Stewardship Update: Understanding Tolerances and MRLs

Attention Canadian Greenhouse Growers

Dear Grower Partners,

As part of the pesticide registration process in Canada, all pest control products undergo rigorous evaluation to ensure both their efficacy and safety — for applicators and, where applicable, for human consumption.

A key component of this process is the establishment of Maximum Residue Limits (MRLs), also referred to as tolerance levels. These limits are determined using data submitted by registrants to regulatory authorities such as PMRA (Canada) and the EPA (U.S.) during product registration. MRLs are based on proposed label rates, application frequency, and pre-harvest intervals (PHIs).

Growers can be confident that any pesticide registered in Canada and used according to the label instructions — including application rates, number of applications, and PHIs — is safe for sale in both Canadian and U.S. markets.

Adhering closely to label directions and PHIs is essential not only for compliance but also for maintaining access to international markets. Consistent stewardship practices help protect the reputation and marketability of Canadian-grown products globally.

Thank you for your continued commitment to responsible crop protection practices.

Best regards,

Darcy Olds
Key Account Manager
darcy.olds@envu.com
905-464-8339
Pest Management/Greenhouse and Nursery/Farm Hygiene Canada