10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 3 2012 (July - September) Fungal pathogens pose a major problem in causing reduction in yield of vanilla crop to considerable level. lessThan i greaterThan Fusarium oxysporum lessThan /i greaterThan , was isolated from naturally infected vanilla plants and an attempt was made to minimize the damage caused by the pathogen using biocontrol agents lessThan i greaterThan Trichoderma lessThan /i greaterThan lessThan i greaterThan harzianum, lessThan /i greaterThan and lessThan i greaterThan Pseudomonas lessThan /i greaterThan lessThan i greaterThan fluorescens lessThan /i greaterThan isolated from soil. The combined inoculation of lessThan i greaterThan Trichoderma harzianum lessThan /i greaterThan with lessThan i greaterThan Pseudomonas fluorescens lessThan /i greaterThan treatment showed maximum disease suppression followed by the single inoculation of lessThan i greaterThan Pseudomonas fluorescens lessThan /i greaterThan , lessThan i greaterThan Trichoderma harzianum lessThan /i greaterThan , lessThan i greaterThan Pseudomonas putida lessThan /i greaterThan , lessThan i greaterThan Trichoderma virens lessThan /i greaterThan , respectively in decreasing order. The results clearly indicated that these bio-control agents suppress the disease incidence. Concerning the interaction effect between used antagonistic microorganisms and method of treatments, there was a highly significant effect. These results suggested that using of lessThan i greaterThan Trichoderma harzianum lessThan /i greaterThan with lessThan i greaterThan Pseudomonas fluorescens lessThan /i greaterThan through soil mixing plus root dipping treatment could be provided not only additional protection against crop loss due to lessThan i greaterThan Fusarium lessThan /i greaterThan diseases but also significantly increased vegetative growth of vanilla. The mechanism of biocontrol involved the production of volatile and non volatile organic acids, siderophore, chitinase, peroxidise and salicylic acid. Application of biocontrol agents for crop protection is very significant as it has several advantages such as possibility of multiple pathogen suppression, low cost and promotion of soil fertility. Athul Sandheep R, Aju K. Asok Ans Jisha M.S. Antagonism, Bio-agents, Root rot disease, Siderophore 706-716