Root-knot nematodes are small soil pests that attack the roots of many plants, including sweet potatoes. These nematodes produce small galls or swellings on the fine feeder roots, but they can also enter the storage roots and feed in the tissues beneath the skin without causing the common galls found on root crops. Symptoms include decayed areas under the skin. surface blemishes and pitting, deformed roots, poor color, and sometimes severe surface cracking. The vines of infested plants are usually stunted and yellowish, the leaves may show brown dead spots, and the plants may be killed in severe cases.

Whenever possible, plant sweet potatoes in soil that is free of this pest. Nematodes are found not only in the soil but also on the roots of plants, and it is important to obtain nematodefree plants for transplanting into the field. The sources of infestation for plants are infested seed stock and plant-bed soils. You can use vine cuttings in clean soil as a sure way of getting clean seed.

Yellow Jersey, Heartogold, and Nemagold have been found resistant to the common rootknot nematode. The nematodes enter the roots of Nemagold but fail to develop and usually die.