Biological screening of Clerodendron inerme leaf extracts for repellency and toxicity potentials against stored product insects

摘要

 Botanicals have been used traditionally as grain and legume protectants against stored product insects. The objective of this study was to evaluate the repellent and insecticidal activity of different solvent extracts of Clerodendron inerme (L.) leaf against the red flour beetle Tribolium castaneum (Herbst), the lesser grain borer Rhyzopertha dominica (F.), and the cowpea weevil Callosobruchus chinensis (L.). The area preference method and dose-mortality was used to determine repellency rate and insecticidal activity. The average repellency of 0.02?l, 0.04?l, 0.08?l of the methanol, petroleum ether and ethyl acetate extract concentrate per cm2 of C. inerme leaves totally achieved class II, III, class IV and class V respectively at different intervals (2, 4, 8 hours) of time. The order of repellent activity was Callosobruchus chinensis < Rhyzopertha dominica < Tribolium castaneum. Theconcentrate of methanol- extract of Clerodendron inerme leaves was found to be more effective than the commercial product teflubenzuron (No: SZBB291XV) and also more effective than other solvent extracts. The order of repellent activity was Callosobruchus chinensis < Rhyzopertha dominica < Tribolium castaneum. The dose-mortality test of methanolic extracts of C. inerme leaf indicates that the LD50 (1.74 mg/cm2)and LD99 (3.01 mg/cm2) was very high in C. chinensis compared to the other two beetles. Our result indicates that the repellent activity was dose and extract dependent in different intervals of time and dose-mortality of the methanolic extract varied depending on the insect species