Search Results (53)

Essential oils have emerged as promising alternatives for pest insect control. However, sublethal effects on insect reproduction and development are rarely explored, despite their relevance to integrated pest management (IPM). This study evaluated the sublethal effects of Piper hispidivervum C. DC. essential oil (EOPH) on the development and population growth of four populations of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), as well as the persistence of safrole residue in treated corn grains. Population development rates were determined using emergence curves and total emerged adults, while population growth was assessed by counting live insects in the feeding substrate at different storage intervals. Safrole residue persistence was analyzed using solid-phase microextraction in headspace mode (SPME-HS). Sublethal exposure to EOPH significantly reduced the development rate, total emergence, and growth in three of the four populations. The population from Crixás, GO, showed no significant reduction, with a population curve overlapping the control. The lethal dose was reduced by 98.20%, indicating low persistence and potential food safety. The EOPH exhibited sublethal effects on S. zeamais populations, reducing both development rates and population growth. This reduction varied among the populations studied. Further research is encouraged to explore its effects on different insect populations and under broader environmental conditions. Full article

Sitophilus zeamais, a major pest of stored grains, causes significant post-harvest losses and challenges effective control. While synthetic insecticides pose risks of resistance and toxicity, essential oils (EOs) offer a safer alternative. However, the insecticidal potential of their individual volatile constituents (VCs) remains largely unexplored. This study evaluated the insecticidal activity of 51 EO-derived volatile compounds (VCs) against S. zeamais, identifying the most toxic ones, optimizing 15 synergistic mixtures, and assessing their effects on key insect enzymes. A structure–activity relationship (SAR) analysis determined functional groups associated with insecticidal activity, while a cluster analysis pre-selected 29 ternary mixtures, later refined using response surface methodology (RSM). Additionally, enzymatic assays explored their impact on detoxification and nervous system enzymes, providing insights into potential mechanisms of action. Among the 51 VCs tested, 37 exhibited significant toxicity, with 11 acting as fumigants and 13 displaying contact toxicity. Monocyclic monoterpenoids with ketone or alcohol functional groups and exocyclic unsaturation demonstrated the highest insecticidal activity via both exposure routes. Notably, pulegone enantiomers were particularly effective (LC₅₀ < 0.1 mg/L, LD₅₀ < 7.5 µg/adult). Among the optimized mixtures, 10 displayed strong insecticidal effects, 8 were active through both routes, and 5 exhibited synergistic fumigant interactions. The most effective formulations were M2 (R-pulegone + S-pulegone + S-carvone, LC₅₀ 0.48 mg/L) and M20 (isopulegone + δ-3-carene, LC₅₀ 2.06 mg/L), showing the strongest fumigant and synergistic effects, respectively. Enzymatic assays revealed that while some compounds mildly inhibited GST and CAT, others, such as δ-3-carene (IC₅₀ 0.19 mg/L), significantly inhibited AChE. Five mixtures exhibited synergistic neurotoxicity, with M20 (IC₅₀ 0.61 mg/L) and M12 (IC₅₀ 0.81 mg/L) emerging as the most potent AChE inhibitors. These findings highlight the potential of plant-derived volatile compounds as bioinsecticides, leveraging synergistic interactions to enhance efficacy, disrupt enzymatic pathways, and mitigate resistance. Full article

Maize (Zea mays) is a critical staple crop whose post-harvest losses, predominantly due to infestations by the maize weevil, Sitophilus zeamais, threaten food security. This study explores the possibility of utilizing S. zeamais, traditionally known as a pest, as an alternative protein source by assessing its nutritional profile and food safety attributes. Cultured under controlled conditions, S. zeamais specimens were processed into flour, which was subsequently analyzed for microbiological safety, protein content, and amino acid composition. Microbiological assays confirmed that the flour met established food safety standards, with aerobic mesophilic bacteria, fungi, and yeast present at negligible levels and no detection of coliforms, Salmonella spp., or Escherichia coli. Protein quantification revealed a high total protein content (48.1 ± 0.3%), although the salt-soluble fraction constituted only 13.7% of the total. The amino acid profile exhibited elevated levels of isoleucine, valine, and threonine, while deficiencies in leucine, lysine, sulfur amino acids, and tryptophan were noted. These findings suggest that, despite certain limitations, S. zeamais flour represents a viable protein source. Integrating targeted insect harvesting for protein into pest management strategies could help reduce post-harvest losses and contribute to improved food security and nutritional availability. Full article

Bacillus thuringiensis is widely utilized as a microbial insecticide due to its production of parasporal crystals during the spore-forming stage. However, lower fermentation efficiency coupled with elevated production costs limit its broad application. Low-frequency ultrasound (LFU) has been employed in the fermentation industry to enhance microbial growth and metabolism. In this study, the effect of LFU on the growth of B. thuringiensis HD1 and the yields of parasporal crystals was investigated. The maximum biomass accumulation of Bacillus thuringiensis and parasporal crystal production yield were achieved following low-frequency ultrasonic (LFU) treatment applied during the logarithmic growth phase (18 h of cultivation) under optimized parameters: a frequency of 40 kHz, a power output of 176 W, and an irradiation duration of 45 min. Under optimal conditions, LFU significantly increased the cell membrane permeability and secretory inositol, favoring cell growth and parasporal crystal production. FESEM/CLSM and TEM analyses visually displayed the changes in cell morphology. In addition, the germination rate of spores was increased after LFU treatment, which further confirmed the positive effect of LFU on the growth of B. thuringiensis. Compared to the control, parasporal crystals harvested under LFU exhibited significant modifications in their physicochemical characteristics; the particle size increased, the surface electronegativity intensified, and there was a morphological transition from spherical to cubic geometry. Importantly, the parasporal crystals exhibited strong insecticidal activity against S. zeamais adults, a typical stored-product insect pest, with an LC₅₀ of 10.795 mg/g on day 14 and a Kt₅₀ of 4.855 days at a concentration of 30 mg/g. These findings will provide new insights into the product development and application of B. thuringiensis in the future. Full article

Stored product pests are controlled primarily through applying pyrethroid and organophosphate insecticides or through fumigation with phosphine (PH₃). However, several populations of weevils are resistant to these insecticides. Essential oils appear to be safe alternatives for both humans and the environment. The objective was to investigate the toxicity of Piper aduncum essential oil (PAEO) to Sitophilus zeamais and evaluate its effects on corn grain quality during the four-month storage period. This study was conducted in two stages. In the first stage, the toxicity of PAEO at concentrations lethal to 50 and 95% of insects (LC₅₀ and LC₉₅) was estimated. The second step evaluated the degree of infestation, water content, apparent specific mass, loss of mass, electrical conductivity, and percentage of germination of grains at 0, 30, 60, 90, and 120 days after exposure to PAEO, deltamethrin (pyrethroid), and the control treatment. PAEO presents toxicity to S. zeamais. The LC₅₀ and LC₉₅ values are 298.50 µL kg⁻¹ and 585.20 µL kg⁻¹, respectively. The increases in infestation degree, water content, electric conductivity, and mass loss, as well as reductions in apparent specific mass and germination, show the loss of corn quality during the 120-day storage period, being more significant when no product is applied. PAEO delays the loss of quality of the grains, presenting a greater capacity to preserve the grains for a longer period. Full article

To contribute to the search for effective substances in pest control, this study describes the fumigant and contact toxicity against Tribolium castaneum and Sitophilus zeamais of four essential oils (EOs) and some of their major chemical constituents. The EOs from Tagetes zypaquirensis, Anethum graveolens, Satureja viminea and Minthostachys mollis were obtained by steam distillation and chemically characterized using GC–MS. In the development of research, some monoterpenoids were isolated from the EOs, others were purchased commercially, and some were synthesized from the most active monoterpenoids present in EOs. The main components in the EOs were dill ether (28.56%), α-phellandrene (25.78%) and carvone (23.67%) for A. graveolens, piperitone oxide (30.40%) and pulegone (25.91%) in M. mollis, pulegone (37.40%) and p-menth-3-en-8-ol (11.83%) for S. viminea, and dihydrotagetone (32.13%), myrcene epoxide (19.64%) and β-myrcene (5.30%) for T. zypaquirensis. The results highlight the fumigant action (LC₅₀) and contact toxicity (LD₅₀) of EO from M. mollis against T. castaneum (LC₅₀ of 4.8 µL/L air and LD₅₀ of 6.5 µg/insect) and S. zeamais (LC₅₀ of 7.0 µL/L air and LD₅₀ of 5.81 µg/insect). Among the chemical constituents evaluated, R-carvone 2, piperitone oxide 5 and R-pulegone 6 stand out for their insecticidal potential against S. zeamais (LC₅₀ between 3.0 and 42.4 µL/L, while LD₅₀ between 14.9 and 24.6 µg/insect) and T. castaneum (LC₅₀ between 2.2 and 4.8 µL/L, while LD₅₀ between 4.8 and 13.1 µg/insect). Preliminary structure–activity analysis suggests that the presence of the carbonyl group with conjugated double bonds in cyclic monoterpenes is important for the insecticidal potential exhibited. Full article

The bioinsecticidal and repellent effect of four plant powders (Chenopodium ambrosioides, Piper auritum, Laurus nobilis, and Origanum vulgare) was evaluated in the control of Sitophilus zeamais adults in corn grains stored in the rural community of Santa María Zacatepec, Oaxaca, Mexico. Using completely randomized experimental designs, concentrations of 1%, 2%, and 3% by mass of corn grains infested with adults of S. zeamais were tested; the controls were corn without powder and aluminum phosphide. The analysis was performed using ANOVA with Tukey’s post hoc and Student’s t-tests. The highest mortality (>80%) and repellent effect (Repellent Index < 0.3) that were statistically significant were obtained with C. ambrosioides and P. auritum at 3%. Both plant species have the potential for weevil control in stored corn and represent a friendly alternative for the environment and public health in the rural community where the study was conducted. Full article

Corn is one of the world’s most economically important cereal crops and can be attacked by Sitophilus zeamais. The control of S. zeamais is mostly based on synthetic insecticides; however, populations of this insect have developed resistance to various chemical compounds. New rational insecticides that prevent the development of resistant populations need to be continuously evaluated. This research aimed to assess the effects mediated by azadirachtin on S. zeamais populations in terms of mortality, survival, food preference, and repellency. Azadirachtin is toxic to S. zeamais at the larval (LC₅₀ = 3.36 ppm), pupal (LC₅₀ = 23.0 ppm), and adult (LC₅₀ = 37.7 ppm) stages. At all stages of insect development, the survival rate was 99.9% in insects not treated with azadirachtin, decreasing to 29.9%, 44.9%, and 68.5% in larvae, pupae, and adults treated with the LC₅₀ of the bioinsecticide, respectively. The preference for untreated corn grains was higher with the LC₂₅ and LC₅₀ of azadirachtin, while the LC₉₅ (209 ppm) repelled adults. Azadirachtin causes lethality in S. zeamais, compromising its survival and reducing the feeding preference on grains protected with repellent activity at high concentrations. Therefore, the use of this bioinsecticide may offer an alternative to control S. zeamais in the field and post-harvest. Full article

Pests in wood pellets are treated using methyl bromide (MB) fumigation, which has low efficacy against pests because of its high adsorption to wood pellets. In this study, we assessed the feasibility of combined MB and phosphine (PH₃) fumigation of adults and pupae of Tribolium castaneum and Sitophilus zeamais. The LC₉₉ of MB for T. castaneum pupae were 31.49, 39.21, and 53.48 mg/L for 24 h treatment at 20, 10, and 5 °C, respectively. For S. zeamais, the LC₉₉ were 24.32, 36.06, and 51.49 mg/L under the same conditions. The addition of PH₃ (0.04 mg/L) to MB against T. castaneum pupae significantly decreased the LC₉₉ of MB to 4.05 mg/L at 20 °C. MB was strongly adsorbed to wood pellets, which prevented complete extermination of T. castaneum at loading ratios between 20 and 60%. However, at the highest filling ratio (60%), the addition of 0.7 mg/L PH₃ with 70 mg/L MB achieved 100% mortality for T. castaneum. When pupae of S. zeamais were targeted, MB + PH₃ effectively disinfected both stages of both pests after 24 h at 5, 15, and 20 °C. Combined MB + PH₃ treatment is an alternative to the currently approved MB treatment for controlling exotic beetles in imported wood pellets in Korea. Full article

The use of essential oils from certain herbal plants offers a promising alternative to synthetic insecticides for controlling the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Dryophthoridae), a major pest that causes significant damage to stored grains. Essential oils, particularly from aromatic herbs in the Apiaceae family, are widely used in medicinal, cosmetic, and food industries and provided insecticidal properties to mitigate the environmental and health hazards associated with synthetic insecticides. This research aimed to investigate the insecticidal and repellent effects of Apium graveolens L. (celery) seed essential oil against S. zeamais. Chemical analysis of the commercially produced essential oil from A. graveolens seeds was conducted using a gas chromatograph–mass spectrometer (GC-MS), and the biological activity of the essential oil was determined by ingestion, contact, fumigation, and repellent tests. The analysis identified D-limonene (64.21%) and α-humulene (17.46%) as primary components of the oil. Toxicity assays revealed an observable contact toxicity, with higher concentrations and prolonged exposure increasing its effectiveness. The contact toxicity assays reported an LC₅₀ of 19.83 nL/adult after 72 h. Additionally, the essential oil displayed repellent effects, effectively deterring weevils at concentrations above 16 µL/L air, but its feeding deterrence was weak. The essential oil’s strong insecticidal and repellent properties, which were concentration- and time-dependent, highlighted its potential as a sustainable alternative to synthetic pesticides for integrated pest management. Full article

This study aimed to assess the efficiency of the use of α-pinene and essential oils of Gaultheria procumbens, Juniperus communis, Protium heptaphyllum, and Protium pallidum in treating corn seeds (Zea mays) under storage conditions for the management of Sitophilus zeamais. Contact toxicity, fumigation, repellency, persistence, and residual effects of the targeted essential oil and phytocompound on germination were performed. G. procumbens oil, high in methyl salicylate (96%), was the most toxic in contact tests, with an LC₅₀ of 26.83 µL/20 g. P. heptaphyllum oil, containing 40.1% limonene, was the second most toxic with an LC50 of 45.78 μL/20 g. When test separately, α-pinene was more toxic than J. communis oil, which has 67% α-pinene. P. pallidum oil, with 31.17% o-cimene, also showed toxicity. In fumigation tests, the toxicity order was G. procumbens ≥ P. heptaphyllum > α-pinene > J. communis > P. pallidum. All products were repellent. G. procumbens had the longest persistence (71 days), while J. communis and α-pinene had shorter persistence. J. communis oil and α-pinene did not affect corn seed germination or vigor. The findings are crucial for managing S. zeamais in stored maize and determining the appropriate use of natural insecticides without affecting their ability to germinate and grow. Full article

This study aimed to evaluate the toxicity of Piper hispidinervum essential oil (PHEO) against 11 Brazilian populations of Sitophilus zeamais (Coleoptera: Curculionidae). The effects of sublethal doses of PHEO on the behavior (walking and flying), respiration, and population growth (r_i) of the insect populations were investigated. PHEO toxicity was determined through concentration–mortality bioassays, with mortality curves established using increasing PHEO concentrations ranging from 140.00 to 1000.00 μL kg⁻¹. Behavior was evaluated based on walking distance, walking time, walking speed, walking time proportion, flight height, and flight takeoff success. Respiration was measured via the respiratory rate, while population growth (r_i) was assessed through the instantaneous growth rate. All 11 populations of S. zeamais were susceptible to PHEO, showing no signs of resistance. The populations exhibited varying behavioral and physiological responses to sublethal exposure to PHEO, indicating different mitigation strategies. The results confirm that PHEO possesses insecticidal potential for controlling S. zeamais populations. However, the observed behavioral and physiological responses should be considered when establishing control measures in pest management programs for stored products. Full article

The behavioural response of adult maize weevil, Sitophilus zeamais, to different types of semolina pasta enriched or not enriched with increasing proportions (5%, 10%, and 15%) of house cricket (Acheta domesticus) powder was investigated in olfactometer arena bioassays by using trap devices. In the five-choice behavioural bioassays, the number of S. zeamais adults attracted to 100% durum wheat semolina pasta was significantly higher than those attracted to the other pasta types enriched with A. domesticus powder. In the two-choice behavioural bioassays, the Response Index for each pasta type was positive and significant. However, although not significant, there was a progressive reduction in the Response Index as the cricket powder content increased. In similar experiments, there were no significant differences between cricket powder alone and the control in the number of attracted S. zeamais, indicating a neutral effect towards insects. These observations suggest that the lower attractiveness of pasta enriched with house cricket powder is mainly due to the masking of host food odours. Solid-phase microextraction coupled to gas chromatography–mass spectroscopy identified a total of 18 compounds in the head-space samples of the different types of pasta, highlighting differences in volatile composition. Some volatile compounds were only present in the pasta produced with cricket powder. In particular, 1-octen-3-ol and phenol were present in the samples containing 5%, 10%, or 15% cricket powder; pentanal, benzaldehyde, and dimethyl disulphide were present in samples containing 10% or 15% cricket powder; and 2,5-dimethyl-pyrazine was present in the sample containing 15% cricket powder. Further investigation with individual compounds and mixtures is needed to define the chemical basis of the differences in the insect olfactory preference observed in this study. Full article

Chlorantraniliprole, an anthranilic diamide insecticide, has emerged as a promising solution for controlling agricultural pests because of its low mammalian toxicity and selectivity towards non-target organisms. This study investigated the sublethal effects of chlorantraniliprole on the mobility behavior of two significant stored-product pests, Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Contact toxicity assays revealed varying susceptibility levels between the two species, with S. zeamais showing higher sensitivity. Subsequent analysis of mobility behavior, both in the presence and absence of food, indicated significant differences between chlorantraniliprole-exposed and control groups. While S. oryzae exhibited altered locomotion patterns and a decreased number of food approaches at sublethal concentrations, S. zeamais displayed increased walking time and reduced immobility periods. These findings highlight the importance of considering sublethal effects in understanding the overall impact of chlorantraniliprole on stored-product pests. Further research into the long-term consequences of sublethal exposure is warranted to inform more effective pest management strategies in storage. Full article

The repellent capacity against Sitophilus zeamais and the in vitro inhibition on AChE of 11 essential oils, isolated from six plants of the northern region of Colombia, were assessed using a modified tunnel-type device and the Ellman colorimetric method, respectively. The results were as follows: (i) the degree of repellency (DR) of the EOs against S. zeamais was 20–68% (2 h) and 28–74% (4 h); (ii) the IC₅₀ values on AChE were 5–36 µg/mL; likewise, the %inh. on AChE (1 µg/cm³ per EO) did not show any effect in 91% of the EO tested; (iii) six EOs (Bursera graveolens—bark, B. graveolens—leaves, B. simaruba—bark, Peperomia pellucida—leaves, Piper holtonii (1b*)—leaves, and P. reticulatum—leaves) exhibited a DR (53–74%) ≥ C⁺ (chlorpyrifos—61%), while all EOs were less active (8–60-fold) on AChE compared to chlorpyrifos (IC₅₀ of 0.59 µg/mL). Based on the ANOVA/linear regression and multivariate analysis of data, some differences/similarities could be established, as well as identifying the most active EOs (five: B. simaruba—bark, Pep. Pellucida—leaves, P. holtonii (1b*)—leaves, B. graveolens—bark, and B. graveolens—leaves). Finally, these EOs were constituted by spathulenol (24%)/β-selinene (18%)/caryophyllene oxide (10%)—B. simaruba; carotol (44%)/dillapiole (21%)—Pep. pellucida; dillapiole (81% confirmed by ¹H-/¹³C-NMR)—P. holtonii; mint furanone derivative (14%)/mint furanone (14%)—B. graveolens—bark; limonene (17%)/carvone (10%)—B. graveolens—leaves. Full article