The insecticidal effect of silica nanoparticles on Callosobruchus maculates (Coleoptera: bruchidae) and its side effects

Abstract

Stored product insect pests were responsible for considerable quantitative and qualitative losses of agricultural products mainly cereals and legumes. Laboratory studies were carried out to evaluate the insecticidal potential based on contact and residual effect of the inert dust of silica nanoparticles (35±5nm) against the adult of stored pulse beetle Callosobrachus maculatus, in addition its effect on germination of the test seeds. Concerning the contact treatment, mortality assessed after 7 and 14 days from exposure to the three treated seeds (cow pea, kidney bean and chick pea) with silica nanoparticles (SNPs) among the different concentrations of SNPs 200 ppm was proved to be superior by recording highest mortality, lowest adults emerged, least seed damage in both cow pea and chick pea seeds up to 14 days of storage. Regarding the residual assay, the treated seeds storage for 7 and 15 days and exposure to C. maculatus was accomplished a complete mortality (100%) after 168 h on the three seeds varieties post treatment for 7 days (one week) concluded that (SNPs) was not proper effect and less efficient with long period. Treated seeds of these three varieties of pulses  revealed no effect on the  germination and the growth rate of root and shoot of cow pea and chick pea, except the kidney bean
was decreased the germination compared to respective control. Scanning electron microscope (SEM) was used to observe the adult insect exposed to silica nanoparticles treated seeds. The particles attached all over the insect body of the bruchid beetle with scratches and splits on the cuticle that lead to the loss of water through dehydration which eventually led to death. Silica is promising material for controlling the tested insect as safe alternative to synthetic insecticides.