2014 Potato blight - an old threat reinvented

2014-Jan-12 to 2014-Jan-12


A new and exceptionally virulent form of potato blight, which is also resistant to most modern pesticides is spreading fast. Literature and news on the new potential threat, picked up by IBIS, alludes to the emergency from 1845, when the destruction of potato crops in Ireland, caused by the same microorganism lead to many deaths and immigration. What's even worse, the pathogen is polyphagus and it can attack multiple hosts. 

Is this a real threat and if so what is going to be the balance of containting the pathogen versus damage in 2014?




"The potato is, like the turkey, a relative newcomer, for it reached European plates less than 300 years ago. It led to a population boom. Within 70 years of the crop arriving in Ireland, the number of citizens there rose from two to nine million. Many had a diet that consisted only of that single item, plus milk or cheese – which, monotonous though it is, will support life. Everywhere, its adoption led to an increase in childhood survival. Its effects on health are shown by the dramatic increase in height, of up to an inch, that followed every introduction.

Then came disaster. In 1845, a plant disease spread throughout Europe, with Ireland the hardest hit. As the tubers rotted, more than a million died and almost a million and a half emigrated.

The late blight, as the condition is called, is due to the mould Phytophthora infestans – the “infectious plant-destroyer”. It multiplies at great speed, sending out spores that blow in the wind or float down streams. Once these reach a host, they hatch to give cells that can swim and can sense a nearby target. In warm, wet weather, these cells can live their life in just four or five days to produce a new and abundant generation that lays waste to fields. 


Fossilised DNA from ancient leaves kept in museums – one of which comes from the famine year – show that a mixture of strains attacked the plants, but that one in particular dominated for 50 years. It then disappeared and was replaced by new forms of blight, but many of those, too, have become extinct.

Now we face an emergency close to that of 1845. Within the past decade, the DNA of late blight shows that a single new and exceptionally virulent form is spreading fast. The first British examples of clone 13 A2, as it is called, emerged in 2005. Within three years that single variant, among all the billions of moulds, made up three quarters of cases, and is set to replace them all. It attacks almost all potato varieties, resists pesticides and causes a much more aggressive infection than did earlier forms. It has now reached India and China, the biggest producers of all. In its belligerence and spread, it reflects many other plant diseases that have raced across the globe in this new era of international trade.

We are too fixed in our dietary habits. Of the 200,000 kinds of flowering plant, only about 300 have ever been grown for food, and most now play only a tiny part. If potatoes become expensive treats, we will face a crisis less challenging than that of the Irish famine, but a crisis nevertheless. Even as we do, the cost of the flour, alcohol and sugar that go into the final course of the celebratory Christmas meal has dropped.

What were luxuries have turned into staples, and what once kept the poor alive may soon become a luxury. Quite what rare delicacy will fill the hole on the festive plate nobody knows. A diet of cake alone would be dull indeed. Perhaps, as Marie-Antoinette almost put it, “Let them eat chips”."