Nematodes as predators and prey: Relationships to biological control and soil processes

Understanding of predator: prey relationships requires consideration of many aspects of the biology of the organism concerned. Predator:prey relations including soil nematodes are reviewed and it is found that statistically significant relationships between predators and their assumed prey may be absent for reasons such as: lack of data for all predators; temporal relations between predator and prey; equilibrium populations do not show underlying predator:prey interactions; predators may have multiple food sources; predator mass or consumption may be more important than number. Not only do generation times of predacious nematodes often appear to exclude their having a significant impart on peaks of plant-feeding nematodes but also there is accumulating evidence that bacterial-feeding nematodes make a greater contribution to their diet than do plant-feeding nematodes. Greater plant yields after attempts to stimulate biological control of plant-feeding nematodes may result from an increased number of predacious nematodes enhancing the cycling of plant nutrients rather than a reduction in root herbivory.