Activity of Rosmarinus officinalis (Lamiales: Lamiaceae) Essential Oil and Its Main Constituent, 1,8-Cineole, against Tribolium castaneum (Coleoptera: Tenebrionidae)1
Rosemary essential oil (EO), from Rosmarinus officinalis L. (Lamiales: Lamiaceae), has potent properties against stored insect pests. This study aimed to evaluate the efficacy of EOs from both manually extracted and commercially produced R. officinalis, as well as the main compound 1,8-cineole, against adults of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Chemical analysis of the R. officinalis EOs was conducted using a gas chromatograph–mass spectrometer. Toxicity and repellent effects were assessed through contact and fumigation bioassays in a factorial experimental design with five replicates. Each R. officinalis EO type showed nine major compounds (>90%), with 1,8-cineol as the predominant component (>52%). Contact toxicity bioassays showed 1,8-cineole had a median lethal concentration of 1.12% at 48 h, 1.54% for manually extracted EOs, and 1.64% for commercially produced R. officinalis EOs. Furthermore, 0.5% of 1,8-cineole displayed strong contact efficacy against T. castaneum. Fumigant toxicity was observed at 140.07, 127.28, and 121.52 μl/L air, respectively. Manually extracted EO at 160 μl/L air demonstrated strong fumigant efficacy against T. castaneum, acting as a contact (66–94%) and fumigant (82–69%) repellent within 8 h, outperforming commercially produced EO and 1,8-cineole. These findings highlight the potential of manually extracted EO from R. officinalis as a natural insecticide, effective in both contact and fumigation against T. castaneum. This offers a promising avenue for using plant extracts in storage pest prevention, potentially leading to the development of insecticide products.Abstract
Weevils and moths are the main insect pests of stored products, resulting in significant grain losses during storage. More than 600 species of coleopteran pests pose a constant threat to stored grains and derivatives (Yadav et al. 2014), resulting in quantitative losses of about 20–30% in tropical and subtropical regions (Rajendran 2002). The growing human population has intensified the challenge of food shortages, making it imperative to implement measures to protect stored food from insect infestation and contamination. These efforts are critical to improving food availability.
The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is a secondary storage insect pest. Unlike the rice weevil, Sitophilus oryzae (L.), it cannot directly penetrate and damage grains but tends to worsen infestations initiated by primary insect pests or when seeds exhibit holes or cracks. It is commonly found in food production facilities, such as mills, crop plants, warehouses, and retail stores, where seeds and grains are processed and stored (Bingham et al. 2017, Popović et al. 2013). Its presence is noted in various food items such as ground grains, cereal products, cookies, nuts, spices, spaghetti, cake flour, dried pet food, dried flowers, chocolate, and nuts (Via 1999). Tribolium castaneum inflicts significant losses on stored foods, including grains, seeds, flour, and milling products (Arthur et al. 2019). Adult T. castaneum are reddish-brown, with a life cycle lasting 5 to 6 mo under optimal conditions of 15°C and 75% relative humidity (RH). They exhibit resilience to temperature ranges of 22–43°C and boast the fastest reproductive rate among stored product insect pests, with numbers potentially increasing by 73–333 times in a month (Devi and Devi 2015). Both larvae and adults contribute to severe infestations, contaminating products with their dead bodies and fecal materials, leading to a grayish appearance with mold growth in the flour. Tribolium castaneum releases benzoquinone, a defensive secretion known as a carcinogen (Unruh et al. 1998), and its unpleasant odor makes the infested products unsuitable for human consumption. Also, it may trigger allergic responses, and the consumption of contaminated food poses serious health hazards to humans and livestock (Magan et al. 2003). Stored food commodities affected by T. castaneum experience both qualitative deterioration and quantitative losses.
Chemical fumigation stands as a widely used and effective method for insect control, with commonly used substances, including methyl bromide (CH3Br) and phosphine (PH3). Methyl bromide, a widely used chemical in storage facilities, possesses advantages over other substances due to its capability to eliminate insects at all growth stages and its efficient dispersion and penetration into products. However, it falls under Class I hazardous substances, posing environmental risks, such as ozone layer depletion and alterations in the Earth’s surface temperature (World Meteorological Organization 1995). The continuous use of such chemical products has led to the development of resistance in the red flour moth population to synthetic pesticides (Bossou et al. 2015), resulting in permanent residues of certain chemicals in the environment and ecosystems, with associated toxic effects on humans (Hill 1989). These factors underscore the need to urgently explore alternative control strategies using natural compounds as substitutes for toxic pesticides (Lamiri et al. 2001).
Presently, several safe methods for humans and animals, including biologic prevention, the use of resistant varieties, vacuum storage, and integrated pest control, are available. Biologic pesticides, offering effectiveness, safety, and ecologic acceptability, have advantages over chemical alternatives (Leonard and Julius 2000). The essential oils (EOs), playing a pivotal role in safeguarding crops from insect infestation, have garnered significant attention, as researchers explore alternative pest control methods (Batish et al. 2008). The use of EOs from plants provides an alternative approach to managing and eradicating insect pests in storage through various applications, such as fumigation, contact, antifeedant, and repellency. As natural extracts, EOs are safe for both users and consumers and possess the ability to decompose naturally (Feldlaufer and Ulrich 2015, Silva et al. 2003). The EOs from different plants exhibit unique complexes with diverse effects, serving as effective pesticides (El-Wakeil 2013).
Rosmarinus officinalis L., commonly known as rosemary, is an aromatic plant with compounds that impart a distinctive odor or aroma (Maia and Moore 2011). Native to Mediterranean countries, rosemary grows under various climatic conditions (Begum et al. 2013). Rosemary EO is renowned for its antibacterial (Fu et al. 2007), antispasmolytic (Mothana et al. 2011), antifungal (Carvalhinho et al. 2012), antioxidant (Hendel et al. 2016), anticancer (Gezici et al. 2017), and insecticidal properties, serving as the active ingredient in various commercial insecticides (Isman et al. 2008). The main components of rosemary EO include borneol, linalool, terpineol, caryophyllene, 1,8-cineole, α-pinene, and verbenone. These components exhibit activity against certain types of insects (Kardinan 2007, Simon et al. 1984, Wibowo 2012). Papachristos et al. (2004) discovered that rosemary EO and its components can prevent and eliminate insect pests in storage, such as the bean weevil (Acanthoscelides obtectus Say). The primary components of R. officinalis EO, including 1,8-cineole, α-pinene, β-pinene, and camphor, have been identified (Isman et al. 2008). Wanna and Ruamjit (2015) reported the efficacy of R. officinalis EO oil in eliminating rice weevil, S. oryzae (L.) and maize weevil (Sitophilus zeamais Motschulsky) with up to 100% mortality. Therefore, this research aimed to assess the effectiveness of the EO derived from R. officinalis and its main component, 1,8-cineole, in preventing and eliminating T. castaneum adults in stored products.
Materials and Methods
Insect
Red flour beetles, T. castaneum, were reared on a substrate of wheat flour and rice bran (10:5, w/w) within a plastic box covered by fine mesh cloth for proper ventilation. The breeding was conducted at the Department of Agricultural Technology, Mahasarakham University (Maha Sarakham, Thailand), maintaining consistent environmental conditions at 29 ± 2°C and 75 ± 10%RH, with a photoperiodic regime of 12 h light–dark. For all bioassays, 10-d-old, mixed sex adults were used. All experimental procedures were conducted under the identical environmental conditions as the insect culture.
Preparation of EO
The EO was obtained from dried R. officinalis flowers purchased at Makro Supermarket (Muang District, Maha Sarakham, Thailand), using the water distillation method, as outlined by Wanna (2021) with slight modifications. Sliced dried flowers (150 g) were subjected to water distillation in a modified Clevenger-type apparatus containing 700 ml of distilled water in a 2,000-ml distillation flask. The setup, secured with a clamp on a heating mantle, operated for 6 h. The EO collected in the water was extracted through a graduated measuring tube, with excess water removed via centrifugation at 10,000 rpm for 10 min. The resulting EO was stored in a sealed amber glass bottle and refrigerated at 4°C in the dark until needed for future use.
Pure rosemary EO derived from R. officinalis chemotype ‘cineole’ was acquired in an amber bottle from Botanicessence Essential Oil (Bangkok, Thailand). The EO was kept in the dark at 4°C until needed for both analyses and bioassays.
Regent grade 1,8-cineole purchased from Toronto Research Chemical (Canada) was used in the bioassays.
Analysis of EO
The chemical composition of R. officinalis EOs was determined following the method of Wanna and Khaengkhan (2023) using a gas chromatograph–mass spectrometer (GC-MS) series Clarus 680 (PerkinElmer, Akron, OH). Separation was achieved on an Elite-5MS capillary column (5% phenylmethyl polysiloxane stationary phase, 30 m, inside diameter: 0.32 mm, 1-μm film thickness; PerkinElmer). A 1-μl sample was injected in split mode (split ratio of 1:100, v/v). Helium was used as the carrier gas with a flow rate of 1 mL/min, and the injector temperature was maintained at 200°C. The oven temperature was initially set at 45°C for 5 min, increased to 280°C at a rate of 10°C/min, and held for 5 min, operating in electron impact mode of 70 eV. A quadrupole mass analyzer was used, and the temperature detector was set at 250°C. Spectra were scanned (m/z) from 40 to 1,000 Da. Identifications of R. officinalis EOs constituents were based on the retention index determined with reference to homologous series of n-alkanes (C10–C15), National Institute of Standards and Technology Mass Spectral Search (Gaithersburg. MD) and Wiley library (Hoboken, NJ), and comparison of retention index and mass spectral data with the literature (Adams 2007). The relative amounts of individual components were calculated based on the relative percentage peak areas, without using a correction factor.
Contact toxicity bioassay
The contact toxicity bioassay was conducted using the impregnated filter paper test, modified from Wanna et al. (2023). Different concentrations of two R. officinalis EOs and 1,8-cineole (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0%) were separately prepared in acetone. Each Whatman (no. 1) filter paper (9 cm diameter and surface area 63.585 cm2) was treated with 1,000 μl of the sample solution and positioned in a 9-cm-diameter petri dish. The control treatment consisted of acetone only. After allowing acetone to evaporate for 2 min at room temperature, 10 unsexed adults of T. castaneum were released into each petri dish and covered with a lid. All treatments were replicated five times using a factorial in completely random design. Petri dishes were maintained under laboratory conditions (29 ± 2°C, 75 ± 10% RH, and a 12 h light–dark photoperiod). Adult mortality of T. castaneum was observed and recorded at 24, 48, and 72 h. Insects were considered dead if they remained immobile with no leg or antennal movements detected (Wanna et al. 2021).
Fumigant toxicity bioassay
The fumigant toxicity bioassay was conducted using the vapor phase test followed by Wanna and Wongsawas (2022). Filter paper (Whatman no.1; 2 cm diameter and surface area 3.14 cm2) was saturated with 500 μl of 10, 20, 40, 80, 160, and 320 μl/L air dilutions of R. officinalis EOs or 1,8-cineole, as previously prepared. The control treatment consisted of acetone only. After allowing the acetone to evaporate for 2 min at room temperature, the filter paper was affixed to the underside of the screw cap of a 40-ml glass vial. The caps were securely fastened onto vials containing 10 unsexed adults of T. castaneum. Each concentration and control were replicated five times in a factorial completely random design. All glass vials were maintained under laboratory conditions (29 ± 2°C, 75 ± 10% RH, and a 12 h light–dark photoperiod). Adult mortality of T. castaneum was observed and recorded at 24, 48, and 72 h. Insects were considered dead if they remained immobile with no leg or antennal movements detected.
Repellent activity bioassay
The repellent activity bioassay on contact was conducted for adults of T. castaneum using the impregnated paper with a choice test, as outlined by Wanna and Wongsawas (2022). Dilutions of two R. officinalis EOs or 1,8-cineole (0.2, 0.4, 0.6, 0.8, 1.0, and 1.2%) were prepared using acetone as the solvent. Each replicate was performed in a 9-cm-diameter petri dish covered with a 9-cm-diameter filter paper (Whatman no.1; surface area 63.585 cm2), with one-half treated with R. officinalis EOs or 1,8-cineole, and the other half treated with acetone alone as a control. Each half of the filter paper disk was individually treated with 500 μl. The acetone in both halves was allowed to evaporate for 2 min at room temperature and then affixed at the center of a petri dish using adhesive tape. Ten unsexed adults of T. castaneum were released at the center of the paper disk, and the dish was covered. Each concentration and control were replicated five times in a factorial completely random design under the same rearing conditions. The number of T. castaneum adults present in the control and treated areas was recorded after 1, 2, 4, and 8 h of testing.
The repellent activity bioassay on fumigant was evaluated using the vapor phase with a choice test, following modified methods from Wanna and Khaengkhan (2023). The repellent test kit included two plastic bottles (each 700 ml, 8 cm diameter, 17 cm height), designated as the test bottle and the alternative bottle. A small plastic tube (0.5 cm diameter, 15 cm length) served as a connection between the bottles, with a hole at the lower side for placement. A drilled hole in the middle of the tube facilitated the release of T. castaneum adults, with a sliding tube to control opening and closing, preventing escape. The EOs or 1,8-cineole were prepared at six concentrations (0.078, 0.156, 0.312, 0.625, 1.25, and 2.5 μl/L air) by dilution with acetone. A 100-μl aliquot of each sample solution was released on a filter paper strip (1.5 cm wide, 5 cm long), evaporating at room temperature for 2 min. The strip was placed in a small glass vial (2.5 cm diameter, 5 cm height) and suspended from the center of the screw cap of the test bottle. The screw cap was tightly closed. For the alternative bottle, a filter paper strip was saturated with 100 μl of acetone, prepared similarly to the test bottle. Ten unsexed adults of T. castaneum were released into the opening in the middle of the connecting tube between the test bottle and the alternative bottle, and the sliding tube was securely closed. Each concentration and each control were replicated five times in a factorial completely random design under the same rearing conditions. The number of T. castaneum adults present in the test bottle and the alternative bottle were recorded after testing at 1, 2, 4, and 8 h.
Statistical analysis
Mortality of T. castaneum adults was determined using the formula % adult mortality = (Nd/Nt) × 100, where Nd represents the number of deceased T. castaneum adults and Nt is the total number of T. castaneum adults involved in the bioassay. Control mortality adjustments were applied following Abbott’s (1925) formula when control mortality ranged between 5 and 20%. The concentration–mortality response of two R. officinalis EOs on T. castaneum adults in terms of contact and fumigant toxicity was assessed through probit analysis (Finney 1971), providing the median lethal concentration (LC50) value and associated parameters. The repellent effect was measured using the repellence index (RI), calculated as RI = 2T/(T+C), where T is the percentage of T. castaneum in the treatment bottle and C is the percentage in the alternative bottle. Contact toxicity, fumigant toxicity, and repellent activity were subjected to one-way analysis of variance. Treatment means were compared using the Tukey honestly significant difference test at P ≤ 0.05.
Results
Chemical composition of R. officinalis EO
The GC-MS analysis of R. officinalis EOs involved identifying components by retention index, determined on an Elite-5MS column using a homologous series of n-hydrocarbons (Table 1). In the manually extracted R. officinalis EO, 30 components were identified, constituting 97.68%. Among these, nine key compounds (90.80%) were identified, with 1,8-cineol (52.70%) being the most abundant, followed by α-pinene (9.70%), borneol (7.77%), terpineol (6.99%), camphor (5.54%), camphene (3.28%), bornyl acetate (2.31%), caryophyllene (1.43%), and terpinen-4-ol (1.10%). The chemical composition of commercially produced R. officinalis EO consisted of 30 compounds (98.52%), including nine key compounds (93.12%). The predominant components were 1,8-cineol (53.23%), followed by α-pinene (14.70%), camphor (9.69%), caryophyllene (4.12%), terpineol (3.46%), camphene (3.13%), borneol (1.95%), α-myrcene (1.55%), and linalool (1.29%). A comparison of the chemical compositions of manually extracted and commercially produced R. officinalis EOs revealed that both types shared nine essential compounds (over 90%). The commercially produced EO had a higher total percentage peak area (93.12%) compared with the manually extracted EO (90.80%). Both types contained 1,8-cineol as the major component, with similar amounts and only four different compounds. Notably, terpinen-4-ol and bornyl acetate were identified in the manually extracted EO, while α-myrcene and linalool were found in the commercially produced EO.
Contact toxicity of R. officinalis EOs and 1,8-cineole
The contact toxicity test results (LC50) on T. castaneum adults, conducted through the impregnated filter paper test using the manually extracted R. officinalis EO, commercially produced R. officinalis EO, and 1,8-cineole diluted with acetone at seven concentrations (0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0%) are presented in Table 2. The LC50 values of the manually extracted R. officinalis EO exhibited LC50 responses of 2.21, 1.54, and 1.39% in T. castaneum adults at 24, 48, and 72 h. In comparison, the commercially produced R. officinalis EO exhibited LC50 of 1.95% at 24 h, 1.64% at 48 h, and 1.43% at 72 h. The 1,8-cineole had LC50 of 1.65, 1.12, and 0.83% at 24, 48, and 72 h, respectively. Notably, at 24 h, 1,8-cineole displayed the highest contact toxicity, resulting in the lowest LC50 value, followed by the commercially produced R. officinalis EO and the manually extracted R. officinalis EO, respectively. This trend continued at 48 and 72 h, where 1,8-cineole maintained the highest contact toxicity, followed by the manually extracted R. officinalis EO and the commercially produced R. officinalis EO. Throughout the test duration, 1,8-cineole consistently demonstrated greater toxicity than both the manually extracted and commercially produced R. officinalis EOs, with the manually extracted R. officinalis EO consistently exhibiting higher toxicity compared with commercially produced R. officinalis EO.
The contact toxicity efficacy against T. castaneum adults is presented in Table 3, revealing significantly differences (P < 0.01) at each tested time point. The mortality of T. castaneum adults increased with higher concentrations and prolonged exposure. At a 3% concentration of the manually extracted R. officinalis EO, commercially produced R. officinalis EO, and the main compound 1,8-cineole, the contact killing effect against T. castaneum adults was the highest, with no significant differences (P > 0.05). However, over a 120-h exposure, 1,8-cineole consistently achieved a maximum mortality of 100% for T. castaneum adults across all concentration ranges. Moreover, the manually extracted R. officinalis EO demonstrated a tendency to be more effective in killing T. castaneum adults compared with the commercially produced R. officinalis EO.
Fumigant toxicity of R. officinalis and 1,8-cineole
The toxicity test results (LC50) for killing T. castaneum adults through the vapor phase test with the manually extracted R. officinalis EO, commercially produced R. officinalis EO, and the main compound 1,8-cineole diluted with acetone at eight concentrations (0, 25, 50, 75, 100, 125, 150, and 200 μl/L air) are shown in Table 4. The manually extracted R. officinalis EO exhibited the fumigation toxicity (LC50) against T. castaneum adults at 24, 48, and 72 h with 140.91, 127.28, and 112.26 μl/L air, respectively. The commercially produced R. officinalis EO had LC50 values of 143.78, 121.52, and 115.12 μl/L air, while 1,8-cineole exhibited of 150.61, 140.07, and 126.90 μl/L air, respectively. At 24 h, the manually extracted R. officinalis EO demonstrated the highest fumigation toxicity, followed by the commercially produced R. officinalis EO and 1,8-cineole. At 48 h, the commercially produced R. officinalis EO had the highest fumigation toxicity, followed by the manually extracted R. officinalis EO and 1,8-cineole. At 72 h, the manually extracted R. officinalis EO exhibited the highest fumigation toxicity, followed by the commercially produced R. officinalis EO and 1,8-cineole. Throughout the 24, 48, and 72 h, the manually extracted R. officinalis EO consistently showed higher fumigant toxicity against T. castaneum adults compared with the commercially produced R. officinalis EO and 1,8-cineole. Notably, the commercially produced R. officinalis EO tended to be more toxic than 1,8-cineole.
The fumigation toxicity efficiency against T. castaneum adults is presented in Table 5, indicating significant differences at 24–72 h (P < 0.01) and at 96–168 h (P < 0.05). Adult mortality of T. castaneum increased with higher concentrations and prolonged exposure. At a concentration of 320 μl/L air, both the manually extracted R. officinalis EO and the commercially produced R. officinalis EO, along with the main compound 1,8-cineole, demonstrated the highest killing effect against T. castaneum adults, with no significant differences. Notably, after 96 h of exposure, the manually extracted R. officinalis EO achieved 100% mortality with concentrations of 160 μl/L air and above. Furthermore, it is noteworthy that 1,8-cineole exhibits a tendency to be more effective against T. castaneum adults compared with the commercially produced R. officinalis EO.
Repellent activity of R. officinalis and 1, 8-cineole
The repellent activity test for adult of T. castaneum, conducted through the impregnated filter paper with a choice test using the manually extracted R. officinalis EO, commercially produced R. officinalis EO, and 1,8-cineole diluted with acetone at six concentrations (0.2, 0.4, 0.6, 0.8, 1.0, and 1.2%), are summarized in Table 6. There was no significant difference (P ≥ 0.05) in repellent activity observed for T. castaneum adults at 1, 2, and 4 h, with repellency percentages ranging between 32 and 96%. However, a significant difference (P < 0.05) was found at 8 h. The manually extracted R. officinalis EO demonstrated a contact effect, repelling T. castaneum adults up to 94.00 ± 8.94% at a concentration of 1.2%. In comparison, 1,8-cineole repelled 90.00 ± 12.25% at a concentration of 0.6%, and commercially produced R. officinalis EO repelled 88.00 ± 8.37% at a concentration of 1%. However, no statistically significant differences were found in the contact bioassay to repel T. castaneum adults.
The repellent activity test for T. castaneum adults, conducted in the vapor phase with a choice test using the manually extracted R. officinalis EO, commercially produced R. officinalis EO, and 1,8-cineole diluted with acetone at six concentrations (0.078, 0.156, 0.312, 0.625, 1.25, and 2.5 μl/L air) are presented in Table 7. There was no significant difference (P ≥ 0.05) in repellent activity for T. castaneum adults at every period tested (1–8 h), with repellency percentages ranging between 30 and 96%. However, the results indicated that the manually extracted R. officinalis EO exhibits a higher efficacy in repelling T. castaneum adults compared with commercially produced R. officinalis EO and 1,8-cineole.
Discussion
The results of this study demonstrate a total of 11 compounds identified in both manually extracted and commercially produced R. officinalis EOs. These compounds primarily belong to the monoterpene and sesquiterpene categories. Upon analysis, it was found that both EOs contained 1,8-cineole (>50%) as the predominant component, aligning with the findings of Isikber et al. (2006), who reported similar chemical composition in R. officinalis EO through GC-MS analysis, identifying 1,8-cineole as the main constituent. The observed insecticidal effects of R. officinalis EO might be attributed to the inhibition of acetylcholinesterase (AChE) enzyme activity, as suggested by Dohi et al. (2009). Such changes induced by EOs can disrupt cholinergic transmission, resulting in uncoordinated leg movements in insects (Lang et al. 2012). Numerous studies on the insecticidal properties of EOs have highlighted AChE inhibitory effects (Kim et al. 2013, Kiran and Prakash 2015, Park et al. 2016, Saad et al. 2018). Abdelgaleil et al. (2009) reported similar outcomes in tests involving various monoterpenes on rice weevils (S. oryzae) and red flour beetles (T. castaneum), with 1,8-cineole being one of the substances that exhibited strong enzyme inhibition. The monoterpene component speculated to be responsible for AChE inhibition aligns with 1,8-cineole, identified as the main component in R. officinalis EOs (Bajalan et al. 2017).
The current investigation demonstrates the toxic effects of both manually extracted and commercially produced R. officinalis EOs on T. castaneum adults through contact and fumigation methods, along with repellent properties observed through both contact and fumigation. This aligns with prior findings highlighting R. officinalis EO as an effective fumigant for preventing and controlling various insect pests, including T. castaneum, Tribolium confusum Jacquelin, Cadra cautella Walker, and Callosobruchus chinesis L. (Isikber et al. 2006, Lee et al. 2002, Sim et al. 2009, Trivedi et al. 2017). The repellent effect against diverse insect types also has been documented (Francikowski et al. 2019). This efficacy is attributed to the composition of EOs, mainly monoterpenoids and sesquiterpenoids, acting as fast-acting poisons affecting insect neurotransmitters and interacting with various receptors (Isman 2019). The potential modes of action of plant EOs on pests encompass contact, fumigant, antifeedant, repellent effects, and growth inhibition, as highlighted by various studies (Bossou et al. 2015, Chu et al. 2012, Lee and Lee 2016, Regnalt-Roger et al. 2012). In addition, the ingestion of EOs has demonstrated significant efficacy against numerous storage insect pests (Fabres et al. 2014). Consequently, R. officinalis emerges as a promising bioinsecticide with substantial potential, particularly in addressing the growing prevalence of general resistance to traditional insecticides.
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