Megan Bame

UV-C Irradiation Improves Vase Live of Cut Gerbera

Decline in postharvest quality of cut flowers is often related to disease, such as infection of Botrytis cinerea. Lesions on the flower petals due to infection have been noted in waxflower, freesia, gerbera and rose, among others. Typical disease management relies on conventional fungicide application, which, after extensive use, may result in fungicide resistance. This study aimed to evaluate the potential of UV-C irradiation to control floret specking and extend vase life in cut gerbera.
The gerbera cultivars ‘Ice Cream’ and ‘Ecco’ were used for this experiment. UV-C doses of 0.5, 1.0, 2.5, 5.0 and 10.0 kJ/m2 were applied for various exposure times. The germicidal effect of UV-C irradiation was assessed by measuring conidial germination and mycelial growth. Vase life was considered terminated when gerbera florets started to senesce and change in color, or when stems were bent over 90 degrees.
UV-C radiation produced a significant negative effect on both mycelium and conidia of B. cenerea. Furthermore, lesion diameters on the florets of both cultivars tested were reduced by all UV-C treatments. Vase life, flower fresh weight and water uptake was maintained or increased at all UV-C treatment levels. For example, the vase-life of  ‘Ecco’ treated with 10.0 kJ/m2 UV-C was extended by 2.4 days, while ‘Ice Cream’ treated with 1.0 kJ/m2 UV-C irradiation saw the incidence of stem breakage delayed by 3.3 days.
Based on the results of this study, the authors propose low UV-C doses ranging from 0.5 to 1.0 kJ/m2 for cut gerbera to maintain postharvest quality and keep B. cinerea infections low. This use of UV-C irradiation is envisioned as a component of an integrated postharvest disease management program.

Darras, A.I., V. Demopoulos and C. Tiniakou. 2012. UV-C irradiation induces defence responses and improves vase-life of cut gerbera flowers, Postharvest Biology and Technology, 64:168-174.

Cocktail for Improving the Vase Life of Cut Tulips

Tulip vase life is often limited by tepal senescence, tepal abscission, leaf yellowing or stem elongation that result in a drooping flower head. This study looks at multiple approaches to determine whether, if applied together, each of the vase life detriments could be addressed with one treatment.
The study initially began with two cultivars, ‘Apeldoorn’ and ‘Frappant’, but ultimately resulted in testing on a range of other cultivars. Also, initially treatments were applied in the vase solution just prior to initiating the vase life study, but further testing looked at a pulse-treatment directly after harvest.
In short, the following combination was used successfully as a continuous treatment starting shortly after harvest: 0.10 mM ethephon, 0.5 mM GA3 (gibberellic acid), 0.05 mM BA (benzyladenine) and 10 mM calcium chloride or calcium nitrate. For an overnight (12-hour) pulse treatment or a 6-hour pulse in daylight, the following concentrations were proposed: 0.50 mM ethephon, 1.5 mM GA3, 0.5 mM BA and 50 mM calcium chloride. Higher concentrations (1.0 mM ethephon, 2.5 mM GA3, 1.0 mM BA and 100 mM calcium chloride) were needed for a 1-hour pulse, lighted at 20C.
Vase life following pulse treatment and a 48-hour dry transport at 5C was also evaluated with results generally indicating an increase in vase life by 2 to 5 days.
As the authors used various chemicals (ethephon, GA3 and BA) to address a negative aspect of tulip morphology during vase life, they were met with at least one negative side effect for each chemical. They note that “remarkably, when these three growth substances were combined, and calcium ions were added to alleviate the negative effect of BA, all negative side effects disappeared.”
Stem bending was prevented by exogenous ethylene (ethephon). Used alone, ethephon would cause early tepal shattering and lack of flower opening, but the addition of gibberellic acid, benzyladenine and calcium ions alleviated the negative side effects and delayed flower and leaf senescence.

van Doorn, W.G., R.R.J. Perik, P. Abadie and H. Harkema. 2011. A treatment to improve the vase life of cut tulips: Effects on tepal senescence, tepal abscission, leaf yellowing and stem elongation, Postharvest Biology and Technology. 61:58-62.

Skip the Soda Tankmix when Battling Thrips

Some greenhouse producers have suggested that adding a sugar substance to an insecticide as a tankmix will help to combat western flower thrips. The theory is that the sugar will attract the thrips from the tightly enclosed areas where they often reside and will encourage them to come in contact with or consume the insecticide. This study tests this theory in laboratory and greenhouse condition to provide quantitative data that will support or refute this practice.
The sugar additives tested were: white sugar, brown sugar, Mountain Dew and Diet Mountain Dew. Nymph and adult stage thrips were used in testing. Attraction to the treatments was measured by how long the thrips visited each treatment. This study found that neither adult nor nymph stage western flower thrips were attracted to any of the sugar-based treatments regardless of rate. Therefore, there is no benefit to adding these types of materials into spray solutions for control of western flower thrips.
Suggestions for best control when using insecticides include: obtaining thorough coverage of all plant parts, applying insecticides frequently enough, and rotating insecticides with different modes of action to avoid populations developing resistance.

Cloyd, R.A., J.D. Gillespie, 2012. Effect of Sugar-based Compounds in Enhancing the Efficacy of Insecticides against the Western Flower Thrips, HortTechnology. 22(2):177-184.

Megan Bame

Megan Bame is a freelance writer in Salisbury, North Carolina. Contact her at [email protected]