An anonymous reader quotes a report from NPR: Dicamba, an old weedkiller that is being used in new ways, has thrust Kevin Bradley, a professor of weed science at the University of Missouri, and a half-dozen other university weed scientists into the unfamiliar role of whistleblower, confronting what they believe are misleading and scientifically unfounded claims by one of the country's biggest seed and pesticide companies: Monsanto. The tensions between Monsanto and the nation's weed scientists actually began several years ago, when Monsanto first moved to make dicamba the centerpiece of a new weedkilling strategy. The company tweaked the genes in soybeans and cotton and created genetically modified varieties of those crops that can tolerate doses of dicamba. (Normally, dicamba kills those crops.) This allowed farmers to spray the weedkiller directly on their soybean or cotton plants, killing the weeds while their crops survived. It's an approach that Monsanto pioneered with crops that were genetically modified to tolerate glyphosate, or Roundup. After two decades of heavy exposure to glyphosate, however, devastating weeds like Palmer amaranth, or pigweed, developed resistance to it. So farmers are looking for new weedkilling tools. Dicamba, however, has a well-known defect. It's volatile; it tends to evaporate from the soil or vegetation where it has been sprayed, creating a cloud of plant-killing vapor that can spread in unpredictable directions. It happens more in hot weather, and Monsanto's new strategy inevitably would mean spraying dicamba in the heat of summer. Monsanto and two other chemical companies, BASF and DuPont, announced that they had solved this problem with new "low-volatility" formulations of dicamba that don't evaporate as easily. Yet the companies -- especially Monsanto -- made it difficult for university scientists to verify those claims with independent tests before the products were released commercially.