Proposed rule to allow Moddus growth regulator use on rye crops

MRL would allow trinexapac-ethyl on rye for first time in Canada

Published: September 11, 2025

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Fall rye near Dugald, Man., 2023. Pic: Dave Bedard

Rye growers may soon have access to a new tool for managing crop height and lodging, thanks to a proposed change that would allow the use of a familiar plant growth regulator in the crop.

Health Canada’s Pest Management Regulatory Agency (PMRA) is proposing a new maximum residue limit (MRL) that would allow trinexapac-ethyl, the active ingredient in Syngenta’s growth regulator Moddus, to be used on rye for the first time in Canada.

Moddus is already registered for use on wheat, barley and oats. Adding rye to the label would give growers another option to help improve standability and harvestability.

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The PMRA evaluation found trinexapac-ethyl to be effective for rye, with no unacceptable health or environmental risks when used according to label directions.

The proposed MRL is three parts per million (ppm), up from the current Canadian default of 0.1 ppm for rye. That level matches MRLs already in place for other cereal crops in Canada and aligns with the international Codex standard used by many trading partners. The U.S., Canada’s top rye export market, allows four ppm, while Japan — another key customer — sets its limit at three ppm.

—> READ MORE: Application timing of PGRs

Krista Zuzak, director of crop protection and production with Cereals Canada, said the proposed change is good news for rye growers.

“It is helpful for growers to have another tool in the crop protection product toolbox,” she said in an email to Grainews.

She notes the move brings rye in line with other cereals on trinexapac-ethyl. Wheat, barley and oats all have MRLs set at three ppm.

Also, “when MRLs are closer or aligned across different export countries, it becomes easier for exporters to meet the requirements of various markets,” she says.

More information is available through the PMRA website. Public comments can be submitted until Oct. 12.

About the author

Don Norman

Don Norman

Associate Editor, Grainews

Don Norman is an agricultural journalist based in Winnipeg and associate editor with Grainews. He began writing for the Manitoba Co-operator as a freelancer in 2018 and joined the editorial staff in 2022. Don brings more than 25 years of journalism experience, including nearly two decades as the owner and publisher of community newspapers in rural Manitoba and as senior editor at the trade publishing company Naylor Publications. Don holds a bachelor’s degree in International Development from the University of Winnipeg. He specializes in translating complex agricultural science and policy into clear, accessible reporting for Canadian farmers. His work regularly appears in Glacier FarmMedia publications.

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