In the early 1990s, 3394 was a magic number for farmers. That was the designation of a spectacularly successful variety of corn developed by Pioneer Hi-Bred International of Des Moines, Iowa. Pioneer 3394 rose in popularity until by 1995, several years after its introduction, it was grown all over the corn belt, from Minnesota to Texas and from the East Coast to Nebraska. That summer, however, it became apparent that the corn crop was in trouble. Pioneer 3394 was falling victim to precisely the kind of epidemic described in "The Last Harvest."
Farmers had made 3394 a cornbelt superstar for two reasons: It yielded more corn than other varieties, and it performed well in many different climates. The ability to grow well in different areas is unusual. Many varieties that do well in warmer areas do not produce the same yields farther north. Varieties that yield well in wetter areas are often unsuitable for drier climates. In variety 3394, however, Pioneer had found a corn with wide adaptability. Sales of that single variety of corn made up 15 percent of the more than $1 billion worth of corn seed Pioneer sold in 1995. That put it far ahead of any other Pioneer corn variety. The result was that a single variety, among the thousands that might have been planted, dominated the U.S. corn belt.
In the summer of 1995, farmers discovered the dire consequence of heavy reliance on a single crop variety. A devastating disease called gray leaf spot, normally a minor problem for corn farmers, became a major problem. It began spreading rapidly, and by mid-summer it was present in cornfields across Missouri, Iowa, Illinois and Indiana. Market analysts worried about the effect of the epidemic, especially because it was occurring in a year when corn was also taking a beating from bad weather. "We may be in for a disaster of Biblical proportions in terms of feed corn," said Paul Prentice, the president of Farm Sector Economics, a consulting firm in Colorado Springs, Colo. A plant pathologist at Purdue University examined cornfields all over Indiana and found gray leaf spot in every field he looked at. Analysts expressed fears about the nation's corn supply--stockpiles of corn were already at a 20-year low.
The widespread adoption of Pioneer 3394 had helped turn a minor problem into an epidemic. Different varieties of corn vary in their susceptibility to gray leaf spot. Some are better able than others to withstand an outbreak. Unfortunately, Pioneer 3394 was not one of the resistant varieties. It was exquisitely vulnerable to gray leaf spot. With the unexpected appearance of gray leaf spot, the farmers who had so enthusiastically embraced Pioneer 3394 realized they had a serious problem.
Pioneer quickly noted that it hadn't fooled anyone about the risk. The company rates each of its hybrid corn varieties for their susceptibility to a variety of diseases. A rating of "1" indicates maximum susceptibility; a rating of 9 means the variety is highly resistant to the disease in question. Pioneer 3394's rating for gray leaf spot was 2--nearly the lowest rating it could have. Farmers knew that when they purchased their seeds. Yet many of them found 3394's appeal irresistible. Its rating for yield was 9--the highest possible.
By the time gray leaf spot appeared, the corn had been planted and farmers had no choice but to ride out the epidemic. The vast areas of the U.S. grain belt that had been planted with 3394 were susceptible to disease. As reports of damage came in, corn prices surged. In February, 1996, analysts warned that prices could break through the once-improbable level of $4 per bushel. By April, corn prices had reached a record $4.97 per bushel, double what they had been a year earlier. Corn stockpiles continued to fall. If the trend continues, one analyst warned, the United States "will run out of corn." Consumers, too, were likely to feel the pinch. Economists warned that food inflation, then between 2 and 3 percent, could double in the year ahead. The average family, spending $6500 a year for food, faced a possible increase of $400 per year in its grocery bill.
Pioneer 3394 provides a dramatic example of the potential dangers of America's growing reliance on a very narrow range of crop varieties. As farmers move increasingly to fewer and fewer varieties of corn and other crops, the gene pool shrinks. As that happens, the danger of a widespread crop epidemic rises.
The reason is simple. Earlier in American history, farmers grew a patchwork of thousands of different varieties of corn. Each year, farmers saved seeds from the best-looking and highest-yielding plants. In effect, individual farmers were breeding their own crop varieties. Corn plants differed from one farmer's field to the next. Each variety had its own profile of vulnerabilities, sensitive to some pests and diseases, and resistant to others. When a new threat arose, some varieties would succumb and others would survive. Farmers, knowing enough to plant multiple varieties to allow for that possibility, would not be wiped out. The odds were that some of the varieties they had planted would survive any threat that arose.
The picture changes when a single, wildly successful variety such as Pioneer 3394 marches across thousands of miles of the corn belt. Instead of a patchwork of different crop varieties, each with its own vulnerabilities to disease, the corn belt is covered with millions of acres of a single variety. If a disease arises to which 3394 is susceptible, the losses can be catastrophic. That is what happened in 1995.
Some analysts and plant pathologists downplayed the importance of gray leaf spot, blaming reduced yields on bad weather. Sorting out the relative contributions of gray leaf spot and weather was difficult, because the two problems are not separate: bad weather not only damages crops directly, it can also exacerbate gray leaf spot.
Whatever the relative contributions of weather and disease were, the debate allowed government officials to shrug off the concerns about crop vulnerability. The scientists whose work is described in "The Last Harvest" understood the dangers. Most others blamed the problem on the weather. The underlying threat posed by the genetic uniformity of American crops remained.