Dicamba

Thank you to the University of Arkansas for the dicamba injury on soybeans photograph.

Dicamba-tolerant seeds were registered for use during the 2016 growing season.  Due to the lack of the accompanying dicamba formulation which was required to be used with the seeds, many growers used older formulations and the resulting drift and volatilization issues caused widespread crop damage and enforcement issues.

EPA registered the new dicamba formulation in the fall of 2016.  So far during the 2017 growing season we are still seeing continued widespread crop damage and enforcement issues in some states.

AAPCO is collecting educational materials, Special Local Need registrations, and dicamba webpages from the states to share in one place.

Please send info to Amy Bamber, AAPCO Executive Secretary, aapco.sfireg@gmail.com

Laboratory considerations follow the state information below.

Arkansas

Arkansas has cancelled the sale and use of agricultural dicamba due to unprecedented enforcement issues.  Arkansas’ Dicamba Updates webpage

Arkansas also has mandatory Dicamba training to use the products in state.

Missouri

Missouri’s Department of Agriculture had issued a temporary SSURO for all dicamba products while they are developing 24(c) labels. The 24(c) labels are now registered and include significant restrictions on wind speed, application timing, only certified applicators (no applications under the supervision of…), must complete a notice of application prior to application, and recordkeeping for all applications, even private applicators, kept for 3 years. See their Dicamba Facts webpage.

Georgia

Georgia has issued 4 Special Local Need/ 24(c) labels for dicamba.  See their 24(c) labels and mandatory training information here:  Georgia’s Auxin Training webpage

Tennessee

Tennessee has issued several restrictions on dicamba due to enforcement issues, including banning all use of older formulations for the remainder of the 2017 growing season.  See their updates here.

Mississippi

Mississippi has classified all dicamba products for use in dicamba-tolerant systems as Restricted Use, has a 10mph wind speed restriction, and requires training prior to purchase of the products.

Alabama

Alabama is requiring training for all dicamba and 2,4-D uses on dicamba and 2,4-D tolerant crops, through 24(c) registrations, as well as a wind speed restriction up to 10 mph.  See their guide here.

Florida

Florida has an Organo-Auxin rule in place, which restricts many uses of auxin herbicides.  Florida’s Extension Service has issued guidance regarding the new dicamba products as well.

North Carolina

North Carolina has issued five 24(c) labels and has an Auxin Resources page.  The 24(c) labels require mandatory training through the Extension Service, and include a 10 mph windspeed restriction.

Indiana

Indiana has an extensive Dicamba resources page that includes details about the state RUP status of the products, as well as tank mix cleaning, reporting damage and other topics.


Laboratory Considerations

Provided by EPA Headquarters:

“We have been told that the EPA lab is telling regional labs that to recover dicamba in resistant crops like cotton and soybeans you need to test down to the 1 ppb level. Can you confirm this information?”

Note, that because dicamba breaks down quickly and completely to DCSA, it is recommended that for dicamba-resistant crops, testing for DCSA be performed in addition to dicamba.

Based on field and laboratory studies for dicamba resistant crops, dicamba breaks down quickly (within hours) into metabolite DCSA.  Therefore, residue of dicamba on those crops will be minimal (estimated to be in low ppb level based on a 1 lb ai/A application rate) during the first day or so after application, and non-existing afterwards.  So if you are looking for dicamba in dicamba resistant crops, sampling of those crops must be done no later than a day or 2 after application, and yes, you need to go down to at least to 5 ppb level or below for LOQ (2 ppb or below for LOD).  Otherwise, look for DCSA.  This metabolite is more persistent and can still be detected in samples that were collected a month or so after application.

As for “Is there any difference when testing if it is a low-volatility formulation or the old suspected of the crop damage”, the answer is “no.”

If you need additional technical information, please contact Thuy or Yaorong.

Thuy Nguyen nguyen.thuy@epa.gov 410-305-2905 or Yaorong Qian qian.yaorong@epa.gov 410-305-2626

Dicamba and Degradates Residue Analysis – Presentation given to the SFIREG Joint Working Committees in April 2017 by Thuy Nguyen


South Dakota Ag Labs can provide Dicamba and DCSA testing to 1ppb LOQ.  Their turn around time is 7-10 days.  The cost is $162. and can do a screen of the PGRs for $212 (13 analytes).  They are working on the 5-OH Dicamba method and awaiting receipt of the standard to perform that method as well.

For more information contact:

Regina L. Wixon, Ph.D.
Director
South Dakota Agricultural Laboratories
1006 32nd Ave. Suite 105
Brookings, SD 57006
Ph 605-692-7325
Fax 605-692-7326
www.sdaglabs.com