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Plant growth regulators

They’re not new, but plant growth regulators 
are not yet common on the Canadian Prairies

test plots of seeded wheat

Prairie farmers might be seeing ads for plant growth regulators for the first time, but PGR’s are not new. “They’ve been using them in Europe for over 30 years,” Tom Tregunno, Engage Agro’s product manager, told farmers at the Indian Head Agricultural Research Foundation (IHARF) Crop Management field day in July.

Plant growth regulators are designed to reduce cereal height. They’re sprayed on crops during the growing season, just like herbicides or fungicides. Treated plants are shorter, with stronger stems, for reduced lodging.


Engage Agro has been conducting trials of its plant growth regulator, Manipulator, for years. In September 2014, Health Canada’s Pesticide Management Regulatory Agency (PMRA) registered Manipulator for use on spring and winter wheat. It will be available to farmers for the 2015 growing season. (Engage Agro is still working on approvals for other cereal crops.)

man standing beside wheat field
Tom Tregunno, Engage Agro’s product manager, told farmers about the Manipulator PGR at the Indian Head Agricultural Research Foundation (IHARF) Crop Management field day in July. photo: Leeann Minogue

Manipulator works by suppressing gibberellins, the hormone “responsible for causing the plant to elongate.” The Manipulator label says it “can improve resistance to lodging through reduced plant height, enhanced root structure and improved stem characteristics.”

When asked if changes to the plant height would also affect the root growth underneath the ground, Tregunno explained, “All you’re really doing is shrinking down the stem.”

One reason it’s taken so long for plant growth regulators to come to the North American market is the narrow window of application. Plants need to be sprayed, “When that stem starts to really shoot up,” Treganno said. The Manipulator label recommends spraying between Growth Stage 12 (the two-leaf stage) to 39 (the flag leaf collar visible stage.

And, Tregunno said, nighttime temperatures must be greater than 8 C.

If you spray too soon, “where you’re preventing the growth is right at the base of the plant.” Too late, Tregunno said, “and you’re reducing the beduncle height.”

“If you’ve got 5,000 acres, there’s no way you’re going to get it all on at that time.”

At Indian Head in July, Tregunno estimated the cost of an application of Manipulator at between $10 and $15 per acre. In Europe, Tregunno said, “they might go out three times a season with a plant growth regulator, that’s not going to happen here.”

Other plant growth regulators

Manipulator is not the only game in town. Different PGRs have different active ingredients — they are all designed to change the plant’s natural hormonal activity.

Bayer sells Ethrel, a PGR with ethylene as an active ingredient. Because the application window is so short and application timing is so critical, Bayer doesn’t actively promote this product for use on cereals in Western Canada.

Syngenta’s PGR is not yet registered for use on Prairie cereals. Allen Terry, Syngenta’s “biolocial assessment manager” says, “we’re working towards collecting data.”

Terry believes PGRs are coming to the market now because with today’s technology technology, we have a better understanding of how crops will respond to chemicals.

“We have a real opportunity in Western Canada to increase cereal yields,” Terry said.

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