Plant growth regulators (PGRs) are used to control or modify plant growth processes. In the case of wheat and barley, PGRs are used to influence the hormones responsible for cell elongation, which results in a crop with thicker, shorter stems.

“Right now there are two plant growth regulators available for wheat in Western Canada,” says Jeremy Boychyn, agronomy research specialist with Alberta Wheat and Barley Commissions. While they achieve the same result, Manipulator and Moddus have slightly different windows of timing for application, which means really having a handle on crop staging.

This staging is based on node movement in the main stem and is sometimes referred to as first and second node (Zadoks 31 to 32) or from the beginning of stem elongation, to second node (Zadoks 30 to 32). The staging numbers from the Zadoks scale are the same as for the BBCH scale, says Boychyn.

“These are very particular products when it comes to application, so getting the right timing means you’re going to get the most out of that product,” says Boychyn. There are many factors that affect the growth of wheat, and staging timing based on the calendar or even on the number of leaves just won’t cut it with these products.

Both Manipulator and Moddus have an on-label window of application, but Boychyn says targeting Zadoks 30 to 32, depending on product, is ideal. Remember that optimum PGR timing and herbicide timing are often different.

In the video below, Boychyn explains how to find the main tiller, determine the number of nodes, and determine the crop’s growth stage. Boychyn notes that determining the growth stage is the same for barley. Please check with your buyer before applying Manipulator on barley.

Related: Wheat School: Getting a PGR application timed right

*This post has been edited for clarity on the ideal vs. on-label application window.

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