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French marigold as a cover crop for root-knot nematodes: does it work?
Sources (0)
Promising Some peer-reviewed or extension evidence, but limited, conditional or mixed.
Grown densely as a cover crop for at least two months where the next crop will go, marigold can suppress root-knot nematodes. Results depend on species and cultivar.
- Krueger R. et al. Marigolds (Tagetes spp.) for Nematode Management. UF/IFAS Extension ENY-056/NG045.
- Soil Organic Matter, Green Manures, and Cover Crops for Nematode Management. UF/IFAS Extension ENY-059/VH037.
Mechanism
Marigold roots produce alpha-terthienyl, a nematode-toxic compound; marigold is a poor host.
What the research found
- UF/IFAS: plant marigold at least two months before the vegetable crop, on the same site, then incorporate it (NG045).
- UF/IFAS cover-crop table rates marigold "Depends" for root-knot nematodes; species and cultivars vary (VH037).
Caveats
Benefit only in the planted area and only as a preceding crop. Nematodes can rebound when a susceptible crop follows.
How to try it
Use French marigold (Tagetes patula) types; grow a solid stand 2+ months, turn it in, then plant.
Other Promising pairings (4)
- Collards as a trap crop for diamondback moth in cabbage
- White clover living mulch under cabbage and other brassicas
- Carrots and onions against carrot fly
- Flowering buckwheat as an insectary strip
Evidence summary checked 2026-10-14. We cite only peer-reviewed studies, university extension and USDA/ARS sources; results may differ in your region. Not professional advice.