Dudley Dabbs
Photo courtesy of Fine Americas

Plant growth regulators (PGRs) are an essential part of many greenhouse operations, and they require careful application and planning to be used effectively. Below, Dudley Dabbs, eastern regional manager for Fine Americas, explains why not all paclobutrazol PGRs are the same, what to do if a PGR is over-applied and more.

Greenhouse Management: Are all paclobutrazol PGRs the same?

Dudley Dabbs: Previously, growers have had to contend with settling in spray tank solutions of paclo PGRs. With the introduction of Piccolo 10XC, that’s no longer an issue. Piccolo 10XC is a true solution, so the active ingredient doesn’t settle out in the container. This translates to results that are more consistent and a spray solution that is more stable.

GM: If a grower over-applies a PGR, can anything be done?

DD: It happens more often than you’d think, where a grower miscalculates, applies too much uniconazole or paclo and ends up with stunted plants. Fresco is actually great for that — for kick starting plants to help re-energize their growth cycle. Whether you apply a single application or more than one depends on the crop, variety and severity of the situation, but Fresco can often keep growers from having to miss a production cycle and save the crop.

GM: How can growers help even out their results with paclo products?

DD: Use a drench and not a foliar application, because the plant’s water-conducting cells, xylem, are what takes up paclo, and they’re most prevalent in the roots and stems. This will help ensure you get the most consistent application possible.

GM: Do PGRs provide benefits in addition to controlling growth?

DD: We call it the best-kept secret — PGRs can also enhance leaf color, help plants use less water and increase their disease suppression. This is all part of how PGRs work, by blocking the GA, or gibberellin, pathway for controlling plant growth.

GM: Is there an easy way for growers to calculate correct dilutions for plant growth regulators?

DD: I like the PGR Mix Master app, which calculates PGR mixing rates for sprays and drenches. It has rates for the most frequently used ornamental PGRs. You just click product, English vs metric, volume, ppm, and that’s it. It’s easy to use and downloadable for free at e-gro.org/mixmaster. In addition, there is the PGR quick dilution table on the back page of the PGR Guide sponsored by Fine Americas.

GM: What should growers be watching for in PGRs?

DD: Look for new developments and new products in the biostimulant and plant health areas to be used along with PGRs. I see a lot of potential for ornamentals there, based on the positive results we’re already seeing in fruits, vegetables and row crops. — Interviewed by Chris Manning