The next pandemic could hit global crop supplies
As plant diseases spread across continents, greater scrutiny is needed
By Caitlin Talbot
Wheat blast, a fungal disease, is poised to turn the world’s breadbasket into a chalky mess. It has spread more than 15,000km in a decade—from Brazil to Argentina, and then Zambia and Bangladesh. It may yet get to India, the second-biggest producer of wheat.
Crop-killing diseases are spreading fast. The same fungus that causes wheat blast destroys enough rice a year to feed 60m people. Potato blight, a water mould, causes up to $10bn in losses annually. Spuds are ravaged too by blackleg, a bacterial disease, and potato virus “Y”. Such pathogens bring chaos to a food system already weakened by war, climate change and export bans.
A plant pandemic could tip the world towards mass hunger. In 2024, that looks ever more likely. Most farmers rely on monocultures, which are efficient but vulnerable. If one plant is infected, the whole crop can be lost. Some diseases thrive in rain, spelling trouble for countries like India as monsoons become more erratic. Global warming also increases the range of pathogens, by enabling them to survive in hitherto hostile regions.
Fungi can travel hundreds of miles as spores in the wind. Viruses and bacteria journey with insects. The largest jumps are made with the help of humans. When diseases arrive in fields, methods of attack are devious. Blast fungus uses specialised infection cells to generate pressure around 40 times that of a car tyre to break open the leaf’s cuticle. Once inside, it kills young plants within four days.
Shipments of grain are inspected for disease, but pathogens manage to hitchhike anyway. Coffee rust, a fungal disease, evaded America’s biosecurity efforts to reach Hawaii. Pesticides afford some protection, but they are pricey and energy-intensive.
The best way to stop diseases, so far, has been to genetically engineer resistant crops. Scientists at the John Innes Centre, a plant-science institute in Britain, found two genes that confer resistance to wheat blast. Crops bred with those are safe. But the fungus will, in time, evolve to overcome them.
Greater scrutiny is needed to stop it. A blueprint is offered by the tracking of avian flu, which threatens human health. Scientists, poultry farmers and the World Health Organisation collaborate to stop its spread. Without similarly dynamic surveillance, wheat will be defenceless when disaster strikes.■
Caitlin Talbot, Social-media editor, The Economist
This article appeared in the Science and technology section of the print edition of The World Ahead 2024 under the headline “The next pandemic?”
