potato image from a photo by:
Rebecca Nelson, International
the poor tubers! These potatoes infected with late blight display white,
slimy lesions on their skins.
Copyright and Courtesy Ohioline
||Return of late blight
Even if you
slept through world history class, you remember the Irish potato famine.
Starting in 1845, a disease called "late blight" attacked the spuds that
were feeding the densely packed island.
The British government
responded fairly well to the starvation at first, but
ultimately failed to prevent the deaths
of at least 1 million Irish during a famine that lasted until about 1850.
Farmers were evicted
in large numbers, the farming system broke apart and emigration became a
way of life, helping the Irish become a key ethnic group in the United States.
Late blight and the famine also left a residue of bitterness that persists
tubers left behind by pickers, gleaners are generally the poorest
of the poor.
Illustrated London News
Now, with the globe
much more crowded, potato experts report that the same disease, properly
called Phytophthora infestans, has returned with a vengeance. (Taxonomic
trivia: Although the pathogen is often called a fungus, it's more closely
related to kelp and other brown algae).
Late blight, by
any name, is a contender.
In the West, those of us who don't farm tend to ignore little pests, especially
hard-to-pronounce plant diseases, assuming that somebody will always find
a spray or another way to control them. Fungicides, unfortunately, are
of little help against the modern strains of late blight, which few potatoes
In other words,
this is one of those times when even untutored acolytes of French fries
must get close and personal with plant doctors. Properly called plant
pathologists, these folks see crop diseases as a kind of triangulation
among plants, pathogens and people.
By the mid 1840s,
the Irish were growing huge amounts of potatoes. Laboring men, says
historian James Donnelly, Jr., typically ate 12 (twelve!) pounds per
day. He adds that according to one calculation, "out of a population
of 8.5 million on the eve of the famine, about 3.3 million would have
been entirely dependent on potatoes for food, and 4.7 million at least
the most productive staple starch for Ireland's cool, damp climate,
but the island also grew barley, oats and wheat. In fact, Donnelly notes,
before the famine, these cereals provided a large proportion of Great
Britain's grain supply -- and their export during early stages of the
famine enraged the starving Irish. Although many potato varieties were
grown in Ireland -- as a kind of insurance against crop diseases --
virtually all were susceptible to Phytophthora infestans, a virulent
pathogen whose Greek name means "plant destroyer" and which turns plants
into a black, dead mush.
is even more true today, transportation played a key role in the crop
disease. William Fry, a plant pathologist at Cornell University, says
Phytophthora infestans originated and remained in Mexico's central highlands
until the mid-19th century. Through an unknown mechanism, it probably
reached United States in the early 1840s.
The blight presumably
jumped the Atlantic aboard ship in 1845, and rapidly infested European
fields. In damp conditions, Fry says, a single infected potato would
be enough to spread the deadly disease. In 1845, late blight obliterated
one-quarter to one-third of the Irish potato crop.
That was the
prologue. In 1846, "It's not too much to say the crop was a total disaster,"
says Donnelly, a professor of history at the University of Wisconsin-Madison.
to Ireland of potatoes, which originated in the Andes, allowed the population
to soar. Between 1750 and 1845, the Irish population "mushroomed from
about 2.6 million to 8.5 million, or by some 325 percent," writes Donnelly
in a new book on the famine (see "The Great..." in the bibliography).
the diet may have been "stodgy and monotonous," but says buttermilk
and fish filled out the protein. British Army records show that Irish
men were relatively healthy, indicating that the boring diet was also
all diseases, the social and political context contributed to the blight.
The deaths were not due just to disease, but also to overpopulation, extreme
fragmentation of holdings, enormous income inequalities between rich and
poor, and British hostility to Ireland. The initial response of the British
government -- removing a ban on grain imports and creating make-work jobs
for destitute farmers and laborers -- was helpful, but London soon washed
its hands of its Irish woes, with deadly effect. "If from the fall of
1847 the government had taken a more interventionist role with respect
to distributing food among the classes that were in misery," Donnelly
says, "it had the capacity to save several hundred thousand lives."
Between 1848 and
1850, he adds, when the Irish "were still dying in large numbers, the
problem was not the absence of food, but the fact that it wasn't being
distributed to those in greatest need." In a pattern that persists today,
the problem was not simply a plant disease, Donnelly insists. "Ultimately,
people died because they were so impoverished and because of appalling
What is late
blight, and why is it back in the news?