Hyderabad: Farm scientists at the city-based Directorate of Rice Research have developed a system to forewarn rice blast and other pests on various varieties of rice grown in the country.
The forewarning system is based on years of on-field studies carried out in various districts in Andhra Pradesh. It helps farmers with accurate information on when and to what extent the rice blast fungus will attack the paddy fields.
Rice blast is caused by fungus, Pyricularia grisea, and is the most feared pest by paddy growers all over the country. The pest hits large stretches of fields and the destruction is usually widespread. Thousands of hectares of paddy fields have been hit by rice blast resulting in huge financial losses to farmers. Paddy growers usually do not suffer from crop failure but are hit mostly by this fungus.
According to DRR scientists, the intensity of the blast infection is greatly influenced by local environment and the variety of the rice grown. Forecasting of the disease has been attempted on the basis of minimum night temperature of 20 to 26 degrees Celsius in association with a high relative humidity of 90 per cent and above lasting for a period of week or more during any of the susceptible phases of growth like seedling stage, post-transplanting tillering stage, and at neck emergence.
The DRR scientists could successfully forecast the onset of the pest at least a fortnight in advance to enable farmers to get prepared to tackle it effectively. Usually diseases on crops emerge suddenly taking farmers unawares and causing heavy damage to the fields in the process. The early warning system has helped in prevention of rice blast in hundreds of hectares of farm lands across the nation.
The experiment was successfully conducted at DRR in Rajendranagar here and at Krishi Viswa Vidyalaya in Palampur of Himachal Pradesh. Data from the blast endemic areas of Andhra Pradesh and Himachal Pradesh showed that the maximum temperature of 23 to 28 degrees Celsius, minimum of 17.6 to 24 degrees Celsius, relative humidity of more than 80 per cent, rainfall of more than 3 mm per day and more than four rainy days per week were critical in the progress of rice blast.
Blast severity was high in the last sown crop in Andhra Pradesh, when compared to early sown crop. Leaf blast severity was high in different sowings, when the maximum and minimum temperatures were 29.3 degrees Celsius and 22.3 degrees Celsius, and relative humidity was 80.1 per cent. Neck phase of the disease was also maximum at these favourable weather conditions.
All these conditions led to the epidemic progress of leaf blast during the last week of September and first fortnight of October and, neck and node blast during the last week of October and first week of November.
The forewarning system developed by DRR can be utilised in agro-advisory services to gear up the crop protection activities at appropriate time. Such information would be useful in linking to the integrated disease management strategy, which will further help in reducing the consumption of fungicides and maximise environmental pollution and health hazards.
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