Investigating the plant metabolite potential as botanical insecticides against Spodoptera litura with different application methods

Abstract

This study investigated the effectiveness of botanical insecticides derived from leaf extracts of Azadirachta indica, Aglaia odorata, and Ageratum conyzoides against third instar larvae of Spodoptera litura through different application methods. The plant materials were mixed in a 1:1:1 ratio, extracted with 96% ethanol. The results showed that the botanical insecticides were effective in killing the S. litura larvae through both oral and topical application techniques. The topical application was more effective, with an average mortality rate of 98.75% compared to 82.5% for oral application. The LT50 values were 5.9991 and 3.8555 days for oral and topical treatments, respectively. The topical application was 35.73% faster in inducing mortality in S. litura compared to oral application. The larvae-treated with oral application had the highest total quinine-equivalent alkaloid content at 312.52 mg L⁻¹, while the larvae-treated with topical application had the highest total flavonoid content at 3963.60 µg L⁻¹ in the total flavonoid test. The highest value of total tannic acid-equivalent tannins was observed in larvae-treated with oral application at 1.76% w/v. All larvae that were treated, both orally and topically, in this study were found to contain terpenoids within their body. In conclusion, the botanical pesticides derived from the extracts of A. indica, A. odrata, and A. conyzoides have proven to be effective in controlling S. litura. The topical application technique has been found to be more efficient than oral application in inducing mortality. However, it is crucial to conduct further testing in both greenhouse and field conditions in the future.

Keywords:

• LT50
• metabolite
• mortality
• oral
• topical

1. Introduction

Spodoptera litura (Lepidoptera: Noctuidae), often known as the tobacco cutworm and the cotton leafworm, is a Noctuidae moth species. It is a prevalent pest in Indonesia and many other Asian countries, as well as certain regions of Africa and Australia. The larvae of S. litura feed on a wide range of crops, including cotton, rice, tobacco, soybeans, and a number of vegetable and fruit crops (Srivastava et al., 2018). The damage caused by the larvae’s feeding can lead to substantial economic losses for growers. The severity of yield loss produced by S. litura can vary based on a number of variables, including the stage of plant development, the crop species, and the population density of the pest. In severe situations, yield loss might be as high as 50 percent or more, causing farmers severe financial damage (Natikar & Balikai, 2015; Sharma et al., 2022).

In order to mitigate and manage the infestations caused by S.litura, farmers must implement effective agronomic practices, such as crop rotation, proper planting and crop management techniques, utilizing biological control agents and planting resistant varieties wherever possible (Srivastava et al., 2018). Regular monitoring of crop fields is also of utmost importance, and prompt action must be taken in case of any observed damage. It is critical to understand that S. litura is a persistent pest that has the potential to significantly affect agriculture in Indonesia (Thakur et al., 2023). Hence, efforts to control and manage this pest are crucial for the long-term viability of agricultural production in the country.

The development of resistance to insecticides by S. litura is a major challenge facing farmers in Indonesia. It is a common phenomenon in agriculture, often resulting from the improper and frequent use of insecticides (Saleem et al., 2016). Overuse or inappropriate use of insecticides can lead to the survival of pests that are not affected by the insecticide, leading to the evolution of resistant strains (Ahmad & Mehmood, 2015). To mitigate the risk of insecticide resistance, farmers are encouraged to implement integrated pest management (IPM) strategies. This approach involves the use of multiple control methods in conjunction with each other, including rotating insecticides with different modes of action, using botanical insecticides, and monitoring crop fields regularly (Prasannath, 2016; Srivastava et al., 2018). The goal of IPM is to reduce the selection pressure for resistant pests and slow down the development of resistance, ensuring the sustainability of agricultural production in Indonesia (Thorburn, 2014).

Botanical insecticides have gained increasing attention as a natural and environmentally friendly alternative for controlling pests in agriculture. These insecticides are derived from various parts of plants, such as leaves, stems, seeds, or roots, and contain natural chemicals that are toxic to specific pests. Some of the commonly used botanical insecticides are neem oil, pyrethrin, rotenone, and sabadilla (Chengala & Singh, 2017; Lengai et al., 2020). Unlike synthetic insecticides, botanical insecticides are considered to have a lower toxicity level towards humans and the environment, making them an ideal choice for organic agriculture (Ngegba et al., 2022). The efficacy of botanical insecticides can be enhanced when they are used in combination with other pest control methods, such as biological control and cultural practices. This integrated approach helps to reduce the populations of pests, minimize damage to crops, and promote sustainable agriculture (Luiz de Oliveira et al., 2018).

In this research endeavor, we sought to determine the efficacy of a combination of three botanical substances, including leaves of Azadirachta indica (Rutales: Meliaceae), Aglaia odorata (Sapindales: Meliaceae), and Ageratum conyzoides (Asterales: Asteraceae), as an insecticide against the larvae of S. litura. Azadirachta indica, commonly referred to as neem, is derived from the neem tree and has a rich history of usage in both traditional agriculture and medicine. The extracts and oil produced from neem contain several active compounds, including azadirachtin, which have been found to be toxic to a wide range of pests, including insects, mites, and nematodes (Benelli et al., 2017). Neem is considered to be a broad-spectrum insecticide and has been utilized for its ability to repel pests, act as an antifeedant, disrupt growth, and sterilize. As a result, neem is frequently employed in integrated pest management strategies and is well-regarded for its role in organic and sustainable agriculture (Chaudhary et al., 2017).

The use of A. odorata, commonly known as Chinese perfume plant or Chinese rice flower, as a botanical insecticide has a long history in traditional agriculture. The plant produces compounds such as linalool and limonene, which possess insecticidal properties against pests like mosquitoes, flies, and beetles (Dougoud et al., 2019; Riyaz et al., 2022). Despite the availability of synthetic insecticides, extracts and essential oils of A. odorata continue to be utilized as a natural alternative in some regions. Its insecticidal properties make it an effective tool in IPM strategies and has been demonstrated to be efficient against specific pests through laboratory and field trials (Olawale et al., 2022). Another plant, A. conyzoides, also known as billy goat weed or Mexican butterfly weed, has a similar history of use as a botanical insecticide. This plant contains pyrrolizidine alkaloids (PAs) that have insecticidal properties against pests like mites, aphids, and whiteflies (Rioba & Stevenson, 2017). The insecticidal properties of PAs are believed to stem from their ability to interfere with the normal functioning of the insect nervous system, resulting in paralysis and death (Paul et al., 2022). The use of botanical insecticides, such as A. odorata and A. conyzoides, offers a promising solution for controlling pests in a more environmentally friendly manner and their combination could be even more effective in pest population management (Hoesain et al., 2021).

It is imperative to acknowledge that the effectiveness of botanical insecticides derived from plant metabolites can vary depending on several factors, such as the method of application, dose, and the species of pest being targeted (Pavela & Benelli, 2016). The method of application plays a crucial role in determining the efficacy of botanical insecticides, as different methods can lead to varying levels of exposure to the targeted pests (Damalas & Koutroubas, 2020). As a result, to achieve the desired outcome, it is necessary to take into account the method of application, rate, and timing of botanical insecticides and to incorporate them into an IPM strategy that aligns with the overall objectives of pest control and management.

2. Materials and methods

2.1. Time and place of research

The study was carried out from September 2021 to March 2022 in the Laboratory of Plant Pest Control Technology, located within the Plant Protection Study Program at the Faculty of Agriculture at the University of Jember.

2.2. Collection and preparation of botanical insecticides

Botanical insecticides were made from a mixture of A.indica, A. odorata, and A. conyzoides leaves that were collected from the Plant Protection Study Collection Garden, Faculty of Agriculture, Jember University—Indonesia. Each of the plant leaves was dried using a controlled oven set to a temperature of 40°C for a duration of 5 days. Following a drying process, the weight of the dry matter obtained from 2000 g of each fresh leaf was 274.3 g, 239.2 g, and 197.1 g, respectively. These values serve to indicate that the plant materials utilized in the production of botanical pesticides from each variety of leaf possessed water content levels of 13.72%, 11.96%, and 9.86%, respectively. The dried plant leaves were then powdered and filtered using a 100 mesh sieve. The filtered powder was then referred to as a simplicia. Each simplicia from the plants above was then mixed in one container with the simplicia from other plants with a ratio of 1:1:1 (w/w/w). The combination of simplicia was then used in the process of extracting active compounds.

150 grams of a combination of simplicia were soaked in 500 mL of 96% ethanol for 48 hours while being shaken at a speed of 100 rpm. After 48 hours, the resulting suspension was filtered using a 300 mesh size filter. The suspension was then evaporated using a rotary evaporator at a temperature of 40 °C until all the solvent was lost and a paste was obtained. This process was repeated until a sufficient amount of paste was obtained for further testing. The resulting paste was then stored at 4 °C until used in further testing (Hoesain et al., 2021).

2.3. Insect source

The third instar larvae of S. litura was procured from the Horticultural Plant Research Institute under the Ministry of Agriculture in the Republic of Indonesia. These larvae were reared under environmental conditions that were consistent with the natural bioecology of S. litura, and were fed with leaves that had not been treated with any foliar fertilizers or pesticides.

2.4. Insecticidal bioassay

Ten third instar larvae of S. litura were placed in a testing container. Sand was added to the bottom of the testing container to ensure that the conditions in the container were similar to the actual conditions in which S. litura live. The tests were conducted using two methods, oral and topical. In both oral and topical tests, the food used was the same, 50 g of castor plant (Ricinus communis) leaves per day. Both tests also used the same concentration of botanical insecticide, 5%. The insecticide suspension was made by dissolving the paste obtained in the previous process in distilled water in a ratio of 5:95 (v/v).

Oral application refers to the ingestion of the pesticide by the insect, which then passes through the digestive system and is absorbed into the body. This method can potentially result in higher concentrations of active ingredients being absorbed, as the compound can affect multiple organ systems and tissues throughout the insect’s body (Pavela & Benelli, 2016). The oral test was conducted by submerging the food in the suspension of botanical insecticide until the entire leaf was immersed in the botanical pesticide suspension. The food was left in the suspension for 30 seconds and then drained on sterile tissue for 15 minutes prior to being placed in the testing container that contained the test insects. The food was changed every day with new food that had undergone the same treatment (Ling et al., 2020).

The topical test was performed by administering 0.25 mL of the botanical insecticide suspension to the entire body surface of the larvae for 10 seconds. The decision to use 0.25 mL was based on the results of a prior test, which demonstrated that this volume would expose the entire body of S. litura to the botanical insecticide without causing the larvae to sink. After exposure to the botanical insecticide, the test insects were transferred to a test container that contained the food, which was not treated in any manner and was changed on a daily basis (Javier et al., 2017).

The experiment described was executed utilizing a completely randomized design pattern, comprising of three treatments and eight replicates. The factors evaluated in this study included larval mortality, LT 50, and the presence of defects in the test insects. The measurement of larval mortality was performed on a daily basis until the tenth day. The quantity of defective insects due to treatment was recorded each day and the data was consolidated at the conclusion of the observation period. Subsequently, the data was analyzed for homogeneity through ANOVA, and if heterogeneity was detected, a Tukey HSD test was conducted with a 95% confidence level. The percent data was transformed into Arcsin prior to analysis.

2.5. Biochemical analysis

This analysis was to identify the quantities of alkaloid, flavonoid, and tannin compounds present within the bodies of the test insects. A qualitative analysis of the terpenoids present within the test insects was also conducted. The testing was conducted on the entire body parts of the larvae that were subjected to oral and topical treatments. Two grams of deceased S. litura larvae, which had been collected from each treatment on the 10^th day of observation, were initially cleansed with distilled water to eliminate any contaminants or residual substances that may have been present on the surface of the larvae. The larvae were then air-dried on tissue paper and homogenized using 2 mL of 96% ethanol. Subsequently, the ethanol was evaporated in a dedicated evaporation chamber, which was maintained at a temperature of 40°C.

2.5.1. Alkaloid analysis

A total of 100 mg sample was weighed and 5 mL of 2 N HCl was then added. The mixture was agitated and washed three times with 10 mL of chloroform using a separating funnel. The chloroform phase was discarded and the solution was neutralized with 0.1 N NaOH. Then, 5 mL of bromocresol green (BCG) solution and 5 mL of Phosphate Buffer were added. The solution was extracted with 5 mL of chloroform and agitated with a magnetic stirrer at 500 RPM for 15 minutes. The extraction was repeated twice with chloroform and the chloroform phase was collected. The solution was evaporated with nitrogen gas and reconstituted with chloroform to a volume of 5 mL. The absorbance was read at a wavelength of 470 nm (Adeosun et al., 2016).

2.5.2. Flavonoid analysis

A total of 0.10 g sample was obtained and treated with the addition of 2 ml of 4 N HCl. The sample was subjected to autoclaving for a duration of 2 hours at a temperature of 110°C and then cooled. The sample underwent ether extraction and the result was transferred to a 10 ml reaction tube. The ether was evaporated and the residue was dried by means of N2 gas. 0.3 ml of 5% sodium nitrite was then introduced, followed by 0.6 ml of 10% aluminum chloride after a 5-minute interval, and finally 2 ml of 1 M NaOH was added after another 5 minutes. The solution was brought to a volume of 10 ml with distilled water using a graduated cylinder. The solution was further diluted 25 times and transferred to a cuvette where the absorption was measured at a wavelength of 510 nm (Moniruzzaman et al., 2014).

2.5.3. Tanin analysis

A total of 100 mg sample was weighed, then extracted with 10 mL of methanol for 20 hours, and filtered. The residual methanol was evaporated and aquadest was added to the sample until the volume reached 10 mL. 1 mL of the sample solution was taken and 0.1 mL of Folin Ciocalteu reagent was added, followed by vortexing and a 5-minute waiting period. 2 mL of 20% Sodium Carbonate was then added and vortexed for another 5 minutes. The solution was diluted 5 times with aquadest to a total volume of 10 mL and absorbance was read at 760 nm after incubation at room temperature for 30 minutes (Galvão et al., 2018).

2.5.4. Terpenoid analysis

A total of 500 mg of the sample was solubilized in 2 mL of ethanol. The test was performed by taking 2 mL of the sample. Then, 3 drops of concentrated HCl and 1 drop of concentrated H₂SO₄ were added. If the solution formed a red or purple color, it was positive for terpenoid content (Malik, 2017).

3. Results and discussion

3.1. Insecticidal activity

The results of the experiment indicate that the leaf extracts of A. indica, A. odorata, and A. conyzoides tested in this study possess potent insecticidal properties. This is demonstrated by the substantial mortality rates of S. litura larvae in both oral and topical treatments, whereas in the control group, no instances of S. litura mortality were recorded in the first day observation. Furthermore, the cumulative mortality of S. litura gradually increased over time from the first day of observation until the tenth day of observation. On the tenth day of observation, the average mortality rate in the control group was recorded at 5%, whereas the oral and topical groups recorded average mortality rates of 82.5% and 98.75%, respectively. These findings suggest that the leaf extracts of A. indica, A. odorata, and A. conyzoides may have the potential to serve as effective insecticides against S. litura. Further information pertaining to S. litura mortality can be found in Figure 1.

Figure 1. Mortality of S. litura as a result of botanical insecticide with oral and topical application techniques.

Note: The value followed by each different box shows a significant difference in each plot based on the Tukey HSD test results with a 95% confidence level.

Overall, the mortality rate of S. litura in the topical treatment was found to be higher than that in the oral treatment. The mean larval mortality on the first day in the oral treatment was 0.375, while in the topical treatment it was 1. This trend continued in the subsequent observations. On the fifth day of observation, it was noted that the cumulative mortality rate in the oral treatment was 3.5, whereas in the topical treatment it was 5.375. On the tenth day of observation, the mean number of individual S. litura deaths in the oral treatment was 8.25, whereas in the topical treatment it was 9.875. These findings suggest that the use of a botanical insecticide extracted from the leaves of A. indica, A. odorata, and A. conyzoides using 96% ethanol is more effective and suitable for controlling S. litura topically, as opposed to orally.

The use of botanical insecticides may result in the mortality of pests through a range of mechanisms. Botanical pesticides are equipped with various modes of action, including neurotoxicity, antifeedant, repellent, growth regulation, and metabolic disruption (Sola et al., 2014). Neurotoxicity is perhaps the most prevalent mode of action associated with botanical pesticides. This mode of action disrupts the transmission of nerve impulses, ultimately inducing paralysis and death in the pest (Riyaz et al., 2022). Antifeedant activity is another mode of action that botanical pesticides can exhibit. This mode of action manifests as the creation of a repellent taste or odor that repels pests and reduces damage caused to plants. Botanical pesticides can also function as repellents, establishing a physical or chemical barrier that repels pests and mitigates damage (Dar et al., 2014). Furthermore, botanical pesticides may interfere with the hormone balance of pests, obstructing growth and development and preventing the attainment of maturity and reproductive ability. This mode of action is commonly known as growth regulation (Hikal et al., 2017).

In this study, it is suspected that the death of S. litura was caused by the presence of active compounds in the material utilized. The primary active compounds in neem, known as azadirachtins, belong to a group of complex tetranortriterpenoids. Azadirachtins are potent insect growth regulators that disrupt the hormone system of insects, inhibiting their feeding, reproduction, and molting. As a result, they are effective in controlling pests such as aphids, spider mites, whiteflies, and caterpillars (Er et al., 2017; Kilani-Morakchi et al., 2021). Additionally, A. odorata contains several chemical compounds that exhibit insecticidal properties, including germacrene-D, benzyl benzoate, and benzyl salicylate (Giang & Son, 2016). These compounds have demonstrated efficacy against various insect pests, including mosquitoes, cockroaches, and houseflies. Coumarins and alkaloids are other compounds present in A. odorata that possess insecticidal properties (Sugijanto & Dorra, 2016; Udebuani et al., 2015). For example, coumarins like scopoletin and umbelliferone have been found to have larvicidal and repellent activity against mosquito larvae, while alkaloids like cananga- and liriodenine exhibit insecticidal activity (Mazimba, 2017). In A. conyzoides, essential oils are the main insecticidal compounds present, containing several bioactive compounds with insecticidal properties, such as limonene, p-cymene, γ-terpinene, and α-pinene (Bayala et al., 2014). These essential oils have exhibited insecticidal activity. Flavonoids, alkaloids, and coumarins are other compounds found in A. conyzoides that possess insecticidal properties (Chahal et al., 2021).

The study findings indicate that the use of different application techniques yields varying rates of mortality response in S. litura. Notably, the LT50 values for oral and topical treatments were found to be 5.9991 and 3.8555 days, respectively (Figure 2). This means that the oral treatment takes 5.9991 days to cause 50% mortality in the S. litura population, while the topical treatment takes only 3.8555 days to induce mortality in 50% of the S. litura population. Thus, it can be inferred that topical treatment provides a 64.27% faster response in inducing mortality in S. litura larvae using a botanical insecticide extracted from A. indica, A. odorata, and A. conyzoides. These results have critical implications for the selection of the appropriate application method for effective pest control.

Figure 2. The LT50 of S. litura due to botanical insecticides using different application methods: (a) oral, and (b) topical.

The lethal time of insecticides is influenced by several factors. Firstly, the type of insecticide used is an important factor as different insecticides have varying modes of action. Secondly, the species and life stage of the insect being targeted can also impact the lethal time of insecticides (Passos et al., 2018). Additionally, the dosage of the insecticide applied, and the method of application can affect the lethal time. Environmental factors such as temperature, humidity, and sunlight also play a role in the lethal time of insecticides (Pavela & Benelli, 2016). Lastly, the behavior of the targeted insect can influence the lethal time, as some insects may avoid or detect the insecticide and thus prolong the lethal time (Sohrabi et al., 2019).

Topical application and oral application are two methods of applying botanical insecticides that have distinct effects on the lethal time to 50% mortality (LT50) of insects. Topical application can result in a more rapid onset of toxicity compared to oral application, due to the direct exposure of the insecticide to the insect’s nervous system and the consequent bypassing of the digestive system (Norris et al., 2022). This allows for the more efficient absorption of compounds within the insecticide that disrupt the nervous system, impede feeding, or hinder reproduction (Mpumi, 2022). Conversely, some botanical insecticides are poorly absorbed through the gut wall, which reduces their effectiveness when applied orally. However, the effectiveness of a botanical insecticide depends on several factors, such as the insect species being targeted, the mode of action of the insecticide, and the formulation and application methods utilized (Campolo et al., 2018). As different insect species have varying susceptibilities to different insecticides, it is essential to consider these factors when using a botanical insecticide for pest management (El-Wakeil, 2013).

The findings of the study showed that exposure to botanical insecticides, either through oral or topical application, had a significant effect on the physical appearance of S. litura. The control group, which was not subjected to any treatment, exhibited normal body shapes and no deformities were observed. In contrast, S. litura in the oral and topical treatment groups exhibited various physical abnormalities or deformities, including wrinkled shapes, skin peeling, and failure to form wings in the moths. These physical deformities were more pronounced in the oral treatment group, with 61.25% of the S. litura displaying deformities. In comparison, only 28.75% of S. litura in the topical treatment group showed deformities. This finding suggests that the oral treatment had a more significant effect on the occurrence of physical deformities in S. litura. The number of insects with physical defects in each treatment can be seen in Figure 3.

Figure 3. The number of S. litura with deformities due to oral or topical treatment with botanical insecticides.

Note: The value followed by each different box shows a significant difference in each plot based on the Tukey HSD test results with a 95% confidence level.

When an insect ingests a botanical pesticide, the compound is absorbed through the digestive system, potentially impacting multiple organ systems and tissues throughout the insect’s body. This disruption can interfere with the insect’s growth, development, feeding, reproduction, and defense mechanisms against predators. With prolonged or repeated exposure, the insect’s immune system may weaken, leading to physical abnormalities such as stunted growth, malformed wings or legs, or even death (Hikal et al., 2017). Conversely, a botanical pesticide applied topically will typically affect only the area of the insect’s body that comes into direct contact with the compound. The result is usually limited to local effects such as paralysis or irritation, which are less likely to lead to widespread physical abnormalities or death (Tak & Isman, 2017). However, the efficacy of a botanical pesticide in causing physical abnormalities in insect pests depends on various factors such as the species of the insect, the developmental stage of the insect, the concentration and formulation of the pesticide, and the duration of exposure (Lengai et al., 2020). As such, it’s important to use botanical pesticides according to the label instructions and to take the necessary safety precautions when handling them.

3.2. Active compounds in test insects

The results of the study indicate that several active compounds were detected in the test insects at varying concentrations (Table 1). Generally, the concentration of active compounds in the control group of S. litura was found to be the lowest, compared to the total active compounds observed in S. litura subjected to botanical insecticide treatments. The highest total quinine-equivalent alkaloid content was found in S. litura subjected to oral botanical insecticide treatments (312.52 mg L⁻¹). The total alkaloid content in orally treated S. litura was found to be 95.77% and 82.78% higher, respectively, than in the control group of S. litura and in the topically treated S. litura group. In the total flavonoid test, it was revealed that S. litura treated with topical botanical insecticides had the highest content (3963.60 µg L⁻¹). This value was found to be 2349.55% and 158.52% higher, respectively, than that observed in the control group of S. litura and in the orally treated S. litura group. In the subsequent test, the highest value of total tannic acid-equivalent tannins was observed in S. litura treated with oral botanical insecticides (1.76% w/v). This value was found to be 880% and 114.28% higher, respectively, than the values in the control group of S. litura (0.2% w/v) and in the topically treated S. litura group (1.54% w/v). The difference in the concentration of active ingredients in the bodies of insects is influenced by the application technique. Generally, oral application provides more accumulation of active ingredients in the bodies of insects (Chaudhary et al., 2017).

Table 1. Active compounds were detected in the test insects after exposure to botanical pesticides through oral and topical application methods

Test Parameter	Control	Oral	Topical
Total quinine-equivalent alkaloid (mg L−1)	299.32	312.52	258.72
Total flavonoid (µg L−1)	168,70	2500.28	3963.60
Total tannic acid-equivalent tannins (% w/v)	0.20	1.76	1.54
Terpenoid	Positive	Positive	Positive

In this particular research, we quantitatively identified total alkaloids, flavonoids, tannins, and the qualitatively detect the presence of terpenoids. Alkaloids are a naturally occurring class of organic compounds containing nitrogen atoms within their chemical structure. Many alkaloids exhibit insecticidal properties, which make them suitable for use in botanical insecticides. The insecticidal effect of alkaloids is attributed to their ability to interfere with the nervous system of insects (Chowański et al., 2016). Alkaloids can bind to specific receptors in the insect nervous system, causing a disturbance in nerve impulses, ultimately leading to paralysis and death. Different alkaloids may have different modes of action and target distinct receptors in the insect nervous system (Matsuura & Fett-Neto, 2015). For example, nicotine, a well-known alkaloid found in tobacco plants, targets the nicotinic acetylcholine receptors in insects (Wink & Theile, 2002). These receptors play a significant role in the transmission of nerve impulses in the insect nervous system. By binding to these receptors, nicotine disrupts normal nervous system functions, which eventually lead to paralysis and death. On the other hand, pyrethrins found in chrysanthemum flowers act by disrupting the ion channels in the insect nervous system, leading to hyperexcitation and paralysis (Wonnacott & Barik, 2007). Additionally, some alkaloids possess feeding deterrence properties, which may prevent insects from feeding on treated plants (Chapman, 1974).

In the context of insecticides, the insecticidal effect of flavonoids is of great interest. The effectiveness of flavonoids as insecticides depends on several factors such as the type of flavonoid and the insect species being targeted. For example, some flavonoids have been found to have feeding deterrent properties by reducing the palatability of plant tissues to herbivorous insects (War et al., 2012). Similarly, some flavonoids act as oviposition deterrents by deterring egg-laying behavior of female insects. Along with feeding and oviposition deterrent effects, some flavonoids exhibit direct toxic effects on insects. The mode of action of flavonoids may involve disruption of the insect’s nervous system, interference with energy production, or damage to cell membranes. Flavonoids may also have inhibitory effects on insect growth by interfering with hormone regulation or reducing nutrient uptake (Ononuju et al., 2016).

Tannins are a class of polyphenolic compounds that are widely distributed in plants, including those used as botanical insecticides. Tannins are known to exhibit insecticidal effects mainly by binding and precipitating proteins and other molecules in the insect’s body, leading to disruption of cellular function and ultimately causing insect death (Ukoroije & Otayor, 2020). Tannins have been shown to have broad-spectrum activity against a wide range of insect pests, including those that are resistant to synthetic pesticides. They can affect the insect’s feeding behavior, causing reduced appetite, decreased feeding efficiency, and increased excretion (Checchia et al., 2022). Furthermore, tannins can interfere with the insect’s growth and development by disrupting the hormone regulation system, leading to growth inhibition and even death. Tannins also have anti-nutritional effects, reducing the bioavailability of nutrients in the insect’s diet, which can contribute to the overall detrimental effects on insect health (Gad et al., 2021).

In the context of botanical insecticides, terpenoids have been found to exhibit a range of insecticidal effects. Some terpenoids can function as insect repellents, repelling pests from plants and minimizing damage. Others can directly kill or inhibit the growth and development of insects by disrupting their physiological processes (Miresmailli & Isman, 2014). The mode of action of terpenoids in insects can vary depending on the specific compound and insect species involved. For instance, some terpenoids can disrupt the nervous system of insects, causing paralysis or death, while others can interfere with insect hormonal balance, leading to abnormal growth and development (Xu et al., 2019). Furthermore, terpenoids may have indirect insecticidal effects, such as acting as antifeedants that reduce an insect’s appetite or disrupting the digestive system and nutrient absorption. Overall, the insecticidal effects of terpenoids make them promising candidates for use in pest management strategies (Pavela, 2007).

In conclusion, it can be inferred that botanical pesticides derived from the leaf extracts of A. indica, A. odorata, and A. conyzoides are capable of effectively killing third instar larvae of S. litura through both oral and topical application techniques. However, the topical application technique is more effective, as it yields a higher level of mortality and a lower LT50 value compared to the oral application method. Additionally, both application techniques resulted in an increase in the active compounds that possess insecticidal properties in the body of S. litura.

Availability of data and materials

The data that support the findings of this study are provided by the corresponding author upon reasonable request.

Authors’ contributions

MH and APP performed the experiment and wrote the manuscript; S and SP prepared the research designs and administered the research materials; FKA and MA co-authored the manuscript and performed statistical analyses.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Mohammad Hoesain

Mohammad Hoesain, Suharto, Sigit Prastowo, and Ankardiansyah Pandu Pradana are affiliated with the Faculty of Agriculture at the University of Jember. They all belong to the same department, namely the Department of Plant Protection. Their research interest lies in developing practical technology to enhance integrated pest management for plant organisms.

Suharto

Mohammad Hoesain, Suharto, Sigit Prastowo, and Ankardiansyah Pandu Pradana are affiliated with the Faculty of Agriculture at the University of Jember. They all belong to the same department, namely the Department of Plant Protection. Their research interest lies in developing practical technology to enhance integrated pest management for plant organisms.

Sigit Prastowo

Mohammad Hoesain, Suharto, Sigit Prastowo, and Ankardiansyah Pandu Pradana are affiliated with the Faculty of Agriculture at the University of Jember. They all belong to the same department, namely the Department of Plant Protection. Their research interest lies in developing practical technology to enhance integrated pest management for plant organisms.

Ankardiansyah Pandu Pradana

Mohammad Hoesain, Suharto, Sigit Prastowo, and Ankardiansyah Pandu Pradana are affiliated with the Faculty of Agriculture at the University of Jember. They all belong to the same department, namely the Department of Plant Protection. Their research interest lies in developing practical technology to enhance integrated pest management for plant organisms.

Fariz Kustiawan Alfarisy

Fariz Kustiawan Alfarisy is currently pursuing a doctoral degree at the Faculty of Agriculture, University of Jember, and actively engages in research related to integrated pest management.

Muh Adiwena

Muh Adiwena is a faculty member at the Faculty of Agriculture, University of Borneo Tarakan, specializing in integrated pest and disease control through the use of indigenous technology.