ABSTRACT
Soil-borne plant pathogens cause serious losses to economically important agricultural crops in the form of root rot, damping-off, blights, fruit decay, wilts, etc. The substantial loss to agricultural crops justifies a judgement of needs for new and improved measures to control seed and soil-borne patho gens, which may pose an alternative disease control measure to replace chemical fungicides. According to Snyder (1960), "biological control relies largely upon an interruption of host-parasite relationships through biological means". It takes a broader view of biological control and includes imparting resistance to the host, usually through plant breeding or by modifying the crop, in order to avoid or reduce infection. Sewell (1965) supported Snyder's view and proposed that "biological control is the in duced or natural, direct or indirect limitation of a harmful organism, or its effects by another organism or group of organisms". Baker and Cook (1974) stated that "biological control is the reduction of inoculum density or dis ease-producing activity of a pathogen or parasite in its active or dormant stage, by one or more organisms, accomplished naturally or through ma nipulation of the environment, host or antagonists, or by mass introduction of one or more antagonists."
