They are not related to earthworms. Nematodes feed on plant roots, damaging and stunting them. The first evidence of a nematode problem is poor growth of plants and poor color of foliage. The damaged roots cannot supply sufficient water and nutrients to the aboveground plant parts, and the plant is stunted or slowly dies. Symptoms are more pronounced during dry weather.
Infested tubers are unsightly, but edible if peeled.
The root-knot nematode causes small inconspicuous root swellings or galls to develop. Nematodes are found throughout the United States, but are most severe in the South. They prefer moist, sandy-loam soils. Nematodes can move only a few inches each year on their own, but they may be carried long distances by soil, water, tools or infested plants. There are no chemicals available to homeowners to kill nematodes in planted soil.