Studies On Colletotrichum Blight Of Bitter-Gourd
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Date
2001
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Birsa Agricultural University, Ranchi
Abstract
Bitter gourd (Momordica charantia Linn.) is an important annual cucurbitaceous vegetable growing widely in Jharkhand as well as in India. The crop was severely affected by a defoliating disease Colletotrichum blight caused by Colletotrichum capsici (Syd.) Butler and Bisby. Intensity of disease varied from 37.4 to 74.9 per cent in different locations of Ranchi.
The characteristic blight symptom of the disease was observed on leaves and fruits. The pathogen was isolated, purified and proved pathogenic following standard techniques.
Among the varieties/lines of bitter gourd screened against the disease, none of them was found to be resistant. Only one variety i.e. Creeper showed moderately resistant reaction against disease. All ten plant species belonging to five families were infected during host range studies.
Disease appeared during second week of September in field and increased gradually upto maturity of the crop. Apparent infection rate was maximum on 10th October in the presence of 20.5-29.1°C and 19.9-29.6°C temperature, 69.0 88.5 per cent and 62.5-91.3 per cent relative humidity, 0.3-9.5 mm mean rainfall and 2-4 numbers of rainy days. Significant negative correlations were established between minimum temperature, maximum and minimum relative humidity, mean rainfall, rainy days and disease development. Stepwise multiple regression analysis clearly indicated that minimum relative humidity and numbers of rainy days significantly negatively contributing in the prediction of disease development and accounted for more than 89 and 84 per cent variation, respectively.
Vitavax, Tilt and Thiram inhibited cent per cent growth of the pathogen in vitro. Rest fungicides in order of superiority were Topsin-M, Kitazin, Bavistin, Captaf, Benlate, Contaf, Indofil M-45, Blitox-50, Kavach and Ridomil.
Vitavax (2g kg seed) and Topsin-M (2g kg seed) treated seeds gave maximum germination and elimination of seed borne infection, respectively.
Under field condition, integration of seed treatment with Vitavax and spraying of Tilt (0.1%) managed the disease efficiently with minimum disease intensity and highest fruit yield. Seed treatment with Vitavax and spraying of Topsin-M (0.05%) was next effective treatment with highest per rupee return..