Fresco Use Tips

Brian Whipker, North Carolina State University

Figure 1. Growth enhancement with the use of Fresco foliar sprays on New Guinea impatiens after the plants were stalled with an overdose paclo application.

When one thinks of plant growth regulators (PGRs), the primary focus is on growth control mainly through regulating internode stretch. There are times when additional growth is needed.  That is where a growth enhancement PGR such as Fresco should be considered.
Fresco is a combination of 1.8% gibberellins A4+A7 [GA4+7] and 1.8% benzyladenine [6-BA].  This combination provides stimulation of intermodal elongation with the GA4+7 and enhancement of axillary shoot growth with the BA.  When mixed together, the combination provides a controlled stimulation of enhanced plant growth.

The other labeled option for enhancing plant growth is Florgib 4L.  It contains gibberellin A3 and only the lowest label rates should be trialed and used to avoid excessive stretch.  By far, the majority of growers prefer to use Fresco because it enhances elongation and fullness of the plant, while providing a wider window of safety for avoiding overdose applications.

In addition, Fresco can be used to enhance bract development on poinsettias and aid in avoiding lower leaf yellowing on lilies.
With Fresco being an excellent tool in providing growth enhancement and improving postharvest quality, it is a handy addition to have in your PGR toolbox.  In order to obtain the most effect from Fresco, below are some application tips to consider.

Application tips

Preventing Lower Leaf Yellowing of Lilies – Fresco can be used to avoid lower leaf yellowing and necrosis when applied to lower leaves. It also delays flower senescence when applied to flower buds.  Fresco can be used on Easter (Lilium longiflorum), LA Hybrid (L. longiflorum-Asiatic crosses) and oriental lilies, but use rates vary.  Fresco is used as a preventative application and does not correct leaf yellowing and flower senescence that has already occurred.

Figure 2. Lower leaf yellowing and necrosis on lilies. An application will help avoid this situation, especially under low light conditions.

Species: Easter and LA Hybrid Lilies (based on the Fresco label)
Timing: Early and Mid-season applications
To avoid lower leaf yellowing, apply 5 to 10 ppm Fresco as a foliar spray to the lower leaves only, 7-10 days before the visible bud stage is reached.
A second repeat application for will provide complete season control. It should be applied 7-10 days after the visible bud stage.
Avoid spray contact with the immature leaves as this may result in excessive stem elongation.

Timing: Late-season application
To reduce leaf yellowing and prolong flowering during and after shipment, apply 100 ppm Fresco when the first bud is at least 8cm long and there is less than 14 days to readiness for shipping the crop or removal to the cooler. Apply as a foliar spray to the foliage and flower buds. Treatment in this way will provide up to 14 days protection from yellowing and 25% longer flower life. Do not treat earlier than 14 days before shipping or removal to the cooler as inadequate protection may occur. Avoiding treating lilies with small buds as this may result in unwanted stem elongation.

Species: Oriental Lilies (based on the Fresco label)
Timing: Early and Mid-season applications

To avoid lower leaf yellowing, apply 100 ppm Fresco as a foliar spray to the lower leaves only, 7-10 days before the visible bud stage is reached.
The first application gives up to 21 days protection.
A second repeat application will provide complete season control. It should be applied 14 days before shipping or removal to the cooler.

Timing: Late-season application
To reduce leaf yellowing and prolong flowering during and after shipment, apply 100 ppm Fresco when there is less than 14 days to readiness for shipping the crop or removal to the cooler.
Avoid treating earlier than 14 days before shipping or removal to the cooler as inadequate protection may occur.  Fresco’s effect lasts for up to 14 days after removal to the cooler.

Bract Enhancement of Poinsettias – Fresco can be applied to poinsettias 7-14 days before anthesis to increase bract size. Fresco may also be used to promote bract expansion on plants treated with late season foliar applications of anti-GA PGRs. Bract coloring on some red varieties may appear less intense immediately following a Fresco treatment. However, over time, the bracts should develop a more intense coloration. Use of Fresco may also result in an increase in plant height.  Test on a few plants to determine the results.

Bracts of white cultivars have been reported to develop a “whiter” appearance, with the use of a late season application.

Timing: Late-season application (based on the Fresco label)
A number of factors can result in treatment variability, including growing conditions and plant cultivar. Therefore, before commercial use, first time users of Fresco must conduct initial trials on a small number of plants for each variety starting with a 3 ppm rate.  Apply Fresco in sufficient volume to thoroughly and uniformly wet bracts (1 gallon per 200 square feet of bench area). The foliage of poinsettias often develops a waxy, spray repellent cuticle. Therefore, the use of a high quality wetting agent approved for use on poinsettia may be needed when applying Fresco. Consult the adjuvant label or manufacturer for rates, crop tolerance and safety information before use.

Growth Enhancement – 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 enhancement is achieved.  Reapplication can be made if additional growth is desired. The goal is to apply only enough Fresco to promote sufficient growth or overcome the PGR effect or lack of growth.  Too high of a rate will result in excessive stem or peduncle stretch 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.

Fresco is the only GA4+7 and 6-BA product registered for drench applications. Drench applications have become increasingly popular because there is more even distribution of Fresco within the plant and less negative effect on leaf and flower growth.

Growth Enhancement Use Tips – Foliar Sprays:

  1. Initially begin with the lower end of the recommended range.  The initial rate range for a foliar spray should be between 1 to 3 ppm.  Avoid applying >10 ppm, or excessive stretch may occur.
  2. Complete coverage is required because Fresco applied to the leaves is not easily transported throughout the plant.
  3. Allow up to 7 days to determine if plant growth is increased before making a second application. When reapplying, many growers will use half of the initial rate if the plants fail to take off.
  4. When using Fresco for the first time, test it on a few plants to determine the results before applying it to your entire crop.
  5. 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.
  6. Spray applications may cause bleaching of red bracts to a dusty pink coloration.
  7. Follow the label recommendations, for it’s the law.

Growth Enhancement Use Tips – Drenches:

  1. Initially begin with the lower end of the recommended range. The initial rate range for a drench should be between 1 to 3 ppm.  Avoid applying >10 ppm, or excessive stretch can occur.
  2. Apply Fresco drenches to with a sufficient volume of water to allow complete coverage of the root system. Make applications to moist but not wet substrates. Drench applications provide the benefit of more even uptake by the plant if a sufficient volume of water is used. The volume of drench applied increases with the pot size.  For example, typically 3 fluid ounces (fl. oz.) of drench solution is added to a 5-inch pot, 4 fl. oz. to a 6-inch pot, and 10 fl. oz. to an 8-inch pot.
  3. When applied as a drench through sub-irrigation, reduce rates normally used for top-of-the-pot applications by 25-50%.
  4. Allow up to 7 days to determine if plant growth is increased before making a second application. When reapplying, many growers will use half of the initial rate if the plants fail to take off.
  5. 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.
  6. When using Fresco for the first time, test it on a few plants to determine the results before applying it to your entire crop.
  7. 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.
  8. Drench applications will only work if the plant has adequate roots for Fresco uptake.
  9. Follow the label recommendations, for it’s the law.

Timing. In order to reap the benefits of a Fresco application, application timing is critical.  Most applications are targeted at a specific stage of development and number of days in which it is effective or requiring sufficient time to realize results.  Those specific timings are outlined on the Fresco label for each use.

Avoid applications to stressed plants.  Enhanced plant quality will occur if Fresco is used correctly. Avoid applying Fresco to plants that are temperature, water, nutrient, or pest stressed. Fresco foliar sprays are best applied in the morning or late afternoon/evening, when leaf drying time will be slower which allows greater uptake by the plant.

Optimal concentrations.  Recommended use rates vary from 1 to 3 ppm foliar sprays for enhancing plant growth, 3 ppm for bract expansion, to 10 to 100 ppm, respectively, for avoiding early and late lower leaf yellowing with lilies.  Refer to each species listed on the Fresco for specific details.  For foliar spray applications, apply 1 gallon of spray solution uniformly over 200 sq. ft. of bench area.  Avoid applying more than 15 ml of spray solution per plant.

Phytotoxicity.  Overdoses of Fresco can result in excessive stretch.  Therefore utilize the lower recommended rate range and test on a few plants to determine the suitability of the rate.

Protective equipment and REI.  Applicators must wear a long-sleeved shirt and long plants, wear chemical-resistant gloves, protective eyewear, socks and shoes, and chemical-resistant apron when mixing, loading, or cleaning equipment.  The restricted entry interval (REI) is 4 hours.