"Genetic uniformity is central to modern farming. It leaves us vulnerable to plant disease breakouts."
"Nobody really knows how the fungus Bipolaris maydis got into the cornfields of the United States. But by summer of 1970, it was there with a vengeance, inflicting a disease called southern corn leaf blight, which causes stalks to wither and die. The South got hit first, then the disease spread through Tennessee and Kentucky before heading up into Illinois, Missouri, and Iowa — the heart of the Corn Belt.
The destruction was unprecedented. All told, the corn harvest of 1970 was reduced by about 15 percent. Collectively, farmers lost almost 700 bushels of corn that could have fed livestock and humans, at an economic cost of a billion dollars. More calories were lost than during Ireland’s Great Famine in the 1840s, when disease decimated potato fields.
Really, the problem with southern corn leaf blight started years before the 1970 outbreak, when scientists in the 1930s developed a strain of corn with a genetic quirk that made it a breeze for seed companies to crank out. Farmers liked the strain’s high yields. By the 1970s, that particular variety formed the genetic basis for up to 90 percent of the corn grown around the country, compared to the thousands of varieties farmers had grown previously.
That particular strain of corn — known as cms-T — proved highly susceptible to southern corn leaf blight. So, when an unusually warm, wet spring favored the fungus, it had an overabundance of corn plants to burn through.
At the time, scientists hoped a lesson had been learned."
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