The importance of rhizosphere interactions in the biological control of plant parasitic nematodes - a case study using Verticillium chlamydosporium

Verticillium chlamydosporium has provided considerable control of root knot nematodes in a range of laboratory experiments and is one of the most promising natural enemies with potential as a biological control agent so far tested. From a detailed study of the biology and ecology of the fungus, it has been possible to identify the key factors which affect its efficacy and a strategy for its exploitation has been developed. The fungus survives in soil throughout a growing season and its concentration in soil may be increased by repeated applications. The rapid multiplication of root-knot nematodes on susceptible crops means that control must be extremely effective to prevent crop damage. If suitable methods of production and application can be developed, V. chlamydosporium, in conjunction with other methods such as the rotation of poor hosts, may provide adequate control, but the reliability of such approaches needs extensive testing. Although genetic manipulation offers the possibility of enhancing the ability of the fungus to kill nematodes, such an approach will require much research and, in the short term, the development of the fungus will rely on the exploitation of carefully selected wild types.