Registration Decision RD2021-03, Imazapyr, Habitat Aqua

Pest Management Regulatory Agency
15 March 2021
ISSN: 1925-0940 (PDF version)
Catalogue number: H113-25/2021-3E-PDF (PDF version)

Table of Contents

Registration decision statementFootnote 1 for imazapyr

Health Canada's Pest Management Regulatory Agency (PMRA), under the authority of the Pest Control Products Act, is granting registration for the sale and use of Imazapyr Technical Herbicide and Habitat Aqua, containing the technical grade active ingredient imazapyr, to control certain invasive plants that grow in and around aquatic sites.

This decision is consistent with the Proposed Registration Decision PRD2020-17, Imazapyr and Habitat Aqua, which contains a detailed evaluation of the information submitted in support of this registration. The evaluation found that, under the approved conditions of use, the health and environmental risks and the value of the pest control product(s) are acceptable. See Appendix I for a summary of comments received during the consultation process as well as Health Canada's response to these comments.

Other information

The relevant test data on which the decision is based (as referenced in PRD2020-17) are available for public inspection, upon application, in the PMRA's Reading Room (located in Ottawa). For more information, please contact the PMRA's Pest Management Information Service by phone (1-800-267-6315) or by e-mail (

Any person may file a notice of objectionFootnote 2 regarding this registration decision within 60 days from the date of publication of this Registration Decision. For more information regarding the basis for objecting (which must be based on scientific grounds), please refer to the Pesticides section of the website (Request a Reconsideration of Decision) or contact the PMRA's Pest Management Information Service.

Appendix I Comments and responses

1.0 Comments on errors to spray drift refinement

The registrant noted the Spray drift refinement Table 10, page 35 of PRD2020-17, Imazapyr and Habitat Aqua, reflects the correct application scenarios that were used for spray drift refinement calculations. Since aerial application is not conducted at the 1680 g a.e./ha rate the following statement on page 22, spray drift refinement section should be corrected:

"the LOC for aquatic vascular plants (Lemna) was exceeded for ground and aerial application…"

Health Canada's response: Health Canada acknowledges the error and the statement is changed here to remove reference to aerial application on page 22, spray drift refinement section of PRD2020-17, Imazapyr and Habitat Aqua to:

"the LOC for aquatic vascular plants (Lemna) was exceeded for ground application…".

2.0 Comments related to the applicator

Comments from 11 stakeholders supported the registration of Habitat Aqua to control invasive plants in and around aquatic sites. Several of these comments noted that Habitat Aqua should only be available to experienced applicators to ensure protect sensitive habitats and nontarget species.

Health Canada's response: This product is classified as restricted and can only be applied by a licensed pesticide applicator with appropriate federal or provincial authorization. Certified applicators will be licensed for either terrestrial or aquatic applications, as required. Application must also be done in accordance with Aquatic Invasive Species Regulations under the Fisheries Act and any other required provincial authorizations.

3.0 Comments on type of application method

3.1 Comment

One stakeholder suggested that application of Habitat Aqua by drones should be allowed to reduce disturbance to sensitive areas.

Health Canada's response: Health Canada has published an Information Note Regarding the Use of Drones When Applying Pesticides. The use of drones (or, remotely piloted aircraft systems – RPAS, as they are currently referred to) is not currently registered for the application of Habitat Aqua. Health Canada recognizes the potential value of RPAS applications in minimizing disturbance to sensitive areas and increasing access to difficult to reach areas. However, the risks to the environment and human health as well as efficacy for this method of application have yet to be assessed by Health Canada. Registrants seeking to add RPAS application to the Habitat Aqua label should contact Health Canada's PMRA through the Pre-Submission Consultation process for further information.

3.2 Comment

One stakeholder expressed the need to be able to use Habitat Aqua by "wicking", which would enable application to the occasional solitary stalks without risking the herbicide getting onto the ground or any adjacent plants.

Health Canada's response: Wicking/wiping and daubing applications involve applying the herbicide solution onto weeds by rubbing the weed with an absorbent material containing the herbicide solution. The occupational risks were shown to be acceptable when Habitat Aqua is applied using wiper/wick systems that allow mechanical contact between the weed and the pesticide such as the hockey stick model or the rope wick model.

Hand wicking involves direct contact with each individual Phragmites stalk using an absorbent glove which has been soaked in the herbicide solution. Since no data were submitted to assess the potential risk to applicators using this application method, a label restriction was required prohibiting the application of Habitat Aqua using the hand wicking application method. In response to the comment received, the label restriction has been amended to specify that wicking applications involving mechanical contact are allowed but not those that involve hand-wicking. The label of Habitat Aqua will be amended to say:

"DO NOT apply using a hand-wicking/wiping method (that is, an absorbent glove soaked in the herbicide). Wicking/wiping with a handheld tool or other system that allows mechanical contact with weeds is permitted."

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