Information Note – Strychnine emergency use request – Final decision

Health Canada's Pest Management Regulatory Agency
6 February 2026

The purpose of this Information Note is to inform stakeholders of the outcome of Health Canada's Pest Management Regulatory Agency evaluation of an Emergency Use Request (EUR) for 2% Liquid Strychnine Concentrate to control Richardson's ground squirrels (RGS) in Alberta and Saskatchewan. The request was submitted by Alberta Agriculture and Irrigation.

Currently, pesticide products containing strychnine are not registered for use in Canada. In 2020, registration of strychnine for use on RGS was cancelled following a re-evaluation that found unacceptable environmental risks.

While the information provided in the Emergency Use Request (EUR) emphasized the severity of RGS infestations and the potential to incur significant economic damages, an EUR can only be considered if there is evidence that the health and environmental risks are acceptable and the product has value in addressing the emergency pest situation.

All information submitted as part of the EUR data package as well as the information received following discussions with the provincial applicant was considered in the final decision.

Following a review of the data package submitted by the applicant, the PMRA determined that the information did not provide sufficient means to address the risks of concern identified in the re-evaluation that led to strychnine's cancellation. The request for an emergency registration of strychnine to control Richardson's ground squirrels has been denied.

The following information outlines the assessments and aspects considered in the review of the emergency use request for strychnine to control RGS.

Value assessment

Richardson's ground squirrel can cause crop and pasture damage, soil erosion, livestock injuries, as well as destruction of infrastructure (for example, chewing cables, gas lines).
The EUR application proposed a 2% liquid strychnine concentrate to be mixed with grain to produce bait containing 0.4% strychnine, applied either in-burrow or via bait stations with daily carcass monitoring for the first week and weekly monitoring thereafter. Proposed application timing included one spring only or one spring and one summer application.
A stewardship program was also proposed that emphasized eligibility, economic action thresholds, controlled access, mandatory training with a knowledge check, audits and reporting, site-level monitoring and disposal practices.
Although strychnine was recognized to have value as an effective rodenticide for Richardson's ground squirrels, questions remained about the proposed application rate used in the bait stations and their distribution in the field as well as concerns about the auditing and enforcement of the proposed stewardship program.

Health risk assessment

The assessed health risk management approach was acceptable as the potential occupational and bystander exposure scenarios and human health concerns associated with the use of strychnine were suitably addressed.
Considerations included the restricted classification of the product, the personal protective equipment for applicators, and the measures required to eliminate accidental or bystander exposures (including children and domestic animals).

Environmental risk assessment

The environmental risk assessment considered risk mitigation measures submitted by the applicant as well as other conditions of registration that were raised during the re-evaluation (for example, field monitoring, carcass removal, bait stations, training, signing of declarations at the time of purchase, product evaluation forms, audits).
Although the use of bait stations may limit bait ejections and non-target poisoning of larger wildlife as compared to in-burrow applications, it would not mitigate primary non-target poisoning of small animals nor reduce the risks associated with secondary poisonings (including species at risk) that occur from scavengers and predators eating poisoned carcasses (RGS or non-target small animals).
Application of strychnine bait into an active burrow and subsequently covering the entrance with soil is the preferred mechanism of bait deployment. However, environmental risks with this method are still present as described in the re-evaluation (RVD2020-06).
The proposed requirements for enhanced training, purchase restrictions, signing of declarations at the time of purchase, mandatory completion of product evaluation forms, and audits conducted by the province are initiatives that have previously been considered in the re-evaluation and were found insufficient to mitigate the risks of non-target poisonings. The information provided as part of this application did not provide clarity on how these initiatives will result in a reduction of non-target poisonings.
Sufficient resources to effectively monitor fields and dispose of poisoned carcasses and unconsumed bait were not described. Field monitoring and carcass removal is labour-intensive and required during a busy period of activity on a farm, suggesting that effective mitigation is not feasible. The use has been requested for the provinces of Alberta and Saskatchewan, which represents a large area over which potential risk to non-target wildlife would be a concern.
The risks to non-target wildlife from primary and secondary poisoning are particularly high with strychnine, and the proposed field monitoring mitigation measures have proved ineffective in the past when strychnine was registered for this use. When strychnine was previously registered, many incidents were reported to the PMRA related to this use in Alberta and Saskatchewan. Incidents were likely underestimated as scavengers are very efficient at finding and consuming or removing poisoned carcasses from the field surface. Following a review of the available scientific information, risks associated with the use of strychnine to control RGS were not shown to be acceptable when used according to the proposed label directions and required mitigation measures. Therefore, the emergency use request is unacceptable from an environmental perspective.

International perspective

Strychnine is not approved for use internationally, including the United States, European Union and Australia, except for under very strict and narrow circumstances.
- In the U.S., strychnine is not permitted for use on ground squirrels in any state but Nevada. In Nevada, the application occurs only in high-value hay land in the State's north and must be made by State-sanctioned personnel.
- Approximately eleven U.S. states permit the use of strychnine to control pocket gophers. Since this species is primarily subterranean, strychnine bait must be deposited into the tunnel system where carcasses remain underground, thus alleviating primary and secondary poisonings of non-target organisms, including species-at-risk.
- In Western Australia only, strychnine is highly regulated and permitted for restricted-use for wild dog and emu control.

Integrated Pest Management (IPM) and registered alternatives

Considering the five registered alternatives (zinc phosphide, chlorophacinone, diphacinone, aluminum phosphide, and a co-formulation of white mustard seed powder and sodium alpha-olefin sulfonate), research and publications consistently show zinc phosphide as an effective alternative with similar timing of application, baiting methods and cost as compared to strychnine.
Zinc phosphide also reduces the risk of secondary poisonings as it is not environmentally persistent, degrading more quickly in the environment and in the stomachs of poisoned animals.
This more rapid degradation has been cited as a reason that zinc phosphide is less attractive as a rodenticide for RGS, however, as it has been shown to be effective, its use along with other integrated pest management strategies (for example, enhancing habitat for predators, trapping/shooting, maintaining vegetation taller than 15 cm) presents a viable option for control of Richardson's ground squirrel.
PMRA is willing to work collaboratively with provincial partners to explore opportunities to expand or develop new tools that target RGS.
The PMRA is committed to continuing to provide support for registrations of new, lower risk products without health or environmental risk outcomes.

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2026-02-06

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