Plant‑parasitic nematodes (PPNs) are tiny worms that live in soil and feed on plant roots. They damage roots, reduce the plant’s uptake of nutrients, and lower crop yields often without plants showing any obvious symptoms.
As part of a much larger soil ecosystem, PPN numbers and activities are influenced by soil microbiomes (communities of microbes living in soil), including beneficial nematodes, and overall soil health. As farmers adopt more sustainable practices and use less chemicals, many are turning to cover crops to improve soil health. However, currently little is known about exactly how cover crops affect PPN populations.
Agriculture and Agri-Food Canada (AAFC) scientists are now studying how cover crops impact these processes in the soil ecosystem and affect PPN populations. The results of this research could help find new ways to manage soil pests using natural processes occurring in the soil and reduce reliance on chemicals.
To start with, the AAFC team conducted field research to study the effects of several cover crop species and mixtures across different production systems, including corn–soybean rotations and vegetable (carrots, potatoes, and spinach) fields. Cover crops tested included winter rye, rye–barley and rye–oat mixtures within corn-soybean rotations; also legume and non-legume (alfalfa, sorghum, cowpea, pearl millet, etc.) and their different mixtures on field vegetables. These studies took place over multiple years, providing insight into long‑term ecological effects of covers. Nematode communities were assessed using both traditional microscopy and DNA metabarcoding, allowing researchers to capture detailed information about soil biodiversity and pest dynamics.
Overall, cover crops were found to influence PPNs through indirect ecological pathways. Both systems with cover crops showed reduced PPN numbers or shifts in nematode community composition compared with fallow soil. Using cover crops, especially when mixed, has the potential to lower PPN populations by greater than 40% in corn-soybean rotation. Long-term winter cover also has the potential to reduce high pathogenic PPNs such as Pratylenchus species. The study shows that the relative abundance of Pratylenchus (root lesion nematode) was lowest in the use of cover crops (<1%) compared to fallow (> 30%) in corn-soybean production tested.
Ongoing Ontario research further shows that mixed cover crops containing both legumes (such as alfalfa) and non‑legumes (such as sorghum) can support PPN management and improve soil health in vegetable systems too. A study conducted in carrot fields with covers found a 63.8% reduction in PPN relative abundance compared to the no cover crop.
These findings highlight that cover crops help manage pests, maybe not through direct suppression, but by strengthening soil biodiversity and stabilizing the soil food web. Choosing the right species or mixtures can support sustainable, chemical‑free approaches to nematode management while improving overall soil health. These findings offer valuable guidance for growers seeking sustainable alternatives to chemical nematicides. By selecting appropriate cover crop species and integrating them into crop rotations and vegetable fields, farmers may improve soil health while indirectly regulating PPNs.
London Research and Development Centre: Dr. Tahera Sultana, Jerry Akanwari (former PhD student), Syed Atif Hasan Naqvi (PhD student), Elyse Aubry (former MSc student), Ana Borrego-Benjumea, Leo VanDriel (retired)
Collaborators:
Brock University: Dr. Ping Liang (Professor)
For more information:
Naqvi, S.A.H., Akanwari, J., Sultana, T. (2026). Metabarcoding reveals cover crop functional type as primary driver of soil nematode community composition in a carrot production system. Biology, 15(15), 1226. https://doi.org/10.3390/biology15151226
Naqvi, S.A.H., Akanwari, J., Sultana, T. (2026). Effects of cover crops and sampling time on soil nematode community structure assessed by metabarcoding and machine learning in a Canadian potato agroecosystem. Discovery Soil (submitted)
Akanwari, J., Islam, M.R., Liang, P., Sultana, T. (2025). Winter cover crops alter nematode community composition and soil health dynamics in corn-soybean systems. Applied Soil Ecology, 216, 106508. https://doi.org/10.1016/j.apsoil.2025.106508
Akanwari, J., Islam, M.R. & Liang, P., Sultana, T. (2025). Metabarcoding–approach–based profiling reveals dynamic nature of sustainable tillage practices on nematode communities in corn–soybean cropping systems. Scientific Reports, 15, 25372. https://doi.org/10.1038/s41598-025-09356-6
Aubry, E., Akanwari, J., Liang, P., Ellouze, W., Gaiero, J., Sultana, T. (2024). Effects of cover crops on nematode communities in spinach production. International Journal of Molecular Sciences, 25(24), 13366. https://doi.org/10.3390/ijms252413366
Akanwari, J., Islam, M.R., Sultana, T. (2024). The impact of winter cover crops on soil nematode communities and food web stability in corn and soybean cultivation. Microorganisms, 12(10), 2088. https://doi.org/10.3390/microorganisms12102088
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