Taken together, the decisions reflect an increasing political resistance to pesticides in Europe and parts of the United States, as well as the specific shortcomings of dicamba, whose tendency to drift has given pause even to the Trump administration’s Environmental Protection Agency, which has otherwise largely acceded to the wishes of the chemical industry. Dicamba has damaged more than 3.6 million acres of soybean crops in 25 states, roughly 4 percent of all soybeans planted this year in the United States.
In a statement, an industry trade group known as the Glyphosate Task Force, which includes Monsanto and Syngenta, called the European decision “discriminatory and unacceptable,” adding that “delays of this nature which are evident during the final stages of the process simply expose acute politicization of the regulatory procedure.”
But Nicolas Hulot, the French environment minister, tweeted after the vote: “Thanks to our opposition glyphosate is not reauthorized for 10 years, nor 5 years. The effort to get out of pesticides continues!”
Regarding the decision in Arkansas, Scott Partridge, vice president of global strategy for Monsanto, said in a statement on Wednesday that the company was disappointed that state regulators “voted to put Arkansas farmers at a disadvantage, but we’ll continue to follow the process to help those growers have greater choice next season.”
The European Union’s decision came after years of haggling and delay. Policymakers largely brushed aside the opinions of two of the bloc’s science agencies, which had found that glyphosate was not a carcinogen.
But glyphosate, which accounts for about a quarter of the global market, has been plunged into controversy since the International Agency for Research on Cancer, part of the World Health Organization, declared it a probable carcinogen in 2015. The finding, which has been disputed by a number of other government agencies, has made the weedkiller a magnet for controversy.
Glyphosate is also at the center of a federal case in the United States over claims that it causes cancer, and California has declared it a carcinogen, following in the footsteps of the international cancer agency.
Use of glyphosate has soared in the United States and other parts of the world over the last two decades, after Monsanto introduced crops that were genetically engineered to be resistant to the chemical. That meant key crops like corn, soybeans and cotton could be sprayed with the herbicide after they emerged from the ground. During that time, the presence of glyphosate in human urine increased 500 percent, according to a recent study by the University of California San Diego School of Medicine and published in the Journal of the American Medical Association.
Europe, by contrast, has largely shunned genetically modified crops, but glyphosate is still the Continent’s biggest seller. In Britain and Germany, it is used on as much as 40 percent of agricultural land, according to an industry trade group.
But political sentiment in Europe has been turning against Monsanto, the American company that has become the face of the agrochemical industry, even though it is in the process of being acquired by Bayer, a German chemicals giant. The European Parliament voted last month to ban glyphosate, a step that was nonbinding. And in September, the Parliament made Monsanto the first company to be banned from lobbying the chamber.
The science around glyphosate has become a muddle of allegations and counterallegations. Environmental activists have accused national regulators of hewing too closely to Monsanto’s wishes, while the industry has been exasperated that European politicians are overruling their science agencies. The litigation in the United States has only muddied the waters further, with evidence emerging that Monsanto ghostwrote both journalism and academic work, eroding trust in a company that had long been a lightning rod.
With dicamba, the industry received warnings years ago that the weedkiller was prone to drifting on crops and vegetation it was not intended to treat. Dicamba is supposed to be used with soybeans that are genetically modified to resist its effects.
Steve Smith, a member of an advisory panel set up by Monsanto, warned as far back as 2010 that “widespread use of dicamba is incompatible with Midwestern agriculture,” according to congressional testimony he gave that year. “Even the best, the most conscientious farmers cannot control where this weedkiller will end up.”
Monsanto has argued that drift is occurring when dicamba is sprayed improperly or when unapproved versions are used. Many farmers and weed scientists say it can also turn into a gas and drift in certain weather conditions.
Environmentalists called for federal action by the Environmental Protection Agency on dicamba.
“It’s long past time the agency heed independent science and protect farmers by prohibiting the use of this hazardous weedkiller,” said Bill Freese, a science policy analyst at the Center for Food Safety.