During 2024 and 2025 and with support from the Missouri Soybean Merchandising Council, we surveyed 19 soybean fields across 8 counties in Southeast and neighboring South Central Missouri (Bollinger, Cape Girardeau, Mississippi, New Madrid, Pemiscot, Ripley, Scott, and Stoddard) to better understand which plant-parasitic nematodes are present and at what population levels. Because only four surveyed fields were located in South Central Missouri, those fields were combined with the Southeast region for this summary.
Nematodes are common, but presence does not always mean damage
Seven types (or taxa) of plant-parasitic nematodes were detected in the region. Soybean cyst nematode (SCN) was found in 89% of fields, root-lesion nematode in 84%, and spiral nematode in 63%. Stunt, root-knot, stubby-root, and lance nematodes were detected less frequently (Figure 1). Finding a nematode does not necessarily mean it is causing yield loss. Risk depends on the nematode, population density, crop, and field conditions.
Figure 1 Prevalence (% of fields with detection) and population densities of plant-parasitic nematodes detected in 19 soybean fields across Southeast and neighboring South Central Missouri. Median and maximum population densities are based on positive soil samples only and are reported per 100 cm³ of soil. In the host column, icons indicate the nematode's potential to feed on soybean and/or corn. Host status may vary among nematode species within each group.
SCN was an important concern in Southeast Missouri because it was widespread and reached high population densities in some fields. Root-knot nematode also stood out in this region. Although detected in 21% of fields, populations reached 2,385 nematodes/100 cm³ soil, showing that root-knot may be an important concern in individual fields.
SCN reproduction differs among resistance sources
We also tested how well these SCN populations reproduce on common sources of SCN resistance. Among the Southeast and South Central Missouri SCN populations tested, for every 100 females that developed on a susceptible soybean, a median of 75 females developed on PI 88788 (the most common SCN resistance source found in Missouri soybean). On Peking, the median was much lower with 16 females per 100 on susceptible soybean. The higher reproduction on PI 88788 reinforces the importance of knowing and rotating with non-host crops and soybean with other SCN-resistance sources.
What could this mean for yield?
Using representative Southeast Missouri conditions and the SCN Coalition Profit Checker, the estimated potential yield loss was 11.9%, or about 6.5 bu/acre and $85/acre. Actual estimates depend on SCN population density, virulence (ability to reproduce on the soybean), field conditions, expected yield, and soybean price.
Don't rely on symptoms alone
Nematode problems can be easy to miss. A field with SCN can look healthy while yield is being lost. Stunting, yellowing, uneven growth, and poorly performing areas can indicate a significant problem; however, those symptoms are not specific to only nematodes.
Management starts with knowing what is in the field. For SCN, use resistant varieties, rotate resistance sources such as PI 88788 and Peking, and rotate with a nonhost crop such as corn. Nematode-protectant seed treatments may also provide early-season protection. Management options for other nematodes depend on the species and population density, and resistant varieties are not available for many of them.
Don't guess. Sample. Missouri soybean growers can currently submit up to four soil samples for free SCN egg counts through SCN Diagnostics, supported by the Missouri Soybean Merchandising Council. Visit SCN Diagnostics for more information.