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Source: Nagaland Post [summ. Mod.DHA, edited]
In 2021, about 60% of rice grown on newly cleared land was devastated by blast disease. Therefore, the Sub Divisional Agriculture Office (SDAO) conducted surveillance and monitoring for early detection and timely management of pests and diseases, with special emphasis on rice blast.

There was marked improvement in the crop compared with 2021, but blast disease was detected in about 4 hectares and management measures were initiated. SDAO will continue to monitor the situation closely and urged farmers to report any pest and diseases promptly for timely intervention. They also conducted sessions with stakeholders for managing rice blast.
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[Rice blast is caused by the fungus _Pyricularia oryzae_ (previously _Magnaporthe oryzae_). It is one of the most destructive diseases of the crop worldwide, with potential yield losses of more than 50%. Symptoms include lesions on all parts of the shoot, as well as stem rot and panicle blight. When nodes are infected, all plant parts above the infection die; yield losses are severe. When infection occurs at the seedling or tillering stages, plants are often completely killed; infection late in the growth cycle generally leads to less severe damage. Depending on which plant parts are affected, the disease may manifest itself as leaf, collar, node or neck blast. More than 50 species of grasses and sedges can be affected by related pathogens, but most strains isolated from rice can infect only a limited number of cultivars.

The fungus also causes wheat blast (for example, see ProMED post 20210324.8267471). Although the pathogens are currently classified as the same species, the wheat blast pathogen is a distinct population (referred to as _P. oryzae_ Triticum population) and does not cause disease in rice.

Symptom severity and spread of the blast fungus are influenced by climatic conditions, including high humidity. The disease is also favoured by high nitrogen levels (for example, from fertilisers). The fungus is spread by infected plant debris, mechanical means (including insect activity), water and wind. Disease management may include fungicides and cultural practices but relies mainly on resistant varieties. Use of certified clean seed is essential; farm-saved seed poses a high risk of carry-over of the fungus to subsequent crops.

The fungus is highly variable; this favours the emergence of new strains with increased virulence, including host resistance breaking strains. Environmental factors may also affect plant resistance. Both resistance and defence-regulator genes have been found to be involved in host resistance against blast (see links below) and could potentially be combined ("pyramided") to develop rice varieties with broad-spectrum host resistance against blast that cannot be as easily overcome by the fungus as varietal resistance based on single genes.

India (with states):

Rice blast symptoms:
(different symptomatic forms) and
Rice fields affected by blast:, and

Information on rice blast: (with pictures),, and
Rice blast disease cycle: and
Research on rice blast host resistance: (review), and
Impact of rice blast (and other fungal crop diseases):
Information on wheat blast: and
_P. oryzae_ taxonomy and synonyms: and
- Mod.DHA


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