Abstract
This study was conducted to evaluate the toxicity of aqueous, ethanolic and acetonic extracts of Lantana camara L. (Verbenaceae), Ruta chalepensis L. (Rutaceae) and Rhazya stricta Decne (Apocynaceae), against larvae of Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), feeding on wheat seeds after 2, 4, and 6 days (d). These plants commonly grow in arid and semi-arid conditions and may provide novel natural insecticides against larvae of T. granarium. Results showed that the plant extracts demonstrated varying levels of toxicities, with the acetonic extracts providing the greatest efficacy. The acetonic extract of L. camara demonstrated a higher toxicity effect, with LC50 of 330.6 ppm (after 2-d) and 110 ppm (6-d), compared to 467 ppm (2-d) and 251 ppm (6-d) for R. stricta, and 576 ppm (2-d) and 317 ppm (6-d) for R. chalepensis. Overall, toxicity of acetonic extracts was about 1.3 fold greater compared with that of aqueous or ethanolic extracts throughout the range of concentrations tested (50-400 ppm). The acetonic extracts required six days to achieve >= 80% mortality of larvae. In conclusion, this study suggests that the acetonic extract of L. camara, R. chalepensis and R. stricta could be used as a sustainable method for controlling Khapra beetle, pest of stored grains.