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In comparison to other antimicrobial agents, ClO2 and 8-hydroxyquinoline sulfate (8-HQS) were more effective in extending the vase life of Gerbera ‘Julia’, ‘Lorka’ and ‘Vilassar’ flowers than other tested biocides (i.e. aluminum sulfate, DICA, Physan 20TM, sodium hypochlorite) when included in vase water containing 0.2 g L−1 citric acid and 10 g L sucrose (Photo 3).

Photo 3.  Chlorine dioxide prolonged vase life of Gerbera ‘Lorka’ by 2.3 days. 

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Chlorine dioxide was very effective in reducing bacteria in solutions, increasing vase life from 7 to 77% in 8 of 10 flower species tested, showed similar levels of efficacy to 8-HQS, and was more effective than all other tested biocides.   

ClO2 is an effective treatment for controlling bacteria in vase solutions and extending cut flower longevity of many popular fresh cut flower species.

Research performed by:
A.J. Macnish, Postdoctoral Researcher,
T.A. Nell, Professor and Chairman,

R.T. Leonard, Biological Scientist, and

A.M. Alexander, Biological Scientist                                   
Department of Environmental Horticulture, University of Florida, Gainesville, 32611

Contact: tanell@ufl.edu
January 2010
©American Floral Endowment. All Rights Reserved.

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Adding 10 ppm ClO2 to vase water inoculated with bacteria (1011 CFU L−1) reduced or eliminated the loss in vase life in 5 out of 10 species tested (Snapdragon, Chrysanthemum, Gypsophila, Stock and Roses) compared to vases inoculated without ClO2.  An increase in water uptake rates and decreased rates of fresh weight loss were also observed when inoculated vases were treated with ClO2.    

Hydrating Gerbera ‘Tsar’ stems immediately after harvest for 72 hours at 40°F with 10 ppm ClO2 extended vase life by 2.6 days.  Combining this treatment with a prior 1 minute 10 ppm ClO2 stem dip, increased vase life 4.2 days compared to flowers with no ClO2 pre-treatments (Table 1).   These combined pre-treatments also prevented bacteria growth in post-shipment hydration water.   

Post Production Research: Cut Flower Longevity

Cut flower longevity is often reduced by an accumulation of bacteria in floral solutions and flower stems.   Chlorine dioxide (ClO2), a broad spectrum bactericide commercially used for sanitizing fruit and vegetable surfaces, was tested to determine its potential use as an antimicrobial agent for fresh cut flower stems and solutions.

Flowering stems of Alstroemeria, Snapdragon, Delphinium, Carnation, Chrysanthemum, Gerbera, Gypsophila, Asiatic Lilies, Stock, and Roses were obtained from production areas in California or Colombia and commercially transported to the University of Florida postharvest laboratory within 2 to 7 days after harvest. 

Various concentrations of ClO2 used for treatments were prepared by diluting a 500 ppm stock ClO2 solution (Selectrocide™ 2L500; Selective Micro Technologies, LLC, Beverly, MA, USA) in deionized water.   In the first study, stems were held in ClO2 concentrations of 0, 2, 5, 10, 20 and 50 ppm to determine the optimum effectiveness of the product. 

A second study evaluated the effectiveness of adding 10 ppm ClO2 to vase solutions with known concentrations of bacteria previously isolated from vase water from each flower species.  In addition, we tested the effectiveness of a farm-level ClO2 hydration and stem dips (10 ppm for 1 minute) and the efficacy of ClO2 vase water treatments compared to other biocides.  Vase life and quality of all studies were evaluated at 70 °F, 70 ftc (12 hrs/day) and 50% relative humidity. 

A 2 ppm concentration of aqueous ClO2 was optimal for extending vase life of Stock, while 10 ppm of aqueous ClO2 was most effective for prolonging vase life of the other responsive flower species.  The highest concentration of 50 ppm reduced vase life for Delphinium and Chrysanthemum and accelerated leaf chlorosis on Alstroemeria and Lilies. 

Adding low concentrations (2 to 10 ppm) of aqueous ClO2 to deionized vase water significantly extended the display life of Alstroemeria, Snapdragon, Carnation, Gerbera, Gypsophila, Asiatic Lilies, Stock, and Roses (Photos 1 & 2). Vase life increased by 0.9–13.4 days (7–77%) compared to flowers not held in ClO2.


Photos 1 and 2 (above).  Examples of increased vase life of Alstroemeria (left) and Snapdragons (right) when held in 10 ppm ClO2.   


ClO2 treatment prolonged vase life in association with a delay in the onset of bacterial colonization in vase water.   Concentrations of 2 and 5 ppm ClO2 significantly reduced bacteria for three days, while higher concentrations delayed bacterial growth longer (Fig. 1). 

Fig. 1.  Number of bacteria in Gerbera vase water treated with various ClO2 concentrations. 

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Vase life (days)

No  dip



+ ClO2

- ClO2

+ ClO2


- ClO2

+ ClO2

4.4 a

7.0 b


8.4 c

8.6 c

 Table 1.  Vase life of Gerbera ‘Tsar’ pretreated with and without chlorine dioxide.

A one minute dip of mixed bouquet stems in 10 ppm ClO2 significantly reduced the number of bacteria that colonized vase water, especially when held afterward in 10 ppm ClO (Fig. 2).  Including ClO2 in the vase water after the dip increased vase life 17 to 56% compared to control flowers.   


Fig. 2.  Chlorine dioxide reduced vase water bacteria of mixed bouquets.

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2010 - Issue Two
In This Issue
   AFE Turns 50!
   MSU Graduate Awarded 2010 Paul Ecke Jr. MS/PhD Scholarship
   Memorial Tribute Established as AFE Mourns the Passing of Trustee Ernesto Velez
   Post Production Research: Cut Flower Longevity
   Floral Design Students Receive Financial Support Through AFE
   Ensuring the Next 50 Years: Consider a Bequest Gift to AFE
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Sponsorship Opportunities!

Join other industry organizations by becoming a sponsor of the 2010 AFE Fundraising Dinner and 50th Anniversary Commemorative Celebration - September 22, in Orlando. 

All sponsors receive recognition during the dinner, in the commemorative printed program, on AFE's web site, and receive special seating during the event.

Sponsorships available:

  • Table Hosts
  • Table Sponsors
  • Entertainment Sponsors
  • Wine/Champagne Sponsors
  • Other Sponsorships are available.

Contact AFE for more information!


Final Research Reports Available on the AFE Web Site!

AFE research addresses a diverse range of topics, from pest and disease management, breeding and genetics, production technology, production and post-production protocols, and consumer behavior.  Final reports on all AFE research are available at www.endowment.org.

** As a follow up to the last AFE Bulletin, Parts II and III of the Special Research Report “The Appeal of Biodegradable Packaging to Floral Consumers” are now published.


Congratulations to Vic and Margaret Ball Scholars!

AFE awarded three students the Vic and Margaret Ball scholarship from the March 1 application deadline.  These students will perform a three to six month internship at a commercial production operation.  Upon completion, they will receive a scholarship ranging from $1,500 – $6,000.  The next application deadline is October 1st – visit the AFE web site for more information.

Aric Compliment, a student at College of Dupage will complete a three-month internship at Heartland Growers, a family owned growing operation in Westfield, Ind.

Dominic Vercelote, a student at University of Georgia will perform a six-month internship at The Sun Valley Group in Arcata, Calif.

Rachel Palmer, a student at the University of Minnesota, will perform a three-month internship at Metrolina Greenhouses in Huntersville, NC.

Attention Growers:  If your business hosts interns and you would like to be considered as a Ball host employer, please contact AFE at (703) 838-5211.

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