UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C

. 20460

MEMORANDUM

Date: May 27, 2015 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

SUBJECT: MCPA. Residue Chemistry Data Requirements for MCPA (2-methyl-4-chlorophenoxyacetic acid) use on Alfalfa and Clover.

PCCode: 030501,030502 , 030516 , 030564 Decision No .: 505072 Petition No.: Not Applicable Risk Assessment Type: Not Applicable TXR No.: Not Applicable MRID No.: None

FROM: Danette Drew, Chemist

_ ......._ _ Risk Assessment Branch V Health Effects Division (7509P) Office of Pesticide Programs DP Barcode: 0427332 Registration No.: Not Applicable Regulatory Action: Registration Review Case No.: 0017 CAS No.: 94-74-6 40 CFR: §I 80.339

THRU: William Donovan, Ph.D., Chemifit 

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# ~**~· ~**  Michael Metzger, Branch Chief 

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Risk Assessment Branch V NII •

TO: Health Effects Division (7509P) Office of Pesticide Programs

Khue Nguyen, CRM Neil Anderson, Branch Chief Risk Management and Implementation Branch 1 Pesticide Re-evaluation Division (7508P) Office of Pesticide Programs

Page 1of3BACKGROUND

The Pesticide Re

- evaluation Division ( PRD ) has requested that the Health Effects Division ( HED ) determine the residue chemistry data t hat would be required to support the use of the selective, post

- emergence, systemic herbicide MCPA (2

- methyl

- 4

- chlorophenoxyacetic acid) on alfalfa and clover . There are currently two uses listed on MCPA labels that could result in residues on alfalfa and clover : 1) application of MCPA to small grains (barley, oats, rye, and wheat) that are underseeded with alfalfa or clover (or other legumes), and 2) direct application of MCPA to established alfalfa and clover stands. There are adequate residue data to su pport the application of MCPA dimethylamine salt (DMAS) and MCPA 2

- ethylhexyl ester (2

- EHE) to small grains underseeded with alfalfa or clover . There
are tolerance s established for residues of MCPA on alfalfa forage (0.5 ppm) and hay (2.0 ppm) based on field trial data for wheat that had been underseeded with alfalfa. There are also the
same tolerances for residues of MCPA on the forage and hay of clover, lespedeza, trefoil, and vetch , based on translation from alfalfa

. This translation was permitted be cause t he MCPA Task Force had stated that use of MCPA on nongrass livestock feeds was to be restricted to small grains underseeded with alfalfa, clover, lespedeza, trefoil, and vetch. There are no outstanding residue data required to support the labeled u se of MCPA on small grains underseeded with alfalfa , clover, lespedeza, trefoil, and vetch (F. Fort, D307890, 8/14/2004, MCPA: Revised Product and Residue Chemistry Chapters for the Reregistration Eligibility Decision ).

There do not appear to be any residue data available to support the direct application of MCPA to alfalfa and clover stands

. Direct application to alfalfa and clover could result in residues greater than those resulting from the application to a small grain crop covering the alfalfa and clover ; the grain crop provides a protective canopy that could potentially decreas e the amount of pesticide reaching the underseed crop

. T he current tolerances for MCPA on the forage and hay of alfalfa and clover may not be adequate to cover residues t hat may r esult from direct application to those crops

. The direct application use s for alfalfa and clover should be removed from the MCPA labels or residue data should be submitted to support those uses

. In order to support the use of MCPA on alfalfa and clover stands, crop field trial data are needed. The tr ial s should be performed according to the 860.1500 Guideline. A minimum of 12 trials for alfalfa and 12 trials for clover are required (for a national, not geographically restricted, use)

. Geographic location of tria ls should represent the distribution of the major growing areas for those crops. T he tr ia ls should reflect the maximum application rates, minimum retreatment intervals, and minimum pre

- harvest intervals (PHIs) on the current labels (alternatively, labels may be changed to reflect the field trial conditions if a different timing and rate are desired )

. Tr ia ls are required for both the of MCPA dimethylamine salt (DMAS) and MCPA 2

- ethylhexyl ester (2

- EHE) formulati ons. Residues of the parent MCPA compound and the metabolite 2

- HMPCA [(4

- chloro

- 2

- hydroxymethylphenoxy) acetic acid] should be determined separately and combined. The tolerances for MCPA on the hay and forage of alfalfa and clover will be re

evaluated af ter receipt of acceptable residue data.

Page 2 of 3Conclusion: There are adequate residue data to support the application of MCPA to small grains underseeded with alfalfa or clover. There are no residue data to support the direct application of MCPA to alfalfa and clover stands which could result in higher residues than applications to an underseeded crop. The uses for direct application to alfalfa and clover should be removed from the MCPA labels or crop field trial residue data should be submitted to support thos e uses. The alfalfa and clover crop field trials should be performed according to the 860.1500 Guideline

.

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