Proposed Re-evaluation Decision PRVD2020-02, Cyromazine and Its Associated End-use Products

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Pest Management Regulatory Agency
5 February 2020
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2020-2E-PDF (PDF version)

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Table of contents

Proposed re-evaluation decision

Under the authority of the Pest Control Products Act, all registered pesticides must be regularly re-evaluated by Health Canada’s Pest Management Regulatory Agency (PMRA) to ensure that they continue to meet current health and environmental standards and continue to have value. The re-evaluation considers data and information from pesticide manufacturers, published scientific reports, and other regulatory agencies. Health Canada applies internationally accepted risk assessment methods as well as current risk management approaches and policies.

Cyromazine is a systemic insecticide and insect growth regulator that is registered for commercial use for the control of a variety of pests on potatoes, greenhouse ornamentals, outdoor ornamentals, mushrooms, greenhouse vegetables, and field vegetables. Cyromazine is also registered for the importation of treated dry bulb and green onion seeds from the United States. Currently registered products containing cyromazine can be found in the Pesticide Label Search and in Appendix I of PRVD2020-02.

This document (Proposed Re-evaluation Decision PRVD2020-02, Cyromazine and Its Associated End-use Products) presents the proposed regulatory decision for the re-evaluation of cyromazine including the proposed risk mitigation measures to further protect human health and the environment, as well as the science evaluation on which the proposed decision was based. All products containing cyromazine registered in Canada are subject to this proposed re-evaluation decision. PRVD2020-02 is subject to a 90-day public consultation period, during which the public including the pesticide manufacturers and stakeholders may submit written comments and additional information to PMRA Publications. The final re-evaluation decision will be published taking into consideration the comments and information received.

Outcome of science evaluation

Cyromazine is the only active ingredient registered in Canada belonging to Insecticide Resistance Action Committee mode of action group 17. Its unique mode of action lends itself to rotation with other insecticides to delay the development of resistance in susceptible dipteran pests.

Cyromazine is a systemic insect growth regulator. It works by contact action, interfering with molting and pupation, so that dipteran insects do not develop. Cyromazine is valued as a tool to manage sciarid flies in mushroom houses, onion maggot in green onions, and leafminer in outdoor ornamentals.

With respect to human health, risks due to occupational exposure have not been shown to be acceptable for most uses of cyromazine. Therefore, cancellation of uses for potatoes, leafy vegetables, celery, leafy brassica vegetables, outdoor ornamentals grown for cut flowers, greenhouse ornamentals (including ornamentals grown for cut flowers), greenhouse lettuce and dry bulb onion seed is proposed. Mitigation measures are required for all remaining uses. Exposure from the remaining uses is unlikely to affect human health when used according to the proposed revised label directions.

Cyromazine enters the environment when used to control insects on crops, or when it is present in water discharged from greenhouses and mushroom houses. To mitigate potential risks to non-target organisms, spray buffer zones to protect sensitive aquatic and terrestrial habitats from spray drift and precautionary label statements to inform users of potential risks to the environment are required. When used according to the proposed label directions risks to the environment from cyromazine have been shown to be acceptable.

Proposed regulatory decision for cyromazine

An evaluation of available scientific information found that certain uses of cyromazine products meet current standards for protection of human health and the environment when used according to proposed label directions, which include new mitigation measures. The following uses of cyromazine are proposed for cancellation as health risks were not shown to be acceptable: potatoes, leafy vegetables, leafy brassica vegetables, celery, outdoor ornamentals grown for cut flowers, greenhouse ornamentals, greenhouse lettuce and imported dry bulb onion seeds.

Under the authority of the Pest Control Products Act, Health Canada is proposing that continued registration of products containing cyromazine is acceptable when the proposed mitigation measures are in place.

Registered pesticide product labels include specific directions for use. Directions include risk mitigation measures to protect human health and the environment that must be followed by law. As a result of the re-evaluation of cyromazine, further risk mitigation measures for product labels are being proposed. The proposed label statements and mitigation measures are summarized below. Refer to Appendix XII of PRVD2020-02for details.

Human health

To protect human health, the following risk mitigation measures are proposed:


To protect the environment, the following proposed measures are required:

International context

Cyromazine is currently acceptable for use in other Organisation for Economic Co-operation and Development (OECD) member countries, including Australia, the EU, Israel, Japan, New Zealand, Switzerland, United States and Turkey. No decision by an OECD member country to prohibit all uses of cyromazine for health or environmental reasons has been identified.

Next steps

The public including the registrants and stakeholders are encouraged to submit additional information that could be used to refine risk assessments during the 90-day public consultation periodFootnote 1 upon publication of this proposed re-evaluation decision.

All comments received during the 90-day public consultation period will be taken into consideration in preparation of re-evaluation decision documentFootnote 2, which could result in revised risk mitigation measures. The re-evaluation decision document will include the final re-evaluation decision, the reasons for it and a summary of comments received on the proposed re-evaluation decision with Health Canada's responses.


Footnote 1

"Consultation statement" as required by subsection 28(2) of the Pest Control Products Act

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Footnote 2

"Decision statement" as required by subsection 28(5) of the Pest Control Products Act.

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