Parasitic Nematode or eel worms are small, non-segmented worms. They are only 50 microns in diameter and about 1mm long or less. They have a resistant cuticle (skin) and an ability to adapt well to environmental change which has enabled them to become the most abundant multi-cellular animals on earth. Most nematode species have a beneficial role in the soil, but parasitic nematodes are a devastating soil pest for many commercial crops as they attack the plant roots and cause decreased production. In some cases they also allow the entry of fungal rots that destroy the roots. Agricultural cultivation tends to encourage an increase in parasitic nematodes over other species.