It’s said timing is everything and that is especially true when it comes to the use of plant growth regulators.

Plant growth regulators (PGRs) are hormone-based compounds used primarily as a harvest management aid to modify plant growth and development. They help produce plants with shorter, thicker and stronger stems and reduce the risk of lodging in a number of different crops while also potentially boosting yields.

While PGRs have been in use in Europe and elsewhere for decades, they are still relatively new here in Canada, where they are largely used in cereals crops such as barley, oats and wheat. Two PGRs are approved for use with cereal crops in Western Canada under the brand names Manipulator and Moddus.

Anne Kirk, a cereals specialist with Manitoba Agriculture, says one of the most important things to be aware of when using PGRs is knowing the right time to apply them.

Right time

PGRs are most often applied as a foliar spray to leaves or as a liquid to the soil around a plant’s base. Kirk explains the best time to apply them is early in the growing season when a plant is between growth stages 31 and 32 and stem elongation has just begun (see photo at top). At that point, the plant should already have developed a tillering node near the root and a second node less than two centimetres further up on the stem.

“In order for (PGRs) to work their best, you want to get them on the plant when the stem is just starting to elongate and not at the end of the plant’s elongation,” she says.

“You want to get them on at the ideal time to prevent the stems from elongating right at the start rather than after the fact because you wouldn’t expect them to have as much of a benefit at that point.”