Evaluating the efficiency of silver nanoparticles prepared using Pseudomonas fluorescens and Bacillus thuringiensis subsp. tenebrionis in controlling eggs and adults of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract

This study aimed to evaluate the efficiency of silver nanoparticles (AgNPs) which are prepared biologically by two bacterial species, Bacillus thuringiensis tenebrionis (Btt) and Pseudomonas fluorescens (P.f) to control southern cowpea beetle insect, Callosobruchus maculatus. Many features of the prepared nanoparticles were examined, and the results obtained showed that the highest absorption value of AgNPs was at 262 nm. Whereas the results of FTIR analysis showed that several compounds played a role in the silver ions reduction process, which included alcohol, alkane, primary amine, and amine group. The scanning electronic microscopic images showed that the average diameter of nanoparticles which was created by P.f was 48.52 nm, while it was 56.08 nm for the nanoparticles prepared by Btt. The study showed no significant differences between the activity of both AgNP types against C. maculatus eggs, while a significant preference was recorded for the activity of Btt AgNPs against the C. maculatus adults. The highest percentage of unhitched eggs was 53.8% recorded at 3000 ppm concentration, while Btt AgNPs gave 59.6% at 3000 ppm. The highest mortality rate of the adults who were treated by Btt AgNPs was 58.8 % at 3000 ppm concentration, while it was recorded 50% at 3000 ppm with P.f AgNPs treatment. The current study demonstrates the efficiency of biologically prepared AgNPs in controlling C. maculatus insect life stages, which encourages using of these nanoparticles as a modern strategy in management of insect pests.