Journal of Taiwan Agricultural Research

Fig. 2.　Control evaluation of Dickeya fangzhongdai Di-001 by spraying treatment with hypochlorous acid (HOCl) solution (B) 5 mg L^-1, (C) 10 mg L^-1, (D) 20 mg L^-1, (E) 50 mg L^-1, (F) 100 mg L^-1, and (A) sterile distilled water for 5 d at 28℃.

Author:Chiao-Wen Huang, Tsung-Chun Lin, Shu-Joan Zeng, Szu-Lun Lai, Ting-Fang Hsieh, and Chia-Hsin Tsai*

Abstract:

Phalaenopsis orchids are important export flowers in Taiwan, with an annual production value of nearly 4.6 billion NT dollars. However, bacterial soft rot significantly affects their cultivation and export value. Therefore, this study evaluates the effectiveness of hypochlorous acid (HOCl) solution as a control material for preventing bacterial soft rot in Phalaenopsis orchids. Different inoculum concentrations of the rot bacteria were tested to assess their impact on disease occurrence. Results showed that at a high concentration of 108 CFU mL^-1, the disease incidence was as high as 58.3−81.3%, while at 106 CFU mL^-1, it was 25.0−43.8%. At a low concentration of 104 CFU mL^-1, the incidence decreased to 0%, indicating a gradual reduction in disease occurrence with lower bacterial concentrations. Laboratory experiments demonstrated that treating the bacteria (108 CFU mL^-1) with a 10 mg L^-1 HOCl solution for 10 min inhibited their growth. Pot experiments revealed that at a HOCl concentration of 20 mg L^-1, the control efficacy against bacterial soft rot ranged from 18.0% to 66.7%. In contrast, the control efficacy increased from 50.0% to 88.9% at 50 mg L^-1, showing significant differences in control effectiveness. Thus, HOCl solution can control the bacterial disease of Phalaenopsis soft rot caused by Dickeya fangzhongdai in orchids.

Key words:Phalaenopsis, Hypochlorous acid, Soft rot, Dickeya fangzhongdai, control