Silica nanoparticles have been successfully created using an easy and environmentally friendly process by using plant metabolite from M. oleifera extract. Plant metabolites, such as terpenoids, polyphenols, sugars, alkaloids, phenolic acids, and proteins, play an essential role in the bio-reduction and capping agents to achieve the stability of the prepared metal nanoparticles compounds (Makarov et al., 2014). It is commonly recognized that using plant extracts for the synthesis of NPs is a competitive and efficient process (Allafchian et al., 2016). Many other studies examined the phytochemical analysis of moringa leaves and found similar consistent (Mensah et al., 2012; Khalid et al., 2023). It was showed that moringa leaves could easily biosynthesize a wide variety of nanoparticles (Jadhav et al., 2022). Many researchers used moringa extract in synthesizing different successful types of nanoparticles (Moodley et al., 2018; Jadhav et al., 2022); Shalaby et al. (2022) prepared FeO, NiO, MgO, CuO, Au, ZnO, Ag, and La2O3 nanoparticles by using moringa. Active ingredients which found in moringa leaves function as stabilizing, reducing, and capping agents as well as producing biosynthesized metal nanoparticles (NPs). Our findings are consistent with the research of Abd Rani et al. (2018); (Bagheri et al., 2020), who found that moringa contains a wide range of phyto-constituents, such as phenolic acids, glucosides, flavonoids, terpenes, alkaloids, saponins, tannins, and steroids which play an essential role in the bio-reduction and capping agents to achieve the stability of the prepared metal nanoparticles compounds (Makarov et al., 2014).
Previous studies used GC-MS analysis for M. oleifera leaves extract and found similar compounds to the present work (Syeda and Riazunnisa, 2020; Adeyemi et al., 2021; Khan et al., 2022). The characterization of SiNPs was confirmed by many researchers using UV-Vis as characterization tool and similar results were detected when SiNPs were produced from other resources (Djangang et al., 2015; Babu et al., 2018; Morales et al., 2019). The spherical shape of SiNPs using plant extract was confirmed by SEM (Periakaruppan et al., 2022; Sankareswaran et al., 2022). The EDX sharp peaks indicated that the synthesized SiNPs had a crystalline structure (Khan et al., 2017).
Numerous studies examined the use of various insecticides to combat the fall armyworm. Most research concurred with our findings, showing that emamectin, indoxacarb, and chlorpyrifos are effective against the fall army worm larvae. However, the median lethal concentration values varied, and this was due to variations in the population, bioassay method, and the instar of larvae. For instance, Liu et al. (2022) studied the effect of emamectin benzoate on 3rd instar larvae of S. frugiperda after 24 h and found that the LC50 was 0.106 mg/L, and Amein (2023) obtained LC50 values = 0.18 mg/L when treated emamectin benzoate on the 4th instar larvae, while Ahissou et al. (2021) evaluated the susceptibility of third instar larvae of different populations to seven commercially insecticide in Burkina Faso and found that emamectin benzoate was the most effective, the LC50 values was within the range 0.00033–0.00038 mg/L. leaf dip bioassays using 3rd instar larvae LC50 values were recorded on emamectin benzoate (0.11–0.12 ppm) (Dileep Kumar and Murali Mohan, 2022). Deshmukh et al. (2020) studied the effect of emamectin benzoate, indoxacarb, and other insecticides on the 2nd instar larvae by the leaf-dipping method. They found that emamectin benzoate showed the highest toxicity among all insecticides with LC50 = 0.0051 mg/L, and indoxacarb demonstrated moderate effect with LC50 = 0.29 mg/L. Field applications supported the same results. Using the corn husk soaking method, three different populations of fall armyworms were used to test the toxicity of emamectin benzoate and indoxacarb. The highest mortality rates were seen with emamectin benzoate (80:100%) when treated with 0.018 g/L, and indoxacarb ranged from 42:65% when treated with 0.047 g/L after 72 h (Bonni et al., 2020).
Suryani et al. (2022) examined the susceptibility of emamectin benzoate by mixing it with an artificial diet against first-instar larvae of five different field populations and one laboratory population of S. frugiperda. After seven days, the LC50 values ranged from 0.11 mg/L: 0.39 mg/L compared to the laboratory population (LC50 = 0.24 mg/L). However, the toxicity of chlorpyrifos on the 4th larval instar of S. frugiperda recorded LC50 value = 470 mg/L (Salem et al., 2023). The effect of chlorpyrifos against the 3rd instar larvae by leaf dip bioassay recorded LC50 values within the range 199–377 mg/L (Dileep Kumar and Murali Mohan, 2022) and 99.73-106.32 mg/L (Ahissou et al., 2021). Long-term usage of synthetic pesticides can harm crops and the environment and lead to insecticide resistance. Researchers are actively looking for options that can safely control this pest while being successful. A family of nanomaterials known as nanocarriers can enable the targeted delivery and controlled release of fertilizers and insecticides in plants (Patra et al., 2018). Nanopesticides' increased surface area to volume ratio and surface energy makes it easier for an effective agent to penetrate and adhere to a plant's surface. Therefore, the use of nanopesticides could significantly boost their efficacy. Silica nanoparticles offer a variety of benefits over bulk silicon sources for use in managing insect pests. SiNPs can act as a carrier for the pesticide to be delivered in a controlled release or as an insecticide to kill the targeted pest insects (Saw et al., 2023). These findings align with many other studies that have used SiNPs as insecticide carriers to boost their potency. It has been established that SiNP is a reliable and safe source of insecticides that may be employed at low and ecologically friendly dosages to control various other insect pests (Attia et al., 2023; Saw et al., 2023).
The residual toxicity of Ch-SNPs against adults of Rhyzopertha dominica and Tribolium confusum was assessed by Satehi et al. (2018) using prepared silica nanoparticles loaded with chlorpyrifos (Ch-SiNPs) as a carrier. Ch-SiNPs was discovered to be successful in controlling both tested insect species. Both species exposed on Petri dishes treated with 0.01 g/m2 Ch-SiNPs had 100% mortality even after 6 hours of exposure, 7 days following treatment. Another study on stored grain insects by Ziaee and Babamir-Satehi (2020) found that the mortality rate of T. granarium larvae was greatly increased by the administration of loaded deltamethrin and chlorpyrifos insecticides in silica nanoparticles. Abamectin 1.8%® and abamectin loaded on mesoporous silica nanoparticles (MSiNPs) were tested for their toxicological effects on Plutella xylostella 3rd instar larvae by Feng et al. (2021). Abamectin/MSNs exhibited a longer duration and control influence on P. xylostella, with a lower survival rate of 30% compared to abamectin®, whose survival rate reached 93%. Indoxacarb-loaded nanoparticles were created by Bilal et al. (2020) and showed greater insecticidal activity against P. xylostella compared to indoxacarb technical at the same doses. Additionally, treatment with indoxacarb-loaded nanoparticles reduced the activity of detoxifying enzymes such GST, CarE, and P450 in P. xylostella.