STUDIES ON CERCOSPORA LEAF SPOT OF OKRA (Abelmoschus esculentus L.)
KrishiKosh
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Title |
STUDIES ON CERCOSPORA LEAF SPOT OF OKRA (Abelmoschus esculentus L.)
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Creator |
SURAJ, P
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Contributor |
SUBBA REDDY, C
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Subject |
STUDIES, CERCOSPORA, LEAF, SPOT, OKRA
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Description |
The fungus causing leaf spot of okra was isolated and identified as Cercospora abelmoschi (Eill. and Ev.) relative efficacy of different methods of inoculation was worked out. Host range studies, suitability of media, effect of pH, temperature and light regimes during incubation on growth and sporulation of the fungus were studied. Effect of weather parameters on disease development and efficacy of various fungicides for the management of the pathogen in the field were investigated. Among the four inoculation methods employed, atomization of spores and mycelial suspension technique was found to be the most effective one. The disease started as minute light olivaceous speck, which enlarged to form angular sooty spots bounded by the vein. The margins of the leaf spots were neither clearly marked nor surrounded by any halo. Defoliation and stunted growth of the plant resulted in poor yield due to severe infection. Among the eight plants selected for the host range studies only the natural host developed symptoms. Potato dextrose agar was the most suitable medium for the mycelial growth of fungi whereas, carrot leaf extract agar found to be most suited for sporulation of the fungus. Maximum growth of the fungus in terms of mycelial dry weight was recorded at pH 5.0. The optimum temperature for mycelial growth and sporulation in culture were 25°C and 30°C respectively. Inoculation of the fungus under light for 6 h followed by 6 h incubation in darkness resulted in sporulation. All the weather parameters studied influenced the incidence of leaf spot disease. The disease incidence increased consistently with increase in relative humidity, maximum temperature and sunshine hours. The incidence had negative correlation with the minimum temperature and rainfall. Studies on the field evaluation of the fungicides against pathogen showed that, copper oxychloride (0.3%) was the most effective fungicide showing minimum per cent disease severity followed by carbendazim (0.1%), propiconazole (0.2%), propineb (0.1%) and hexconazole (0.2%). mancozeb (0.25%) and thiophanate methyl (0.2%) were relatively less effective. |
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Date |
2016-08-20T09:54:01Z
2016-08-20T09:54:01Z 2004 |
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Type |
Thesis
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Identifier |
http://krishikosh.egranth.ac.in/handle/1/73101
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Language |
en
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Relation |
D7620;
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Format |
application/pdf
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Publisher |
ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
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