New strategies for the management of plant parasitic nematodes with especial emphasis on biological control

Since 1950s nematicides have provided effective control of a wide range of nematode pests on many crops throughout the world. However, their high cost and environmental and health hazards associated with their use have tended to limit their application.Frequently, alternatives to chemicals have proved impractical or inadepquate. Hence, the development of sustainable methods of nematode control is dependent upon the integration of several control techniques, which usually rely on the accurate identidfication and qualification of the pest species and on a detailed knowledge of their ecology and biology. Even for the most extensively studied nematode pests, such information is often lacking. New methods based on immunoassays appear to have great potential for the identification of specific nematode pests and their quantification in soil. Moplecular techniques for the production of transgenic p[lants with novel resistances to both sedentary and migratory nematodes are well advanced and some nematicidal genes have been identified. However, experience with resistant has indicated that their use requires careful management to prevent the development of virulent nematode populations capable of overcoming such resistance. Soils that suppress the multiplication of several nematode pests have been identified throughout the world and have been associatred with the build up of antagonists. Such natural control has proved difficult to manipulate but studies on suppressive soils have led to the identification of a range of microbial agents which may have potential for biological control. Two parasites, Verticillium chlamydosporium and Pasteuria penetrans, are being studied at Rothamsted for their potential as biological control agents for root-knot nematodes in vegetable crops. Key factors affecting the efficacy of these organisms have been identified and their application at a specific cropping cycle may provide consistent and effective control. Clearly, there are exciting new prospects for the management of nematode pests but there is a need for much research and development before many of the new approachers are available to the grower