الخلاصة:
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.
