Deadly disease wheat blast reaches South Asia

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By Mike Listman/CIMMYT

EL BATAN, Mexico (April 7,2016)- One of the most fearsome and intractable wheat diseases in recent decades is wheat blast, caused by the fungus Magnaporthe oryzae.

First sighted in Brazil in 1985, blast is widespread in South American wheat fields, affecting as much as 3 million hectares in the early 1990s and seriously limiting the potential for wheat cropping on the region’s vast savannas.

Blast wheat Duveiller Brazil 2009 (2)

Diseased wheat spikes carry shriveled or no grain at all. Photo: CIMMYT

The pathogen can be spread by seed and also survives on crop residues. Currently, most varieties being planted are susceptible and fungicides have not been effective in controlling the disease.

Experts had feared the possible spread of blast from Latin America to regions of Africa and Asia where conditions are similar. A severe outbreak of blast in key wheat districts of southwestern Bangladesh in early 2016 has confirmed the truth of these predictions. The consequences of a wider outbreak in South Asia could be devastating to a region of 300 million undernourished people, whose inhabitants consume over 100 million tons of wheat each year.

For more detail regarding wheat blast disease, suggested control measures, and links to selected scientific literature, click here.

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Comments (3)

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    DrP.Bhattacharyya

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    As Cimmyt is also working West Bengal ,India and neibouring country is Bangladesh,we also fear the outbreak of wheat blast disease in the adjoining blocks of south western Bangladesh.In West Bengal,we have area in 3.50 lakh ha.
    Kindly suggest some preventive steps to combat the disease.
    Dr.P.Bhattacharyya,Director of Agriculture,Govt. of West Bengal.

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    Dr.P.Bhattacharyya

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    Let me know how we can take up preventive steps to stop entry of wheat blast disease from southwestern areas of Bangladesh to adjoining blocks in West Bengal,India?

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    Pawan Singh

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    Dear Dr. Bhatacharyya

    The preventative steps could include:
    1) Seed quarantine, which is the most important measure when the disease has not entered the region; Use new and clean seed. New seed that is used for planting should be grown in a region not infected with Wheat Blast. Seed treatment is very effective and should be done as a additional preventive measure.
    2) MoT spore surveillance. Since the spores are air borne, it is very likely that they can cross the India-Bangladesh border and cause epidemics in West Bangal. So active spore surveillance is critical. The protocols are available in publications by South American researchers and should not be difficult to learn and adopt in India. Once the spores are identified, fungicide application in the neighboring region is strongly recommended to prevent the further spread and epidemics.
    3) Field blast survey. Once fields with blast infected spikes are identified, fungicide application is recommended, not only to control the disease but also to control the pathogen concentration. And it is very critical not to use the grains harvested from the fields as seeds.
    4) Sowing wheat varieties with some level of resistance to blast. Since if a susceptible cultivar is sown, then the disease will be difficult to be controlled by fungicide application. Fungicides usually show their best control on cultivars having moderate level of resistance to blast.

    Hope the words are useful.

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