Nanopesticides, particularly biosynthesized ones using organic reductants, hold great promise as a cost-effective and eco-friendly alternative to chemical pesticides. However, their efficacy on stored product pests, which can cause damage to dried grains, has not been extensively tested, especially on immature stages. Here, we biosynthesized six types of nanoparticles (NPs) using extracts from the fungusFusarium solani: silver (AgNPs), selenium (SeNPs), silicon dioxide (SiO2NPs), copper oxide (CuONPs), titanium dioxide (TiO2NPs) and zinc oxide (ZnONPs) ranging in size from 8 to 33 nm. To test their efficacy on stored bean pests, they were applied to the eggs and larvae of pest beetlesCallosobruchus chinensisandCallosobruchus maculatus(Coleoptera: Chrysomelidae: Bruchinae), which burrow into seeds as larvae. Susceptibility to the NPs was species-dependent and differed between developmental stages; eggs were more susceptible than larvae inhabiting in seeds. SeNPs and TiO2NPs reduced the hatchability ofC. chinensiseggs by 23% and 18% compared to the control, respectively, leading to an 18% reduction in egg-to-adult survival by SeNPs. InC. maculatus, TiO2NPs applied to eggs reduced larva-to-adult survivorship by 11%, resulting in a 15% reduction in egg-to-adult survival. The egg mass ofC. chinensiswas 23% smaller than that ofC. maculatus: the higher surface-area-to-volume ratio of theC. chinensiseggs could explain their higher acute mortality caused by the NPs compared toC. maculatuseggs. The biosynthesized SeNPs and TiO2NPs have potential for controlling major stored bean pests when applied to their eggs. This is the first to show the efficacy of biosynthesized SeNPs and TiO2NPs on stored product pests and the efficacy ofFusarium-synthesized NPs on insects.