be challenging due to their uneven distribution in fields. The SCN Coalition advises:

• Divide fields into 10-20-acre sections based on natural boundaries like varying topographies, areas with previous sudden death syndrome or SCN symptoms, and low-yielding field sections.

• Collect 15-20 soil cores from each section in a zigzag pattern, each core measuring 1 inch in diameter and 8 inches deep.

• Mix the cores within sections and place them in sample bags.

• Submit samples for each section separately to SCN Diagnostics.

• National Nematode Day encourages proactive nematode management to protect soybean crops and ensure future harvests.

Download the sample submission form at (opens in new window). For more detailed sampling instructions, go to (PDF).

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