Development of microbial consortia for the management of leaf blight disease of coconut

Abstract

The leaf blight disease caused by Lasiodiplodia theobromae is an important foliar disease in coconut that results in a yield reduction of 10–24 per cent in Tamil Nadu, India. In the present study, five Trichoderma viride isolates, Pseudomonas fluorescens and Bacillus subtilis strains were isolated from the coconut rhizosphere and tested against L. theobromae. P. fluorescens Pf1, B. subtilis (Km1) and T. viride (TNAU) isolates were found highly effective against the leaf blight pathogen under in vitro conditions and hence, all the three antagonists were combined together to develop microbial consortia and tested against leaf blight disease under field conditions. Soil application of microbial consortia formulated using talc as a carrier material at 150 g (50 g each) and 300 g (100 g each) doses at different intervals (quarterly, half-yearly and annually) was evaluated for three years from 2011 to 2013. Among the treatments, the fungicide carbendazim was found to be the most effective against coconut leaf blight. Among the treatments with bioagents, soil application of microbial consortia @ 300 g+5 kg of farm yard manure at quarterly interval/palm/year was the best treatment which was followed by the treatment with TNAU Bacillus subtilis (Bs1) mixture in two locations. Confirmatory results were obtained in similar experiments carried out at two different locations during 2013–2014, too.