Characterisation of silver nanoparticles synthesised by Bacillus thuringiensis as a nanobiopesticide for insect pest control

Nanotechnology has become one of the most promising new approaches for pest control in recent years. In this research, biocompatible silver nanoparticles (Btk-AgNPs) were synthesised by using the entomopathogenic bacterium, Bacillus thuringiensis kurstaki (Btk) as a low-cost and eco-friendly production system. The AgNP samples exhibited a brownish-yellow colour that is characteristic for silver nanoparticles synthesis. Btk-synthesised AgNPs were produced using both the supernatant and pellet of Bt culture at various concentrations and AgNP particles were characterised by UV-Vis spectrophotometer and Dynamic Light Scattering (DLS). The variation of hydrodynamic diameter (Dh) and UV-Vis spectra of silver particles produced by various concentration of culture showed that production of AgNPs was maximised when using 20% for either supernatant or pellet treatments of Bt of culture and the size of particles was around 85 nm for both. The insecticidal efficacy of Btk-synthesised AgNPs against larvae of the cabbage looper, Trichoplusia ni (Hubner) and black cutworm, Agrotis ipsilon (Hufnagel) was tested. Results demonstrated that the treatments of either Btk-synthesised AgNP (s) made with Bt supernatant or Btk-synthesised AgNP(p) using Bt pellet were found to be significantly more virulent toward larvae of T. ni than to A. ipsilon.