The ubiquitous Russet Burbank is the king of potatoes in America, thanks in large part to the fact that it is the primary potato used to make McDonald’s French fries. But while it may produce the perfect fry—and boasts a superb shelf life—the Russet Burbank is also greedy, requiring lots of water and fertilizer. Though originally bred for resistance to late blight, the fungal disease that caused the Irish potato famine, in production-scale agriculture it’s susceptible to early blight, late blight and the Colorado potato beetle. It’s virtually impossible to produce in quantity without herbicides, insecticides and fungicides. The rebirth of Wisconsin’s potato industry coincided with the growing use of these agricultural chemicals in commercial agriculture after World War II.
At first this was considered progress. But perceptions of pesticides began to shift in 1962 with the publication of Rachel Carson’s exposé of DDT, Silent Spring. Environmental concerns mounted every time a new substance—alar, aldacarb, atrazine—made headlines.
That was the terrain in 1979 when Walt Stevenson PhD’73, now an emeritus plant pathologist, arrived back in Madison to assume the chair of his Ph.D. mentor. That year an epidemic of late blight had farmers spraying potato fields relentlessly, 12 to 16 times a year, sometimes as soon as the plants broke the ground. And understandably so: When late blight surfaced it cost producers $12 million, out-of-pocket. “When you have late blight in the area, you just don’t sleep when you’re a grower,” says Stevenson.
But for all the cost and potential health risk, growers weren’t necessarily spraying scientifically. They followed product labels and their instincts. But these chemical tools are not one-size-fits-all, and CALS researchers began working with growers on a more scientific, interactive approach. Scientists closely studied environmental conditions to identify when blight emerged, while scouts scoured fields, reporting back on pest and crop conditions. Researchers crunched the numbers to determine whether the risk of blight was high, alerting farmers to spray only when the situation merited.
The project focused on late blight first, and the forecasting soon reached the point of preventing from two to four chemical treatments. The real surprise came from Steve Diercks, a potato grower in Coloma, Wisconsin, who had volunteered a field where Stevenson and his students were testing their early blight forecasting techniques. Not only had Diercks sprayed the test plot only when told to, he revealed at the end of the year that he had scaled up the experiment, running his entire operation on the recommendations: “He followed the science and he believed in the science,” says Stevenson, still flattered and a little flabbergasted.
The success of disease forecasting meant farmers could reliably reduce the number of fungicide applications and still get good—or maybe even better—disease management. The technique gained power when other inputs were added. For example, using monitoring to inform irrigation cut back on water use, which in turn reduced the leaching of pesticides and fertilizers into the water. This meant more nitrogen available to the plant, making it more resistant to early blight, and less pollution.
This ecologically informed technique is at the heart of integrated pest management, or IPM. It’s adaptive, science-based and sometimes downright clever. In the case of the Colorado potato beetle, for instance, simple science deduced at which point in development the beetle was most vulnerable to insecticide. But it was a stroke of ingenuity to plant a “trap crop” bordering the field to attract the beetles. The innovation allowed farmers to get more mileage out of using less pesticide.
IPM engages a farmer’s stewardship and entrepreneurial instincts. For example, while Diercks was using the early blight forecasting, he realized he was just three weeks from harvest and still hadn’t sprayed. He wondered: How much damage could early blight do in those three weeks? Could he avoid spraying altogether?
“He never would have asked that question if he hadn’t already eliminated the first four sprays,” says Stevenson. “He wasn’t doing this blindly. He was looking at the environmental data, he was plugging this into the software, he was walking the field. He was making an informed decision and asking what I think were the right questions.”