Soybean Nematodes Can Hide in Plain Sight: What a 200-Field Survey Means for Growers

Featured field photograph: Viktor Friesen / Unsplash. Illustrative image; not the Missouri survey field.

A new October 22, 2026 soybean nematode webinar highlights an important lesson: growers can lose yield to root-feeding nematodes without seeing unmistakable symptoms above ground.

Why invisible nematode pressure deserves attention

Plant-parasitic nematodes feed on soybean roots, potentially limiting water and nutrient uptake. But yellowing, stunting, and uneven growth can also result from many other problems. Healthy-looking plants do not rule out nematode pressure. This is why the most useful management decisions begin with sampling and diagnosis rather than assumptions.

On October 22, the North Central Integrated Pest Management Center published a recording of a University of Missouri webinar on plant-parasitic nematodes in soybean. Presenters discussed a 2024–2025 survey spanning 200 fields in 81 Missouri counties. Researchers identified 10 plant-parasitic nematode taxa and examined soybean cyst nematode (SCN) population densities and virulence profiles. Those are survey findings, not proof that every Missouri field—or fields elsewhere—faces the same nematode risk.

SCN management starts with knowing your field

SCN (Heterodera glycines) is especially important because infestations can persist and reduce yield even when foliar symptoms are subtle. Monitoring helps growers decide whether resistant varieties, rotation, seed treatments or other practices deserve greater attention. The right choice depends on the nematode species present, its population density, field history, locally adapted cultivars and current regional recommendations.

Six practical steps after harvest

Sample fields strategically. Ask your local diagnostic laboratory about soil sampling depth, timing, number of cores and packaging. Sample problem spots and representative areas using laboratory-specific instructions.
Request the right test. Identify whether your concern is SCN specifically or a broader group of plant-parasitic nematodes. Different laboratories offer different assays.
Record the baseline. Save the lab report, sampling date, field location, previous crop and cultivar. A baseline makes future comparisons possible.
Review resistance choices. If SCN is confirmed, discuss resistant soybean varieties with an agronomist, including whether repeated reliance on the same resistance source is still appropriate.
Plan a realistic rotation. Use nonhost crops as recommended locally to help manage SCN; do not assume a one-year rotation eliminates an infestation.
Check results over time. Repeat sampling using a consistent approach so you can evaluate population trends alongside yield and field observations.

What growers should not conclude

The Missouri survey does not mean all 10 nematode taxa are equally damaging or that a particular commercial biological treatment has been shown to control them. Neither a new seed treatment nor a microbial product should replace species identification and an integrated field management plan. Research into beneficial soil microbes is promising, but individual laboratory or greenhouse successes do not establish reliable field performance.

Prepare now for next season

For growers coming out of the 2026 season, postharvest sampling may be one of the most actionable steps toward better decisions in 2027. Iowa State University Extension recently emphasized the value of fall SCN soil sampling as a basis for adjusting next season’s resistance and seed-treatment plans.

Wise Farmer encourages producers to learn, apply and grow through careful observation, accurate diagnosis and evidence-based management. Explore our farmer education courses for additional practical learning.

Discussion question: Have you ever found a damaging root problem in an otherwise healthy-looking soybean field?