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Cover Crops

 Although no single crop will act as a "magic bullet" against all nematodes, specific problems may be controlled successfully in preplant situations by planting certain cover crops. Cover crops work for different reasons, depending upon the specific nematode-crop combination. In some cases, the cover crop may be a nonhost for the nematode. Since nematodes do not feed on plants outside of their host range, such plants will starve out the population with the same effect as fallow cultivation. Other plants are known to be susceptible to nematode invasion but prevent the development of larvae into adults. Such plants are referred to as "trap crops." Crotalaria, for example, has been used successfully in this way to reduce populations of root-knot nematodes. Still other "antagonistic" plant species have been found to naturally exude chemicals toxic to nematodes. French marigolds and asparagus are examples of such crops. While antagonistic and trap crops have been used successfully to control nematodes, little is understood about the principles involved. Clearly, this is an area in which more research is needed.