The control of Culex pipiens and Anopheles pharoensis considered as important strategy in eliminating diseases transmitted by the two mosquito species. Application of plantderived products in mosquitos' control reported as much effective, less expensive and safer to human, as well as environment than their synthetic counterparts. The present study investigated the activity of Lagenaria siceraria leaves aqueous extract and L. siceraria- synthesized silver nanoparticles (AgNPs) against immature stages of C. pipiens and A. pharoensis. Immature stages of both tested mosquito species were exposed to 50, 100, 200, 300 and 400 ppm of L. siceraria leaves aqueous extract and 5, 10, 20, 30 and 40 ppm of L. sicerariasynthesized AgNPs for 24 h. It was found that L. siceraria leaves aqueous extract can reduce aqueous silver ions to generate silver nanoparticles suspended in water. The results of DLS revealed that, the average hydrodynamic diameter calculated for AgNPs was 33.25 nm, while the TEM images showed the occurrence of individual silver nanoparticles
(13.38-27.70 nm) and a number of aggregates in the test suspension. In addition, L. siceraria- synthesized AgNPs were more toxic against tested mosquito species than L. siceraria leaves aqueous extract. The LC50 values recorded 15.2, 18.2, 22.5, 24.7 and 29.4 ppm against C. pipiens first to fourth instar larvae and pupae; whereas LC50 values were 11.9,
14.5, 17.7, 19.8 & 23.1ppm against A. pharoensis first to fourth instar larvae and pupae, respectively.