by Brian Whipker, North Carolina State University
Figure 1. Plant growth can be stalled by many factors. In this case, an excessively high rate of flurprimidol was applied to the mum plants that resulted in a tight mounding habit.
Fresco can be applied as a foliar spray, substrate drench or through chemigation. Typical recommended spray rates are in the range of 1 to 5 ppm. One should begin with the lowest rate, make the application and then wait 7 days to determine if the desired level of growth is achieved (Figure 2).
Figure 2. The effects of Fresco applications on promoting growth of wax begonias. Fresco foliar sprays of 0, 1, 3, or 6 ppm (parts per million) were applied twice (2 and 3 weeks after the plugs were transplanted). Thus the plants received either 0, 2, 6, or 12 ppm Fresco in total. No other PGR was applied.
Reapplication can be made if additional growth enhancement is desired. The goal is to apply only enough Fresco to promote sufficient growth or overcome the PGR effect. Too high of a rate will result in excessive stem or peduncle stretch (Figure 3 and 4) and a light yellowing of the newly developing leaves. Growers have found that the 1 to 5 ppm range works in most cases, but growers have reported that the response rate can vary significantly by cultivar. So it is best to start with a small trial to determine optimal rates.
Figure 3. Too high of a rate will result in excessive stem or peduncle stretch. As a test, the grower applied 10 ppm to a plant to determine the results.
Additional tips for use
- Initially begin with the lower end of the recommended range.
- The initial rate range should be between 1 to 3 ppm. Never apply 10 ppm, or excessive stretch can occur.
- Allow up to 7 days to determine if you increased plant growth before making a second application.
- Many growers will use half of the initial rate applied if the plants fail to take off.
- Excessive rates will result in undesirable stretch, and often requiring an application of an anti-gibberellin plant growth regulator such as Piccolo 10XC to check the elongation.
- Drench applications have been reported to be more effective than spray applications on poinsettias. Spray applications may cause bleaching of red bracts to a dusty pink coloration. If in doubt, test Fresco on a few plants to determine the results before applying it to your entire crop.
- Drench applications will only work if the plant has adequate roots for Fresco uptake.
- Follow the label recommendations, for it is the law.
Figure 4. Excessive peduncle stretch which resulted from a 10 ppm foliar spray.
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