Marigold can suppress 14 genera of plant-parasitic nematodes, with lesion nematodes (Pratylenchus spp.) and root-knot nematodes (Meloidogyne spp.) the most affected (Suatmadji 1969).
Marigold roots release the chemical alpha-terthienyl, one of the most toxic naturally occurring compounds found to date (Gommers and Bakker, 1988). This compound is nematicidal, insecticidal, antiviral, and cytotoxic (Arnason et al., 1989; Marles et al., 1992).The presence of alpha-terthienyl inhibits the hatching of nematode eggs (Siddiqui and Alam, 1988).
Nematode trapping fungi, or “nematophageous fungi,” are carnivorous fungi that have developed methods and structures that enable them to successfully trap and consume nematodes. Nematode trapping fungi are responsible for keeping the nematode population in check and are an important part of the subsoil ecosystem. These fungi prey on nematodes and are in turn consumed by organisms on the next trophic level. Nematophageous fungi use several methods to hunt their prey. These methods include living within the nematode and slowly consuming them as well as spreading diseases through nematode populations. The fungi also live in the soil and set traps for the nematodes to squirm into.