Publication E-79
January 1979
Purdue University
Cooperative Extension Service
West Lafayette, Indiana 47907

Nematodes
C. Richard Edwards and David L. Matthew, Extension Entomologists and John M. Ferris, Research Nematologist
Nematodes are tiny, thread-like worms so small that most kinds can be seen only through a microscope. Many species live in the soil and water; others invade plant tissues; and some are even parasites in the bodies of animals, including man. Although most soil-inhabiting nematodes will not harm plants, a number can become serious pests. Most plant parasitic nematodes attack the plant roots; however, a few species, like the foliar nematodes, cause injury within the leaves and flowers.
Nematodes seldom kill plants outright, but they can reduce yields — often to a point where it becomes unprofitable to grow susceptible crops in infested soils. Since nematodes are usually too small to be seen without a microscope, the only way to detect their presence is to have the soil examined by a plant nematologist or to depend upon your own ability to recognize nematode damage symptoms. However, these symptoms can be misleading. Insects, diseases or other factors can cause similar symptoms.

HOW TO DETERMINE DAMAGE
A few kinds of nematodes do produce plant damage symptoms that are rather easy to recognize. Examples are the galls caused by root knot nematodes and dead areas between the veins of chrysanthemum leaves caused by foliar nematodes. More often, the symptoms are those characteristic of any unhealthy plant — for example, wilting; stunting; yellowing; lack of plant vigor; malformation of leaves, flowers, fruits and seeds. Those species of nematodes which attack underground plant parts often
cause discolored areas on the roots or produce root galls or other root malformations.
To determine whether nematodes are a problem, first examine the plants carefully to eliminate other likely causes. Check for insects, diseases, possible soil deficiencies, fertilizer damage, frost injury, too much or too little water. Examine all parts of the plant.
After examination, if nematodes are still suspected, you may wish to send samples of soil and/or plant materials to Purdue University for laboratory diagnosis. There is no charge for this service. A proper soil sample consists of at least one quart of soil taken directly from the root zone of affected plants. Include some of the roots, and place the entire sample in a plastic bag for mailing. If foliar nematodes are