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Dicamba Updates--Nov. 2018

The much-anticipated EPA decision regarding the re-registration of dicamba for use on dicamba-tolerant crops was published on Oct. 31, 2018. Click here for the EPA News Release and here for more information from the EPA about dicamba and its use on tolerant crops. The following label changes that pertain to soybeans are copied from these articles.

•    Two-year registration (until December 20, 2020).

•    Only certified applicators may apply dicamba over the top (those working under the supervision of a certified applicator may no longer make applications).

•    Prohibit over-the-top application of dicamba on soybeans 45 days after planting and cotton 60 days after planting. (Author comment: According to Dr. Bob Hartzler of Iowa State University, the initial labels stated that dicamba could be applied up to and including the R1 growth stage of soybean. Now it states that dicamba must be applied prior to R1 or no more than 45 days after planting, whichever comes first. For MG IV varieties planted on most dates in Miss., the 45-day cutoff likely will allow applications up to R1. For MG V varieties planted on most dates in Miss., the 45-day cutoff will likely not allow applications up to R1. Midsouth soybean producers should use SOYMAP to determine the estimated date of R1 for the specific Xtend variety they intend to plant on a particular date at their latitude or location.)

•    For cotton, limit the number of over-the-top applications (OTT) from 4 to 2 (soybeans remain at 2 OTT applications).

•    Applications will be allowed only from 1 hour after sunrise to 2 hours before sunset. (Author comment: This restriction is intended to prevent applications during periods when inversions are more likely to occur.)

•    In counties where endangered species may exist, the downwind buffer will remain at 110 feet and there will be a new 57-foot buffer around the other sides of the field (the 110-foot downwind buffer applies to all applications, not just in counties where endangered species may exist).

•    Clarify training period for 2019 and beyond, ensuring consistency across all three products.

•    Enhanced tank clean out instructions for the entire system.

•    Enhanced label to improve applicator awareness on the impact of low pH’s on the potential volatility of dicamba.

•    Label clean up and consistency to improve compliance and enforceability.

•    The registration for all dicamba products will automatically expire on December 20, 2020, unless EPA further extends it.

Producers should be aware that restrictions that will place additional limitations on dicamba applications in 2019 likely will be imposed by individual states.

Results from 2018 research (Delta Farm Press Oct. 17, 2018 and Oct. 23, 2018) conducted by Dr. Jason Norsworthy of the Univ. of Ark. indicate that water movement from a field or portion of a field (either from rainfall or irrigation) where dicamba was applied to a dicamba-tolerant crop can lead to off-target movement of dicamba in the water that leaves that field. Thus, producers who irrigate non-Xtend soybeans with water from a ditch or canal (relift or tailwater recovery) should consider whether or not that water came from a dicamba-treated field.

Dr. Norsworthy’s research also indicates that the addition of Roundup to dicamba in a spray mix lowers the pH of the spray solution, and this increases the formation of the dicamba acid, which is known to be highly volatile. This provides impetus to look at other herbicides such as SelectMax with grass efficacy to mix with dicamba since it has no effect on pH of the spray solution.

Composed by Larry G. Heatherly, Nov. 2018,