Forewarning Rice Blast in India

VI. STRATEGIES FOR THE CONTROL OF BLAST
Although blast can be managed through host resistance, cultural practices or
fungicidal treatments, the strategy for its management should be through an integrated
crop management approach, which is the most effective way to manage the disease.
However, among these the most effective and economical control of blast disease is
the development and use of resistant varieties, though most of the currently cultivated
rice varieties and Basmati varieties do not have adequate resistance.
High nitrogen application at critical growth stages is required for high yields,
but this high nitrogen levels increases susceptibility of host plants. Potash application
as per the recommendation is critical as it increases host resistance against blast and
helps in proper grain filling. However, the most practical way to control blast epidemics
is to use fungicides judiciously. Through fungicidal application, the life span of a
variety in terms of durability of resistance is prolonged. There are effective blasticides
under current usage. But, they are not used at initial stages of disease development
to curb the epidemic. Any chemical control strategies that do not allow the farmers to
economically maximise the yields have no value even if the disease is controlled.
Therefore, the time of application of fungicide need to be integrated with cultural
practices to manage the disease cost-effectively.
During vegetative stage, the blast spots initially are seen on lower leaves and
gradually spreading to the top leaves. When the initial spots of pin-head size are
seen, further N application has to be suspended and if favourable weather conditions
for the spread of the disease persist, immediate spray with an effective fungicide has
to be taken, as the records of blast incidence in the country reveal that weather
parameters are more important than other epidemiological factors. To prevent the
flare-up of the disease a regular surveillance of the crop is required because if the
sensitive stage of the disease escapes unnoticed, the later application of fungicides
will not be cost effective. The number of sprays and intervals between sprays depend
on disease prevalence and weather conditions. However, a minimum of two sprays
at fortnight intervals will keep the disease under control. To prevent neck blast, a
fungicide spray has to be given during late booting, early heading stage followed by
one more spray after 10 days to protect late emerging panicles from neck blast.
Efficient management of blast is mostly dependent on the adequate
technologies for its management, which are available and recommended at present
for the control of blast. They are given below:
1. Resistant Varieties
Forewarning Rice Blast in India
Ø Avoid planting susceptible varieties.
Ø Grow resistant varieties, such as: Rasi, IR 36, IR 64, Sasyasree, Srinivas,
Tikkana, Simhapuri, Parijatha, Salivahana or Gauthami.
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