Trichodorids constitute a group of nematodes, together with tylenchs and longidorids, that are parasitic on plants. The trichodorids form the smallest group in a number of genera, species and also individuals in the soil. Trichodorids are important in strictly agronomical research, as they are able to cause direct damage to the root system of various crops; they are the agent of the "docking disorder" of the sugar beet, a severe disease in Europe. They are also able to transmit various viruses to a series of important crops. These viruses differ from those transmitted by the longidorids and also - as opposed to longidorids - they are not strictly associated with one or a restricted number of species. Trichodorids therefore constitute a potentially active group of direct and indirect predators.