Check with your grain buyer before using plant growth regulators

By Mitchell Japp, MSc, PAg, Provincial Specialist, Cereal Crops, Crops and Irrigation Branch and Clark Brenzil, PAg, Provincial Specialist, Weed Control, Crops and Irrigation Branch

Plant growth regulators (PGRs) are generally synthetic compounds that change plant growth by altering the plant’s hormonal balance. PGRs are not new to agriculture, but have not been commonly used in Western Canada because they are mostly used in conditions of high moisture and high fertility to shorten and strengthen straw. In Western Canada, we normally have drier weather tendencies and several varieties with good lodging resistance.

However, new, higher yielding genetics are now available in Western Canada and producers are targeting higher yields than in the past. PGRs can be used to manage detrimental effects of higher crop inputs, such as lodging and more straw to process through the combine.

There are many semi-dwarf wheat varieties that have short, strong straw, but some popular varieties are tall, including all currently available midge tolerant wheat varieties and several fusarium tolerant varieties. Growing these in high fertility, high moisture environments may lead to lodging problems that could potentially be reduced with the use of a PGR.

The PGR product Manipulator (Engage Agro) was recently registered in Canada for use on spring and winter wheat (durum pending review). Manipulator suppresses gibberellins, a group of plant hormones responsible for stem elongation. Manipulator can cause plants to have shorter and thicker stems, potentially reducing lodging.

“Spraying crops in the evening dusk” by Tamina Miller is licensed under CC BY-NC 2.0

Other PGRs, such as Ethrel (Bayer) and Cycocel Extra (BASF), have been registered in Canada for decades, but they have not been widely used. In Western Canada, Ethrel is registered on spring wheat. Cyclocel Extra has the same active ingredient as Manipulator (chlormequat chloride), but is registered for winter wheat only.

PGRs generally have a specific application window to be effective. Application outside of the application window may not only be ineffective, but also potentially detrimental to the crop. Manipulator for a single application is best applied at the one-to-two node stage (Zadoks growth stage 31-32) and Ethrel at flag-leaf-emergence to swollen-boot stage (Zadoks GS 37-45).

While new products like Manipulator may be of interest agronomically, using new products may cause problems with marketing the grain.

Manipulator is currently approved in Canada but not in all markets of Canadian grain, such as the United States. When an export market has not established maximum residue limits (MRLs) for a crop input like pesticides or PGRs, grain treated with that product may not be accepted by that country. Producers are cautioned to be certain that their grain buyer will accept grain treated with Manipulator, or any other product, before applying the product.