Some plants may act as trap crops that prevent nematodes from maturing and reproducing once they invade the roots. Some marigolds, a few varieties of chrysanthemums, castorbeans, partridge peas, several Crotalaris spp., velvetbeans, and rapeseed are considered nematode suppressive plants. Nematode populations often rebound to pretreatment levels when a susceptible vegetable is grown following a nematode suppressive crop. Nevertheless, the use of a nematode suppressive crop has been shown to be as effective as or somewhat better than fallowing an area to reduce the nematode population. The material works by increasing the soil microorganisms that feed on chitin.
Chitin is one of the primary components in the body wall of nematodes.
The feeding activities of the chitin-loving microorganisms have been shown to reduce the number of nematodes for two cropping sequences. Control is sporadic, however, and requires large quantities of an expensive product. Chitin products should be incorporated into the soil about two weeks before planting. There are no nematicides on the market that can be used by homeowners. Currently, licensed pesticide applicators can still use metam sodium, a preplant fumigant, on home gardens, but this chemical requires important safety precautions and may carry significant legal liabilities.