Dispersant Agents of Essential Oil for Stored Grain Pest Control

Dispersant Agents of Essential Oil for Stored Grain Pest Control | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Dispersant Agents of Essential Oil for Stored Grain Pest Control ALESKA BATISTA SILVA, ALESKA BATISTA DA SILVA, KAREN MENEZES DE OLIVEIRA, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8239124/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract The control of insect pests in stored grains carried out through insecticides that may select resistant populations and generate environmental risks. Secondary plant compounds are alternatives to control insect pests. However, the high volatility has been an obstacle in their practical use. This study develops natural dispersants for the application of Mentha piperit a essential oil for the control of Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae). Two types of dispersants were tested: a gypsum-based dispersant prepared with a mixture of gypsum and water molded in aluminum, and a sachet dispersant composed of polyester sachets. The efficiency of the dispersants was assessed by contact, fumigation and repellency tests. For that, unsexed S. zeamais up to 15 days old were used and evaluated after 48 hours of experiment assembly. The persistence effects of the essential oil in dispersants were also evaluated. The fumigation test with essential oil in the sachet and gypsum dispersants generated, respectively, LC 50 values of 23.78 and 34.32 and LC 99 values of 54.27 and 79.28 µL. For the contact test, the sachet dispersant presented sublethal and lethal concentrations of LC 50 25.84 and LC 99 48.40 µL, respectively. However, only the 26 µL concentration was repellent for both dispersants. The repellent and fumigant effects of the sachet lasted for 15 and 24 days, while these effects in gypsum dispersants lasted 21 and 30 days, respectively. Both dispersants were considered promising as they persistently retained and released the compounds present in the essential oil, enhancing the fumigant and repellent effect against S. zeamais . Alternative Control Formulation Inert Powder Mentha piperita S. zeamais Figures Figure 1 Figure 2 1. INTRODUCTION Post-harvest insect pests represent a major constraint to global grain storage systems, causing quantitative and qualitative losses that reduce market value and may lead to the rejection of grain or seed lots (NAPOLEÃO et al., 2013; CAMPBELL; ARTHUR, 2019). Among these pests, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), the maize weevil, stands out as one of the most destructive primary pests of stored cereals, capable of penetrating intact grains and rapidly establishing high infestation levels (NOOMHORM et al., 2013; SULEIMAN et al., 2015). Chemical fumigants remain the primary method for S. zeamais management. However, the indiscriminate and recurrent use of synthetic insecticides has contributed to the evolution of resistant insect populations, increased toxicological risks, environmental contamination, and restrictions on chemical residues in food products (SPARKS; NAUEN, 2015; PIMENTEL et al., 2022). These limitations have intensified the search for alternative, sustainable, and residue-free pest control strategies. Among the emerging alternatives, the use of plant-derived essential oils has gained considerable attention due to their bioactivity, biodegradability, and broad modes of action, including fumigant, repellent, and contact toxicity (SHAH; KHAN, 2014; MOSSA, 2016). Despite their proven efficacy against stored-product insects, the major barrier to large-scale application of essential oils is their low environmental persistence and rapid volatilization, which reduces long-term insecticidal activity (REGNAULT-ROGER et al., 2012; MOSSA, 2016). In this context, developing suitable dispersing or carrier agents capable of stabilizing essential oils and enabling gradual release of their active components represents a promising technological advance. Using materials that exhibit high absorption capacity and controlled release can extend the persistence of essential oils and enhance their effectiveness against storage pests (YE et al., 2011; LIU et al., 2020). Gypsum, widely applied in construction, possesses desirable characteristics such as strong absorption, retention, rapid hardening, and structural stability. These properties make it a potential carrier for incorporating essential oils into solid matrices (tablets), facilitating controlled volatilization and sustained insecticidal activity over time. Among essential oils evaluated for stored-grain pest control, Mentha piperita L. (Lamiaceae) peppermint oil has shown promising insecticidal properties, acting as a fumigant, repellent, antifeedant, and contact toxicant against several stored-product insects, including Sitophilus species (KHANI et al., 2012 ; JACOB; OMAR, 2013; LASHGARI et al., 2014; KUMAR et al., 2021). Given the need for sustainable pest control strategies and the potential advantages of carrier-based delivery systems, the objective of this study was to evaluate dispersing agents for the controlled application of M. piperita essential oil aiming at the management of S. zeamais in stored maize. 1. MATERIAL AND METHODS The experiments were carried out at the Laboratory of Entomology - Alternative Pest Control, located at the Campus of Engineering and Agricultural Sciences (CECA), of the Federal University of Alagoas (UFAL), in Rio Largo, Alagoas, under controlled temperature conditions of 25 ± 2°C, 60 ± 10% RH and 12 hour photophase. 1.1. Rearing of Sitophilus zeamais Motschulsky 1855 (Coleoptera: Curculionidae) The Catingueiro variety of maize grains were stored in a freezer at 10°C for a minimum of 10 days to eliminate any potential biological agents. Subsequently, they were placed in hermetically sealed glass jars at room temperature for another 10 days until they reached hygroscopic equilibrium. These grains were then used for experiments and rearing. To carry out laboratory breeding, a portion of the grains was placed in 2.5L glass containers, in which the total capacity was 1/3 filled with corn grains and closed with voile fabric to allow for ventilation. Approximately 40 non-sexed S. zeamais were introduced into each container on a weekly basis to infest the grains. After 10 days, the insects were removed, and the F1 generation was allowed to develop before testing. 1.2. Development of dispersing agents Gypsum tablet-type dispersing agent . The dispersant based on gypsum was prepared by combining 8 g of gypsum with 5.5 mL of water. The resulting solution was poured into aluminum molds (0.3 x 0.2 x 0.1 cm) to form tablets. After approximately 30 minutes, the tablets were removed from the molds and left to dry at room temperature for at least 72 hours. Sachet-type dispersing agent. The tea-type sachet dispersant was obtained from a commercial establishment in the dimensions of 3 x 5 cm, in white color, and made of 100% polyester material. An 80g qualitative filter paper was cut into 1 x 5 cm pieces and inserted inside the sachet. 1.3. Chromatographic analysis and chemical identification of Mentha piperita essential oil The essential oil of M. piperita was obtained from Quinarí®, a company located in Ponta Grossa, PR, Brazil. The oil was reported to have 100% purity and was free of any diluent solutions. The country of origin of the oil was the United States of America, and it was extracted from the plant shoot through steam distillation. The oil's chemical compounds were identified using High-Resolution Gas Chromatography on an AGILENT 7820A Gas Chromatograph. The column used was Supelcowax 10–15m x 0.2mm x 0.2 µm (supelco), with the column temperature set to 50°C for 2 minutes, followed by an increase of 3°C per minute until it reached 200°C. The injector temperature was set to 200°C, and the split ratio was 1/50. The FID detector was set to 220°C, and the injection volume was 1 µL. The identification of the chemical compounds was confirmed using gas chromatography coupled with mass spectrometry (GC-MS). 1.4. Fumigant Effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The fumigation chambers were constructed by filling 1.8 L glass containers with 40 g of corn grains and 20 unsexed adult S. zeamais aged up to 15 days, with each chamber representing one repetition. After 48 hours, the percentage of mortality was evaluated. For the fumigant effect tests using the gypsum tablet dispersant, several concentrations of the M. piperita essential oil were impregnated onto the tablets using a dosing pipette. Control samples consisted of tablets without any added liquid. The tablets were then placed inside the fumigation chambers over the grains. Preliminary tests were performed at different concentrations to determine the mortality values that were close to the control (lower limit) and close to 100% (upper limit). The Bliss formula (1934) was used to define the following concentrations for the definitive bioassay: 25, 31, 47.6, 59.1, and 90.0 µL L -1 . These concentrations were used to estimate the lethal and sublethal concentrations. To test the fumigant effect of sachet dispersant, filter paper was impregnated with different concentrations using a dosing pipette. The filter paper was then inserted into the sachets, which were placed in the fumigation chambers and suspended through a cord to avoid direct contact with the grains. The control group consisted only of sachets containing filter paper without any liquid. Preliminary tests were conducted with several concentrations to determine the mortality values close to the control (Lower Limit) and close to 100% (Upper Limit). Based on the Bliss (1934) formula, the following concentrations were assessed for the definitive bioassay: 15.0, 19.3, 32.4, 41.9, and 70.0 µl L -1 . The experiments completely randomized designed with five replications per treatment. The concentration-response data were analyzed using Probit analysis, and the lethal concentrations for 50 and 90% (LC50 and CL90) were estimated using the SAS (2002) computational program. 1.5. Repellent effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The repellency tests were conducted using arenas composed of two glass containers connected to a central container through two glass tubes. One container had 20 g of untreated corn grains (control), while the other container had the same amount of grains treated with different concentrations of M. piperita essential oil in dispersants agents (gypsum tablets and sachets). In the central container, 16 unsexed adults of S. zeamais aged up to 15 days were released. The concentrations (18.0, 22.0, and 26.0 µl) were determined based on previous testing. After 48 hours, the insects in each container were counted. The average percentage of repellency was calculated using the formula of Lin et al. (1990). The RI or repellency index was calculated using the formula: RI = 2G/(G + P), where G represents the percentage of insects attracted by the essential oil treatment and P represents the percentage of insects attracted to the control. The RI values range between zero and two, where RI = 1 indicates similar repellency between the treatment and the control (neutral treatment), RI > 1 indicates less repellence of the treatment compared to the control (attractive treatment), and RI < 1 corresponds to a higher repellency of the treatment in relation to the control (repellent treatment). The confidence interval used to determine whether the essential oil is repellent or not was calculated from the mean RI and the corresponding standard deviation (± SD). If the mean RI is less than 1 - SD, the essential oil is repellent; if the mean is greater than 1 + SD, the essential oil is attractive, and if the mean is between 1 - SD and 1 + SD, the essential oil is considered neutral. This index is an adaptation of the formula cited by Lin et al. (1990) for the consumption index. 1.6 Persistence of the fumigant effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The experiment was designed as a completely randomized design with five replications per treatment, using 2.5 L glass fumigation chambers equipped with an Eppendorf Safe-Lock® microtube attached to the lid. This microtube was used to insert the insects to avoid any openings that could result in air leakage and subsequent loss of fumigation conditions. The residual effect of M. piperita essential oil in each type of dispersant (gypsum tablets and sachets at lethal concentrations of 54.27 and 79.28 µL, respectively) was evaluated using the same methodology as in the previous fumigation experiment, modifying only the treatments, which were storage intervals: 0, 3, 6, 9, 12, 15, 18, 21, 24 days and 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 days, respectively, for the dispersant gypsum tablets and sachet. In the controls, only the dispersant gypsum tablet and sachet with filter paper were used without any addition of liquids. All treatments were set up on the same day to assess the residual effect. At each storage interval, five replicates were infested, each containing 20 unsexed adult insects aged between 0 and 15 days, inserted into the fumigation chambers through the Eppendorf present in their lid. The evaluations were performed 48 hours after each infestation, counting the number of dead insects. The data were analyzed using the chi-square test, analysis of variance (ANOVA), and mean values were compared using the Tukey test (SAS Institute Inc, 2003). 1.7 Persistence of the repellent effect of Mentha piperita essential oil in dispersing agents on Sitophilus zeamais The experiment was carried out in a completely randomized design with five replications per treatment. The same methodology as the previous repellency experiment was followed, except for modifications made to the exposure periods. The exposure periods were 0, 3, 6, 9, 12, 15 days and 0, 3, 6, 9, 12, 15, 18, 21, 24 days in the concentrations of essential oil in the dispersant of gypsum tablets and sachets with filter paper, respectively, at concentrations of 18, 22, and 26 µL. The average percentage of repellency was obtained by counting the insects on each side of the containers after 48 hours of each infestation, and was calculated using the formula by Kogan and Goeden (1970). Statistical analysis was performed using the non-parametric chi-square test using the SAS statistical program with a 5% error probability (SAS Institute Inc 2003). 2. RESULTS 2.1. Chromatographic analysis and chemical identification of Mentha piperita essential oil The essential oil of M. piperita comprises 13 compounds: α-pinene, β-pinene, limonene, 1,8-cineol, menthone, mentholfuran, isomenthone, menthyl acetate, isopulegol, neo-isomenthol, pulegone, menthol, and piperitone. Chromatographic analysis indicated that the major constituents of the oil used were menthol (45%), menthone (23.3%), and menthyl acetate (5.5%) (Table A.1 ). Table A.1 Chromatography of Mentha piperita essential oil. Peak RI calc. Constituents % 1 1171 α-pinene 0.8 2 1177 β-pinene 0.4 3 1211 limonene 1.4 4 1214 1,8-cineole 4.7 5 1419 menthone 23.3 6 1440 mentofuran 2.2 7 1444 isomenthone 3.7 8 1531 menthyl acetate 5.5 9 1549 isopulegol 2.2 10 1573 neo-isomenthol 4.2 11 1600 pulegone 1.3 12 1621 menthol 45.0 13 1682 piperitone 1.0 Others 4.3 Total 100.0 RI calc., calculated retention index; Percentage based on the total area of the chromatogram. Essential oil analyzed in a Carbowax 20M polar column. Ik polar column. Source: Quinarí ® , 2021. 2.2. Fumigant Effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The fumigation of M. piperita essential oil in the sachet and gypsum dispersants proved toxicity on S. zeamais . In the sachet, the estimated values for sublethal (LC 50) and lethal (LC 99 ) concentrations were 23.78 (95% CI = 22.50–25.11) and 54.27 (95% CI = 48.42–62.91) µl L of air, respectively (n = 500; Slope ± SD = 6.49 ± 0.47; χ 2 = 5.39; p = 0.14). In the gypsum, the sublethal (LC 50) and lethal (LC 99 ) concentrations were 33.32 (32.61–36.12) and 79.28 (70.28–92.01) µL of air, respectively (n = 500; Slope ± SD = 6.40 ± 0.46; χ2 = 1.26; p = 0.73). 2.3. Repellent effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The essential oil of M. piperita , when used in sachet dispersants at concentrations of 18 and 22 µL, did not show any repellent effect on S. zeamais after 48 h of exposure. The repellency only occurred at a concentration of 26 µL. In contrast, the use of gypsum as dispersant caused repellency at all tested concentrations (as shown in Table A.2 ). Table A.2 Repellency of Mentha piperita essential oil on Sitophilus zeamais . Product Dispersant Concentrations (µl) Mean (± DP a ) of repellency index b Effect Mentha Piperita Essential Oil Sachets (filter paper) 18 1.44 ± 0.55 Neutral 22 1.46 ± 0.53 Neutral 26 1.26 ± 0,76 Repellent Gypsum tablet 18 1.29 ± 0.70 Repellent 22 1.23 ± 0.76 Repellent 26 1.20 ± 0.79 Repellent (*) a Standard deviation, b Repellency index calculated from the formula described by Lin et al. (1990) Persistence of the fumigant effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The dispersant based on gypsum exhibited a higher level of persistence of the M. piperita essential oil, resulting in mortality rates above 70% even 24 days after application (F = 2.33; p < 0.001) (Figure A.1). Until the 9th day after application (DAA), the essential oil in both types of dispersants, at concentrations of 54.27 and 79.28 µL of air (LC 99 ), did not differ in terms of fumigant action. The essential oil in the sachet dispersant gradually declined in fumigant activity from the 14th to the 18th DAA, with average mortality ranging from 80.0 to 65.0% (Figure A.1). On the other hand, the essential oil in the gypsum dispersant persisted for 15 days after the 9th DAA (until the 24th DAA), with an average mortality of 90% up to the 15th DAA, which gradually decreased to 87.0 and 68.0% on the 18th day to 24th DAA, respectively. There were significant decreases in S. zeamais mortality from the 27th DAA in the treatment with the gypsum dispersant and from the 21st DAA with the sachet dispersant (Figure A.1). Figure A.1 Persistence of fumigant activity Mentha piperita essential oil (LC 99 ) in gypsum and sachet dispersants with filter paper on Sitophilus zeamais for 33 days. 2.5 Persistence of the repellent effect of Mentha piperita essential oil in dispersing agents on Sitophilus zeamais The sachet dispersant allowed the repellent effect of the essential oil of M. piperita on S. zeamais to persist up to 15 DAA (χ 2 = 10.96; P = 0.0471) (Figure B.1), while the gypsum tablet dispersant provided persistence for up to 24 DAA (χ 2 = 11.54; P = 0.0398) (Figure A.2). Figure A.2 Persistence of the repellent effect of Mentha piperita essential oil in a sachet dispersant (A) and a gypsum tablet dispersant (B) on Sitophilus zeamais adults (n = 80) at different evaluation times. 3. DISCUSSION 3.1. Chromatographic analysis and chemical identification of Mentha piperita essential oil The chromatographic profile of the Mentha piperita essential oil supplied by the Quinari company aligns with the chemical composition commonly reported for this species. As described in the literature, M. piperita oils are typically characterized by a predominance of oxygenated monoterpenes, particularly menthol, which constitutes the major active component (NICULAU et al., 2013; BARROS et al., 2015). Menthol concentrations in peppermint essential oil generally range from 30% to 55%, depending on factors such as plant chemotype, cultivation conditions, and extraction methods (HUGHES, 2018; KUMAR et al., 2021). This consistency reinforces the reliability of the chemical profile obtained and supports its expected biological activity in subsequent bioassays. 3.2. Fumigant Effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais Thus, the sachet dispersant proved more effective in releasing the toxic compounds of the essential oil than the gypsum tablet. This difference may be attributed to the inherent retention capacity of gypsum, which interacts with air during its hardening process, forming a matrix capable of absorbing and retaining volatile metabolites (YE et al., 2011). As a result, a greater quantity of essential oil is required in gypsum-based formulations to achieve mortality levels comparable to those obtained with sachet dispersants, which allow more rapid and efficient volatilization. The dispersing systems evaluated in this study demonstrate promising potential for the practical application of essential oils as an alternative strategy for managing stored-grain pests. In contrast to conventional fumigation with synthetic pesticides, essential oils are easily accessible, relatively low-cost, and can be dispersed through the environment without the need for sealing structures or using specialized protective equipment. Traditional fumigation requires hermetic conditions and strict safety measures due to the release of toxic gases, increasing operational complexity and overall costs (LORINI et al., 2015). The dispersants proposed herein can be placed directly among stored grains, inside bags, or throughout warehouses in a practical, user-friendly, and non-toxic manner, thereby offering a feasible and safer approach for smallholder and large-scale storage systems. 3.3. Repellent effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The absence of repellency observed for the essential oil applied in sachets at lower concentrations may be attributable to its rapid volatilization within the environment. This rapid release likely reduced the residual activity of the compounds, suggesting that the sachet dispersant was not sufficiently effective in mitigating the inherently low persistence of essential oils (ESTRELA et al., 2006). In contrast, the gypsum-based dispersant demonstrated a greater capacity to retain bioactive metabolites, allowing them to remain available for extended periods and thus sustaining repellency even at reduced concentrations. Previous studies corroborate the repellent properties of Mentha spp. essential oils against several stored-product insects. For example, the essential oil of Mentha longifolia L. (Lamiaceae) has shown significant repellency toward S. zeamais (ODEYEMI et al., 2008). Similarly, essential oil from Mentha arvensis L. (Lamiaceae) has been effective against Callosobruchus chinensis (Coleoptera: Chrysomelidae) (KUMAR et al., 2009 ), while Mentha spicata L. (Lamiaceae) produced up to 60% repellency against the same species (KEDIA et al., 2014). These findings highlight the broad potential of Mentha essential oils for integrated pest management in stored grains. Persistence of the fumigant effect of Mentha piperita essential oil in dispersing agents against Sitophilus zeamais The biodegradable nature of essential oils represents an important advantage for the management of stored-grain pests, reinforcing their suitability for sustainable and environmentally compatible protection programs. However, their practical application is limited by the low molecular weight of their constituents, which promotes rapid volatilization and consequently reduces residual effectiveness (PRAKASH et al., 2015). In this context, gypsum appears to function effectively as a binder with aerial and porous agglomerative properties, enhancing the retention of bioactive compounds and enabling their gradual release over time. This mechanism likely contributed to the more prolonged insecticidal activity observed in gypsum-based formulations compared to the filter paper sachet dispersant (HAGEMANN, 2011). The low persistence observed in the present study is consistent with previous research involving other essential oils. For instance, Eucalyptus globulus Labill. (Myrtaceae) essential oil induced 100% mortality of S. zeamais adults immediately after application; however, its efficacy declined sharply, with negligible mortality recorded after 60 and 120 days of storage (COITINHO et al., 2006). Similarly, essential oil from Melaleuca leucadendron Linnaeus (Myrtaceae) caused 93.8% mortality shortly after impregnation, but mortality dropped to only 1.6% after 30 days (COITINHO et al., 2010). These findings reinforce the inherent challenge of essential oil volatility and highlight the importance of developing dispersing systems, such as gypsum matrices, that improve stability and extend biological activity. Persistence of the repellent effect of Mentha piperita essential oil in dispersing agents on Sitophilus zeamais Other studies support the observation that essential oils generally persist in the environment for approximately 15 days after application (DAA) and that gypsum tablet dispersants are capable of retaining volatile compounds and releasing them gradually, thereby extending their residual activity against insect pests. For instance, Gott et al. (2010) reported that the essential oil of Curcuma longa Linnaeus (Zingiberaceae) exhibited repellency toward S. zeamais at 24 hours and 15 days after application, although this effect was no longer detected at 30 days. The growing interest in natural repellents is largely driven by their demonstrated capacity to match or even surpass the repellent performance of synthetic products. However, the practical use of essential oils in stored-grain protection remains strongly dependent on their persistence, volatility, and toxicity profiles (NERIO et al., 2010). Consequently, further research is needed to evaluate the feasibility of incorporating natural repellents into integrated pest management programs, which may offer sustainable and environmentally compatible alternatives to conventional chemical insecticides (CONTI et al., 2010). Repellency represents a critical complementary mechanism of essential oils in the control of stored-grain pests. Even at concentrations capable of inducing up to 99% mortality, the repellent action helps prevent reinfestation by deterring any surviving insects from recolonizing the stored commodity, thereby contributing to long-term protection. 4. CONCLUSIONS Gypsum is a suitable inert ingredient for dispersing essential oil; Gypsum tablets and sachets dispersants enable the use of essential oil of M. piperita in the control of S. zeamais by fumigation and repellency; Gypsum tablets and sachets dispersants prolong the persistence of the fumigant and repellent effects of M. piperita essential oil on S. zeamais . Declarations Thanks I would like to thank the Coordination for the Improvement of Higher Education Personnel (PEHIC) for financing the researcher. Ethical Approval Not applicable. Conflict of Interest The authors declare no competing interests. Funding Not Funded. Author Contribution The idea of ​​the project was all authors. SILVA A.B. performed the experiments and prepared the original manuscript; OLIVEIRA K.M. contributed to the analyzes of the data; ESPINOSA D.J.L. read and approved the manuscript, ARAÚJO A.M.N. Contributed to the execution of the project methodology, PIMENTEL T.A. 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Journal of the Science of Food and Agriculture. v. 89, n. 43, pp. 2643–2649, 2009. https://doi.org/10.1002/jsfa.3768 LASHGARI, A.; MASHAYEKHI, S.; JAVADZADEH, M.; MARZBAN R. Effect of Mentha piperita and Cuminum cyminum essential oil on Tribolium castaneum and Sitophilus oryzae . Archives of phytopathology and plant protection. v. 47, pp. 324–329, 2014. https://doi.org/10.1080/03235408.2013.809230 LIN, H.;1 KOGAN, FISCHER M et al (1990) LIN, D. Induced resistance in soybean to the mexican bean beetle (Coleoptera: Coccinellidae): comparisons of inducing factors. Environmental Entomology, v. 19, pp. 1852–1857, 1990. https://doi.org/10.1093/ee/19.6.1852 LORINI, I.; KRZYZANOWSKI, F. C.; JOSÉ DE BARROS FRANÇA-NETO, J. B.; HENNING, A. A. Principais pragas e métodos de controle em sementes durante o armazenamento – série sementes. Londrina: Embrapa Soja (Embrapa Soja. 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Insecticidal activity of essential oils of Pelargonium graveolens Herit and Lippia alba (Mill) N. E. Brown against Spodoptera frugiperda (J. E. Smith). Química Nova, v.36, n. 9, pp. 1391–1394, 2013. https://doi.org/10.1590/S0100-40422013000900020 NOOMHORM, SIRISOONTARALAK A, URAICHUEN P et al (2013) NOOMHORM, J., AHMAD I. Efficacy of atmospheric and pressurized carbon dioxide or air against Sitophilus zeamais Motchulsky (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in milled rice. Journal of Stored Products Research. v. 54, pp. 48–53. 2013. https://doi.org/10.1016/j.jspr.2013.05.002 ODEYEMI, MASIKA OO, AFOLAYAN P et al (2008) ODEYEMI, A. J. Insecticidal activities of essential oil from the leaves of Mentha longifolia L. subsp. capensis against Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae). African Entomology, v. 16, n. 2, pp. 220–225, 2008. https://doi.org/10.4001/1021-3589-16.2.220 PRAKASH, KEDIA B, MISHRA A, DUBEY N. K (2015) PRAKASH, P. K.;. Plant essential oils as food preservatives to control moulds, mycotoxin contamination and oxidative deterioration of agri-food commodities – Potentials and challenges. Food Control, v. 47, pp. 381–391, 2015. https://doi.org/10.1016/j.foodcont.2014.07.023 SAS. Institute Inc. Statistical Analysis System user’s guide, Version 9.00. Cary: Sas Institute. 2002 SHAH MA, KHAN AA (2014) Use of diatomaceous earth for the management of storedproduct pests. International Journal of Pest Management, London, v. 60, n. 2, pp. 80–89. https://doi.org/10.1080/09670874.2014.918674 SPARKS T. C.; NAUEN R. IRAC: Classification of the mode of action and management of resistance to insecticides. Pesticide Biochemistry and Physiology. v. 121, n. 2, pp. 122–128, 2015. https://doi.org/10.1016/j.pestbp.2014.11.014 SULEIMAN, WILLIAMS R, NISSEN D, BERN A, ROSENTRATER CJ et al (2015) SULEIMAN, K. A. Is flint corn naturally resistant to Sitophilus zeamais infestation? Journal of Stored Products Research. v. 60, pp. 19–24, 2015. https://doi.org/10.1016/j.jspr.2014.10.007 TORRES, AMÉRICO NH, FERREIRA JHP, GRANJA LFR et al (2014) TORRES, A. C. R.; HARDER, M. N. Aproveitamento sustentável dos subprodutos da madeira e das folhas para extração de óleos essenciais. Bioenergia em Revista: Diálogos, v. 4, n. 1, pp. 09–22, 2014. https://doi.org/10.19142/rpq.v13i26.538 WANG, QIU DC, SHI DR, PAN LN, WEI HY, LI YW, SUN JZ, XUE YJ, WEI DS, LI X, ZHANG YM, QIN JC et al (2018) WANG Identification of insecticidal constituents of the essential oils of Dahlia pinnata Cav. against Sitophilus zeamais and Sitophilus oryzae . Advances in Crop Science and Technology. v. 6, p. 404, 2018. https://doi.org/10.1080/14786419.2014.998218 YE, Q.; GUAN B.; LOU W.; YANG L. Effect of Particle Size Distribution on the Hydration and Compressive Strength Development of α-Calcium Sulfate Hemihydrate Paste. Powder Technology. n.1, v. 207, pp. 208–214, 2011. https://doi.org/10.1016/j.powtec.2010.11.001 Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revisions 10 Feb, 2026 Reviewers agreed at journal 12 Dec, 2025 Reviewers invited by journal 06 Dec, 2025 Editor invited by journal 01 Dec, 2025 Editor assigned by journal 01 Dec, 2025 First submitted to journal 29 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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18:52:18","extension":"html","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":98121,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8239124/v1/34e8e5bc48a9b4bd75cc8fae.html"},{"id":98096055,"identity":"da42a1ad-3a7b-47f7-87c5-bacfaacb5f15","added_by":"auto","created_at":"2025-12-12 18:52:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":6014,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure A.1 \u003c/strong\u003ePersistence of fumigant activity \u003cem\u003eMentha piperita\u003c/em\u003e essential oil (LC\u003csub\u003e99\u003c/sub\u003e) in gypsum and sachet dispersants with filter paper on \u003cem\u003eSitophilus zeamais\u003c/em\u003e for 33 days. \u0026nbsp;\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8239124/v1/1c99d70e5d4a0f8aa5d0279b.png"},{"id":98429325,"identity":"e46b2a7d-7f93-4607-8c6e-036fcf9c4077","added_by":"auto","created_at":"2025-12-17 16:43:13","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":377053,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure A.2\u003c/strong\u003e Persistence of the repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in a sachet dispersant (A) and a gypsum tablet dispersant (B) on \u003cem\u003eSitophilus zeamais\u003c/em\u003eadults (n = 80) at different evaluation times.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8239124/v1/f863a45fa11d6ad343b8d681.jpeg"},{"id":98444509,"identity":"c32814dd-027d-4f61-bd11-3644238cd281","added_by":"auto","created_at":"2025-12-17 17:16:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1448992,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8239124/v1/c32769f6-b7ba-4caf-bd52-a675cf6ebaf9.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eDispersant Agents of Essential Oil for Stored Grain Pest Control\u003c/p\u003e","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003ePost-harvest insect pests represent a major constraint to global grain storage systems, causing quantitative and qualitative losses that reduce market value and may lead to the rejection of grain or seed lots (NAPOLE\u0026Atilde;O et al., 2013; CAMPBELL; ARTHUR, 2019). Among these pests, \u003cem\u003eSitophilus zeamais\u003c/em\u003e (Motschulsky) (Coleoptera: Curculionidae), the maize weevil, stands out as one of the most destructive primary pests of stored cereals, capable of penetrating intact grains and rapidly establishing high infestation levels (NOOMHORM et al., 2013; SULEIMAN et al., 2015).\u003c/p\u003e\u003cp\u003eChemical fumigants remain the primary method for \u003cem\u003eS. zeamais\u003c/em\u003e management. However, the indiscriminate and recurrent use of synthetic insecticides has contributed to the evolution of resistant insect populations, increased toxicological risks, environmental contamination, and restrictions on chemical residues in food products (SPARKS; NAUEN, 2015; PIMENTEL et al., 2022). These limitations have intensified the search for alternative, sustainable, and residue-free pest control strategies.\u003c/p\u003e\u003cp\u003eAmong the emerging alternatives, the use of plant-derived essential oils has gained considerable attention due to their bioactivity, biodegradability, and broad modes of action, including fumigant, repellent, and contact toxicity (SHAH; KHAN, 2014; MOSSA, 2016). Despite their proven efficacy against stored-product insects, the major barrier to large-scale application of essential oils is their low environmental persistence and rapid volatilization, which reduces long-term insecticidal activity (REGNAULT-ROGER et al., 2012; MOSSA, 2016).\u003c/p\u003e\u003cp\u003eIn this context, developing suitable dispersing or carrier agents capable of stabilizing essential oils and enabling gradual release of their active components represents a promising technological advance. Using materials that exhibit high absorption capacity and controlled release can extend the persistence of essential oils and enhance their effectiveness against storage pests (YE et al., 2011; LIU et al., 2020).\u003c/p\u003e\u003cp\u003eGypsum, widely applied in construction, possesses desirable characteristics such as strong absorption, retention, rapid hardening, and structural stability. These properties make it a potential carrier for incorporating essential oils into solid matrices (tablets), facilitating controlled volatilization and sustained insecticidal activity over time.\u003c/p\u003e\u003cp\u003eAmong essential oils evaluated for stored-grain pest control, \u003cem\u003eMentha piperita\u003c/em\u003e L. (Lamiaceae) peppermint oil has shown promising insecticidal properties, acting as a fumigant, repellent, antifeedant, and contact toxicant against several stored-product insects, including \u003cem\u003eSitophilus\u003c/em\u003e species (KHANI et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; JACOB; OMAR, 2013; LASHGARI et al., 2014; KUMAR et al., 2021).\u003c/p\u003e\u003cp\u003eGiven the need for sustainable pest control strategies and the potential advantages of carrier-based delivery systems, the objective of this study was to evaluate dispersing agents for the controlled application of \u003cem\u003eM. piperita\u003c/em\u003e essential oil aiming at the management of \u003cem\u003eS. zeamais\u003c/em\u003e in stored maize.\u003c/p\u003e"},{"header":"1. MATERIAL AND METHODS","content":"\u003cp\u003eThe experiments were carried out at the Laboratory of Entomology - Alternative Pest Control, located at the Campus of Engineering and Agricultural Sciences (CECA), of the Federal University of Alagoas (UFAL), in Rio Largo, Alagoas, under controlled temperature conditions of 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C, 60\u0026thinsp;\u0026plusmn;\u0026thinsp;10% RH and 12 hour photophase.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e1.1. Rearing of \u003cem\u003eSitophilus zeamais\u003c/em\u003e Motschulsky 1855 (Coleoptera: Curculionidae)\u003c/h2\u003e\u003cp\u003eThe Catingueiro variety of maize grains were stored in a freezer at 10\u0026deg;C for a minimum of 10 days to eliminate any potential biological agents. Subsequently, they were placed in hermetically sealed glass jars at room temperature for another 10 days until they reached hygroscopic equilibrium. These grains were then used for experiments and rearing. To carry out laboratory breeding, a portion of the grains was placed in 2.5L glass containers, in which the total capacity was 1/3 filled with corn grains and closed with voile fabric to allow for ventilation. Approximately 40 non-sexed \u003cem\u003eS. zeamais\u003c/em\u003e were introduced into each container on a weekly basis to infest the grains. After 10 days, the insects were removed, and the F1 generation was allowed to develop before testing.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e1.2. Development of dispersing agents\u003c/h2\u003e\u003cp\u003e\u003cem\u003eGypsum tablet-type dispersing agent\u003c/em\u003e. The dispersant based on gypsum was prepared by combining 8 g of gypsum with 5.5 mL of water. The resulting solution was poured into aluminum molds (0.3 x 0.2 x 0.1 cm) to form tablets. After approximately 30 minutes, the tablets were removed from the molds and left to dry at room temperature for at least 72 hours.\u003c/p\u003e\u003cp\u003e\u003cem\u003eSachet-type dispersing agent.\u003c/em\u003e The tea-type sachet dispersant was obtained from a commercial establishment in the dimensions of 3 x 5 cm, in white color, and made of 100% polyester material. An 80g qualitative filter paper was cut into 1 x 5 cm pieces and inserted inside the sachet.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e1.3. Chromatographic analysis and chemical identification of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil\u003c/h2\u003e\u003cp\u003eThe essential oil of \u003cem\u003eM. piperita\u003c/em\u003e was obtained from Quinar\u0026iacute;\u0026reg;, a company located in Ponta Grossa, PR, Brazil. The oil was reported to have 100% purity and was free of any diluent solutions. The country of origin of the oil was the United States of America, and it was extracted from the plant shoot through steam distillation. The oil's chemical compounds were identified using High-Resolution Gas Chromatography on an AGILENT 7820A Gas Chromatograph. The column used was Supelcowax 10\u0026ndash;15m x 0.2mm x 0.2 \u0026micro;m (supelco), with the column temperature set to 50\u0026deg;C for 2 minutes, followed by an increase of 3\u0026deg;C per minute until it reached 200\u0026deg;C. The injector temperature was set to 200\u0026deg;C, and the split ratio was 1/50. The FID detector was set to 220\u0026deg;C, and the injection volume was 1 \u0026micro;L. The identification of the chemical compounds was confirmed using gas chromatography coupled with mass spectrometry (GC-MS).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e1.4. Fumigant Effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe fumigation chambers were constructed by filling 1.8 L glass containers with 40 g of corn grains and 20 unsexed adult \u003cem\u003eS. zeamais\u003c/em\u003e aged up to 15 days, with each chamber representing one repetition. After 48 hours, the percentage of mortality was evaluated.\u003c/p\u003e\u003cp\u003eFor the fumigant effect tests using the gypsum tablet dispersant, several concentrations of the \u003cem\u003eM. piperita\u003c/em\u003e essential oil were impregnated onto the tablets using a dosing pipette. Control samples consisted of tablets without any added liquid. The tablets were then placed inside the fumigation chambers over the grains.\u003c/p\u003e\u003cp\u003ePreliminary tests were performed at different concentrations to determine the mortality values that were close to the control (lower limit) and close to 100% (upper limit). The Bliss formula (1934) was used to define the following concentrations for the definitive bioassay: 25, 31, 47.6, 59.1, and 90.0 \u0026micro;L L\u003csup\u003e-1\u003c/sup\u003e. These concentrations were used to estimate the lethal and sublethal concentrations.\u003c/p\u003e\u003cp\u003eTo test the fumigant effect of sachet dispersant, filter paper was impregnated with different concentrations using a dosing pipette. The filter paper was then inserted into the sachets, which were placed in the fumigation chambers and suspended through a cord to avoid direct contact with the grains. The control group consisted only of sachets containing filter paper without any liquid. Preliminary tests were conducted with several concentrations to determine the mortality values close to the control (Lower Limit) and close to 100% (Upper Limit). Based on the Bliss (1934) formula, the following concentrations were assessed for the definitive bioassay: 15.0, 19.3, 32.4, 41.9, and 70.0 \u0026micro;l L\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe experiments completely randomized designed with five replications per treatment. The concentration-response data were analyzed using Probit analysis, and the lethal concentrations for 50 and 90% (LC50 and CL90) were estimated using the SAS (2002) computational program.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e1.5. Repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe repellency tests were conducted using arenas composed of two glass containers connected to a central container through two glass tubes. One container had 20 g of untreated corn grains (control), while the other container had the same amount of grains treated with different concentrations of \u003cem\u003eM. piperita\u003c/em\u003e essential oil in dispersants agents (gypsum tablets and sachets). In the central container, 16 unsexed adults of \u003cem\u003eS. zeamais\u003c/em\u003e aged up to 15 days were released. The concentrations (18.0, 22.0, and 26.0 \u0026micro;l) were determined based on previous testing. After 48 hours, the insects in each container were counted. The average percentage of repellency was calculated using the formula of Lin et al. (1990).\u003c/p\u003e\u003cp\u003eThe RI or repellency index was calculated using the formula: RI\u0026thinsp;=\u0026thinsp;2G/(G\u0026thinsp;+\u0026thinsp;P), where G represents the percentage of insects attracted by the essential oil treatment and P represents the percentage of insects attracted to the control. The RI values range between zero and two, where RI\u0026thinsp;=\u0026thinsp;1 indicates similar repellency between the treatment and the control (neutral treatment), RI\u0026thinsp;\u0026gt;\u0026thinsp;1 indicates less repellence of the treatment compared to the control (attractive treatment), and RI\u0026thinsp;\u0026lt;\u0026thinsp;1 corresponds to a higher repellency of the treatment in relation to the control (repellent treatment). The confidence interval used to determine whether the essential oil is repellent or not was calculated from the mean RI and the corresponding standard deviation (\u0026plusmn;\u0026thinsp;SD). If the mean RI is less than 1 - SD, the essential oil is repellent; if the mean is greater than 1\u0026thinsp;+\u0026thinsp;SD, the essential oil is attractive, and if the mean is between 1 - SD and 1\u0026thinsp;+\u0026thinsp;SD, the essential oil is considered neutral. This index is an adaptation of the formula cited by Lin et al. (1990) for the consumption index.\u003c/p\u003e\u003cp\u003e\u003cp\u003e\u003cb\u003e1.6 Persistence of the fumigant effect of\u003c/b\u003e \u003cb\u003eMentha piperita\u003c/b\u003e \u003cb\u003eessential oil in dispersing agents against\u003c/b\u003e \u003cb\u003eSitophilus zeamais\u003c/b\u003e\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eThe experiment was designed as a completely randomized design with five replications per treatment, using 2.5 L glass fumigation chambers equipped with an Eppendorf Safe-Lock\u0026reg; microtube attached to the lid. This microtube was used to insert the insects to avoid any openings that could result in air leakage and subsequent loss of fumigation conditions.\u003c/p\u003e\u003cp\u003eThe residual effect of \u003cem\u003eM. piperita\u003c/em\u003e essential oil in each type of dispersant (gypsum tablets and sachets at lethal concentrations of 54.27 and 79.28 \u0026micro;L, respectively) was evaluated using the same methodology as in the previous fumigation experiment, modifying only the treatments, which were storage intervals: 0, 3, 6, 9, 12, 15, 18, 21, 24 days and 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 days, respectively, for the dispersant gypsum tablets and sachet. In the controls, only the dispersant gypsum tablet and sachet with filter paper were used without any addition of liquids.\u003c/p\u003e\u003cp\u003eAll treatments were set up on the same day to assess the residual effect. At each storage interval, five replicates were infested, each containing 20 unsexed adult insects aged between 0 and 15 days, inserted into the fumigation chambers through the Eppendorf present in their lid. The evaluations were performed 48 hours after each infestation, counting the number of dead insects. The data were analyzed using the chi-square test, analysis of variance (ANOVA), and mean values were compared using the Tukey test (SAS Institute Inc, 2003).\u003c/p\u003e\u003cp\u003e\u003cp\u003e\u003cb\u003e1.7 Persistence of the repellent effect of\u003c/b\u003e \u003cb\u003eMentha piperita\u003c/b\u003e \u003cb\u003eessential oil in dispersing agents on\u003c/b\u003e \u003cb\u003eSitophilus zeamais\u003c/b\u003e\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eThe experiment was carried out in a completely randomized design with five replications per treatment. The same methodology as the previous repellency experiment was followed, except for modifications made to the exposure periods. The exposure periods were 0, 3, 6, 9, 12, 15 days and 0, 3, 6, 9, 12, 15, 18, 21, 24 days in the concentrations of essential oil in the dispersant of gypsum tablets and sachets with filter paper, respectively, at concentrations of 18, 22, and 26 \u0026micro;L. The average percentage of repellency was obtained by counting the insects on each side of the containers after 48 hours of each infestation, and was calculated using the formula by Kogan and Goeden (1970). Statistical analysis was performed using the non-parametric chi-square test using the SAS statistical program with a 5% error probability (SAS Institute Inc 2003).\u003c/p\u003e\u003c/div\u003e"},{"header":"2. RESULTS","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Chromatographic analysis and chemical identification of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil\u003c/h2\u003e\u003cp\u003eThe essential oil of \u003cem\u003eM. piperita\u003c/em\u003e comprises 13 compounds: α-pinene, β-pinene, limonene, 1,8-cineol, menthone, mentholfuran, isomenthone, menthyl acetate, isopulegol, neo-isomenthol, pulegone, menthol, and piperitone. Chromatographic analysis indicated that the major constituents of the oil used were menthol (45%), menthone (23.3%), and menthyl acetate (5.5%) (Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003eA.1\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable A.1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eChromatography of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePeak\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRI calc.\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConstituents\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e%\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eα-pinene\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1177\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eβ-pinene\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1211\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003elimonene\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1214\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1,8-cineole\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1419\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ementhone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e23.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1440\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ementofuran\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1444\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eisomenthone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1531\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ementhyl acetate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1549\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eisopulegol\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1573\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eneo-isomenthol\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003epulegone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1621\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ementhol\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e45.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1682\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003epiperitone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eOthers\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eRI calc., calculated retention index; Percentage based on the total area of the chromatogram. Essential oil analyzed in a Carbowax 20M polar column. Ik polar column.\u003c/p\u003e\u003cp\u003eSource: Quinar\u0026iacute;\u003cb\u003e\u0026reg;\u003c/b\u003e, 2021.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Fumigant Effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe fumigation of \u003cem\u003eM. piperita\u003c/em\u003e essential oil in the sachet and gypsum dispersants proved toxicity on \u003cem\u003eS. zeamais\u003c/em\u003e. In the sachet, the estimated values for sublethal (LC\u003csub\u003e50)\u003c/sub\u003e and lethal (LC\u003csub\u003e99\u003c/sub\u003e) concentrations were 23.78 (95% CI\u0026thinsp;=\u0026thinsp;22.50\u0026ndash;25.11) and 54.27 (95% CI\u0026thinsp;=\u0026thinsp;48.42\u0026ndash;62.91) \u0026micro;l L of air, respectively (n\u0026thinsp;=\u0026thinsp;500; Slope\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u0026thinsp;=\u0026thinsp;6.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47; χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;5.39; p\u0026thinsp;=\u0026thinsp;0.14). In the gypsum, the sublethal (LC\u003csub\u003e50)\u003c/sub\u003e and lethal (LC\u003csub\u003e99\u003c/sub\u003e) concentrations were 33.32 (32.61\u0026ndash;36.12) and 79.28 (70.28\u0026ndash;92.01) \u0026micro;L of air, respectively (n\u0026thinsp;=\u0026thinsp;500; Slope\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u0026thinsp;=\u0026thinsp;6.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46; χ2\u0026thinsp;=\u0026thinsp;1.26; p\u0026thinsp;=\u0026thinsp;0.73).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe essential oil of \u003cem\u003eM. piperita\u003c/em\u003e, when used in sachet dispersants at concentrations of 18 and 22 \u0026micro;L, did not show any repellent effect on \u003cem\u003eS. zeamais\u003c/em\u003e after 48 h of exposure. The repellency only occurred at a concentration of 26 \u0026micro;L. In contrast, the use of gypsum as dispersant caused repellency at all tested concentrations (as shown in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003eA.2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable A.2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRepellency of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil on \u003cem\u003eSitophilus zeamais\u003c/em\u003e.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProduct\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDispersant\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConcentrations (\u0026micro;l)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean (\u0026plusmn;\u0026thinsp;DP\u003csup\u003ea\u003c/sup\u003e) of repellency index\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eEffect\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003e\u003cem\u003eMentha\u003c/em\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003ePiperita\u003c/em\u003e Essential Oil\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eSachets\u003c/p\u003e\u003cp\u003e(filter paper)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNeutral\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNeutral\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0,76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eRepellent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eGypsum tablet\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.29\u0026thinsp;\u003cb\u003e\u0026plusmn;\u003c/b\u003e\u0026thinsp;0.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eRepellent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.23\u0026thinsp;\u003cb\u003e\u0026plusmn;\u003c/b\u003e\u0026thinsp;0.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eRepellent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.20\u0026thinsp;\u003cb\u003e\u0026plusmn;\u003c/b\u003e\u0026thinsp;0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eRepellent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e(*) \u003csup\u003ea\u003c/sup\u003eStandard deviation, \u003csup\u003eb\u003c/sup\u003eRepellency index calculated from the formula described by Lin et al. (1990)\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePersistence of the fumigant effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eThe dispersant based on gypsum exhibited a higher level of persistence of the \u003cem\u003eM. piperita\u003c/em\u003e essential oil, resulting in mortality rates above 70% even 24 days after application (F\u0026thinsp;=\u0026thinsp;2.33; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Figure A.1).\u003c/p\u003e\u003cp\u003eUntil the 9th day after application (DAA), the essential oil in both types of dispersants, at concentrations of 54.27 and 79.28 \u0026micro;L of air (LC\u003csub\u003e99\u003c/sub\u003e), did not differ in terms of fumigant action. The essential oil in the sachet dispersant gradually declined in fumigant activity from the 14th to the 18th DAA, with average mortality ranging from 80.0 to 65.0% (Figure A.1).\u003c/p\u003e\u003cp\u003eOn the other hand, the essential oil in the gypsum dispersant persisted for 15 days after the 9th DAA (until the 24th DAA), with an average mortality of 90% up to the 15th DAA, which gradually decreased to 87.0 and 68.0% on the 18th day to 24th DAA, respectively. There were significant decreases in \u003cem\u003eS. zeamais\u003c/em\u003e mortality from the 27th DAA in the treatment with the gypsum dispersant and from the 21st DAA with the sachet dispersant (Figure A.1).\u003c/p\u003e\u003cp\u003e\u003cb\u003eFigure A.1\u003c/b\u003e Persistence of fumigant activity \u003cem\u003eMentha piperita\u003c/em\u003e essential oil (LC\u003csub\u003e99\u003c/sub\u003e) in gypsum and sachet dispersants with filter paper on \u003cem\u003eSitophilus zeamais\u003c/em\u003e for 33 days.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cp\u003e2.5 Persistence of the repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents on \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eThe sachet dispersant allowed the repellent effect of the essential oil of \u003cem\u003eM. piperita\u003c/em\u003e on \u003cem\u003eS. zeamais\u003c/em\u003e to persist up to 15 DAA (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;10.96; P\u0026thinsp;=\u0026thinsp;0.0471) (Figure B.1), while the gypsum tablet dispersant provided persistence for up to 24 DAA (χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;11.54; P\u0026thinsp;=\u0026thinsp;0.0398) (Figure A.2).\u003c/p\u003e\u003cp\u003e\u003cb\u003eFigure A.2\u003c/b\u003e Persistence of the repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in a sachet dispersant (A) and a gypsum tablet dispersant (B) on \u003cem\u003eSitophilus zeamais\u003c/em\u003e adults (n\u0026thinsp;=\u0026thinsp;80) at different evaluation times.\u003c/p\u003e"},{"header":"3. DISCUSSION","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Chromatographic analysis and chemical identification of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil\u003c/h2\u003e\u003cp\u003eThe chromatographic profile of the \u003cem\u003eMentha piperita\u003c/em\u003e essential oil supplied by the Quinari company aligns with the chemical composition commonly reported for this species. As described in the literature, \u003cem\u003eM. piperita\u003c/em\u003e oils are typically characterized by a predominance of oxygenated monoterpenes, particularly menthol, which constitutes the major active component (NICULAU et al., 2013; BARROS et al., 2015). Menthol concentrations in peppermint essential oil generally range from 30% to 55%, depending on factors such as plant chemotype, cultivation conditions, and extraction methods (HUGHES, 2018; KUMAR et al., 2021). This consistency reinforces the reliability of the chemical profile obtained and supports its expected biological activity in subsequent bioassays.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Fumigant Effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThus, the sachet dispersant proved more effective in releasing the toxic compounds of the essential oil than the gypsum tablet. This difference may be attributed to the inherent retention capacity of gypsum, which interacts with air during its hardening process, forming a matrix capable of absorbing and retaining volatile metabolites (YE et al., 2011). As a result, a greater quantity of essential oil is required in gypsum-based formulations to achieve mortality levels comparable to those obtained with sachet dispersants, which allow more rapid and efficient volatilization.\u003c/p\u003e\u003cp\u003eThe dispersing systems evaluated in this study demonstrate promising potential for the practical application of essential oils as an alternative strategy for managing stored-grain pests. In contrast to conventional fumigation with synthetic pesticides, essential oils are easily accessible, relatively low-cost, and can be dispersed through the environment without the need for sealing structures or using specialized protective equipment. Traditional fumigation requires hermetic conditions and strict safety measures due to the release of toxic gases, increasing operational complexity and overall costs (LORINI et al., 2015). The dispersants proposed herein can be placed directly among stored grains, inside bags, or throughout warehouses in a practical, user-friendly, and non-toxic manner, thereby offering a feasible and safer approach for smallholder and large-scale storage systems.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eThe absence of repellency observed for the essential oil applied in sachets at lower concentrations may be attributable to its rapid volatilization within the environment. This rapid release likely reduced the residual activity of the compounds, suggesting that the sachet dispersant was not sufficiently effective in mitigating the inherently low persistence of essential oils (ESTRELA et al., 2006). In contrast, the gypsum-based dispersant demonstrated a greater capacity to retain bioactive metabolites, allowing them to remain available for extended periods and thus sustaining repellency even at reduced concentrations.\u003c/p\u003e\u003cp\u003ePrevious studies corroborate the repellent properties of \u003cem\u003eMentha\u003c/em\u003e spp. essential oils against several stored-product insects. For example, the essential oil of \u003cem\u003eMentha longifolia\u003c/em\u003e L. (Lamiaceae) has shown significant repellency toward \u003cem\u003eS. zeamais\u003c/em\u003e (ODEYEMI et al., 2008). Similarly, essential oil from \u003cem\u003eMentha arvensis\u003c/em\u003e L. (Lamiaceae) has been effective against \u003cem\u003eCallosobruchus chinensis\u003c/em\u003e (Coleoptera: Chrysomelidae) (KUMAR et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), while \u003cem\u003eMentha spicata\u003c/em\u003e L. (Lamiaceae) produced up to 60% repellency against the same species (KEDIA et al., 2014). These findings highlight the broad potential of \u003cem\u003eMentha\u003c/em\u003e essential oils for integrated pest management in stored grains.\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePersistence of the fumigant effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents against \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eThe biodegradable nature of essential oils represents an important advantage for the management of stored-grain pests, reinforcing their suitability for sustainable and environmentally compatible protection programs. However, their practical application is limited by the low molecular weight of their constituents, which promotes rapid volatilization and consequently reduces residual effectiveness (PRAKASH et al., 2015).\u003c/p\u003e\u003cp\u003eIn this context, gypsum appears to function effectively as a binder with aerial and porous agglomerative properties, enhancing the retention of bioactive compounds and enabling their gradual release over time. This mechanism likely contributed to the more prolonged insecticidal activity observed in gypsum-based formulations compared to the filter paper sachet dispersant (HAGEMANN, 2011).\u003c/p\u003e\u003cp\u003eThe low persistence observed in the present study is consistent with previous research involving other essential oils. For instance, \u003cem\u003eEucalyptus globulus\u003c/em\u003e Labill. (Myrtaceae) essential oil induced 100% mortality of \u003cem\u003eS. zeamais\u003c/em\u003e adults immediately after application; however, its efficacy declined sharply, with negligible mortality recorded after 60 and 120 days of storage (COITINHO et al., 2006). Similarly, essential oil from \u003cem\u003eMelaleuca leucadendron\u003c/em\u003e Linnaeus (Myrtaceae) caused 93.8% mortality shortly after impregnation, but mortality dropped to only 1.6% after 30 days (COITINHO et al., 2010). These findings reinforce the inherent challenge of essential oil volatility and highlight the importance of developing dispersing systems, such as gypsum matrices, that improve stability and extend biological activity.\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePersistence of the repellent effect of \u003cem\u003eMentha piperita\u003c/em\u003e essential oil in dispersing agents on \u003cem\u003eSitophilus zeamais\u003c/em\u003e\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eOther studies support the observation that essential oils generally persist in the environment for approximately 15 days after application (DAA) and that gypsum tablet dispersants are capable of retaining volatile compounds and releasing them gradually, thereby extending their residual activity against insect pests. For instance, Gott et al. (2010) reported that the essential oil of \u003cem\u003eCurcuma longa\u003c/em\u003e Linnaeus (Zingiberaceae) exhibited repellency toward \u003cem\u003eS. zeamais\u003c/em\u003e at 24 hours and 15 days after application, although this effect was no longer detected at 30 days.\u003c/p\u003e\u003cp\u003eThe growing interest in natural repellents is largely driven by their demonstrated capacity to match or even surpass the repellent performance of synthetic products. However, the practical use of essential oils in stored-grain protection remains strongly dependent on their persistence, volatility, and toxicity profiles (NERIO et al., 2010). Consequently, further research is needed to evaluate the feasibility of incorporating natural repellents into integrated pest management programs, which may offer sustainable and environmentally compatible alternatives to conventional chemical insecticides (CONTI et al., 2010).\u003c/p\u003e\u003cp\u003eRepellency represents a critical complementary mechanism of essential oils in the control of stored-grain pests. Even at concentrations capable of inducing up to 99% mortality, the repellent action helps prevent reinfestation by deterring any surviving insects from recolonizing the stored commodity, thereby contributing to long-term protection.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. CONCLUSIONS","content":"\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eGypsum is a suitable inert ingredient for dispersing essential oil;\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eGypsum tablets and sachets dispersants enable the use of essential oil of \u003cem\u003eM. piperita\u003c/em\u003e in the control of \u003cem\u003eS. zeamais\u003c/em\u003e by fumigation and repellency;\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eGypsum tablets and sachets dispersants prolong the persistence of the fumigant and repellent effects of \u003cem\u003eM. piperita\u003c/em\u003e essential oil on \u003cem\u003eS. zeamais\u003c/em\u003e.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cb\u003eThanks\u003c/b\u003e\u003c/p\u003e\u003cp\u003eI would like to thank the Coordination for the Improvement of Higher Education Personnel (PEHIC) for financing the researcher.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eNot Funded.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe idea of ​​the project was all authors. SILVA A.B. performed the experiments and prepared the original manuscript; OLIVEIRA K.M. contributed to the analyzes of the data; ESPINOSA D.J.L. read and approved the manuscript, ARA\u0026Uacute;JO A.M.N. Contributed to the execution of the project methodology, PIMENTEL T.A. Contributed to the execution of tests, BREDA M.O. performed the editing, analysis and interpretation of the data, TRINDADE R.C.P. designed the project.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBARROS, MORAIS AS, FERREIRA SM, VIEIRA PAT, CRAVEIRO IGP, FONTENELLE AA, MENEZES ROS, SOUSA JESA;SILVAFWF et al (2015) BARROS, H. A. Chemical composition and functional properties of essential oils from \u003cem\u003eMentha\u003c/em\u003e species. Industrial Crops and Products, v. 76, pp. 557–564, 2015. https://doi.org/10.1016/j.indcrop.2015.07.004\u003c/li\u003e\n\u003cli\u003e, CARVALHO FP (2017) CARVALHO, Pesticides, enviroment, and food safety. Food and Energy Security, v. 6, n. 2, pp. 48–60, 2017. https://doi.org/10.1002/fes3.108\u003c/li\u003e\n\u003cli\u003eCHAUDHARI A. K.; SINGH, V. K.; KEDIA, A.; DAS S.; DUBEY N. K. Essential oils and their bioactive compounds as eco-friendly novel green pesticides for management of storage insect pests: prospects and retrospects. Environmental Science and Pollution Research, 2021. https://doi.org/10.1007/s11356-021-12841-w\u003c/li\u003e\n\u003cli\u003eCHU, LIU SS, DU ZL, DENG SS et al (2012) CHU, Z. W. Chemical Composition and Insecticidal Activity Against \u003cem\u003eSitophilus zeamais\u003c/em\u003e of the Essential Oils Derived from \u003cem\u003eArtemisia giraldii\u003c/em\u003e and \u003cem\u003eArtemisia subdigitata\u003c/em\u003e. Molecules. v. 17, n. 6, pp. 7255–7265, 2012. https://doi.org/10.3390/moléculas17067255\u003c/li\u003e\n\u003cli\u003eCOITINHO, OLIVEIRA RLB, GONDIM JV, JUNIOR MGC, CAMARA et al (2010) COITINHO, C. A. G. 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Aproveitamento sustentável dos subprodutos da madeira e das folhas para extração de óleos essenciais. Bioenergia em Revista: Diálogos, v. 4, n. 1, pp. 09–22, 2014. https://doi.org/10.19142/rpq.v13i26.538\u003c/li\u003e\n\u003cli\u003eWANG, QIU DC, SHI DR, PAN LN, WEI HY, LI YW, SUN JZ, XUE YJ, WEI DS, LI X, ZHANG YM, QIN JC et al (2018) WANG Identification of insecticidal constituents of the essential oils of \u003cem\u003eDahlia pinnata\u003c/em\u003e Cav. against \u003cem\u003eSitophilus zeamais\u003c/em\u003e and \u003cem\u003eSitophilus oryzae\u003c/em\u003e. Advances in Crop Science and Technology. v. 6, p. 404, 2018. https://doi.org/10.1080/14786419.2014.998218\u003c/li\u003e\n\u003cli\u003eYE, Q.; GUAN B.; LOU W.; YANG L. Effect of Particle Size Distribution on the Hydration and Compressive Strength Development of α-Calcium Sulfate Hemihydrate Paste. Powder Technology. n.1, v. 207, pp. 208–214, 2011. https://doi.org/10.1016/j.powtec.2010.11.001\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-plant-diseases-and-protection","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpdp","sideBox":"Learn more about [Journal of Plant Diseases and Protection](https://www.springer.com/journal/41348)","snPcode":"41348","submissionUrl":"https://www.editorialmanager.com/jpdp","title":"Journal of Plant Diseases and Protection","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Alternative Control, Formulation, Inert Powder, Mentha piperita, S. zeamais","lastPublishedDoi":"10.21203/rs.3.rs-8239124/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8239124/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe control of insect pests in stored grains carried out through insecticides that may select resistant populations and generate environmental risks. Secondary plant compounds are alternatives to control insect pests. However, the high volatility has been an obstacle in their practical use. This study develops natural dispersants for the application of \u003cem\u003eMentha piperit\u003c/em\u003ea essential oil for the control of \u003cem\u003eSitophilus zeamais\u003c/em\u003e (Motschulsky) (Coleoptera: Curculionidae). Two types of dispersants were tested: a gypsum-based dispersant prepared with a mixture of gypsum and water molded in aluminum, and a sachet dispersant composed of polyester sachets. The efficiency of the dispersants was assessed by contact, fumigation and repellency tests. For that, unsexed \u003cem\u003eS. zeamais\u003c/em\u003e up to 15 days old were used and evaluated after 48 hours of experiment assembly. The persistence effects of the essential oil in dispersants were also evaluated. The fumigation test with essential oil in the sachet and gypsum dispersants generated, respectively, LC\u003csub\u003e50\u003c/sub\u003e values of 23.78 and 34.32 and LC\u003csub\u003e99\u003c/sub\u003e values of 54.27 and 79.28 \u0026micro;L. For the contact test, the sachet dispersant presented sublethal and lethal concentrations of LC\u003csub\u003e50\u003c/sub\u003e 25.84 and LC\u003csub\u003e99\u003c/sub\u003e 48.40 \u0026micro;L, respectively. However, only the 26 \u0026micro;L concentration was repellent for both dispersants. The repellent and fumigant effects of the sachet lasted for 15 and 24 days, while these effects in gypsum dispersants lasted 21 and 30 days, respectively. Both dispersants were considered promising as they persistently retained and released the compounds present in the essential oil, enhancing the fumigant and repellent effect against \u003cem\u003eS. zeamais\u003c/em\u003e.\u003c/p\u003e","manuscriptTitle":"Dispersant Agents of Essential Oil for Stored Grain Pest Control","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-12 18:52:13","doi":"10.21203/rs.3.rs-8239124/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revisions","date":"2026-02-10T13:19:00+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-12-12T11:49:08+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-06T17:33:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Journal of Plant Diseases and Protection","date":"2025-12-01T22:31:48+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-01T15:37:43+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Plant Diseases and Protection","date":"2025-11-29T15:46:11+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-plant-diseases-and-protection","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpdp","sideBox":"Learn more about [Journal of Plant Diseases and Protection](https://www.springer.com/journal/41348)","snPcode":"41348","submissionUrl":"https://www.editorialmanager.com/jpdp","title":"Journal of Plant Diseases and Protection","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2622df1e-0cd7-44c5-b84b-7b3c12c1d121","owner":[],"postedDate":"December 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-30T05:55:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-12 18:52:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8239124","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8239124","identity":"rs-8239124","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}