The Lethal Effect of Nanosilica (SiO2) and Nanocopperoxide (CuO) against Ephestia kuehniella Zeller

Introduction According to the international organizations, stored-product insects can cause serious postharvest losses. The Mediterranean flour moth, Ephestia kuehniella Zeller is a world-wide pest of the main stored products. This pest was attracted to a large variety of food types and grain in stores where its larvae can cause serious damages. The feces and webbings of the larvae cause additional quantitative degradations of the product. Fumigants are commonly used for control of the stored product pests, but awareness of the health hazard from pesticide residue and the growing problem of insect resistance to the conventional insecticides have provoked the discussion among the researchers to explore the alternative strategies for protection of the stored products. Using of nanoparticles as pesticide is another alternative for conventional pesticides. Nanoparticles due to being less dangerous for the environment, the warm-blooded animals can be used as an alternative for conventional pesticides. Nanoparticles are ultra- fine particles which have at least one dimension which is less than 100 nm. Because of having increased ratio of surface to volume, nano-particles are more reactive than their bulk counterpart. So, the present study was performed to investigate the potential effect of nanosilica and nanocopper oxide against larvae of E. kuehniella.
Materials and Methods Ephestia kuehniella larvae were reared on broken wheat grain at 27± 1°C, 50% ± 5 RH with a photoperiod of 14L: 10D. Nanosilica (SiO2) and nanocopperoxide (CuO) was synthesized in the laboratory by ultrasonication method (ref: Rao et al. Size of nanoparticles was measured by scanning electron microscope. To study the oral toxicity of the nanoparticles, different concentrations of nanosilica (0.200, 0.287, 0.412, 0.592 and 0.850 mg/kg) and nanocopper oxide (1.20, 1.60, 2.135, 2.848 and 3.80 mg/kg) was mixed with a certain amount of diet and then 30 three-day old larvae were kept in each treatment. Larval mortality was recorded after 7 and 21 days and adult emergence was counted after 51 days. The experiments were carried out with four replications. Distilled water was used in the control treatment. To study the contact toxicity of nanosilica, fifteen-day-old larvae (third instar) were transferred into Petri dishes (n=10 larvae). Larvae were sprayed with 750 ml of aqueous emulsions of different concentrations (0.800, 1.640, 1.414, 1.880 and 2.500 mg/L) of nanosilica. The spray was applied by using Potter Precision Spray Tower. The experiments were carried out with nine replications. Distilled water was used in the control treatment. Larval mortality was recorded over five days. Statistical analysis was performed using SPSS 18 software followed by Duncan’s multiple range test (P