Study of the Insecticidal Effect of Essential Oils and Extracts of Two Medicinal Plants and Evaluation of Their Synergistic Potential in Vivo

Abstract

Plants synthesize secondary metabolites, which are chemical substances (bioactive molecules) that play a vital role in chemical defense, fight against herbivores, and infectious agents.In this perspective, we conducted a study to evaluate the toxicity of essential oils formulated from the leaves of PistacialentiscusL. and Juniperusphoenicea L. and their synergistic effect on the populations of citrus aphid (Aphis).The objective of our study was to compare the physicochemical properties of extracts from two medicinal plants, to evaluate their synergistic potentials in vivo, and to determine the insecticidal activity by using different treatments with essential oils and extracts, depending on the time and solvent used.

The recorded results gave promising values of mortality rates for their individual or synergistic use, which are of the order of 83.43% for the essential oil of P.lantiscus and 99.03% for the essential oil of J.phoenicea. The synergy of the essential oils was 88.63%, which is higher than the effect of the essential oil of J .phoenicea alone, indicating a synergistic effect between the two plants. A mortality rate of 97% was recorded for the acetone extract of J.phoenicea and 56.60% for the acetone extract of P. lantiscus. The synergy of the acetone extracts was 75.03%, which means that their effect was between the acetone extract of J.phoenicea and the acetone extract of P.lantiscusalone, indicating that certain molecules are partially synergistic between the two plants. The mortality rates for the methanolic extracts were 80% for the methanolic extract of J.phoenicea and 99% for the methanolic extract of P.lantiscus. The synergy of the methanolic extracts was 94.65%, which means that their effect was lower than the effect of the methanolic extract of P.lantiscus alone, indicating that certain molecules are partially synergistic between the two plants. A mortality rate of 87.47% was recorded for the aqueous extract of J.phoenicea and 91% for the aqueous extract of P.lantiscus. The synergy of the aqueous extracts was 93.27%, which means that their effect was higher than the effect of the aqueous extract of P.lantiscus alone, indicating that there is a positive effect between the two plants.The lethal times determined by probit analysis (TL20, TL50, TL90) showed that the treatment "synergistic essential oil" showed the shortest TL50 with 4.98 hours, while the treatment "methanolic extract of P.lentiscus" showed the shortest TL90 with 12.06 hours.These same results allowed us to say that the bioproducts based on essential oils have shown a very significant effect on the citrus aphid (Aphis).