Though, silica nanoparticle (SNP) synthesized by sol-gel method is being used in various fields for the last two decades, its application in agro-veterinary sector is very limited. The potential of surface functionalized SNP as a novel nanocide was investigated for its prospective use in agrochemical industry. Spherical, monosidperse SNP was synthesized from silicon alkoxide and it was functionalized in situ with 3-Mercaptopropyltriethoxysilane and Hexamethyldisilazane. These two types of SNPs were applied against second instar larvae of Spodoptera litura. S. litura is a polyphagous insect pest and causes huge damage to a number of crops. Both of these SNPs could effectively kill the insect larvae. Silica is comparatively non-reactive and these SNPs have almost no crystalline impurity. So this silica based nanocide can be an alternative to the commercial insecticides which have numerous health hazards. Moreover, as the action of these nanocides is physical, insects are unlikely to grow resistance against them. (c) 2012 Elsevier B.V. All rights reserved.