Root-knot nematodes are caused by microscopic eelworms that….

Live in the soil. To fix a problem with them, plant resistant varieties of tomatoes. Try rotating tomatoes with marigolds. Select a French variety such as 'Nema-gone', 'Golden Guardian' or 'Tangerine'. Plant the entire affected area heavily with the marigolds. Grow them for at least three months and then till them into the soil.