Principles of biological control of soil-borne plant diseases

Unexpected results derived from applications of chemicals to soils led to investigations of the soil biology, discovery of the rhizosphere and eventually to research on mechanisms of biological control. Decisively, chemicals have staved off major disasters in agriculture. In instances of successful monoculture, below ground pathogens appear to be suppressed by an injurious biology, in principle not unlike an injurious host-specific biology which increases with repeated cultivation of the same crop. Crop diversity, nevertheless, is basic to continued successful production agriculture. Decoy hosts which initiate germination of resisting structures may deplete pathogens of energy reserves, and serve to protect the major host. Endogone, which occupies root cortical tissue of most plants, in addition to the traditional mycorrhizal function, may afford protection against invasion by pathogens. Healthy Endogone may be essential to healthy crops.