Maize weevil is one of the most common and critical storage pest in the world. In this study, the insecticidal activity of the methanol extracts derived from Caesalpinia sappan was evaluated against adults of maize weevil, using by direct contact and fumigant methods. Based on the two methods, ethyl acetate fraction of the C. sappan extracts had 100% mortality against Maize weevil adults at 10 mg. The biological constituent of C. sappan extract was isolated by various chromatographic techniques and identified as juglone. On the basis of 72 h LD50 values, in the direct contact bioassay, the insecticidal activity of juglone (0.010 mg/cm2) was the most effective, followed by 1,4-NQ (0.018 mg/cm2) and menadione (0.087 mg/cm2). In a fumigant bioassay, the insecticidal activity of juglone (0.014 mg/cm2) was the most effective, followed by 1,4-NQ (0.015 mg/cm2) against maize weevil adults. On the other hand, menadione, lawsone, and 2-methoxy-1,4-NQ observed no insecticidal activity or weak. These results suggested that active compound of C. sappan materials could be used as biological control agent against maize weevil. Therefore, further research should be performed to the structure activity relationship of juglone and compared with its derivatives.

• Hoi-Seon Lee(Department of Agricultural Chemistry, Chonbuk National Universi)