Proactively Monitoring Plant-Parasitic Nematodes in Soybean Fields

Principal Investigator

• Paul Esker, Ph.D., Professor of Epidemiology and Extension Field Crop Pathology

Co-Investigators

• Alyssa Collins, Ph.D., Associate Research Professor of Plant Pathology and Director SEAREC
• Adriana Murillo Williams, Ph.D., Extension Educator
• Mihail Kantor, Ph.D., Assistant Research Professor of Nematology
• Dilooshi Weerasooriya, Ph.D., Laboratory Coordinator, Plant Pathology and Environmental Microbiology

Background

Plant-parasitic nematodes are major threats to crop production worldwide, causing significant yield losses and economic damage. Among these pests, soybean cyst nematode (SCN; Heterodera glycines) is the most destructive soybean pathogen in North America, capable of reducing yields by more than 50% under severe infestations. SCN was first reported in Pennsylvania in Lancaster County in 2002. Since 2018, we have documented its continual spread through our surveillance program. Other nematodes of concern include root lesion nematodes (Pratylenchus spp.), which are widely distributed, and root-knot nematodes (Meloidogyne spp.). Understanding their prevalence and interactions with soil microbes is critical for sustainable soybean production.

Objective

To monitor the distribution and prevalence of major plant-parasitic nematodes in Pennsylvania soybean fields, identify species-level diversity, and provide science-based management recommendations to minimize yield losses and economic impact.

Methods

Starting in 2018, we have operated a free statewide nematode monitoring program for stakeholders. Participants receive pre-labeled soil sampling bags, instructions, and a field history form. Since the program began, 1,077 soil samples have been collected from 52 Pennsylvania counties. Screening primarily targets SCN, root lesion, and root-knot nematodes. Due to the high prevalence of root lesion nematodes across most surveyed counties (Figure 1), in 2024, our research was expanded to species-level identification of root lesion nematodes using PCR and soil metabarcoding, enabling investigation of nematode–microbe interactions and their combined effects on soybean health.

Results

Figure 1 illustrates plant-parasitic nematode prevalence by county. Numbers below each county abbreviation represent the total number of samples received to date, followed by the percentage of samples testing positive for each nematode type. These visualizations highlight regional hotspots for SCN and root-knot nematodes, as well as the near-ubiquitous presence of root lesion nematodes.

Figure 1. Current prevalence of soybean cyst nematodes (upper), root lesion nematodes (middle), and root-knot nematodes (lower) in Pennsylvania. Since 2018, 1,077 samples have been received and tested from 52 Pennsylvania counties. 

Results show that the distribution of plant-parasitic nematodes varies significantly across the state:

• SCN has been confirmed in 12 counties, including several major soybean-producing regions in south-central and southeastern Pennsylvania. Although SCN prevalence remains relatively low compared to other nematodes, its presence in key production areas is concerning because it can cause yield losses exceeding 50% under severe infestations.
• Root-knot nematodes have been detected in 14 counties, primarily in regions with diverse cropping systems. While their overall prevalence is lower than SCN and root lesion nematodes, their presence indicates an emerging threat that warrants close monitoring, especially as cropping patterns and soil conditions evolve.
• Root lesion nematodes are the most widespread nematode group, documented in 51 counties. High prevalence was observed across central and northern Pennsylvania, suggesting that these nematodes are well adapted to local soil conditions and cropping systems. Their broad distribution underscores the need for further work on diagnostics (species identification) and targeted management strategies.

Conclusion

The widespread occurrence of root lesion nematodes and the ongoing detection of SCN emphasize the urgent need for proactive monitoring and integrated management strategies. Molecular research offers essential insights into nematode–microbe interactions, aiding the development of effective, science-based solutions. By providing farmers with practical recommendations, this program helps protect soybean yields and lessen economic and environmental impacts in Pennsylvania and beyond.

Acknowledgements

Funding for this project has been provided by the Pennsylvania Soybean Board. We thank all cooperators who submitted samples over the past eight years.

Contacts

For more information, contact any of our team members: 

• Paul Esker, Ph.D.
• Alyssa Collins, Ph.D.
• Adriana Murillo Williams, Ph.D.
• Mihail Kantor, Ph.D.
• Dilooshi Weerasooriya, Ph.D.

This report is part of the 2025 Agronomy Research Report.