STUDIES ON GREY BLIGHT OF COCONUT CAUSED BY Pestalotiopsis palmarum (COOKE) STEYAERT
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Date
2023-01-31
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University of Agricultural Sciences, Bangalore
Abstract
Grey blight of coconut caused by Pestalotiopsis palmarum is one of the emerging disease in the southern Karnataka causing considerable yield loss. Disease symptoms characterized by greyish centre with dark brown margins. P. palmarum produces five celled conidia with three middle cells of brown colour, hyaline at basal and apical end with one to three setulae. The Koch’s postulate was proved by pin prick method. The pathogen was further confirmed as P. palmarum by molecular characterization by using ITS1 and ITS4 primers. The cultural and physiological studies recorded the highest colony growth on potato dextrose agar medium ( 90 mm) and the colony colour varied from greyish white to white with completely serrated to smooth margin, while the temperature 25oC and pH 6.0 were found to be the best for the growth of the pathogen. Among the different fungicides, bioagents and botanicals tested under laboratory conditions, the mean mycelial inhibition was highest among the fungicides such as ziram (1000 ppm), carbendazim and thiophonate methyl (500 ppm), trifloxystrobin 25 per cent + tebuoconazole 50 per cent (1000 ppm). Among fungal and bacterial bioagents, highest mycelial inhibition was found in Tricoderma viride-2 (Tv-2) of 71.30 per cent and Bacillus subtilis (Bs-O) with 52.22 per cent while among botanicals, turmeric extracts (20 %) were found most effective
against the growth of the pathogen.