Proposed Maximum Residue Limit PMRL2017-29, Clethodim

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Pest Management Regulatory Agency

2 November 2017

ISSN: 1925-0843 (PDF version)

Catalogue number: H113-24/2017-29E-PDF (PDF version)

Under the authority of the Pest Control Products Act, Health Canada’s Pest Management Regulatory Agency (PMRA) has concluded that the addition of new uses on various commodities to the product labels of Select EC Herbicide and Centurion EC Herbicide, containing technical grade clethodim, is acceptable. The specific uses approved in Canada are detailed on the label of Select EC Herbicide and Centurion Herbicide, Pest Control Products Act Registration Number 22625 and 27598, respectively.

The evaluation of these clethodim applications indicated that the end-use products have value and the human health and environmental risks associated with the new uses are acceptable.

Before registering a pesticide for food use in Canada, the PMRA must determine the quantity of residues that are likely to remain in or on the food when the pesticide is used according to label directions and that such residues will not be a concern to human health. This quantity is then legally established as a maximum residue limit (MRL). An MRL applies to the identified raw agricultural food commodity as well as to any processed food product that contains it, except where separate MRLs are specified for the raw agricultural commodity and a processed product made from it.

Consultation on the proposed MRLs for clethodim is being conducted via this document (see Next Steps). A summary of the field trial data used to support the proposed MRLs can be found in Appendix I.

To comply with Canada’s international trade obligations, consultation on the proposed MRLs is also being conducted internationally by notifying the World Trade Organization, as coordinated by Canada’s Notification Authority and Enquiry Point.

The proposed MRLs, to replace or be added to the MRLs already established for clethodim, are as follows.

Table 1. Proposed Maximum Residue Limit for Clethodim
Common Name Residue Definition MRL (ppm) Footnote 1. Food Commodity



hydroxy-2-cyclohexen-1-one, including

metabolites containing the 2-cyclohex-

1-enone moiety expressed as clethodim


3.0 Spices (crop subgroup 19B) Footnote 2. Footnote 3.
0.9 All dried herbs within crop subgroup 19A Footnote 4.
0.7 All fresh herbs within crop subgroup 19A Footnote 5.
0.5 Hops (dried); garlic
0.2 Cherry subgroup (crop subgroup 12-09A)

MRLs are proposed for each commodity included in the listed crop groupings in accordance with the Residue Chemistry Crop Groups webpage in the Pesticides and Pest Management section of Health Canada’s website.

MRLs established in Canada may be found using the Maximum Residue Limit Database on the Maximum Residue Limits for Pesticides webpage. The database allows users to search for established MRLs, regulated under the Pest Control Products Act, both for pesticides or for food commodities.

International Situation and Trade Implications

MRLs may vary from one country to another for a number of reasons, including differences in pesticide use patterns and the locations of the crop field trials used to generate residue chemistry data.

Table 2 compares the MRLs proposed for clethodim in Canada with corresponding American tolerances and Codex MRLs.Footnote 1  American tolerances are listed in the Electronic Code of Federal Regulations, 40 CFR Part 180, by pesticide. A listing of established Codex MRLs is available on the Codex Alimentarius Pesticide Residues in Food and Feed website, by pesticide or commodity.

Table 2. Comparison of Canadian MRLs, American Tolerance and Codex MRLs
Food Commodity Canadian MRL (ppm) American Tolerance (ppm) Codex MRL (ppm)
Garlic 0.5  


(Onion, bulb, subgroup 3-07A)

Hops (dried) 0.5  0.5 Not established
Cherry subgroup (crop subgroup 12-09A) 0.2  


(Fruit, stone, group 12-12)

Not established
All fresh herbs within crop subgroup 19A 0.7


(Herb subgroup 19A)

Not established

All dried herbs within crop subgroup 19A

Spices (crop subgroup 19B) 3

Not established

Not established

Next Steps

The PMRA invites the public to submit written comments on the proposed MRLs for clethodim up to 75 days from the date of publication of this document. Please forward your comments to Publications. The PMRA will consider all comments received before making a final decision on the proposed MRLs. Comments received will be addressed in a separate document linked to this PMRL. The established MRLs will be legally in effect as of the date that they are entered into the Maximum Residue Limit Database.

Appendix I

Summary of Field Trial Data Used to Support the Proposed Maximum Residue Limits

Residue data for clethodim in hops, dry bulb onions, sweet cherries, tart cherries, chives, basil, fenugreek, caraway and dill were submitted to support the domestic use of Select EC Herbicide and Centurion EC Herbicide on hops, garlic, sweet cherries, tart cherries, and herbs and spices (crop group 19).

Maximum Residue Limits

The recommendation for maximum residue limits (MRLs) for clethodim was based upon the submitted field trial data, and the guidance provided in the OECD MRL Calculator. Table A1 summarizes the residue data used to calculate the proposed MRLs for hops (dried), garlic, crop subgroup 19A (herbs subgroup; fresh and dried), crop subgroup 19B (spices subgroup) and crop subgroup 12-09A (cherry subgroup).

Table A1. Summary of Field Trial Data Used to Support the MRLs
Commodity Application Method/ Total Application Rate (g a.i./ha)Note de bas de page * Preharvest Interval (days)

Lowest Average Field Trial Residues (ppm)

Highest Average Field Trial Residues(ppm)

Caraway seed

Foliar application/ 87-92

52-60 <0.22 <0.34
Dill seed

Foliar application/ 92-95

36-47 0.20 1.29
Dried basil leaves

Foliar application/ 90-91

30-31 <0.10 <0.26
Fenugreek seed

Foliar application/ 86-87

29-30 0.225 0.392
Fresh basil leaves

Foliar application/ 90-91

31 <0.14 <0.14
Fresh chive leaves

Foliar application/ 87-92

30-31 <0.094 0.115
Hops (dried) Banded ground application/ 556-581 20-22 <0.18 <0.18
Onions, dry bulb Foliar post-emergent application/ 560-594 44-45 <0.094 <0.24
Sweet and tart cherries Directed application to the ground at the base of the tree/ 556-594 13-16 <0.19 <0.19

Following the review of all available data, the MRLs as proposed in Table 1are recommended to cover residues of clethodim. Residues of clethodim in these crop commodities at the proposed MRLs will not pose an unacceptable risk to any segment of the population, including infants, children, adults and seniors.

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