EPIDEMIOLOGY AND MANAGEMENT OF BLAST DISEASE OF RICE
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Date
2013
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Punjab Agricultural University, Ludhiana
Abstract
Disease surveys revealed that disease incidence and severity of rice blast on nursery plants of
Pusa basmati 1121 cultivar varied from 15.0 to 40.0 per cent and 10.0 to 35.0 per cent
respectively at different locations of Punjab during 2011 crop season. The basmati rice fields
which had high disease severity at seedling stage in the villages of Deep Singh Wala (22.0
%), Sarala Kalan and Avan Khalsa (15.0 %) were also visited during the adult plant stage and
disease severity in all the above fields varied only from traces to 4.0 per cent. Disease survey
at adult plant stage revealed that the highest disease incidence and severity was recorded from
village Dhurial (Jalandhar) and Murthli (Gurdaspur) on cultivar Pusa basmati 1121 during
2011 and 2012 crop season. Maximum colony growth and sporulation of Pyricularia grisea
was observed on Oat meal agar medium. A temperature of 250C was found to be highly
suitable for colony growth and sporulation of the pathogen. Minimum colony growth and
sporulation was observed at 15°C. Maximum colony growth and sporulation was observed at
pH 6.0 followed by pH 7.0. Among different substrates tested maximum sporulation was
observed on makra grass followed by carrot cubes. A minimum of 12 hours of leaf wetness
was required for infection and symptoms appeared within 7 days of incubation period.
Thereafter, the incubation period decreased while disease severity increased significantly with
increase in leaf wetness from 12 to 48 hours. A positive correlation between leaf wetness
duration and disease severity was observed. Maximum increase in lesion length was recorded
at 250C followed by 200C. Increase in lesion length was minimum at 100C. Under in vitro
conditions, tebuconazole proved most effective followed by azoxystrobin + difenconazole,
propiconazole and difenconazole. Under pot house conditions tebuconazole was most
effective in reducing the disease followed by propiconazole. Under field conditions,
propiconazole followed by azoxystrobin + difenconazole and tricyclazole were most effective
in reducing the disease and increasing the paddy yield.
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