Selection of biocides for use in floral preservatives

The effects of concentrations of various biocides, in a solution containing 0.2 g l citric acid and 10 g l glucose, were tested on cut roses (Rosa hybrida L., ‘Classy’), Alstroemeria pelegrina L. and carnations (Dianthus caryophyllus L.). Compounds were evaluated for their effects on flower life (time to decline in fresh weight), maximum gain in fresh weight, solution uptake from 4 to 6 days, resistance to water flow in the stem, stem respiration and solution absorbance. Longer flower life and higher gain in fresh weight of roses were observed with a concentration of 0.05 g l than with higher concentrations of most biocides. At this concentration, bromopropanediol, Dantogard and thiabendazole did not prevent a rise in stem resistance to water flow, or solution absorbance. Aluminium sulphate up to 0.8 g l was also ineffective in these respects. Stem respiration was inhibited by sodium benzoate, hydroxyquinoline citrate (HQC), Isocil and Physan-20. Principal component analysis on the rose data indicated that the best treatments were 0.05 g l benzoate, cetylpyridinium chloride, Isocil and Physan-20, 0.05 and 0.2 g l dichloroisocyanuric acid, and 0.2 and 0.8 g l HQC. Tests with carnation and Alstroemeria indicated that HQC, Isocil and Physan most consistently promoted fresh weight increase and maintenance. © 2000 Elsevier Science B.V. All rights reserved.