Herbicide Resistance: Dicamba Dancing with EPA – DTN

    Kirk Martin finds it a little more than ironic that the latest news on dicamba soybeans came on April Fool’s day. The Mason City, Ill., farmer was one of the first farmers to raise dicamba soybeans for seed. He’s been anxiously waiting for news that an herbicide to go with the trait is officially headed to the field.

    On April 1, Monsanto announced that EPA has finally moved their dicamba product to a public comment period. That would seem to be good news for farmers like Martin who are struggling with tough to control weeds such as marestail and waterhemp. However, the product still isn’t likely to make it through all the regulatory rigors in time to be used this season.

    EPA’s initial public comment period is 30 days. The agency almost always extends that comment period another 30 days and then, they have to weigh the comments and render a decision. Dow AgroScience’s Enlist Duo label offers clues of what might happen — that took five months from public comment to registration.

    Last week EPA officials informed DTN: “In early spring 2016, EPA will solicit public comments for 30 days on our proposed regulatory decision. After the comment period closes, EPA will review all of the comments and reach a final decision, which the agency expects to issue in late summer or early fall 2016.”

    Monsanto’s initial application was for what they’ve called M1691 — based on the same salt as Clarity herbicide. Once that registration is received, the company plans to immediately apply for approval of their single dicamba (XtendiMax) and glyphosate/dicamba premix (Roundup Xtend) that contain VaporGrip. In other words, those updated products are even further out. BASF has a dicamba-only low-volatility product called Engenia and it appears it will not have a separate comment period.

    Martin said he’s disappointed he won’t likely have this tool this year because he’s seen how effective the technology can be, but he also isn’t shocked by the news. “Right now, without dicamba what I’m planting is still a RR2 soybean. I get another year to look at yield data and that’s what I get.

    “I’m going into the season prepared that there will not be any dicamba used this season. I’ll load up on pre-emergence residuals and to get as clean as possible early,” he said.

    If weed resistance to glyphosate has taught farmers anything, it is that depending on any single herbicide has long-term implications. Weed scientists have been harping for years that these new herbicide trait technologies are not the answer to weed resistance. University of Missouri weed scientist Kevin Bradley’s recent blog should be required reading for every soybean grower. He warns that growers will still need to rely on pre-emergence residual herbicides, mix effective herbicide sites of action at every application and make timely applications to small weeds.

    “Let’s not forget that there are 2,4-D and dicamba-resistant weeds already,” Bradley said. “In fact, we have recently confirmed the presence of a 2,4-D resistant waterhemp population in a corn/soybean field in Missouri, as have weed scientists in Illinois. And although there are no known dicamba-resistant pigweeds in the U.S. yet, weed scientists in Arkansas selected for a dicamba-resistant Palmer amaranth in a greenhouse setting using less than labeled rates of dicamba over three generations,” he added.

    The Arkansas experiment was done in a controlled environment, but it showed that “abusing” the technology will result in weeds that are resistant to dicamba. That’s no April Fool’s.

    You can read Kevin Bradley’s entire blog here.

    Pamela Smith can be reached at


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