Clarifying data requirements for herbicides used over the top of herbicide tolerant crops

This consultation closed on 27 September 2013

Consultation period

30 August 2013 to 27 September 2013

Earlier this year, the APVMA published an Operational Notice clarifying data requirements for herbicides used in genetically-modified crops and sought input and comment from stakeholders. 

The operational notice clarified the existing data requirements for a new product or a variation to a product that contains a herbicide active constituent for use in crops that have been genetically-modified for tolerance to these active constituents. For example, this includes, but is not limited to, the use of glyphosate or glufosinate on genetically-modified (GM) herbicide resistant crops such as GM cotton and GM canola.

In response to this notice, the APVMA received a number of comments by various stakeholders and based on stakeholder comments, plus subsequent discussions, the APVMA is proposing to amend the operational notice. Based on the fact that risks identified (with efficacy/crop safety, residue profiles and resistance management) arise regardless of the method of modification employed in conferring herbicide tolerance, the notice is amended to also cover all methods of modifications to achieve herbicide tolerance. Other amendments to the text have also been made to improve readability and minimise duplication where possible.

Whilst maintaining the initial purpose of the notice, due to the proposed amendment, the APVMA is providing stakeholders a further opportunity to provide comment. All comments must be provided by the closing date of 27 September 2013.

View the draft operational notice—Data requirements for herbicides used over the top of herbicide tolerant crops.

Please send your written submission by email to or by postal mail to:

Contact Officer
Pesticide Registration
Australian Pesticides and Veterinary Medicines Authority
PO Box 6182
Kingston ACT 2604

Phone: +61 2 6210 4748
Fax: +61 6210 4776



Draft Operational Notice—Data requirements for herbicides used over the top of herbicide tolerant crops


This notice clarifies the existing data requirements for registering a new chemical product or a variation to a chemical product that contains a herbicide active constituent for use over the top of a crop that contains a herbicide tolerant trait where the particular herbicide tolerant crop has been previously commercially released in the Australian market.

Herbicide tolerant crops are developed to be treated over the top with a relevant herbicide during an application window that is wider than would be the case in a non-herbicide tolerant crop.

The application of a herbicide over the top of a herbicide tolerant crop may present increased risk in regards to:

  • the efficacy and crop safety or phytotoxicity of the herbicide
  • the resulting residues, and
  • potential development of weed resistance.

An applicant for such herbicide product registration must address these areas of risk via the provision of appropriate data and/or  scientific argument. The data requirements for each of the above identified risks arising from over the top use patterns for such products are described below.

Applicants should also refer to the applicable requirements and guidelines in the Agricultural Manual of Requirements and Guidelines (Ag MORAG)  in regards other relevant legislative criteria. It is always beneficial to consider discussing requirements with the APVMA prior to commencing trials for data generation or lodging the registration application.

Efficacy and crop safety data

Efficacy and crop safety data must be provided from trials over two growing seasons of the herbicide tolerant crop using the specific formulation contained in the proposed new or varied product application. The trials must be conducted over the top of the specific herbicide tolerant crop for which over the top use is being sought. Data from trials conducted on crops with superseded commercial herbicide tolerant traits or varieties are not acceptable.

Herbicide tolerant crop varieties are grown under a wide range of climatic and edaphic conditions. Therefore, crop safety data for the relevant herbicide must be generated from an appropriately representative number of growing regions. For example, herbicide tolerant cotton crops grown in hot (tropical) conditions are more susceptible to phytotoxicity when treated with certain herbicides. Applicants must provide appropriate data to satisfy the APVMA that the particular formulation for which over the top registration is being sought does not affect crop safety of the specific herbicide tolerant crop in all such representative environments.

Residue data

The trait conferring herbicide tolerance may alter the way in which the herbicide is transformed into a residue. Those transformation pathways may be quite different to the pathways in a conventional crop. OECD Test Guideline 501 clearly describes the situations under which additional metabolism studies need to be conducted for a herbicide tolerant crop to determine if the residue definition resulting from the application of a herbicide over the top of a herbicide tolerant crop is different to the definition that results from use in a non-herbicide tolerant crop. OECD Residue Chemistry Test Guidelines are available on the OECD website.

Herbicide tolerant crops may modify the behaviour of the chemical degradation pathways which therefore impacts upon the resulting residue profile. These pathways may respond differently to variations in formulation, application timings and rates which compared to those of conventional crops. The arguments that would be made for a non-herbicide tolerant crop do not apply to herbicide tolerant crops and the over the top use of a herbicide. Assessment of residues data have established that the differences in residues concentrations of a herbicide used over the top of a herbicide tolerant crop when compared to a non-herbicide tolerant crop can be significant and residues data will be required to support these uses.

Comparability of formulation, application timing and use rates are not considered sufficient grounds on which to make a determination on the adequacy of an existing MRL. Data or scientific argument  that may be provided for a non-herbicide tolerant crop is not acceptable for a herbicide tolerant crop owing to possible variations in the response of the herbicide tolerant plant to the herbicide.

Residue Guideline 24 (RGL 24) outlines the numbers of trials that are required for different crops for the purposes of setting an MRL.

A with efficacy and crop safety trials, the APVMA requires residues trails to be conducted on the specific herbicide tolerant crop for which over the top use is being sought, and in locations that are representative of the main growing regions in Australia. Data from trials conducted with superseded commercial herbicide tolerant traits or varieties are not acceptable. The maximum use pattern (as per label) must be trialled and samples collected, in accordance with the guidance provided in RGL 24. If the directions for use specify a variety of application timings, each trial must include a number of treatment regimens to ensure that the maximum residue scenario is addressed.

Please contact the APVMA and discuss the trial protocol if unsure about the required number of confirmatory trials. Where the commercially available herbicide tolerant crop is considered to be a major crop, GLP requirement will apply.

Resistance management and conditions of registration

The repeated application of a herbicide increases the potential for weeds to develop resistance to the active constituent/s contained in the herbicide product/s. The APVMA will impose specific conditions of registration that are designed to enforce the practice of preventative weed resistance management by users of the chemical product. Registrants will be required to implement an appropriate resistance management strategy that:

  1. Provides users with adequate instructions regarding the need for preventative resistance management on the product label.
  2. Includes regular consultation with a suitable group of experts that is acceptable to the APVMA for the purposes of reviewing the ongoing adequacy of the strategy for managing resistance. Typically for herbicide tolerant cotton, the approval of the resistance management strategy is required from the Transgenic and Insect Management Strategies (TIMS) Committee of the ACGRA.

The APVMA will also place obligations on registrants regarding the conduct of weed audits, the reporting of weed escapes identified from such audits, and taking follow up action to deal with weed escapes. These conditions are necessary as over-the-top use pattern of a herbicide in the manner described in 'Scope' above, is recognised as having an increased  potential for the development of weed resistance to the relevant active constituent.

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