Etiology, pathogenicity and management of collar rot in Cockscomb (Celosia argentea).
Collar rot induced by Macrophomina phaseolina, recently appeared as one of the most significant constraints to the production of Cockscomb (Celosia argentea L.), an ornamental plant. Symptoms include, wilting of the plant, chlorosis of lower leaves, shrinking of stem at collar region, which becomes black at later stage and affected plant become shredded, consequently a clear mycelial growth of the fungus can be seen if the stem of the affected plant is split open. In this study, the causal fungus was isolated from the diseased tissues (collar and stem regions, externally and internally). Then the pathogenicity test of isolated pathogens was confirmed through Koch’s postulates. Considering the management trials, five fungicides (Carbendazim, Thiophenate-M, Ridomil Gold, Antracol and Score) and five different plant extracts (Azadirachta indicia L., Melia azedarach L., Eucalyptus cameldulensis L., Syzygium cumini L. and Moringa oleifera L.) were evaluated against the collar rot disease pathogen (Macrophomina phaseolina) by poison food technique at different concentrations viz., 100, 150, 200 and 250 μg/mL for fungicides and 10, 15 and 20% for plant extracts. Out of five fungicides used, Topsin M and Antracol were found to be most effective in reducing the mycelial growth of M. phaseolina by (83%) and (76%) followed by Ridomil Gold, Score and Carbendazim (46, 39 and 29% reduction). In case of plant extracts, A. indicia and E. cameldulensis extracts were more effective by reducing the mycelial growth of M. phaseolina by 77 and 74%, respectively, followed by M. oleifera, M. azedarach, and S. cumini (61, 45 and 18% reduction). © 2015 Friends Science Publishers