Abstract

Essential oils extracted from two medicinal plants Peganum harmala and Rhanterium epapposum native to the Arabian Peninsula specially Saudi Arabia, were evaluated for their larvicidal effects and emergence of Khapra beetle (Trogoderma granarium) adults. The oil analyzed by thin layer chromatography, the results of phytochemical analysis indicated that the presence of Alkaloids, flavonoids Triterpenes, Cumarins and Tannins in the two ethanolic extracts. The most abundant compounds were alkaloids and flavonoids. The essential oil of P. harmala showed toxicity against T. granarium third instar larvae with equivalent LD50 values of 23.5 μg/ml, when fed on treated seeds, with significant mortality rates up to 66% in three days. Whereas the toxicity effect was 49.7 μg/ml against T. granarium third instar, larvae contact treated surface. The essential oil of R. epapposum resulted into higher toxicity with LD50 values of 22.3 μg/ml with significant mortality up to 70% in three days. Comparing total mortality percentages of R. epapposum and P. harmala ethanoic extract on different treatments gives a good insight about their bioactivity.

Key words: Insecticidal effect, oil extract, botanical insecticide, khapra beetle.