Bioinsecticidal activity of aspergillus-derived endophytes from Olea europaea against Culex pipiens: toxicity, histology, and GC-MS profiling.

Endophytic fungi offer a sustainable and eco-friendly alternative to synthetic insecticides, providing targeted pest control with reduced environmental toxicity and lower risk of resistance development. In this study, four endophytic fungi were isolated from Olea europaea and their ethyl acetate extracts' larvicidal efficacy of Culex pipiens. Boxplot distributions revealed a positive correlation between metabolite concentration and larval mortality, with higher doses inducing greater lethality. Extracts 1 and 2 exhibited the highest larvicidal activity, with median mortality rates exceeding 60%, while Extracts 3 and 4 demonstrated significantly weaker effects. Dose-response curves further confirmed the potency of Extracts 1 and 2, with lower LC₠₀ values (148.36 and 153.36 µg/mL) compared to Extracts 3 and 4. The histological analysis revealed a dose-dependent impact, with minimal tissue alterations at 25-50 µg/mL, while 150-200 µg/mL caused severe disorganization, apoptosis, and inflammatory responses. The most potent isolates, Aspergillus niger(Extract 1) and Aspergillus flavus(Extract 2), were identified morphologically and molecularly, with NCBI accession numbers PQ269689 and PQ269690, respectively. GC-MS analysis identified key bioactive compounds, including oleic acid and hexadecanoic acid, supporting their insecticidal potential. These findings highlight A. niger and A. flavus ethyl acetate extracts as promising sources of bioinsecticides for pest control.