Jojoba (Simmondsia chinensis) Leaf Extracts as Biodegradable Botanical Insecticides against Lepidopteran Pests and the Cotton Aphid

During the past few decades, the excessive use of chemical insecticides has resulted in pest resistance and environmental contamination, necessitating the urgent need for low-toxicity and effective treatments. We investigated the insecticidal properties of jojoba [ Simmondsia chinensis (Link) Schneider] leaf extracts obtained from solvents of varying polarity (water, acetone, ammonium hydrogen peroxide, and isopropanol) against Spodoptera exigua Hübner, Pieris rapae L., and the cotton aphid ( Aphis gossypii Glover). Standardized topical bioassays were performed using concentrations ranging from 0.25% to 8% (w/v) applied to second-instar larvae and adult aphids, with mortality rates recorded over a period of 168 h and analyzed through probit regression to determine the values for the lethal concentration that kills 50% (LC 50 ) and the lethal concentration that kills 90% (LC 90 ). All extracts demonstrated significant concentration- and time-dependent mortality ( P < 0.001), with the polarity of the solvent having a substantial impact on efficacy. Acetone extracts displayed the greatest and most rapid toxicity, achieving LC 50 values of 3.2 and 3.5 mg·mL –1 against S. exigua and P. rapae , respectively, and an LC 90 mortality rate of 95.4% in A. gossypii . Aqueous extracts exhibited slower action but comparable final efficacy (LC 90 = 96.7%), whereas ammonium hydrogen peroxide and isopropanol extracts were less effective (LC 90 = 72%–78%). The dose–response relationships were strongly linear ( r = 0.884–0.997), confirming the analytical robustness of the study. These results indicate that jojoba leaves contain a variety of bioactive phytochemicals that can be extracted using simple, environmentally friendly solvents. Furthermore, our research underscores the potential of jojoba leaf extracts as scalable and biodegradable, which could significantly reduce reliance on chemical pesticides and promote sustainable pest management.