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Cord Evaluation Of Fungicides And Antagonistic Organism Against Major Pathogens Of Leaf Rot Disease Of Coconut And Their Eco-friendly Management

Leaf rot is an integral part of coconut root (wilt) disease complex. In the management of root (wilt), leaf rot control is of vital importance. Leaf rot phase is due to a complex of fungal pathogens - Colletotrichum gloeosporioides, Exserohilum rostratum, Fusarium solani etc. Investigations on effect of fungicides confirmed strong inhibition of all major pathogens in vitro by Contaf (Hexaconazole), Indofil M- 45 ((Mancozeb), Tilt (Propiconazole) and Bavistin (Carbendazim). Antracol (Propineb), Tag cop 50 (Copper oxychloride) and Calixin (Tridemorph) inhibited F.  solani to a lesser extent than others. Bacillus subtilis was found relatively tolerant to fungicides (Contaf, Indofil M- 45) as compared to Pseudomonas fluorescens. B. subtilis was able to tolerate lower concentrations of Tilt or Bavistin in the medium while P.  fluorescens did not. B. subtilis, P.  fluorescens and Trichoderma harzianum were tolerant to Antracol in lower concentrations. As such, integrated use of bio agents with fungicides (at minimal concentrations) can be employed in disease management. Amelioration of leaf rot affected palms in the field was consistently effected by a talc-based preparation of P.  fluorescens.  Antagonistic potential of B. subtilis and P.  fluorescens against the pathogens alone and in combination eliciting synergism in inhibition of pathogens have also been established. T. harzianum was found to inhibit C.  gloeosporioides and E.  rostratum.  However, a reverse effect of F.  solani on the fungal antagonist was seen. Combined use of fungicide (Contaf as a test case) and bacterial antagonist(s) when tested in vitro against the pathogens, synergism in antagonism against C.  gloeosporioides and E.  rostratum was evident. Prevalence of antagonistic bacteria (Bacillus sp.) and fungi (Aspergillus sp.) in the phylloplane of coconut was also brought out. Knowledge thus gained on various aspects are important in identifying effective/superior isolates of antagonists, formulation of effective microbial consortia and appropriate integration of bio agents and fungicides in the integrated management of the disease complex.

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