Étude de l'activité insecticide des extraits organiques de Citrullus colocynthis Schard. (Cucurbitatceae), Pergularia tomentosa L. (Asclepiadaceae) et Datura stramonium L. (Solanaceae) récoltées dans la région de Oued Metlili.

Abstract

This study aims to evaluate the insecticidal activity of foliar extracts of three spontaneous plants collected in the Algerian Sahara at Ghardaia (Oued Metlili). For the present study, solid-liquid extraction by maceration, two organic extraction solvents, namely ethanol and acetone, were chosen for this method. The evaluation of the effectiveness of the extracts is done by the contact test on insects. It was noted that the extracts obtained are rich in secondary compounds such as: Flavonoids, Coumarins, Steroids, Free Quinones. The parameters measured are the mortality rate, the lethal dose 50 (LD50) and the lethal times (TL50). Citrullus colocynthis acetone extract achieved a 100% mortality rate after 66 hours. The mortality percentages recorded for the ethanolic extract are also remarkable, reaching 100% after 72 hours. In contrast, the acetone extract of Pergularia tomentosa produced a 100% mortality rate, while the ethanolic extract reached 90%. Similar results were observed for Datura stramonium extract, with a mortality rate of 100% for the acetone extract and 86% for the ethanolic extract at a dose of 50 mg/mL after 72 hours. The evaluation of lethal doses 50 (LD50) made it possible to verify the degree of toxicity of the extracts tested: the low LD50 values for the acetone and ethanolic extracts underline the strong insecticidal power by contact of these extracts with respect to imagos. of Tribolium castaneum. After 72 hours, the LD50 for the acetone and ethanolic extract of C. colocynthis are respectively 1.36 mg/mL and 1.42 mg/mL, which is lower than for the two other plants tested, which demonstrates the strong power of extracts from this plant. In addition, the evaluation of lethal times 50 (LT50) shows that the extract of C. colocynthis presents a particular speed of action with respect to imagos of T. castaneum, especially at high concentrations.