Plant Health Week – day 2

A couple of years ago I was writing a paper on how modelling can be used to address the epidemiology aspects of One Health. I was looking for examples when outbreaks of plant pests and pathogens were linked to catastrophic changes in human health. It was then that I became aware of the Bengal Famine of 1942-43.

In 1942 in Bengal, a province of then British India, a fungal infection, Cochliobolus miyabeanus (Brown Spot), was spreading through rice fields. The impact of the disease was intensified by tropical storms on 16-17 October which widely distributed the fungal spores while also killing 14,500 people and destroying fields and rice paddies.

When rice plants were attacked by the fungus, brown patches and discolouration appeared on leaves and stems, and the plants started to die.

Brown spot patches
http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/diseases/item/brown-spot

The resulting carnage caused estimated yield losses of up to 91% of rice.

Massive starvation followed with the resulting decrease in resistance to diseases. Meanwhile, the weather also created conditions conducive to mosquito breeding leading to an outbreak of malaria. While the first wave of deaths (Winter 1942) was largely caused by starvation, the second wave (1943-44) was dominated by human disease, with malaria, cholera and smallpox thriving in an already affected population. As a result, an estimated 2-3 million people died in a population of 60m.

Bengal Famine
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Even today, rice seedling mortality rate of up to 60% caused by Brown Spot is recorded in some countries and crop yield can be reduced by up to 40%. Prevention is based on disease-free seed and resistant varieties as well as such practices as less dense planting and keeping weeds down. Soil and plant pesticides are also used to fight the disease.

There is an ongoing dispute about the origin and course of the Bengal Famine. The context was the middle of World War 2 with a threat of Japan invasion of British India. But, the British and local government and merchants have been accused of gross mismanagement of food supplies and thus of either causing or not alleviating the famine and death of so many people.

“Though administrative failures were immediately responsible for this human suffering, the principal cause of the short crop production of 1942 was the [plant] epidemic … nothing as devastating … has been recorded in plant pathological literature”.

Padmanabhan SY. The Great Bengal Famine. Annu.Rev.Phytopathol. 1973; 11(1): p. 11-24.doi:10.1146/annurev.py.11.090173.000303

Without going deeply into the political and social causes of and mechanisms for the Famine, the events of 1942-43 show how a plant disease outbreak can become a tipping point and trigger massive suffering.

On a personal note, here is me in India, working with colleagues on plant pest detection and control:

Own library.