Efficacy of Substrate Based Bioformulation of Microbial Antagonists in the Management of Bacterial Disease of some Solanaceous Vegetables in Assam

Abstract

A study was undertaken to explore effective organic substrate-based bioformulation using virulent cells of antagonists <em>Pseudomonas fluorescens, Bacillus subtilis</em> and <em>Trichoderma viride</em> during 2010-13. Three organic substrates, viz. vermicompost, farm yard manure and mustard oil cake (MOC) were compared for mass multiplication of the antagonists. All the substrate based antagonists showed effective results in suppression of bacterial wilt <em>(Ralstonia solanacearum</em> Yabuchi et al.) incidence in vegetable crops tomato, brinjal and chill. Quantitative aspect of population dynamics of the antagonists at different days of storage was made to evaluate the shelflife of the biopesticide and found that the antagonists maintained a steady population count upto 180 days of storage at room temperature. The combination of vermicompost <em>P. fluorescens</em>, carboxy methyl cellulose (CMC) and mannitol showed best shelf-life as it maintained highest population recovery of<em> P. fluorescens</em> and <em>B. subtillis</em> at different days of storage. The combination of MOC, <em>T. viride</em>, CMC and mannitol showed best shelf-life in case of <em>T. viride</em> and maintained highest population recovery of the antagonist at different days of storage. Application of the substrate based bioformulations as combination of seed treatment, root application, soil application at transplanting and soil application at 30 days after transplanting showed minimum wilt incidence and maximum yield in tomato, brinjal and chilli. Maximum disease reduction (81.85%) was shown by bioformulation comprising <em>P. fluorescens</em> with vermicompost as substrate followed by <em>T. viride</em> with MOC as substrate (79.07%). Following the trend of reduction in disease incidence, yield was maximum in tomato (36.0 t/ ha), when the crop was treated with vermicompost based <em>P. fluorescens</em> followed by treatment with MOC based <em>T. viride</em> (33.35 t/ha). Yield of brinjal (27.60 t/ha) and chilli (26.30 t/ha) was similarly maximum when bioformulation of vermicompost based <em>P. fluorescens</em> was applied.