Silica nanoparticle: a potential new insecticide for beet armyworm, Spodoptera exigua Hubner (Lep.: Noctuidae) control

Abstract

Application of pesticides for controlling crop pest produces deleterious effect on natural enemies, humans and the environment.  Therefore, the use of non-invasive and safe alternative methods is essential. Nanotechnology is a promising field of interdisciplinary research, and its practical applications into agriculture is receiving attention nowadays due to the potential benefits that nanomaterials (NMs) can guarantee pests management. In this study, potency of silica nanoparticle (SNPs) in  controlling the second larval instar of beet armyworm, Spodoptera exigua in laboratory and field condition, damage of pest and effect on total chlorophyll contents were evaluated. The LC₅₀ and LT₅₀ values of SNPs in three methods of application including dust spray, leaf dipping and solution spray were determined. The LC₅₀ value of SNPs against 2^nd larval stage after 24, 48 and 72 hours in dust spray, leaf dipping and solution spray were (660.40, 431.35, 893.10), (460.44, 833.31, 690.12) and (279.28, 565.59, 323.96) mg. L^-1, respectively. The LT₅₀ value of SNPs against 2^nd larval stage of S. exigua by three methods showed that dust application can cause 50% mortality in shorter time in comparison to leaf dipping and solution spray methods. In field trail, the result of mortality and damage assessment showed that dust SNPs had significant differences with control treatment (P≤0.05). Total chlorophyll contents in dust SNPs treatment had no significant differences with control treatment (P≥0.05). In summary, it can be noted that SNPs could be a new alternative to chemical insecticides and could be used in dust spray without using water in the development of new natural insecticides in integrated pest management program.