nematodes, microscopic roundworms generally found in soil which can seriously harm vines and other plants. Some feed on bacteria or fungi and are part of the normal vineyard ecosystem. Others, however, feed on grapevine roots and thus reduce both the size and efficiency of the root system. Although the vines do not necessarily die, they suffer water stress and deficiencies in vine nutrition and grow weakly. Some species of nematodes are important because they transmit virus diseases. The viruses spread by nematodes are called nepoviruses. They can be spread throughout the vineyard from just one infected plant by nematode feeding. Often they show up as a few yellow vines in the vineyard.
