Prefatoryin silicostudies andin vitroinsecticidal effect ofNigella sativa(L.) essential oil and its active compound (carvacrol) against theCallosobruchus maculatusadults (Fab), a major pest of chickpea

Abstract

AbstractTo help discover a reasonable and eco-friendly insecticide, we undertook a study on the insecticidal potential of carvacrol and essential oils extracted by hydrodistillation using a Clevenger apparatus from the plant speciesNigella sativaseeds essential oils ofNigella sativa(EONS) onCallosobruchus maculatusadults. Several tests including contact toxicity, repellent effect, topical contact test, and inhalation effect were conducted. Adults ofC. maculatushave been exposed to the toxic effects of different concentrations of these essential oils as well as with carvacrol. The results obtained showed that both EONS and carvacrol exhibited a moderate repellent effect (class II) onC.maculatusadults. EONS showed the highest toxicity by inhalation test, with an LD50of 13.386 and an LD95of 33.186 μL/cm2, compared to carvacrol (LD50= 21.509 and LD95= 38.877 μL/cm2). The EONS by contact test exhibited more toxic effects, with an LD50of 23.350 µL/100 g and an LD95of 45.315 µL/100 g, compared to carvacrol (LD50= 27.853 µL/100 g and LD95= 45.184 µL/100 g). For the topical contact test results, carvacrol was more toxic, with an LD50of 3.915 and an LD95of 7.696 µL/mL, compared to EONS (LD50= 14.509 and LD95= 25.516 µL/mL). The high toxicity of EONS can be explained by the presence of 25.8% ofo-cymene, 8.53% of cyclofenchene, and 7.71% of beta-pinene, as well as 4.6% of carvacrol, in its chemical composition. Unmitigatedly, these data suggest that the essential oils ofN. sativamay present a raw material for the development of new bio-insecticidal products againstC. maculatus, one of the main pests of stored foodstuffs.