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
Abstract
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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