Green Insecticidal Approach: Toxicity of Peganum harmala Fixed Oil against Tribolium castaneum

Abstract

This study investigated the insecticidal effect of the fixed oil of Peganum harmala L., collected from the Reguiba region in Oued Souf Province, against the stored-product pest Tribolium castaneum (Herbst, 1797). The fixed oil was extracted from the seeds using a Soxhlet apparatus, yielding 24.33%, whereas mechanical cold pressing produced an exceptionally higher yield of 30.13%. Bioassays were conducted using two methods: direct contact and fumigation. Three concentrations (2.5, 5, and 10 μl mL-1) were tested, with three replicates for each. In direct contact tests, mortality reached 100% after 24 h at 2.5 and 5 μl mL-1, and 90% after 6 h at 10 μl mL-1, with a median lethal concentration (LC50) of 2.34 μl mL-1 after 12 h. During fumigation, 100% mortality was observed after 48 h at 5 μl mL-1 and after 24 h at 10 μl mL-1, with an LC50 of 7.52 μl mL-1 after 12 h. Mortality data were analyzed using probit analysis and corrected with Abbott’s formula. These results demonstrate that the toxicity of P. harmala fixed oil is both dose- and time-dependent, as adult T. castaneum mortality increased progressively with higher concentrations and longer exposure periods. Overall, the study highlights the potential of P. harmala fixed oil as a natural biopesticide for the management of major stored-product pests.