Abstract
Biological control is a non chemical measure which is usually as effective as chemical control. Several mechanisms are involved in biological control that include, among others, competition for nutrients, induced resistance and secretion of inhibitory substances etc. Trichoderma is a soil borne mycoparasitic fungus effective against many soil borne and foliar diseases. Trichoderma spp. are often used in agriculture as biocontrol agents against a number of pathogenic fungi in vitro and in vivo. Culture filtrate of five Trichoderma species (viz. T. viride, T. virens, T. harzianum, T. koningii and T. pseudokoningii) were used against Alternaria solani. Culture filtrate of all the species of Trichoderma retarded the growth of A. solani but T. viride and T. harzianum most strongly suppressed the growth of Alternaria solani.
