Use of emulsifiers for control of rice blast and sheath blight in organic rice cultivation

摘要

Currently, practices for controlling disease in organically produced rice (Oryza sativa L.) crops are not as effective as conventional ones. The objective of this research was to determine the effectiveness of various organic emulsifiers (natural emulsifier A and B, loess sulphur, brown rice vinegar, and insecticidal soap) on the suppression of fungal pathogens, rice blast (Pyricularia oryzae Cavara) and sheath blight (Rhizoctonia solani Kuhn), and rice growth. Suppression activity of emulsifiers onmycelia growth of rice blast was proportional to dosage, and the order of effectiveness was: loess sulphur > natural emulsifier B > insecticidal soap > brown rice vinegar > natural emulsifier A. Rice sheath blight suppression of mycelia growth was also proportional to emulsifier concentration. Rice sheath blight was totally suppressed by 0.5% loess sulphur, 3% brown rice vinegar or insecticidal soap. The order of effectiveness of these emulsifiers was: loess sulphur > insecticidal soap > brown rice vinegar > natural emulsifier B > natural emulsifier A. Rice injuries due to blast infection were significantly reduced by the organic emulsifiers (0.5-10%), compared to untreated control. Therefore, the results suggest that organic emulsifiers could effectively control rice blast and sheath blight without contributing to adverse in rice growth.