Bacterial Soft Rot of Dendrobium phalaenopsis and Phalaenopsis Species by Erwinia chrysanthemi

Occurrence of soft rots was observed on Dendrobium phalaenopsis and Phalaenopsis sp. that were grown at the greenhouses in Sunchon and Kwangyang areas, Chonnam province of Korea in 1997 and 1998. Typical soft rot symptom appeared frequently on young plants of D. phalaenopsis and Phalaenopsis sp. Soft rot symptom usually appeared on old leaves of D. phalaenopsis, and extended into whole leaves, accompanying blighting of whole plants. Symptom began as a small water-soaked lesion on old leaves of Phalaenopsis sp., which enlarged rapidly on the leaves and eventually resulted in soft rots of whole plants. The causal organism isolated from the infected lesions was identified as Erwinia chrysanthemi based on its pathogenicity, physiological and biochemical characteristics, and the results of the BIOLOGTM program. The bacterial soft rot caused by e. chrysanthemi was firstly describe din D. phalaenopsis and Phalanopsis sp. in Korea.