Dicamba and the Metabolite DCSA

South Dakota Agricultural Labs are testing for Dicamba with an LOQ of 1 ppb and are now offering DCSA testing with an LOQ of 1 ppb.  Find below the response from Oklahoma regarding testing...

 

Here is the response to the query from Oklahoma regarding laboratory testing of the resistant cotton and soybean crops.

 

“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 toDCSA, 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 forDCSA.  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.”

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