AbstractBacterial stem rot, due toErwinia chrysanthemi, is a serious problem in ornamental crop protection, e.g. inDieffenbachia. It was our aim to compare the effect of the synthetic compound CGA 78039 and streptomycin sulphate on the suppression of stem rot disease inDieffenbachia. Different treatments were applied under natural and artificial infection pressures. Pretreatment of the mother plants with CGA 78039, followed by dipping of the cuttings overnight in the same solution before potting and five subsequent weekly foliar sprays during growth reduced the expression of stem rot inDieffenbachiasignificantly.