Insects quickly develop resistance to conventional chemical insecticides. The use of silica nanoparticles (SiO₂NPs) is a promising new approach for managing insect pests. The insects that have been studied are, in most cases, external feeders and internal leaf feeders have not been well studied. Here, we investigate the efficiency of SiO₂NPs in controlling the American serpentine leafminer Liriomyza trifolii (Diptera: Agromyzidae), a devastating insect pest of a wide range of crops. SiO₂NPs at concentrations of 50, 100, 200 and 400 mg/L compared to a control of distilled water were applied to intact Phaseolus vulgaris leaves by spraying to evaluate their effects, via the plant, on the number, survival, developmental/feeding speed, body mass/size and sex ratio of L. trifolii released after spraying. A qRT-PCR analysis was conducted to assess oxidative stress in L. trifolii based on the gene expression level of the two major antioxidant enzymes; catalase and superoxide dismutase. The number of mines, survival rate and puparia weight were lower than the control at the highest concentration of SiO₂NPs, while pupariation was delayed at most of the concentrations studied and puparium weight/size decreased at low concentrations. Sex ratio was not affected by SiO₂NPs. Gene expression levels of the antioxidant enzymes at the pupal stage were not significantly affected by SiO₂NPs at any concentration but some individuals showed up-regulation at low SiO₂NP concentrations, inferring development of resistance. This study demonstrated that a priori application of the highest concentration of SiO₂NPs to plants effectively reduces a leafminer population but that application of even the lowest concentration can decrease the life history trait values of surviving leafminers.