Introduction: Recently, the use of photosynthesis to produce nanoparticles has emerged as a reliable method in contemporary research. There is also a growing demand for the production of environmentally friendly insecticides. The primary objective of this research was to synthesize silver nanoparticles through a biological approach, using extracts from the algae Enteromorpha ralfsii, now classified as Ulva ralfsii (Harvey). Additionally, the study aimed to evaluate the performance attributes of the synthesised nanoparticles, including material formation, physicochemical characteristics, and long-term stability, for potential pest control applications. Methods: The nanoparticles were biologically synthesized using the extract of E. ralfsii. Their physical properties were analyzed using UV-Vis spectroscopy and scanning electron microscopy. The successful synthesis of Er-AgNPs was visually indicated by a color change. Additionally, the insecticidal potential of the biosynthesized silver nanoparticles from E. ralfsii was evaluated against O. surinamensis. Results: Observations from scanning electron microscopy indicated that the crystal sizes of the nanoparticles ranged from 29.3 nm to 79.14 nm. We also compared the effectiveness of nanoparticles with an aqueous extract of E. ralfsii. The results demonstrated that the biosynthesis of silver nanoparticles using E. ralfsii was most effective against the saw-toothed grain beetle. Specifically, the percentage of mortality observed was 100% for eggs, 80.4% for second-instar larvae, and 70.6% for adults at the fourth larval stage. In contrast, the aqueous extract achieved 75% mortality in eggs and 66.4% mortality in the second-instar larval stage when used at a concentration of 500 μg/mL. Discussion: The insecticidal activity of silver nanoparticles (AgNPs) involved multiple mechanisms. One such mechanism includes exposure to nano-biogenerated compounds, which leads to alterations in various biochemical parameters within insects. Specifically, reductions in total lipid and protein levels were observed, along with decreases in certain enzyme activities. These changes contribute to impaired growth and development, ultimately resulting in insect death. Conclusion: The findings of this study indicate that E. ralfsii represents a promising candidate for the development of naturally derived nanopesticides.
Mahmood et al. (Fri,) studied this question.