Nipping wheat blast in the bud

Recently wheat blast disease found its way into India, through the Bangladesh border, affecting the crop in the bordering districts of Murshidabad and Nadia in West Bengal. ‘Blast’ is a fungal disease that infects crops such as rice, wheat and oats.

What is it?

Wheat blast is caused by a fungus, which was first identified in Brazil in 1985. It infects all the parts of the wheat crop above the ground, particularly the cereal head. It closely resembles the symptoms of ‘blight’ disease (small brown dots that appear on leaves and stems). The infection leads to reduction in crop yield and grain quality.

This fungal disease is spread through infected seeds, airborne spores and infected crop residues and seeds. The symptoms are completely or partially bleached spikes and it affects the stem, impacting spike formation in the wheat crop. Infection during the growth of the crop would lead to no grain but, if the fully grown crop is infected, it leads to shrivelled, small or light-weight grains or discolouration of the wheat. Deformity in the grain could happen within a week, leaving farmers no time to respond to the threat.

Most fungicides are ineffective in controlling this blast. Scientists and researchers have not fully understood the complexity of the wheat blast fungus, making it difficult to control the attack. In Asia, wheat blast was first reported in Bangladesh in 2016 and caused havoc in over 15,000 hectares of wheat.

How to prevent it?

Farmers burn the infected wheat crops to stop the disease from spreading. Some also quarantine the infected area to stop the disease from spreading to healthy crops. Crop rotation is another method to prevent and reduce pathogens in the field. However, if wheat is to be sown in the neighbouring fields or surrounding areas, immediate removal of crop residues and weeds post harvest is compulsory for infection-free crop growth. Since wheat blast is usually a seed-borne disease, treatment of wheat crops with fungicides and chemicals at the seedling stage can make the crop immune to the disease. Continuous monitoring and surveillance of wheat fields is necessary during and after a wheat blast situation, says the government. Using wheat varieties having genetic resistance to fungal infection too can help prevent blast in wheat crops, it adds.

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