When it is available, host plant resistance to a specific pest is usually the least expensive and most effective means of minimizing losses to that pest. However, successful use of varietal resistance requires knowing the extent of the resistance and which pests are present in a particular situation. There are "nematode resistant" varieties of tomatoes, soybeans, southern peas, sweet potatoes, cotton, and tobacco, but each of these varieties has resistance, which is effective against only one, two, or at most three, species of nematodes. None are "nematode proof." Therefore, to be able to use the resistance available in a particular crop species, you must know the pest species present in the field. In addition, varieties with the appropriate resistance must be adapted to cultural conditions and requirements of your area. It still is necessary to use other methods to control any other nematodes that are present, because resistance against one or two species does not affect the ability of any other nematodes to injure the crop.

Nematologists around the world are working very hard to identify and learn to manipulate natural enemies of nematodes so they can be used as biological control agents. Many different bacteria and fungi have been able to reduce populations of some kinds of nematodes under laboratory conditions, but successes at field scale are rare. Most organisms recognized to be promising for biological control of nematodes are quite specific in which nematodes they will attack, or have been very difficult to culture in sufficient quantities to be useful for field application, or both. The conditions under which each is most effective are often quite specific and limited. In all, then, commercially effective biological control as a means to reduce the effects of nematodes on lawns still appears to be many years away.

These are chemicals used to control plant parasitic nematodes. Two major groups of nematicides are distinguished by the manner in which they spread through the soil. Soil fumigants are gases in cylinders or liquids which spread as gases from the point where they are injected into the soil. Non-fumigant nematicides include a variety of water soluble compounds which are applied to the soil as liquid or granular formulations. Most belong to the carbamate or organophosphate families of pesticides. Their distribution in the soil depends on physical mixing during application and moving in solution in soil water. Some are absorbed by the plant and distributed to other parts of the plant ("systemic") where they may be effective for nematode or insect control. There is no perfect nematicide for all purposes. Nematicides vary in their effectiveness against different kinds of nematodes, ease of handling, cost, effect on other classes of pests (weeds, disease organisms, insects), behavior in different soils, toxicity to different plants, and availability. There are many cases where some nematicides offer the only effective means of reducing or preventing nematode injury to a crop. There are others in which nematicides provide a quick and easy means of controlling a nematode problem which should not have occurred if the other available management options had been exercised. Sometimes, the practical and economic feasibility of using a nematicide depends on the level at which other management components are being maintained in the system. Generally, a higher yield potential and higher capital risk, because of such management components as fertility levels and irrigation, are more apt to justify the expenditure and effort to use a nematicide than are low levels of management or return. The factors affecting the decision to use a nematicide, and to select an appropriate one, are complex.