Nematodes, also known as eelworms and roundworms, are one of the most abundant creatures living in soil. Nematode species are very difficult to distinguish, over 28.000 species have been described, of which over 16.000 are parasitic. The total number of nematode species has been estimated to be about 1 million. Although some of these tiny, worm-like animals are beneficial, about 50% are detrimental to plant health and on a global scale it has been estimated that these parasitic species reduce agricultural production by a figure in the order of 12%.

Plant parasitic nematodes behave in different ways, some feed externally on plant roots (ectoparasitic forms) whilst others invade the roots internally (endoparasitic forms).  The resultant damage that nematodes cause food crops worldwide can vary from a reduction in yield and/or reduced marketability of the affected crop. The damage levels sustained by an individual crop will of course vary from field to field and will be influenced by a wide range of factors. These factors will include the density of the nematode population, the virulence of the species or strain which has targeted the individual crop and the level of tolerance/resistance which the affected crop can muster against the attack.

An integrated approach to nematode control is essential, but the growing of a cover crop is a very effective way of controlling nematode populations as well as improving the soil structure and returning valuable nutrients for the following crop to utilize. Choosing the correct variety to grow needs careful thought and pre-planning.