Sitophilus Zeamais Research Articles

Contact Toxicity and Repellent Activity of a Powder Extracted from Tridax Daisy (Tridax procumbens) against Maize Weevil (Coleoptera: Curculionidae)1

Abstract The maize weevil (Sitophilus zeamais Motschulsky) is a significant pest affecting stored seeds and grains, leading to substantial losses in both quantity and quality. Utilizing crushed plant powders derived from specific natural plants offers a promising alternative to synthetic insecticides, which pose risks to both consumers and the environment. This study aimed to evaluate the contact toxicity of Tridax daisy (Tridax procumbens L.) plant powder derived from its aerial parts against S. zeamais when incorporated into jasmine brown rice, Oryza sativa L., grains. Laboratory experiments were conducted at 30°C ± 5°C and 70% ± 5% relative humidity following a completely randomized design with four replications and five treatments. Jasmine brown rice grains were treated with different application rates of 0 (control), 20, 40, 60, and 80 g/kg, with five pairs/replicate of 7-d-old S. zeamais. Results showed that T. procumbens powder exhibited a contact toxicity of 93.08 g/kg of grain after 12 d, resulting in a mortality of 27.5%. Additionally, the F1 generation comprised 51 adults, indicating an 85% reduction in adult progeny emergence. These findings demonstrate the potential of T. procumbens powder as a natural grain protectant to control S. zeamais populations in storage.

Chemical composition and influence of essential oil from Croton pulegiodorus Baill. leaves on the nutrition and survival of Sitophilus zeamais Mots. (Coleptera: Dryophthoridae) as well as survival and behavior of Nasutitermes corniger Mots. (Blattodea: Termitidae)

Essential oils have been studied to develop sustainable alternatives for controlling pest-species. This study determined the chemical composition and toxicity of an essential oil from Croton pulegiodorus leaves against Sitophilus zeamais and Nasutitermes corniger. Ascaridole (22.75%) and camphor (18.11%) were the major compounds. The essential oil showed toxicity upon ingestion on S. zeamais, with LC50 and LC90 of 24.24 and 46.76 μL/g for 15 days, respectively. It presented a moderate (10.0 and 12.5 μL/g) to strong (15 μL/g) deterrent effect, interfering with nutritional parameters, causing a reduction in the relative consumption rate, relative biomass gain rate and efficiency in conversion of ingested food. Furthermore, it stimulated in vitro S. zeamais β-D-xylanase (+33.39%), endoglucanase (+8.28%), exoglucanase (+84.77%), and α-amylase (+359.18%) activities and reduced in vitro the activity of trypsin-like enzymes (-79.67%). The essential oil showed fumigant effect against N. corniger termites with LC50 and LC90 (24 h) of 0.57 and 3.26 μL/mL of air for workers and 1.63 and 4.74 μL/mL of air for soldiers respectively. In workers, it caused 100% mortality through contact in 2.08 and 0.49 min (at 0.4 μL/μL and neat oil). A significant increase in the number of self-cleaning and falls indicated behavioral changes induced by the oil in N. corniger workers. The study shows the potential of the essential oil of C. pulegiodorus leaves as an alternative method in the management of maize weevil and N. corniger.

Sulcatone as a Plant-Derived Volatile Organic Compound for the Control of the Maize Weevil and Its Associated Phytopathogenic Fungi in Stored Maize.

Stored maize is frequently attacked by different pests, such as insects and microorganisms. The aim of the present study was to evaluate the bioactivities of sulcatone (6-methyl-5-hepten-2-one) against the maize weevil Sitophilus zeamais and the phytopathogenic fungi Fusarium verticillioides, Aspergillus flavus, and A. parasiticus. Sulcatone showed a strong repellent effect with a maximum value of -92.1 ± 3.2% at 40 µM in two-choice olfactometer bioassays and an LC95 value of 17.2 µL/L air (95% 16.5-18.1) in a fumigant toxicity experiment. The antifungal effect of sulcatone was evaluated through the fumigant method, reporting MIC values of 3.5, 3.8, and 3.9 mM for F. verticillioides, A. parasiticus, and A. flavus, respectively. Additionally, a silo-bag experiment containing all pests was conducted to evaluate the potential use of sulcatone in a real storage system. Sulcatone caused 71.69 ± 1.57% weevil mortality in silo-bags and proved to be effective as a fungicidal and antimycotoxigenic agent since both ergosterol and fumonisin B1 content were significantly reduced by 60% in silo-bags containing sulcatone. This study demonstrated that sulcatone has the potential to be used for the control of both insects and fungi of stored maize, without affecting the germination of grains.

The role of maize sap beetles (Coleoptera: Nitidulidae) and maize weevils (Coleoptera: Curculionidae) in the spread of Aspergillus flavus in pre-harvest maize in Kenya

Abstract The spread of toxigenic Aspergillus into maize by insects and the subsequent aflatoxin contamination poses a risk to humans and animals and has been investigated in North and South America. To evaluate this effect in an African context, Greenhouse studies were conducted in 2022 to determine the role of sap beetles, Carpophilus dimidiatus Fabricius, 1792 (Coleoptera: Nitidulidae) and maize weevils, Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) on infection of maize kernels by Aspergillus flavus Link and the resultant aflatoxin accumulation. To test the beetles’ efficacy, treatments were applied on partially opened primary ears at 3 different stages of kernel development (BBCH 75, 83, and 87). The treatments were: (i) distilled water, (ii) water with A. flavus spores, (iii) maize grits, (iv) maize grits with A. flavus spores, (v) C. dimidiatus, (vi) C. dimidiatus with A. flavus spores, (vii) S. zeamais, and (viii) S. zeamais with A. flavus spores. Data on kernel infection, maize rotting, yield, and aflatoxin content in kernels were collected. The highest kernel spoilage and yield loss were recorded for the co-inoculation of S. zeamais and A. flavus spores, followed by S. zeamais without A. flavus spores, and then C. dimidiatus with the fungal spores. Inoculation of maize at the BBCH 83 growth stage resulted in the highest kernel damage and aflatoxin contamination. S. zeamais and, to a lesser extent, C. dimidiatus effectively spread the A. flavus inoculum into non-wounded ears, resulting in fungal and aflatoxin contamination. The yield loss from S. zeamais-Aspergillus co-inoculation occurred due to the grain rotting and actual feeding of the maize weevils. Thus, insect management is important in reducing pre-harvest contamination of maize with mycotoxigenic fungi and their resultant toxins.

Insect pests of dried yam (Dioscorea sp.) chips and the perception of processors and marketers on their control

This survey was aimed at understanding the perception of Dried yam chips (DYC) Processors and Marketers on insect pests' infestation of DYC and their damage through the use of structured questionnaires. Data on socio-economic characteristics and technical information were analyzed using descriptive statistics such as frequency distribution, percentages, and means. Data on the perception of insect pests and measures of pest control were placed on a 3-point Likert Rating Scale (LRS). Analysis of variance (ANOVA) was done on the population density of the identified insects and significant mean values were compared using Fisher's Least Significant Difference. Seven insect pests; Prostephanus truncatus, Rhyzopertha dominica, Tribolium castaneum, Stegobium paniceum, Heterobostrychus aequalis, Sitophilus zeamais, Areacerus fasciculatus, and one natural enemy; Peregrinator biannulipes were associated with DYC. However, P. truncatus, R. dominica, and A. fasciculatus were the most prevalent insect pests, causing significant damage to DYC. Approximately, 49% of processors reportedly control insect infestation in DYC using conventional insecticides, 23% by re-drying, 14% by botanicals, and the others by removing affected DYC. These findings provide useful information for extension workers involved in community education, and intervention programs by government or non-governmental organizations including public health experts and researchers.

Efficacy of invasive plant powders and inert dusts against Sitophilus zeamais (Motschulsky) in wheat grain

Cereal grain insect pests, specifically Sitophilus zeamais, pose significant challenges to farmers and distributors worldwide, leading to substantial economic losses. Traditional pest control methods often rely on fumigants, raising environmental and health concerns. As an alternative, this study explores the efficacy of unconventional repellents derived from five invasive plant species powders and inert dusts such as wood ash, quartz sand, and zeolite in controlling S. zeamais infestations. The study employs laboratory experiments to evaluate the repellent effects of these substances on adult weevils and progeny emergence on wheat grain under different environmental conditions. Results indicate that plant powders showed some repellent effect (average significant difference in live weevil counts between treated and untreated grain was 13.4 %) and mortality rate (mostly around 20 %), but they were less effective compared to the well-known substances such as SilicoSec® and wood ash (both over 80 % mortality). Similar effects were observed in the progeny emergence experiment. Despite the lower effectiveness compared to conventional substances, the combined application of plant powders with other low-risk methods like the decreasing of temperature and humidity may offer viable pest management strategies in certain scenarios. Additionally, the study underscores the need for further exploration of alternative plant species and the potential for synergistic effects when combining repellent substances.

Bioactive paints with volatile organic alcohols for the control of Sitophilus zeamais

Cereals represent a large percentage of food inputs in food production, with annual losses estimated to vary between 7 and 50% due to the actions of pests. Argentina is one of the main producers and exporters of corn globally. Post-harvest pests, such as the insect Sitophilus zeamais, can cause losses of more than 10%, representing a very important negative economic impact on the industry. For pest control many synthetic insecticides are used. Nevertheless, these insecticides show toxicity to mammals and environmental contamination and cause resistance. For this, there is a constant need to introduce new substances used in the protection of crops and the plant extracts and their volatile products are an interesting alternative. In this work we evaluate the effectiveness of natural VACs for the control of S. zeamais and the prolonged effect of the more toxic alcohol incorporated in a paint on its survival. 1-heptyn-3-ol was the most toxic alcohol tested (LC50 = 0.74 μL/L). In the presence of food, the fumigant toxicity of 1-heptyn-3-ol was lower (LC50 = 14.73 μL/L). Also, the non-phytotoxic effect of 1-heptyn-3-ol was determined. When the 1-heptyn-3-ol was included in the polyvinyl paint, the toxic effect was prolongated in the time, causing even 80% mortality at 14th day. Regarding the repellent effect of 1-heptyn-3-ol, it was observed that this alcohol included in the bioactive paint, in the presence of food, presented a repellency similar to that determined for the pure compound, in the absence of food, and greater than the repellency determined for the pure compound in the presence of food. In conclusion, compounds such as 1-hetpyn-3-ol is a potential candidate for insecticidal formulations that allow adequate management of S. zeamais in stored grain. This study presents a preliminary design of a biopaint with insecticidal and repellent activity against the pest insect S. zeamais.

Toxicity and Sublethal Effects of Piper hispidinervum Essential Oil on Behavioral and Physiological Responses of Sitophilus zeamais Populations.

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 (ri) 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 (ri) 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.

Olfactory Response of Sitophilus zeamais Adults to Odours of Semolina Pasta and Semolina Pasta Enriched with Different Amounts of Acheta domesticus Powder.

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.

Toxicity and repellency of essential oils against the maize weevil Sitophilus zeamais (Motschulsky, 1855) (Coleoptera: Curculionidae)

Usually, Sitophilus zeamais control is carried out through chemical fumigation, which is relatively effective, albeit highly toxic, potentially causing damage to the agroecosystem. In the search for alternative management methods, research on the use of essential oils has increased, as they contain compounds with insecticidal action. The aim of the present study was to verify the effects of some essential oils on S. zeamais. Glass jars were used as fumigation chambers, with a filter paper on the lid, where 20 µL of each essential oil were pipetted. The oils of Piper nigrum, Melaleuca alternifolia, Lavandula officinalis, and Foeniculum vulgare were used. After 24 hours, mortality assessment was conducted by counting the number of dead insects. The repellency test was executed through an arena system with 5 plastic containers arranged equidistantly in a circle. In the central container, 5 adult female S. zeamais were placed in each repetition, and in the others, 20 g of corn were placed in each, with two treated with a 2% essential oil solution in distilled water and Tween 80® and two treated only with distilled water and Tween 80®. After 72 hours, repellency evaluation was performed by counting the number of insects in each container and the percentage of damaged grains. It was observed that the essential oils showed moderate toxicity against S. zeamais; however, they exhibited repellency at the evaluated dose. It is concluded that the tested essential oils have repellent properties against S. zeamais and can be used as a control method.

Insecticidal formulation based on essential oil from Ocimum basilicum Linn. Herb supported onto modified kaolinite for stored maize protection

In this study, essential oil was obtained by hydrodistillation from the leaves of Ocimum basilicum and it was analyzed by GC-MS. Eucalyptol (11.19 %), trans-iso eugenol (13.12 %), hexadecanoic acid methyl ester (19.26 %) and 9-octadecenoic acid (z)-methyl ester (25.12 %) had been the leading four main components of the plant leaves of the essential oil. The unmodified and modified kaolin was characterized and analyzed by XRD, FT-IR, TGA and SEM/EDX and thus the principal mineral of the nanoclay was proved to be kaolinite. The hydrodistiled essential oil in the absence of the clay support was evaluated within 24 h of exposure time and the outcome revealed that it was insecticidally active against the maize weevil, S. zeamais adults. Moreover, the exposure time effect, the formulation efficiency, the effect of remnant and stability of the prepared formulations were investigated and the results indicated an enhancement of bioinsecticides for a long period with upgraded persistence against the S. zeamais. Finally, the results recommend that O. basilicum essential oil - modified kaolinite formulations should be used as best options to chemical insecticides in pest control of stored products like stored maize grain insects, S. Zeamais.

Insecticidal activity of Schinus terebinthifolius essential oil for the management of permethrin-resistant Sitophilus zeamais (Coleoptera: Curculionidae)

Maize weevil, Sitophilus zeamais, is a major cause of damage to corn. The preventive control of this agricultural pest is performed with permethrin. However, due to the intensive use of insecticides, the population of S. zeamais has developed resistance to more than 10 synthetic insecticides, including the active ingredient permethrin. In the search for techniques aiming to reduction of the use of synthetic pesticides for the integrated management of S. zeamais, the present study was evaluate the effects of Schinus terebinthifolius essential oil – by fumigation, contact and ingestion methods – against populations of S. zeamais, both susceptible and resistant to the insecticide permethrin. Chemical profile identification showed α-pinene, β-myrcene, α-phellandrene, δ-3-carene and β-phellandrene were the major components in S. terebinthifolius essential oil. Permethrin susceptibility of the S. zeamais revealed four resistant populations (STPR, STP1, STP2 and STP3). But, in the Fumigant bioassay, STPR and STP1 permethrin-resistant populations were susceptible to the essential oil. When the insects were put in direct contact with treated maize grains, only STPR permethrin-resistant population was susceptible this essential oil. Resistance ratio of the permethrin on S. zeamais populations revealed differences of permethrin susceptibility among the groups tested. S terebinthifolius essential oil exhibited high insecticidal activity, reducing the populations of S. zeamais through fumigation and contact/ingestion methods. The present findings suggest that use of permethrin can be substituted with the preparation of botanical insecticide with S. terebinthifolius essential oil.

First record of Hyphopichia burtonii isolated from the storage pest Sitophilus zeamais and its bioactivity against mycotoxigenic fungi

Summary Corn weevil (Sitophilus zeamais) is one of the most destructive pests of corn seeds during storage. The weevil may be a vector of mycotoxigenic fungi or yeast contaminating seed lots. In this study, an unknown yeast species was isolated from corn weevils found in stored corn seeds. We hypothesized that this yeast had an antifungal activity thereby inhibiting growth of mycotoxigenic fungi in corn seeds. The yeast species was identified as Hyphopichia burtonii, using combined morphological and molecular assays, and its potential inhibitory activity was assessed in vitro (spread plate and dual culture) against three known mycotoxigenic fungi, Fusarium verticillioides, Aspergillus niger and A. fl avus. Screening of the antagonistic activity of the yeast isolate showed 50 – 69% colony growth inhibition of three fungi when the yeast was spread plated on PDA but only slight inhibition (5.8 – 13.7% growth inhibition) in the dual culture assay. The sporulation of the fungi was also affected at 57 – 96% and 29 – 40% in spread plating and dual culture assay, respectively. In addition, volatile and non-volatile fractions also showed a reduction in mycelial growth. Variable responses were observed among the mycotoxigenic fungi. Further research would be interesting on the potential utilization of the antagonistic yeast to reduce fungal growth and sporulation, and possible mitigation of mycotoxin contamination in corn grains. To our knowledge, this is the first record of H. burtonii isolated from an insect, specifically S. zeamais.

PENGARUH KONSENTRASI EKSTRAK DAUN KELOR (Moringa oleifera L.) TERHADAP MORTALITAS Sitophilus zeamais Motsch.

Corn is the strategic commodity in Indonesia. The quality of many domestic corn does not meet feed factory standards. High yield losses icause of damage due to warehouse pests. Sitophilus zeamais Motsch or powder beetle is a warehouse pest that causes seeds to become hollow, break quickly and disintegrate into flour. Sitophilus zeamais Motsch pest control still relies on synthetic pesticides. The use of synthetic pesticides will cause various negative impacts such as pest resistance, residue, resurgencies, high costs and environmental pollution. One alternative for controlling Sitophilus zeamais Motsch is to use natural ingredients, namely Moringa. Moringa leaves contain phenol, hydroquinone, flavonoids, steroids, triterpenoids, tannins, alkaloids and saponins. The experiment began by drying 10 grams of Moringa leaves. then puree using a blender and continue with maceration. 200, 400, 600, 800, and 1000 mg of Moringa leaf powder were dissolved in 1 L of distilled water solution and left for 24 hours. After 24 hours, the solution was filtered 3 times so that all the substances contained in the Moringa leaves are extracted. The insecticide was tested by observing the number of S. zeamais pests that died when given Moringa leaf extract. The mortality data that was obtained was analyzed using ANOVA, if there was a real effect then continued using the 5% DMRT test. Determination of LC50 using a probit test. Moringa extract can function as a vegetable insecticide for S.zeamais. The higher concentration of Moringa leaf extract can increase the mortality of S.zeamais

Insecticidal activity of Thymus pallescens de Noë and Cymbogon citratus essential oils against Sitophilus zeamais and Tribolium castaneum

The thrust of the study was to determine the chemical composition of the essential oils extracted from Thymus pallescens de Noé and Cymbogon citratus Stapf. as well as to evaluate their efficacy in controlling Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) in either single or combined populations. Carvacrol (56.04%) and geraniol (20.86%) were identified as the major constituents of T. pallescens and C. citratus respectively. The tested essential oils showed pronounced insecticidal activity against the pest species in relation with the applied doses. T. pallescens EO had the highest efficacy and S. zeamais was found to be more susceptible to both individual and combined treatments. With reference to the contact and fumigation assessments, T. pallescens EO effectuated corrected mortality rates ranging from 42.5–100% to 25–100% in S. zeamais with corresponding lethal concentration (LC50) values of 17.7 µl/ml and 15µL/L air respectively. Whereas, the T. pallescens EO exhibited corrected mortality rates of 42.5–100% and 20–100% with corresponding LC50 values of 18.1 µl/ml and 15.5 µL/L air against T. castaneum in contact and fumigation assessments, respectively. The corrected mortality rates increased for both insect species when using combination treatments, with significant increases in the LC50 values, ranging from 8.59 to 49.9% for both pest species. Analysis of energy biomarkers in the treated insects indicate significantly increased protein and carbohydrate contents and decreased lipids levels. The study therefore demonstrated the bio-insecticidal toxicity of the EOs from T. pallescens and C. citratus against two important maize post-harvest pests, concurrently revealing significant positive and negative insecticidal activity gradients in relation to single or combined populations.

Toxicity of Essential Oil from Plectranthus amboinicus (Lamiales: Lamiaceae) against Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract Maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), is a major insect pest of stored grain products, causing extensive damage to both grain quantity and quality. The application of synthetic insecticides to control this insect has a negative impact on human health and the environment. Essential oils derived from natural plants are recognized as user- and environmentally friendly alternatives. The use of essential oils from Lamiaceae, which exhibit toxic properties through contact, fumigation, and repellency, provides another option for protecting stored products from various insect pests. The aim of this research was to study the chemical constituents and insecticidal activity of essential oil extracted from the leaves of Indian borage, Plectranthus amboinicus (Lour.) (Lamiales: Lamiaceae), against S. zeamais adults.The chemical composition of the essential oil was analyzed using gas chromatography–mass spectrometry, and the insecticidal activity against adult maize weevils was investigated in the laboratory. The experimental plan followed a completely randomized design with five replications of seven treatments or concentrations of the essential oil: 0, 0.5, 1, 1.5, 2, 2.5, and 3 µl/ml air. The results revealed that the essential oil from the leaves of P. amboinicus contained 23 chemical constituents (97.51%). Thymol (49.96%) was identified as the main compound followed by caryophyllene, trans-α-bergamotene, 3-methyl-4-isopropylphenol, γ-terpinene, p-cymene, caryophyllene oxide, humulene, 4-hydroxy-2-methylacetophenone, 2-hydroxy-2-phenylbutyramide, (2-oxazolidinylidene)malononitrile, hexestrol, terpinen-4-ol, 1-octen-3-ol, (1R,7S,E)-7-isopropyl-4,10-dimethylenecyclodec-5-enol, α-bisabolene, isoaromadendrene epoxide, α-farnesene, 4-carene, α-muurolene, 3-hexen-1-ol, ledene oxide-(II), and α-myrcene, respectively. The fumigation toxicity (median lethal concentration) to maize weevil adults at 48 h was 292.53 µl/ml air. The essential oil from the leaves of P. amboinicus, when applied at a concentration of 2 µl/ml air for 144 and 168 h, resulted in adult maize weevil mortality exceeding 90%. The highest concentration tested (3 µl/ml air) led to exceptionally high mortality rates, with 99–100% of the maize weevils succumbing to the treatment. These findings demonstrate that essential oil from P. amboinicus leaves holds promise as a fumigation insecticide for reducing the population of maize weevils, a significant pest in stored products.

Suppression of Trehalase Activity by Validamycin Induces Mortality and Developmental Delays in Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract The maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), is a major pest of stored grains that feeds on and develops inside the grain. The trehalose analog validamycin has a strong inhibitory effect on insect trehalase. Studies have found that validamycin affects several insects; however, no information is available on its inhibitory and physiological effects on these insects. In this study, validamycin’s inhibitory effect on trehalase was examined by incorporating it into artificial seeds and feeding them to S. zeamais. Trehalase activity was recorded throughout the developmental stages of the exposed weevils and was highest in the larval followed by adult, pupal, and egg stages. We found that feeding adult S. zeamais artificial seeds containing validamycin resulted in a significant reduction of trehalase activity in both males and females, although the primary source of trehalase was in the intestinal tract rather than in the reproductive organs. The validamycin treatment also had a concentration-dependent lethal effect, resulting in approximately 90% mortality, with females being more susceptible than males. In addition, the validamycin treatment caused a significant reduction in the number of first-generation progeny and S. zeamais demonstrated delayed development in a concentration-dependent manner. These data show that validamycin influences trehalase enzyme activity, reproductive success, and development of S. zeamais. The results obtained from this research will be valuable tools for designing a control strategy.

Sublethal Effects of Chlorantraniliprole on the Mobility Patterns of Sitophilus spp.: Implications for Pest Management.

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.

Effectiveness of Packaging Integrated with Plant Extracts in Controlling Maize Weevil <i>Sitophilus zeamais</i>

Maize weevil Sitophilus zeamais is one of the storage pests that compromise both quality and quantity of stored maize grains. In Malawi, most smallholder farmers use botanicals like Tephrosia vogelii Hook and Lantana camara to manage S. zeamais. This study was conducted to investigate the effectiveness of packaging integrated with plant extracts in controlling this pest. Ziploc bags, paper cartons, grass jars, paper envelopes and polyethylene terephthalate (PET) water bottles are the common packaging and storage materials for these botanical pesticides used by small holder farmers. This study involved preliminary experiments in which plant extracts within packaging materials were tested, for their efficacy against S. zeamais for five months. PET water bottle provided significant (p<0.01) control over other treatments to store the maize seeds against S. zeamais. Thereafter, the effect of botanicals packaged and stored for one month in PET water bottle was studied on grain damage caused by the weevils. The inhibition effect of the botanicals on grain damage was significant (p<0.01). This study obtained vital information that can be utilized by farmers as a sustainable way to manage storage pests.

Insecticidal properties of lemon grass, clove and star anise essential oils and their main chemical compounds against maize weevil (Sitophilus zeamais Motschulsky)

Insecticidal properties of lemon grass, clove and star anise essential oils and their main chemical compounds against maize weevil (<i>Sitophilus zeamais</i> Motschulsky)