Introduction

Helicoverpa armigera is a species of Lepidoptera in the family Noctuidae and one of the most devastating, cosmopolitan and polyphagous pest attacking a wide range of crops including cotton, chick pea, maize, sorghum and vegetables like tomato, okra, cabbage, brinjal1. It has a wide geographical adaptability exhibiting its presence in almost all the continents. It can cause yield losses (20–60%) and expected to inflict 2 billion USD annual loss in various crops2. Therefore, management strategies for this pest have become necessary in almost every cropping system employing chemical pesticides. However, the injudicious, indiscriminate and continuous use of conventional chemical insecticides led to alteration of genetic characteristics leading to development of insecticide resistance3. Conventional pesticide formulations may also have an assortment of other shortcomings; including higher doses per unit area, limited solubility in water, drift and operational hazards, residue on food products, and detrimental impacts on non- target organisms. Therefore, it is imperative to develop safe alternatives to existing pesticide formulations. In this context, nanopesticides arise as a promising solution, offering a viable approach to address the challenges associated with conventional pesticide formulations.

The utilization of nanotechnology in agriculture implies a revolutionary shift from the use of hazardous conventional pesticides. The small size, enhanced wettability, adsorption of the target, and enhanced adhesive qualities on the plant surface of nano-pesticides make them highly effective when compared to conventional pesticide formulations4,5. Nanoemulsions are the most widely accepted type of nanoformulation due to its superior stability against droplet flocculation, coalescence, sedimentation, or creaming. The nanosize of the droplets increases the bioefficiency of nano-insecticidal formulation against insects by enhancing its penetration and transmission through the larval exoskeleton6. It also provides advantages in terms of longer shelf life, less pesticidal residue and low dosage application per unit area7. Nanoemulsions provides a better kinetic stability to pesticides formulation, improves its solubility by dissolution of weakly water-soluble components, provides low surface tension and wettability8. Indeed, the nanoemulsion serves a dual role by not only delivering the active ingredients effectively but also acting as a protective coating layer9. Periodically, a more recent class of insecticides, diamides has been developed to address the issue of pesticide resistance. The mode of action of diamide insecticides is based on the anomalous regulation of ryanodine receptor sites, which results in the uncontrollable release of calcium from the sarcoplasmic reticulum to muscle fibers. Irreversible muscle contraction results in rapid food uptake, heart muscle failure, paralysis, lethargy and ultimately, insect death10. Chlorantraniliprole, [3-bromo-N- [4-chloro-2 -methyl-6- [(methyl amino) carbonyl] phenyl]-1-(3-chloro-2-pyridinyl)-1 H-pyrazole-5-carboxamide] (Fig. 1), is a novel ryanodine receptor pesticide belongs to anthranilic diamide group developed by DuPont Crop Protection, having many upsides including high effectiveness, low toxicity, extended persistence, and low residue generation11. The current research aimed to develop and characterize chlorantraniliprole nanoemulsion (O/W) and evaluate its toxicity against H. armigera (Hubner) under in vitro conditions.

Fig. 1
figure 1

Chemical structure of Chlorantraniliprole ( Drawn using Chem Draw version-20.0).

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Materials and methods

Chemicals

Chlorantraniliprole (98%) was procured from Sigma Aldrich (Technical grade). Organic solvents (acetone, butanol, cyclohexane, dimethyl sulfoxide (DMSO), methyl benzene, and N-methyl-2-pyrrolidone (NMP) were purchased from Merck Chemicals Ltd. India (Analytical grade). Other reagents such as deionized water (D.I.), Polyoxyethylene sorbitan monooleate (tween 80), and sodium lauryl sulphate (SLS) were purchased from Sigma Aldrich (Analytical grade) and used without further purification.

Synthesis of nanoemulsion

Chlorantraniliprole nanoemulsion was synthesized by following the methodology of Sugumar, et al.12 with slight modifications. Briefly, nanoemulsion was synthesized using chlorantraniliprole as an active ingredient, solvents (Dimethyl sulfoxide, butanol, toluene), tween- 80 (non-ionic surfactant) sodium laurel sulfonate (anionic co-surfactant), and deionized water. The concentrations of the components (solvents, tween 80 and water) were standardized to develop a stable nanoemulsion. Moreover, the concentration of active ingredient (chlorantraniliprole) was taken as 5%, 8% and 12% to synthesize nanoformulation I (NFI), nanoformulation II (NFII) and nanoformulation III (NFIII), respectively. Firstly, the solvents were taken in a 250 ml beaker and chlorantraniliprole was thoroughly mixed in solvents under continuous magnetic stirring. In aqueous phase, surfactants were mixed with deionized water in a beaker. The organic (oil) phase consists of chlorantraniliprole mixed in solvents (Dimethyl sulfoxide, butanol, toluene) and aqueous phase contains mixture of deionized water and surfactant (tween- 80 & sodium laurel sulfonate). A coarse emulsion was prepared by dropwise addition of organic phase into aqueous phase under stirring. Then, coarse emulsion was ultrasonicated (20 kHz) using probe sonicator to reduce size in nanometer (nm).

Stability analysis

Nanoemulsion stability was analysed using stress tests13,14. The prepared nanoformulations was centrifuged at 2500 rpm for 30 min and observed for stability and phase separation. freeze thaw cycle stability test was done by keeping the prepared formulations at temperature range − 21 °C and + 25 °C for 48 h in triplicates. Then, Heating-cooling test was performed by keeping the prepared nanoemulsion at temperature range 4ºC to 40ºC for 48 h in triplicates.

pH measurement

pH is an important aspect of nanoemulsions which determine its stability due to changes by chemical reactions. The pH of prepared nanoemulsion was analysed by using digital pH meter (µ pH system 361, Systronics). The samples were repeated thrice under. Furthermore, for nanoemulsion screening, pH phtotoxicity test was also performed on 15 plants of brinjal (Solanum melongena) in three replicates under isolated conditions. Phytotoxicity is the damage shown on plant and its growth as a result of any toxic compound. However, nanoemulsion and commercial formulation of chlorantraniliprole were thoroughly mixed in water at median lethal concentration before spraying on plants.

Particle size and morphology characterization

Particle size of nanoemulsion (5% dilution in D.I. water) was measured using particle size analyser (PSA, Malvern zetasizer) based on dynamic light scattering (DLS) principle. Moreover, stability of nanoemulsion was confirmed by Zeta potential analyser (Malvern zetasizer). Surface morphology and nanosize of emulsion was analysed using a transmission electron microscopy (TEM, Tecnai G2 20 TWIN, FEI, USA) and field emission scanning electron microscope (FESEM, JSM-6700 F, JEOL Ltd., Japan) at magnifications (x30k and x50k) and at 15 kV accelerating operating voltage. The particle size was estimated using image J software. The polycrystalline nature and crystallite size of lyophilized nanoformulation was analysed using X-ray diffractogram (XRD, Rigaku Smart Lab 3 kW) having Cu-Kα radiation energy source (40 kV, 40 mA) of wavelength 0.154 nm, scanned over a range of (2θ = 5°-80°) at a scan speed of 2 º /min, and scanning step of 0.02º. Surface chemistry of nanoemulsion was analyzed through Attenuated Total Reflectance-Fourier transformation infrared spectroscopy (ATR-FTIR) in the spectral range of 600–4000 cm− 1 through 8 scans at 4 cm− 1 resolution.

Bio-efficacy of chlorantraniliprole nanoformulation

Bio-efficacy of chlorantraniliprole nanoemulsions having active ingredients 5% (NFI), 8% (NFII), and 12% (NFIII) were evaluated against H. armigera to determine the lethal concentrations (LC50 and LC90) and relative toxicity (RT) in vitro using topical application method15 and diet incorporation method16. H. armigera adults were collected from unsprayed fields of sunflower and chickpea (Research Farm, Department of Entomology) and reared on chickpea flour based artificial diet under laboratory conditions [Temperature: 27–29 °C, Relative Humidity13: 65 ± 5% and Photoperiod:14 h (Light)-10 h (Dark)]17. Ten pairs of male and female H. armigera were released in wired cylindrical cages of iron frame wrapped with muslin cloth and provided 10% honey solution by soaking the cotton swab. Then, eggs were laid on muslin cloth, and once they hatched, the neonates were detached with a wet camel hair brush and transferred on an artificial diet. The cultures of larvae were maintained by transferring approximately 10–12 neonates per magenta box containing artificial diet. After 2–3 days each larva was separated into rearing box to prevent the cannibalism. A homogeneous stock of 3rd instar larvae was selected for toxicity assessment at different concentrations of chlorantraniliprole nanoformulations by using topical application method. However, 1st instar larvae were chosen to evaluate the toxicity using diet incorporation method. Larvae were starved for 12 h before all bioassay experiments.

Topical application method

Concentrations (0.07, 0.05, 0.03, 0.023, 0.017, 0.013, and 0.009 ppm) of nanoformulations as well as commercial formulation were prepared by serial dilution method and sprayed (1 ml) over the ten newly molted 3rd instar larvae of H. armigera by using Potter’s tower under pressure (3.4 × 104 N m− 2) in triplicates. A homogenous stock 10 larvae per replications were used. Moreover, distilled water was sprayed over larvae as control. After 1 h, each larva was transferred to separate culture cubes containing artificial diet. The bioefficacy was studied under in vitro conditions (Temperature: 27 ± 1 °C and Relative Humidity (RH): 65 ± 5%). Mortality at different concentrations of nanoformulation was evaluated after 24 h of exposure18.

Diet incorporation method

Insecticidal activity at seven concentrations (0.07, 0.05, 0.03, 0.023, 0.017, 0.013, and 0.009 ppm) of chlorantraniliprole nanoformulations as well as commercial formulation were also evaluated using diet incorporation method against one day old F1 generation of H. armigera larvae in three replications. A homogenous stock of newly hatched 10 larvae per replications were used. 3 ml of the solution was taken into a 40 ml plastic cup and lukewarm diet (at ~ 60 °C) was poured, to make a total volume of 30 ml. After placing the lid, the cup was shaken vigorously for a minute to mix it properly. Then, the diet was poured into wells of a 25-cell insect rearing tray up to a height of 0.5 cm and allowed to cool at room temperature for 1 h. The strength of stock solutions used for diet preparation was tenfold of required concentration, therefore, the final concentration of insecticide was diluted tenfold in diet. Control larvae were released on untreated diet. Subsequently, 1st or early 2nd instars larvae of H. armigera were released in trays at the rate of one larva per well. Diet tray was covered with semi-permeable wrap and lid was closed. Mortality at different concentrations of nanoformulation was evaluated after 24 h of the exposure16.

Relative toxicity refers to the comparative measure of the toxic effects of compounds, such as insecticides, on different organisms or systems. It quantifies the degree to which one substance is more or less toxic than another based on various metrics and can be calculated using the given formula.

$$Relative\,toxicity = \frac{median\:lethal\:concentration\:of\:standard\:insecticide\:}{median\:lethal\:concentration\:of\:tested\:insecticide}$$

In given study standard insecticide is chlorantraniliprole commercial formulation 18.5SC & tested insecticide is nanoformulations of chlorantraniliprole.

Data analysis

The data was analyzed using one-way analysis of variance (ANOVA) and Duncan’s multiple range test using software package IBM SPSS 23.0 with a statistically significant value of p < 0.05. Median lethal concentration (LC50) was calculated using automated algorithm POLO19,20 based on log-probit technique and value of p < 0.05 was deemed to be statistically significant. The graphical work was done through Origin lab 9.0 (2018) software.

Results

Synthesis and stability of nanoformulations

Optimized nanoformulation (NFI, NFII, and NFIII) are obtained by mixing chlorantraniliprole (active ingredient, or\ a.i.), solvent and surfactant in different ratio (1:18:1, 1:12:1, 1:6:1). Combinations of polar and non- polar solventsand surfactants enhance the stability of nanoemulsion as no precipitation or phase separation is observed. Centrifugation can accelerate the rate of sedimentation due to the action of gravitational and centripetal force yet, on centrifugation (2500 rpm) no creaming, sedimentation or phase separation are observed indicating stability of nanoemulsion. Thermodynamic stability test such as freeze thaw cycle and heating-cooling test shows no coalescence, cracking or phase separation thus, also indicating the thermal stability of nanoemulsion. Hence, the synthesized chlorantraniliprole nanoformulations are stable and easy to use. Moreover, pH of nanoemulsion formulations are acidic (3.8-4) at 25 ± 1 °C and are safe to use on dilution with water as no phytotoxic effects is observed on brinjal. DLS studies shows the size of nanoformulations as 54 nm (NFI), 62 nm (NFII), and 79 nm (NFIII). The zeta potential of nanoemulsions are 27.88 mV (NFI), 30.51 mV (NFII) and 38.97 mV (NFIII) indicates stability and PDI of nanoformulations are < 0.7, indicates monodispersed particles in nanoformulations.

Characterization of nanoformulation

Surface chemistry and functional group analysis

Qualitative analysis of functional groups presents on chlorantraniliprole nanoemulsion (NFII), in primarily used solvents such as butanol and DMSO, are estimated by ATR-FTIR under frequency range 600–4000 cm− 1 (Fig. 2a). The ATR-FTIR analysis shows a broad peak at ~ 3392 cm− 1 corresponding to intermolecular H-bonding (NH—OH) between the hydroxyl (-OH) group of butanol and amide (-CONH-) functional group of chlorantraniliprole. There is also a strong possibility of intramolecular H-bonding (NH—O = C-) between amine (-NH) and carbonyl (-C = O) functional groups of chlorantraniliprole. However, the O-H stretching peak corresponding to intramolecular H-bonding has less peak intensity and merged in O-H stretching peak corresponding to broad intermolecular H-bonding. The characteristic stretching peak of sp3 hybridized -C-H of alkane present in butanol is observed at 2930 cm− 1. Sharp Peak at 1713 cm− 1 designates the -C = O stretching vibrations of carbonyl of secondary amide functional group present in chlorantraniliprole. The carbonyl peak of secondary amide has shifted to 1713 cm− 1 from its normal position (1600–1690 cm− 1) due to the presence of electron withdrawing 2-chloro-4-methylphenyl and 3-bromopyrazole substituents which shows inductive effect (-I effect) and attracts electron density from -C = O groups towards themselves, hence increase frequency of -C = O stretching vibrations to 1713 cm− 1. Sharp peak at 1644 cm− 1 indicates the aryl -C = C stretching vibrations. The peak at 1507 cm− 1 indicates the aryl -C = C bending vibrations. The peak at 1470 cm− 1 is corresponding to the -C-N stretching vibrations. Peaks at 1170 cm− 1 and 1014 cm− 1 attributes the -C-S and -S = O stretching vibrations of dimethyl sulfoxide. Peak at 950 cm− 1 is corresponding to the = C-H out of plane bending vibrations of aryl rings. Peak at 840 cm− 1 and 656 cm− 1 designates the -C-Cl and -C-Br stretching vibrations.

Powdered X- Ray diffraction (pXRD)

Technical chlorantraniliprole has prominent diffraction peaks at 8.77°, 17.32°, 21.87°, 25.10°, 30.20°, and nanoformulation of chlorantraniliprole (NFII) has the characteristic peaks at 15.92°, 19.98°, 25.98°, 32.36°, 38.20°, 50.64° (Fig. 2b). The synthesised nanoformulations are polycrystalline in nature. The intense characteristic peak of chlorantraniliprole indicates crystalline nature. However, the less intense peak and broad humps of chlorantraniliprole nanoformulation indicates a certain degree of amorphous nature. The average crystallite size of chlorantraniliprole nanoformulation is 42.9 nm using Debye Scherrer equation indicating the nanosize of synthesized formulations.

$$\:D=\frac{K\:\lambda\:}{\beta\:\:Cos\theta\:}$$

Where, D is crystallite size of nanoformulation, K = Debye Scherrer constant (0.9), λ is X-ray wavelength (0.154 nm), β is Full width at half maxima (FWHM), and θ is Bragg’s diffraction angle.

Fig. 2
figure 2

(a) ATR-FTIR analysis of technical chlorantraniliprole and nanoformulation (b) XRD diffractogram of technical chlorantraniliprole and nanoformulation.

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SEM and TEM analysis

The morphology and nanosize of chlorantraniliprole nanoformulation (NFII) is examined through Field emission scanning electron microscopy (FE-SEM) and Transmission electron microscopy (TEM). The SEM image indicates the spherical shape of nanoemulsion particles (Fig. 3a and b). The size distribution shows the particle size lies in the range of 30–100 nm indicates some particles has agglomerated during lyophilizing (Fig. 3c). The average size of the nanoemulsion (NFII) is 55 ± 5 nm which is accordance with PSA of NFII (62.43 nm). The TEM analysis is done to evaluate the size of individual particle of nanoemulsion. The TEM images of nanoemulsion (NFII) shows that particles are dark and spherical in morphology (Fig. 3a). The size distribution exhibits the particles size lies in the range 5–35 nm. And the average size of the particle is 22.5 ± 2.5 nm (Fig. 3b).

Fig. 3
figure 3

SEM image of nanoemulsion at (a) x 50k, (b) x 30k, (c) SEM size distribution of nanoemulsion particles, (d) TEM image of nanoemulsion, (e) TEM size distribution of nanoemulsion particles.

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Bio efficacy of nanoemulsions against H. armigera

Under topical application, the LC50 and LC90 are 0.032 ppm and 0.077 ppm for NFI, 0.013 ppm, and 0.028 ppm for NFII, 0.011 ppm, and 0.025 ppm for NFIII against H. armigera at 24 h exposure time period (Fig. 4a). However, the commercial formulation of chlorantraniliprole shows LC50 and LC90 as 0.037 ppm, and 0.108 ppm, respectively. It elucidates that nanoemulsion NFI, NFII and NFIII are 1.2, 2.8 and 3.3 times more effective than commercially available chlorantraniliprole formulation (Table 1).

Diet incorporation method shows LC50 and LC90 as 0.035 ppm and 0.100 ppm for NFI, 0.014 ppm, and 0.034 ppm for NFII, 0.012 ppm and 0.027 ppm for NFIII against H. armigera at exposure time period of 24 h (Fig. 4b). The commercial chlorantraniliprole nanoformulation shows LC50 and LC90 as 0.026 ppm and, 0.180 ppm, respectively. Diet incorporation method shows that nanoemulsions NFII and NFIII are 1.8 and 2.2 times more effective than commercially chlorantraniliprole nanoformulation (Table 2). However, NFI is not so effective as compare to commercial formulation, due to low amount of active ingredient (a.i.) resulting less ingestion of pesticides in larval body.

Table 1 Toxicity values (LC50, LC90) and relative toxicity (RT) of nanoemulsions and commercial formulation of chlorantraniliprole against 3rd instar larvae of H. armigera using topical application method.
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Table 2 Toxicity values (LC50, LC90) and relative toxicity (RT) of nanoemulsion and commercial chlorantraniliprole against 1st instar larvae of H. armigera using diet incorporation method.
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Fig. 4
figure 4

(a) Toxicity values (LC50, LC90) of nanoemulsions and commercial chlorantraniliprole against 3rd instar larvae of H. armigera using topical application method. (b) Toxicity values (LC50, LC90) of nanoemulsion and commercial chlorantraniliprole against 1st instar larvae of H. armigera using diet incorporation method.

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Discussion

Stability of any pesticide formulation is a major concern to make it commercially available for insect pest management. For a nano-based delivery system, a nanoformulation should remain stable throughout its defined storage period. Smaller droplet size of nanoemulsions leads to higher transparency in appearance21, which requires low concentration of surfactant as compared to microemulsion and EC formulations of insecticides22,23. Moreover, the percentage of active ingredient, amount of emulsifier, water percentage, sonication time and power of sonication affects the stability of nanoemulsion24. Chlorantraniliprole nanoemulsion is prepared using tween 80 as surfactant in combination with sodium lauryl sulfonate as co surfactant. The concentration of surfactant controls the size of the emulsion droplets. When the concentration of tween 80 is low, insufficient amount of surfactant leads to agglomeration and increases the particle size. However, when surfactant amount is sufficient to stabilize the emulsion the particle size decreases. This is because there is enough surfactant in the bulk to enable quick surfactant diffusion and adsorption to freshly produced droplets. Further, increase in surfactant amount increases the surfactant diffusion thus, reduces droplet coalescence. Flax seed oil nanoemulsion using tween 40 (surfactant) prepared using ultrasonication showed the similar results25. The DLS studies shows that chlorantraniliprole nanoemulsions have particle size 54 nm, 62 nm and 79 nm for the NFI, NFII and NFIII, respectively and are stable as proved by centrifugation, thermal stability tests (freeze-thaw cycle, heating cooling tests) and zeta potential analysis. The centrifugation (2500 rpm) shows no change in physical appearance even after 4–5 months. Centrifugation accelerates the rate of deposition which indicates the breakdown of nanoemulsions due to gravitational force. Thermal stability test such as freeze thaw cycle and heating cooling test also shows stability of nanoformulation by maintaining the homogenous state. The zeta potential (> 25 mV) is also an indicator of stability of nanoemulsions26. The PDI < 0.7 of nanoformulations indicates monodispersed particles in nanoformulations and shows stability alongwith good uniformity of nanoparticles. Stable nanoemulsions have low surface tension, can be used efficiently in agricultural fields due to uniform application on plants and improved spreading and impregnation27,28. Results of present investigation is supported by the study of many researchers. Similar particle size (29 nm and 96 nm) and PDI (0.26) were obtained for chlorantraniliprole solid nanodispersion11. Fenpropathrin nanoemulsion had 62 nm particle size and 0.6 PDI that less than EC formulation29.

The characterization techniques such as FTIR and XRD confirm the synthesis of chlorantraniliprole nanoformulation. The FTIR studies reveals the presence of qualitative functional groups such as amide (-CONH-), carbonyl (-C = O), halogen groups (-Cl, -Br) on its surface and suggests inter and intramolecular H-bonding interaction between the solvents and chlorantraniliprole nanoformulation indicating the solubility in water (Fig. 2a). XRD studies shows that the chlorantraniliprole nanoformulation is polycrystalline in nature. Nanoformulation have some broad humps the chlorantraniliprole acquired some amorphous character during formation (Fig. 2b). The coexistence of crystalline and amorphous nature of chlorantraniliprole nanoemulsion promotes its importance and application in agriculture. The crystalline nature improves its storage stability by resisting agglomeration and amorphous nature enhances water solubility, hence improves bioavailability of poorly soluble chlorantraniliprole (a.i.)11,30. The SEM micrographs shows that the particles of synthesized nanoemulsion are spherical in shape and confirm the size in nano range (Fig. 3a). The particle size of NFII observed by SEM (55 ± 5 nm) is in accordance with the size obtained by dynamic light scattering (62.43 nm). Transmission electron microscopy (TEM) shows the size of individual nanoparticle. The TEM micrograph depicted in results illustrates the spherical shape of droplets, showcasing the typical appearance of an oil-in-water nanoemulsion (Fig. 3d). Transmission electron microscopy (TEM) analyses further verified that the droplet diameter in the formulations is within the nanometric scale (22.5 ± 2.5 nm). Furthermore, the nanoemulsion shows the uniformity of particles and no aggregation and coalescence. This is attributed to the stabilizing effect of surfactant surrounding the particles and prevent them from agglomeration. The results are supported by many researchers as the nanoemulsions of specific pesticides exhibit similar microostructure and size distribution patterns31,32,33,34.

Chlorantraniliprole is a novel anthranilic diamide pesticide developed by DuPont Crop Protection11, represents a significant advancement in pest control technology. This selective insecticide exhibits efficacy against a diverse array of pests, including Lepidoptera, Coleoptera, Diptera, and Isoptera. Among these pests, H. armigera stands out as a particularly problematic polyphagous pest of agricultural crops. The synthesized chlorantraniliprole nanoformulation is found to be more toxic against H. armigera than commercially available SC formulation of chlorantraniliprole. Bio efficacy studies shows that NFI, NFII and NFIII are 1.2, 2.8 and 3.3 times more effective than commercial chlorantraniliprole under topical application (Fig. 4a). However, nanoemulsions NFII and NFIII are 1.8 and 2.2 times more effective than commercially chlorantraniliprole nanoformulation under diet incorporation method (Fig. 4b). The high toxicity of nanoformulation against H. armigera is due to nano size of emulsion droplets that cover more surface area on insect body, have faster reach to target sites and adsorbs more pesticides35. Hence, increases the penetration of chlorantraniliprole nanoformulation in the larval body. Results of present investigation are supported by many researchers. The chlorantraniliprole formulation showed 0.03 ppm LC50 against some field strains of H. armigera36. Similarly, Chlorantraniliprole formulation showed 0.036 ppm LC50 against H. armigera37. Bio efficacy of chlorantraniliprole against H. armigera in tomato investigated by Patel, et al.38, found chlorantraniliprole 35 WG @ 30 g a.i./ha was more effective as compare to other doses and all doses were safer to spiders and other natural enemies. The higher toxicity of synthesised nanoformulations than commercially available formulation is also inspected by many researchers. Acorus calamus L. nanoemulsion was developed by using ultrasonication and tested for bio efficacy against pulse beetle (Callosobruchus maculatus f.). The developed formulation showed higher toxicity against C. maculatus as compared to macroemulsion at lower concentration39. Taktak, et al.40 prepared nanoemulsion of four pyrethroids i.e. include alpha-cypermethrin, deltamethrin, lambda- cyhalothrin, and permethrin by using high energy ultrasonication method. The toxicity of nanoemulsions was evaluated against Culex pipiens larvae showed higher toxicity (1.5-2 folds) compared with the technical and commercial formulations. Nano pyridalyl was 3.13 times more effective than commercially available formulation against H. armigera larvae35. Imidacloprid nano crystals encapsulated with chitosan alginate showed higher toxicity (1.36 times) against the adult of Martianus dermestoides, when compared to 95% imidacloprid41. Solid nano dispersion of chlorantraniliprole was 2.8 and 3.3 times more toxic than aqueous suspension concentrates and technical compound against diamond back moth11. Thus, these studies support the present research work and proposed chlorantraniliprole nanoformulation as a candidate pesticide having high efficiency to control the H. armigera.

Conclusion

Advancements in agricultural science and technology have revolutionized pesticide usage, offering greater flexibility in safeguarding crops against insect attacks. However, the indiscriminate use of chemical-based pesticides has led to resistance in plants, rendering them more susceptible to insect pest outbreaks. Integrating potential insecticides with nanotechnology presents a promising avenue for integrated pest management in plant protection sciences. Traditional pesticide formulations have adverse effects on non-target organisms and environment, highlighting the necessity for developing nanoformulations of novel pesticide groups to facilitate targeted delivery and reduce pesticide doses. Among these, diamides have shown potential in combating a variety of insect pests having peculiar mode of action that promotes disfunctions in ryanodine receptors in insects. The Chlorantraniliprole nanoemulsion was synthesized by using high energy ultrasonication method, found to be stable and in nanometric range validated by DLS (62.43 nm), SEM (55 ± 5 nm) and TEM (23 ± 2 nm). The bio-efficacy studies showed that, the nanoformulation (a.i.:12%.) had 3.3 times and 2.4 times more insecticidal activity than commercially available chlorantraniliprole (a.i.:18.5%) against H. armigera using topical application and diet incorporation methods, respectively. Hence, due to its demonstrated effectiveness and reduced environmental impact, chlorantraniliprole stands as a beacon of hope in the ongoing battle against agricultural pests, offering farmers a potent weapon to safeguard their crops for enhancement of agricultural productivity.