Plant growth regulators (PGRs) are used to control or modify plant growth processes. There are a few products on the market, and in the case of cereals, the most common PGR is used to influence the hormones responsible for cell elongation, which results in shorter, thicker stems.
Alberta Agriculture and Forestry, Agronomic Research Scientist, Sheri Strydhorst, outlines current PGR tools available for cereal growers and talks particulars about wheat with Kara Oosterhuis in this episode of the Wheat School.
Strydhorst says that there are a few products registered or not yet registered for cereals: Manipulator (works well on wheat, recently barley and oats have been added to the label), Moddus (not registered yet, but has a great fit on barley), and Ethrel (for use on many crops, including wheat).
For a product like Manipulator in particular, the label says application can be made from the two-leaf to the flag-leaf stage. Preliminary research from Strydhorst has found that the optimal stage for application on wheat is actually from growth stage 30 to 32 (on the Zadoks growth scale), or just when the stem is starting to elongate.
Strydhorst’s research program focuses on how PGRs perform on different cultivars. Some studies from other parts of the world found that, when testing PGR performance on four cultivars, and one out of four had a yield boost, or only two out of the four had a height reduction, Strydhorst says.
A different mindset is required when using PGRs because we’re used to expecting the same result from a herbicide every time, but PGRs are different, and not every wheat variety or crop year is going to deliver the same results every time.
Strydhorst says that farmers thinking about using a PGR should first use the seed guide as a reference for what varieties have higher lodging risks, but know that there isn’t a “textbook method” to find out if a PGR will work. Strydhorst explains that one product may work better on one variety than another. Generally, if a variety doesn’t lodge, it doesn’t need a PGR. (Strydhorst provides more detail about varieties in the video, story continues after):
Strydhorst explains that in her research, even though not statistically significant, a protein reduction in a CWRS wheat was often found when a PGR was applied. If protein is a management concern for you and lodging isn’t a problem, then a PGR might not be the right choice.
Alos, keep in mind that herbicide timing is very early, and it’s different from PGR timing, so tank mixing the two together, isn’t a best management practic. “The PGR isn’t going to last forever in the plant, so we miss that window if we spray too early,” says Strydhorst. She says to keep in mind that the target for PGR timing is at stem elongation which falls between herbicide and fungicide timing, requiring a separate pass over the field.