Nerium oleander Leaf Extract Causes Midgut Damage and Interferes with the Survival of Culex pipiens L. Larvae

Background: Diseases vectored by mosquitoes are one of the major causes of diseases and death worldwide. Insecticide resistance of Cx. pipiens increased the suffering of the people. Plants are a promising source of secondary metabolites to help resolve this problem. Methods: This study investigated the larvicidal potential of N. oleander methanol aqueous extract against Cx. Pipiens. Result: Post 24 h, 48 h and 72 h of exposure, the LC50 value was 4.94 mg/mL, and the LC90 value was 8.01 mg/mL. After 72 h of exposure, the values were 2.93 mg/mL and 4.79 mg/mL, respectively. Larvae treated with N. oleander leaf extract displayed degraded microvilli, degenerating peritrophic membrane and degenerating nuclei with blebbing compared to the control. The GC-MS analysis revealed the presence of eleven phytoconstituents in the leaf extract. 1-Methyl-1H-Tetrazol-5-yl)thio]acetic acid (80.67%), 2-Furancarboxaldehyde, 5-1 (hydroxymethyl)- (8.10%), and 9,12-Octadecadienoic acid (Z, Z)- (4.33%) were the main secondary metabolites found in the leaf extract.