Nematode Interactions in Nature: Models for Sustainable Control of Nematode Pests of Crop Plants?

Plant-parasitic nematodes are major crop pests in agro-ecosystems while in nature their impact may range from substantial to no significant growth reduction. The aim of this review is to determine if nematode population control in natural ecosystems may provide us with a model for enhancing sustainable control of nematodes in crops. In agricultural systems, monocultures, narrow rotations, alteration of the soil habitat, and fertilization may alter plant-parasitic nematode dynamics and boost nematode numbers while reducing diversity and effectiveness of top-down control organisms and protective mutualisms (endophytes and arbuscular mycorrhizal fungi). Traditional agro-ecosystems (still applied in tropical regions) involve the development of complex practices such as a broad range of plant species of high genetic diversity grown in associations, rotations, and shifting cultivation, which all influence the complexity of plant-parasitic nematode communities and of control organisms. In nature, plant-parasitic nematodes (and other root feeders and soil pathogens) drive plant community processes, such as succession and plant species diversity. Natural soils contain a wide variety of potential nematode control organisms, but the consequences of this diversity are not known. Wild plant populations also contain more genetic variability than crops, but consequences for coevolution and Red Queen processes for nematode populations have not been studied. We conclude that integrated crop pest control may benefit from studying plant-parasitic nematode-natural antagonist interactions in natural systems, which have been coevolved for longer than crop-nematode-antagonist systems. Understanding how wild plants control their plant-parasitic nematodes may ultimately result in improving the sustainability of crop protection against plant-parasitic nematode