When the Arkansas state officials banned use of the weedkiller dicamba on corn and soybeans for the rest of this growing season, it was the latest roadblock in the search for an alternative to glyphosate, which is losing its effectiveness against some invasive weeds. A little over two years ago, when farm groups told the EPA that growers needed “new technology to address the weed control challenges on U.S. farms now,” they meant Dow’s combination of glyphosate and 2,4-D, not dicamba.
Sold as Enlist Duo, the glyphosate-2,4-D combo is paired with GMO seeds designed to tolerate the chemical and was considered a potential money-maker for Dow, one of the largest seed and ag-chemical companies in the world and rival of Monsanto, which makes dicamba. The Enlist Duo weedkiller also was the target of environmental groups, such as the Environmental Working Group, which faulted the EPA for a “deeply flawed and incomplete” assessment of the weedkiller.
Critics had an easy handle for attacking the weedkiller: 2,4-D, in use since the 1940s, was a component of Agent Orange, used as defoliant during the Vietnam war.
The EPA approved Dow’s new weedkiller in 2014 for use on corn and soybeans, but a year later, in November 2015, said it had new information about the synergistic effects of mixing 2,4-D and glyphosate and the possible impact on endangered species. The agency ran a new review with additional information from Dow, found there was no increased toxicity to plants, and reaffirmed its approval of the herbicide combination on Nov. 1, 2016. A court decision allowed sale of the herbicide during the review.
Dow began selling GMO cotton seeds that tolerate Enlist Duo in 2016, and said in June that it will launch GMO corn varieties under the brand name Enlist in the United States and Canada for the 2018 crop year, now that China approved import of the new strains. China is a major customer for U.S. corn. It roiled the corn market earlier this decade when it rejected cargoes that contained an unapproved Syngenta GMO variety. Dow said it was ready for “full commercialization” of Enlist soybeans “and is considering options for the 2018 season as it awaits final import approvals.” There have been “stewarded” sales of Enlist corn under Dow supervision for the past couple of seasons.
While Dow was traveling the regulatory path with its pair of herbicide and GMO seeds, Monsanto received the federal go-ahead for its dicamba-resistant cotton, soybean and corn varieties. The soybean and cotton seeds were approved in early 2016, making them a potential successor to its glyphosate-resistant strains in regions with weed problems. The EPA did not approve low-volatility formulations of dicamba for cotton and soybeans until late 2016. Monsanto, BASF and DuPont sell the new formulations.
When complaints arose in 2016 of damage due to dicamba drifting onto adjacent fields, it was blamed on over-eager farmers using older, unapproved versions of dicamba on the newly available dicamba-tolerant crops.
The problem was expected to wane this year with the release of drift-resistant formulations, but it got worse. A University of Missouri weed scientist says his survey shows complaints of dicamba damage on 3.1 million acres of soybeans this year, or 3.5 percent of all soybean plantings.
“The most important discussions we can have now are what to do moving forward,” the Missouri weed scientist, Kevin Bradley, told Farm Journal. “We can’t get into another situation where a stop sale happens and hamstrings someone’s weed management plan.”