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EPA Announces Changes to Dicamba Registration

Updates to label address concerns to surrounding crops and plants.

On October 31, the EPA announced that it is extending the registration of dicamba for two years for over-the-top use (application to growing plants) to control weeds in fields for cotton and soybean plants genetically engineered to resist dicamba.

This action was informed by input from and extensive collaboration between EPA, state regulators, farmers, academic researchers, pesticide manufacturers, and other stakeholders, according to an EPA news release. 

“EPA understands that dicamba is a valuable pest-control tool for America’s farmers,” said EPA Acting Administrator Andrew Wheeler in an EPA news release. “By extending the registration for another two years with important new label updates that place additional restrictions on the product, we are providing certainty to all stakeholders for the upcoming growing season.”

Wheeler said the following label changes were made to ensure that these products can continue to be used effectively while addressing potential concerns to surrounding crops and plants.

Dicamba registration decisions for 2019-2020 growing season

  • 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 (OTT) application of dicamba on soybeans 45 days after planting and cotton 60 days after planting
  • For cotton, limit the number of over-the-top applications 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
  • 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 cleanup 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.

EPA has reviewed substantial amounts of new information and concluded that the continued registration of these dicamba products meets FIFRA’s registration standards. The agency has also determined that extending these registrations with the new safety measures will not affect endangered species.

Over-The-Top Application Specifics

Several states placed date application restrictions in 2018. Minnesota, for example, prohibited over-the-top applications on soybeans after June 20. Per the new federal rules, soybeans planted on May 1 in states with no state date restrictions would fall within a June 20 application deadline, due to the 45-day window. However, soybeans planted on May 20 could have dicamba applied to it until July 4.

“The data was clear in 2017 that (off-target) incidents increase after June 20 and especially in July,” says Jeff Gunsolus, University of Minnesota Extension weed specialist. 

Compared with states that did not have cutoff dates, Minnesota had limited complaints of off-site dicamba movement in 2018, says Gunsolus. In 2017, there were over 250 reports of dicamba damage, he says. As of late September 2018, MDA has so far fielded 52 reports of dicamba damage covering 1,850 acres, says Joshua Stamper, director of the pesticide and fertilizer management division for the MDA. Of those acres, most were soybeans but not all, he says. 

Gunsolus says applicator training did help reduce off-target movement of dicamba in many states. However, states with no additional state restrictions like Illinois had problems with off-target dicamba movement in 2018. 

As of late September, the Illinois Department of Agriculture had recorded 330 dicamba complaints in 2018. That’s up from 246 in 2017. With no temperature and/or date cutoffs, complaints continued to come in through July and August, says Jean Payne, president of the Illinois Fertilizer and Chemical Association.

“Nearly all are soybean related,” she says.

Time of Day Applications 

The new federal label allows dicamba applications only from one hour after sunrise to two hours before sunset. In summer, this allows applications into the evening in the longest days of summer, when sunsets between 9 p.m. and 10 p.m. occur. University of Missouri (MU) researchers have found temperature inversions setting up at 5 p.m. or 6 p.m., a time when many applicators would still be spraying in June under the federal guidelines if no state restrictions applied. 

“If you read almost all pesticide labels, there is a line that says don’t apply during temperature inversions,” says Mandy Bish, MU senior research specialist. 

Temperature inversions can key off-target movement. 

Although not foolproof, smoke bombs are one way to detect temperature inversions. Smoke bombs set off at 4 p.m. by MU scientists showed fairly rapid dispersal. Ones set off at 7:30 p.m. lingered around 50 seconds, which indicated inversion presence, she says.

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