What to know about plant growth regulators

Is this the year you should try PGRs in your crop management program?

Would you try a product if you’d never heard of that category of compounds? Odds are you would say, “No thanks.” But what if your input supplier suggested a product with a proven track record for increasing yields? The term “PGR” may mean nothing to you. On the other hand, a 3-bushel-per-acre corn yield increase over time in reputable plots might be worth investigating.

Here is your chance to learn more about plant growth regulators, or PGRs. WinField United markets PGRs with a proven track record.

“PGRs have been around for over 20 years,” explains Jon Zuk, crop protection product manager for WinField United, covering Wisconsin, Minnesota and northern Illinois. “However, we’ve learned that the keys to maximizing performance are having the right ratio of individual PGRs in the plant and formulating solutions in the right way.”

All about PGRs

If you are not familiar with PGRs, here’s a brief introduction:

Classes. There are five classes of plant growth regulators: auxins, gibberellins, cytokinins, ethylene and abscisic acid. Auxins help create more cells by stimulating cell division, Zuk explains. Gibberellins, which have no connection to the corn ear rot organism, initiate various plant development processes. Cytokinins help determine the role of various cells in plants.

Ethylene, which helps fruit ripen, and abscisic acid, related to dormancy, aren’t PGRs targeted in the attempt to improve plant growth.

Ratio. “The important thing is getting the ratio of the first three PGRs right when you develop a product,” Zuk says. “To get a positive response, the first three classes of compounds must be present in the ratio most beneficial to plants. We’ve zeroed in on this, especially in corn.”

Formulation. “The formulation of the PGR product is the key to having the right solution and source of PGRs in the plant,” Zuk says. In fact, ratio and solution are so important that WinField United holds two patents related to these properties.

Application method. In-furrow applications are the current method of choice for achieving consistent results, Zuk says. “Often you may be planting in cool, wet soil, and it’s ideal if emerging roots access the PGR compound quickly,” he notes.

He adds that 2-by-2 placement can work, and foliar applications are also possible. If you’re going to make a foliar application, choose a product designed for it.

Example products. Ascend 2 is one of the latest PGRs offered by WinField United. Ascend 2 and Ascend Pro are both formulated specifically for in-furrow application in corn. Ascend SL is the company’s PGR for foliar applications in all crops.

Results. Four years’ worth of yield data from 67 Answer Plots in the company’s test plot program indicate a 3-bushel-per-acre advantage for a PGR vs. no PGR. These results include only in-furrow placement of Ascend 2 at 5.3 fluid ounces per acre.

Some local testing outside these plots included 2-by-2 placement. “It is possible to see the benefit later with 2-by-2 placement, once roots access it,” Zuk says.

Other uses. If you’re applying the PGR in a foliar application in corn, V5 to V8 or tasseling are recommended times, Zuk says. In soybeans, apply at R1 to R3 stages.