PITH NECROSIS IN CHRYSANTHEMUM CUTTINGS AND FACTORS INFLUENCING ITS OCCURRENCE

Erwinia carotovora subsp. carotovora was associated with the internal hollowing and browning of the stem of chrysanthemum cuttings during rooting, known as pith necrosis.

The incidence of the disease increased when the cuttings were rooted in pressed peat blocks instead of in a loose rooting medium of peat and perlite.
Increased moisture levels resulting from longer misting periods or from addition of more water to the mixture of peat before pressing the blocks, promoted the disease.

Between cultivars differences in susceptibility were found; ‘Cassa’ was more susceptible than ‘Regoltime’ and ‘Westland’.

Cuttings from stock plants grown in nutrient solution with a higher electric conductivity (EC) than 1.5 mS.cm^-1 tended to be less susceptible to the disease.

Spraying the cuttings with or dipping them into an aqueous solution of streptomycin sulphate (60 mg a.i. per l) reduced the incidence of the disease.

Working-party on Greenhouse Chrysanthemum

N.A.M. van Steekelenburg, A.P. van der Hoeven, J.D. Janse

https://doi.org/10.17660/ActaHortic.1987.197.12