BIOLOGY AND MANAGEMENT OF STYLOSANTHES ANTHRACNOSE CAUSED BY Colletotrichum gloeosporioides (PENZ.) PENZ. AND SAGO.

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Date
2001-08-06
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
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Colletotrichum gloeosporioides was isolated from anthracnose infected stylosanthes leaf. The pathogenicity was proved by spraying monoconidial culture which resulted in formation of cream to light grey centres and dark margins and elliptical stem lesions similar in colour to leaf lesions. The conidia were cylindrical or oblong, hyaline single celled and measured 16.23 x 7.81 pm from culture, while 15.60 x 7.42 pm from infected tissue of Dharwad isolate. Richards's medium was the best synthetic medium to support maximum mycelial growth of the fungus. The fungus reached maximum growth on 14th day of incubation, sucrose, tyrosine and magnesium sulphate yielded maximum dry mycelial growth of the fungus among carbon, nitrogen and sulphur sources respectively. The temperature of 30°C, alternate cycles of light and darkness and RH 95 per cent were found to be best for the funged growth. The pathogen was able to survive in unsterilised soil for a period of two months. But survival was for more than seven months on infected leaves fallen on ground. The pathogen C. gloeosporioides was found seed transmissible and survived in the seeds for upto one year and no host except stylosanthes was infected. Plants were more susceptible from 30 to 45 days period for infection by the fungus. In vitro studies indicated that, 30''C temp>erature, 100 per cent relative humidity and continuous light intensity period for 72 hours showed maximum anthracnose lesion development. Benomyl, bayleton and difenconazole were most effective systemic fungicides. Whereas, Dithane M-45, captan, clerodendron and Trichoderma harzianum were found to be best non-systemic fungicides, plant extract and bioagent respectively in inhibiting the mycelial growth of the fungus. The addition of plant extract (Clerodendron inerme) and bioagent (T. harziarmm) in the spraying schedule along with benomyl was found to effective in reducing the disease.
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