Chemical Insecticides Research Articles

Spatial variation in the sensitivity of freshwater macroinvertebrate assemblages to chemical stressors

Assessing spatial variation in the chemical sensitivity of natural assemblages will enhance ecological relevance and reduce uncertainty in ecological risk assessments and the derivation of environmental quality standards (EQSs). However, the majority of species in natural communities have not undergone toxicity testing for any chemical, which poses a major challenge when assessing their sensitivity. We investigated spatial variation and patterns in the sensitivity of 4084 freshwater macroinvertebrate assemblages across England to 5 general-acting chemicals (heavy metals) and 13 specifically acting chemicals (insecticides) using a novel hierarchical species sensitivity distribution method based on taxonomic relatedness. Furthermore, we explored how river typology relates to spatial variation in assemblage sensitivity to chemicals and the potential impacts of such variation on current EQSs. Our findings revealed that, whereas assemblages with similar taxonomic compositions exhibit comparable sensitivity distributions, assemblages with different taxonomic compositions could have very similar or very different sensitivity distributions. The variation in assemblage sensitivity was greater for specifically acting chemicals than for general-acting chemicals and exhibited spatial clustering patterns. These spatial clustering patterns varied depending on the chemical, and the regions where assemblages were most sensitive to metals were generally not the same as the regions where assemblages were most sensitive to insecticides. Spatial variation in assemblage sensitivity was related to river typology with sensitive assemblages being more common than expected in lowland calcareous (or mixed geology) rivers within very small to small catchments. Comparing spatial variation in assemblage-specific chemical sensitivity to EQSs, we found that the operational EQSs in England would protect most study assemblages (i.e., > 99.5 %), although a small proportion of assemblages may face potential risks associated with azinphos-methyl, copper, and malathion. In many cases the EQSs were very precautionary, potentially requiring expensive control measures or restricting beneficial chemical use with no additional environmental benefit. The development of spatially defined EQSs, possibly based on river types, could be developed to target areas that require the highest level of protection and thus strike a balance between the benefits of chemical use and environmental protection.

Susceptibility of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Sitophilus oryzae (Coleoptera: Curculionidae) to the fungal entomopathogen Beauveria bassiana (Balsamo-Crivelli) Vuillemin s.l. (Hypocreales: Clavicipitaceae)

Control measures of stored grain pests include the excessive utilization of chemical insecticides that generate negative environmental impact. Current trends in integrated pest management are oriented towards the preservation of the environment using natural biopesticides, among these products arise entomopathogenic fungi. This study aimed to test the efficacy of a native strain of Beauveria bassiana to control two main stored grain pests such as Sitophilus oryzae and Rhyzopertha dominica and also evaluate the persistence of the fungus on wheat grains. The B. bassiana strain controlled 89%±0.07 of R. dominica adults and 80% ±0.14 of S. oryzae. The survival analysis showed that MST was 4.27 ±0.19 days for R. dominica adults and 4.27 ±0.20 days for S. oryzae. Furthermore, results of long rank test for the comparison of the Kaplan-Meier curves did not present significant differences between the survival of both stored grain pests. Dual choice tests demonstrated that B. bassiana LPSc1227 presented a repellent action against both stored grain pests. The seed persistence of conidia was 100% in treated seeds after 45 days. Further research will contribute to elucidate more insecticidal features of the B. bassiana LPSc 1227 strain against S. oryzae and R. dominica, two main stored grain insect pests. Highlights: bassiana presented insecticidal activity against R. dominica and S. oryzae. bassiana demonstrated a repellent action against both stored grain pests. bassiana was able to persist on the surface of wheat grains after 45 days storage.

Immunological responses and gut microbial shifts in Phthorimaea absoluta exposed to Metarhizium anisopliae isolates under different temperature regimes.

The invasive tomato leaf miner, Phthorimaea absoluta, is conventionally controlled through chemical insecticides. However, the rise of insecticide resistance has necessitated sustainable and eco-friendly alternatives. Entomopathogenic fungi (EPF) have shown potential due to their ability to overcome resistance and have minimal impact on non-target organisms. Despite this potential, the precise physiological mechanisms by which EPF acts on insect pests remain poorly understood. To attain a comprehensive understanding of the complex physiological processes that drive the successful control of P. absoluta adults through EPF, we investigated the impacts of different Metarhizium anisopliae isolates (ICIPE 665, ICIPE 20, ICIPE 18) on the pest's survival, cellular immune responses, and gut microbiota under varying temperatures. The study unveiled that ICIPE 18 caused the highest mortality rate among P. absoluta moths, while ICIPE 20 exhibited the highest significant reduction in total hemocyte counts after 10 days at 25°C. Moreover, both isolates elicited notable shifts in P. absoluta's gut microbiota. Our findings revealed that ICIPE 18 and ICIPE 20 compromised the pest's defense and physiological functions, demonstrating their potential as biocontrol agents against P. absoluta in tomato production systems.

Residual Pattern of Chlorantraniliprole, Thiamethoxam, Flubendiamide and Deltamethrin in Tomato Fruit and Soil.

Tomato, Lycopersicon esculentum L. is grown widely as an important day-to-day demand vegetable. The crop is attacked by various polyphagous insect pests like tomato fruit borer, stink bug, cabbage looper, flea beetle, aphids, whitefly, two-spotted spider mite, etc., and oligophagous insects like leaf-miner, five-spotted hawkmoth, etc. To combat the damage and yield loss, various chemical insecticides were sprayed on tomatoes under field conditions. The residual pattern of insecticides like chlorantraniliprole, thiamethoxam, flubendiamide, and deltamethrin residues was studied following applications of chlorantraniliprole 18.5% SC (Coragen) @ 30g a.i./ha, thiamethoxam 25% WG (Actara) @ 50g a.i./ha, flubendiamide 39.35M/M SC (Fame) @ 48g a.i./ha and deltamethrin 2.8% EC (Decis 100) @ 12.5g a.i./ha using Reverse Phase High-Performance Liquid Chromatography (RP-HPLC). Fruit samples were collected at 0 (1h after application), 1, 2, 3, 5, 7 days and at harvest time. All the residues of insecticides such as chlorantraniliprole (0.09mg kg- 1), thiamethoxam (0.03mg kg- 1), flubendiamide (0.02mg kg- 1), and deltamethrin (0.01mg kg- 1) were persisted up to 5th day. There were no residues found at harvest time. The residues of chlorantraniliprole and deltamethrin persisted up to 3rd day of spraying whereas the residues of flubendiamide and thiamethoxam were not detected on the same day in the soil.

Analysis of the virulence, infection process, and extracellular enzyme activities of Aspergillus nomius against the Asian corn borer, Ostrinia furnacalis guenée (Lepidoptera: Crambidae)

ABSTRACT The control of Ostrinia furnacalis, a major pest of maize in Xinjiang, is challenging owing to the occurrence of resistant individuals. Entomopathogenic fungi (EPF) are natural insect regulators used as substitutes for synthetic chemical insecticides. The fungus Aspergillus nomius is highly pathogenic to O. furnacalis; however, its virulence characteristics have not been identified. This study aimed to analyse the lethal efficacy, mode of infection on the cuticle, and extracellular enzyme activity of A. nomius against O. furnacalis. We found that the mortality and mycosis of O. furnacalis were dose-dependent when exposed to A. nomius and varied at different life stages. The egg-hatching and adult emergence rates decreased with an increase in conidial suspension. The highest mortality (83.33%, 7 d post-infection [DPI]) and mycosis (74.33%, 7 DPI) and the lowest mortality response (8.52 × 103 conidia mL−1) and median lethal time (4.91 d) occurred in the 3rd instar larvae of O. furnacalis. Scanning electron microscopy indicated that numerous conidia germination and infection structure formation may have contributed to the high pathogenicity of A. nomius against O. furnacalis. There were significant correlations between O. furnacalis mortality and the activities of extracellular protease, lipase, and chitinase of A. nomius. This study revealed the infection process of the highly pathogenic A. nomius against O. furnacalis, providing a theoretical basis and reference for strain improvement and field application of EPF.

Potential Application of Organic Electronics in Electrical Sensing of Insects and Integrated Pest Management towards Developing Ecofriendly Replacements for Chemical Insecticides.

Synthetic insecticides are widely used against plant pest insects to protect the crops. However, many insecticides have poor selectivity and are toxic also to beneficial insects, animals, and humans. In addition, insecticide residues can remain on fruits for many days, jeopardizing food safety. For these reasons, a reusable, low-cost electronic trap that can attract, detect, and identify, but attack only the pest while leaving beneficial insects unharmed could provide a sustainable, nature-friendly replacement. Here, for the first time, research results are presented suggesting the great potential and compatibility of organic electronic devices and technologies with pest management. Electrical characterizations confirm that an insect's body has relatively high dielectric permittivity. Adaptive memcapacitor circuits can track the impedance change for insect detection. Other experiments show that printed polymer piezoelectric transducers on a plastic substrate can collect information about the weight and activity of insects for identification. The breakdown voltage of most insects´ integument is measured to be <200V. Long channel organic transistors easily work at such high voltages while being safe to touch for humans thanks to their inherent low current. This feasibility study paves the way for the future development of organic electronics for physical pest control and biodiversity protection.

Pilot Testing of an Area-Wide Biological Control Strategy against the Coffee Berry Borer in Colombia Using African Parasitoids.

The coffee berry borer (CBB), Hypothenemus hampei (Ferrari, 1867) (Coleoptera: Curculionidae: Scolytinae), native to Africa, is a major global insect pest of coffee. It has invaded many coffee production areas around the world that do not have natural enemies. In this study, two African parasitoids, Prorops nasuta Waterston (Hymenoptera: Bethylidae) and Phymastichus coffea Waterston (Hymenoptera: Eulophidae), were mass-reared for field release against H. hampei in Chinchiná, Colombia. More than 1.5 million wasps of each species were released on a 61-hectare coffee farm in replicated plots, resulting in parasitism rates of up to 7.7% for P. nasuta and 56.3% for P. coffea. This led to a maximum reduction in H. hampei field populations of 81% from dispersal coffee plots (old coffee crops before plant stumping) and 64.3% in colonization coffee plots (new coffee crops with active growing and fruiting plants) within the farm. As a result of this area-wide strategy, the percentage of CBB-infested coffee berries in colonization coffee plots decreased from 51.1 to 77.5% compared to coffee plots without parasitoid releases. This approach offers a promising alternative to the use of chemical insecticides and could be integrated into current pest management programs to control H. hampei.

Efficacy of recent chemical insecticides against mealy plum aphid Hyalopterus pruni on plum and Spirea aphid Aphis spiraecola on apple in Bulgaria

The aim of this study was to establish the efficacy of new and little-known chemical insecticides, from different chemical classes, which are offered for control of Mealy plum aphid Hyalopterus pruni on plum and Spirea aphid Aphis spiraecola on apple in Bulgaria. Four products were tested - flupyradifurone (Sivanto prime), sulfoxaflor (Closer 120 SC), flonikamid (Teppeki 50WG) and acetamiprid (Mospilan 20SG). The tested concentrations of the chemical insecticides were applied according to their registrations for these and other pests. The experiments were carried out under field conditions. The results show that all the tested chemical insecticides are suitable for efficient control of both aphids, even at their lowest permitted concentration. Keywords: insecticides, aphids, Sivanto Prime, Closer, Teppeki, Mospilan, Hyalopterus pruni, Aphis spiraecola

Morphological and molecular identification of the local entomopathogenic fungus Purpureocillium lilacinum and its pathogenicity against the larvae of superworm Zophobas morio (Coleoptera: Tenebrionidae)

Entomopathogenic fungi (EPF) are used as a sustainable substitute for chemical insecticides and have been recognized as effective biocontrol agents for mitigating insect pest populations. In this study, a naturally-occurring beneficial EPF, Purpureocillium lilacinum CBBS3.12 (Hypocreales: Ophiocordycipitaceae) from a cabbage farm was isolated and identified by combining morphological and molecular (ITS rDNA region) diagnostic characters. Fungal morphological key characters were consistent with the established species description and were subsequently validated through their ITS rDNA sequences, showing high sequence similarities to P. lilacinum isolates from diverse geographical locations, such as Mexico, the USA, Austria, Israel, China, and India. Additionally, the pathogenicity of P. lilacinum CBBS3.12 against the last instar larvae of Zophobas morio (Coleoptera: Tenebrionidae) was investigated, revealing significant variations in insect mortality based on different fungal concentrations. The highest mortality was recorded at a concentration of 6.0 x 108 spores mL−1, 6 and 12 days post-inoculation. This investigation underscores the promising capabilities of P. lilacinum CBBS3.12 as a biocontrol organism targeting Z. morio. The present study warrants a more comprehensive evaluation of its virulence against diverse agricultural pests and the identification of its active metabolites and compounds to enhance our understanding of its potential application in pest management programs.

Larvae of Colorado potato beetle (Leptinotarsa decemlineata Say) resistant to double-stranded RNA (dsRNA) remain susceptible to small-molecule pesticides.

Implementation of resistance management tools is crucial for the continued efficacy of insect control technologies. An important aspect of insect resistance management (IRM) is the combined or sequential use of different modes-of-action to reduce selection pressure and delay evolution of resistance. This is especially important for insect pests with established ability to develop resistance to insecticides, such as the Colorado potato beetle (Leptinotarsa decemlineata, CPB). A new class of insecticides, based on double-stranded RNA (dsRNA) activating the gene silencing RNA-interference (RNAi) pathway, are currently under review for regulatory approval and commercial use in the USA against CPB. However, there is no information available on the potential for cross-resistance between RNAi insecticides and other classes of insecticides used against CPB. Herein, we aim to fill this knowledge gap by capitalizing on the availability of a CPB strain highly resistant to dsRNAs and test its susceptibility to diverse small-molecule insecticide classes compared to reference dsRNA-susceptible CPB strains. Differences in activity were observed among the four insecticides tested, with abamectin demonstrating highest activity against all three strains of CPB. However, no differences were observed among the dsRNA-resistant and susceptible CPB strains for any of the tested compounds. Overall, these results demonstrate lack of cross-resistance to commonly used chemical insecticides in the dsRNA-resistant strain of CPB. These data support the use of these different insecticide classes along with RNAi-based insecticides as part of an effective insect resistance management framework aimed at delaying resistance in CPB. © 2023 Society of Chemical Industry.

Field Evaluation of Cotton Expressing Mpp51Aa2 as a Management Tool for Cotton Fleahoppers, Pseudatomoscelis seriatus (Reuter).

The cotton fleahopper (Pseudatomoscelis seriatus Reuter) is considered a highly economically damaging pest of cotton (Gossypium hirsutum L.) in Texas and Oklahoma. Current control methods rely heavily on the use of foliar-applied chemical insecticides, but considering the cost of insecticides and the critical timeliness of applications, chemical control methods are often not optimized to reduce potential yield losses from this pest. The Bacillus thuringiensis (Bt) Mpp51Aa2 (formerly Cry51Aa2.834_16) protein has proven effective against thrips and plant bugs with piercing and sucking feeding behaviors, but the impact of this toxin on cotton fleahoppers has not been investigated. To evaluate the Mpp51Aa2 trait effectiveness towards the cotton fleahopper, field trials were conducted in 2019, 2020, and 2021, comparing a cotton cultivar containing the Mpp51Aa2 trait to a non-traited isoline cultivar under insecticide-treated and untreated conditions. Populations of cotton fleahopper nymphs and adults were estimated weekly by visually inspecting cotton terminals. Square retention was also assessed during the first week of bloom to provide some insight on how the Bt trait may influence yield. While cotton fleahopper population differences between the traited and non-traited plants were not consistently noted during the pre-bloom squaring period, there was a consistent increase in square retention in cotton expressing Mpp51Aa2 relative to non-traited cotton. Additionally, cotton expressing Mpp51Aa2 offered similar square protection relative to non-traited cotton treated with insecticides for the cotton fleahopper. These findings indicate that the Mpp51Aa2 protein should provide benefits of delayed nymphal growth, population suppression, and increased square retention.

Population dynamics and insecticide resistance in Tuta absoluta (Lepidoptera: Gelechiidae), an invasive pest on tomato in Kenya

Tuta absoluta feeds on solanaceous plants with preference on tomato. Management of the pest is mostly with chemical insecticides. This study identified insecticide resistant populations and predicted resistance to insecticides. Insecticide resistance development was modelled using system thinking, and system dynamics approaches. The model showed the pest resistance development is alarming with an exponential increase of the resistance strength mostly in recent years. Furthermore, we used seven insecticide-resistance gene markers to resolve the population structure and genetic differentiation of insecticide-resistant populations in Kenya. The genes for resistance (knockdown resistance (kdr) mutations, acetylcholinesterase (AChE) and voltage gated sodium channel (para)) were detected in all populations. Population structure analyses separated T. absoluta populations into three genetic clusters with resistant genes that are interconnected. A better insight on the population dynamics and the genetic structure T. absoluta resistant genes in Kenya will help estimate resistance strength and determine the most effective pest control strategies.

Relevance of molecular systematics in insect pest management

Relevance of molecular systematics in insect pest management

Empowerment of Farmer Group in Controlling Spodoptera frugiperda on Corn Using Entomopathogenic Fungi

Raden Farmer Group is one of the farmer groups in Pabuwaran, Purwokerto District, Banyumas Regency. This group faced the problem of encountering the attack of Spodoptera frugiperda on corn. This pest caused a detrimental loss in corn cultivation. The common control technique used to control this pest is by applying chemical insecticides. The use of this chemical insecticide causes negative effects on both the environment and human health. The offered solution to overcome this problem is technology transfer using entomopathogenic fungi, which is environmentally safe. Technology transfer was conducted through mentoring, education, and demonstration plots (demplots). Evaluation was carried out by pre-test and post-test for each activity to find out how well the partners understood the presented materials. The improvement in skills was measured by assessing the entomopathogenic fungi-based bioinsecticide product that was successfully made in the training activity by the partners, the decrease in S. frugiperda attack intensity, and the increase in yields in demplot. The evaluation results showed: (a) improvement of the partner’s knowledge and skills regarding S. frugiperda and its control technique using entomopathogenic fungi; (b) the results on demplot showed that the use of entomopathogenic fungi could replace the application of chemical insecticides to control S. frugiperda. (c) Farm analysis showed that the use of entomopathogenic fungi in corn cultivation was efficient and profitable for farmers.

Current and future opportunities of autodissemination of pyriproxyfen approach for malaria vector control in urban and rural Africa

Despite the progress made in reducing malaria burden, new ways to address the increasing challenges of insecticide resistance and the invasion and spread of exotic malaria vectors such as Anopheles stephensi in Africa are urgently needed. While African countries are adopting larviciding as a complementary intervention for malaria vector control, the autodissemination technology has the potential to overcome barriers associated with the identification and treatment of prolific habitats that impede conventional larviciding approaches in rural settings. The autodissemination technology as a “lure and release” strategy works by exploiting the resting behavior of gravid mosquitoes to transfer lethal concentration of biological or chemical insecticide such as pyriproxyfen (PPF), an insect growth regulator (IGRs) to their oviposition sites and result in adult emergence inhibition. Despite the evidence of the autodissemination approach to control other mosquito-borne diseases, there is growing and promising evidence for its use in controlling malaria vectors in Africa, which highlights the momentous research that needs to be sustained. This article reviews the evidence for efficacy of the autodissemination approach using PPF and discusses its potential as efficient and affordable complementary malaria vector control intervention in Africa. In the previous studies that were done in controlled semi-field environments, autodissemination with PPF demonstrated its potential in reducing densities of captive population of malaria vectors such as Anopheles gambiae and Anopheles arabiensis. Of importance, empirical evidence and biology-informed mathematical models to demonstrate the utility of the autodissemination approach to control wild populations of malaria vectors under field environment either alone or in combination with other tools are underway. Among others, the key determining factors for future introduction of this approach at scale is having scalable autodissemination devices, optimized PPF formulations, assess its integration/complementarity to existing conventional larviciding, and community perception and acceptance of the autodissemination approach.

Microbial Pesticides: A Nigerian Perspective on Sustainability of Health and Agriculture

The concerns on the use of insecticides have been in areas of agriculture and human health. Insect pests populating the farms damage crops leading to food insecurity. The use of chemical insecticides to treat insect infestation is quite popular in Nigeria in area of food crop production and in animal and human health management. These chemical insecticides often pose some health challenges to man and animals hence the need for safer bio-pesticides. Microbial insecticides consist of living cells of microorganisms Research method employed was by collection of secondary data from literatures on previous research works done. These include reports, journal articles, seminars, symposia, and conference papers. Literatures were collected online using the Dennis Osadebay University e-library. These organisms are reared using basic microbiological techniques. Mode of action of microbial pesticides is by contact, which is by entering the host through the outer protective covering or the intestine of the insect. These microbes act on the host (insects) either by elimination or by altering some of their physiological functions. They may act directly on the insects or by the action of their toxins. The toxins can be used independently as bioactive substances in place of the microbial species. Microbial insecticides can be applied as sprays, dusts, liquid drenches, liquid concentrates, wet-table powders or granules. The bio-insecticides have the capacity to ensure the safety of humans and other non-target organisms. They leave less or no residue deposits in food and are ecologically friendly.

Nanoemulsion-based plant essential oil formulations: in vitro evaluation of pesticidal activity against ectoparasites in poultry

Ectoparasite infestations significantly impact the health and productivity of poultry. Chemical applications, although common for pest control, lead to pesticide residues and parasite resistance in poultry. Nanoemulsion-based plant essential oil formulations (NEOFs) provide a promising alternative for controlling poultry ectoparasites. This study aimed to assess the efficacy of NEOFs from clove, cinnamon, and turmeric essential oils (EOs) against ectoparasites, Menopon gallinae and Megninia ginglymura, under laboratory conditions. The toxicity and repellent properties of the NEOFs were examined, with the major chemical compounds of the EOs analyzed using chromatography mass spectrometer. Results identified eugenol as the dominant component in clove and cinnamon EOs (84.60 and 75.19%, respectively), while turmerone (68.46%) was the major compound in turmeric EO. NEOFs with clove:cinnamon:turmeric ratios of 4:0:0, 2:2:0, and 2:0:2 had particle size of 20.76 nm, 20.66 nm, and 89.56 nm, respectively, while those based on eugenol and turmerone standards had sizes <21.0 nm. In addition, NEOFs at 0.3% concentration with ratios of 4:0:0 and 2:2:0 achieved full control of both ectoparasites. These formulas demonstrated exceptional potency in exterminating ectoparasites, with LC50 and LC90 at <0.160 and <0.250%, respectively, 6 h after treatments. Furthermore, both NEOFs showed higher repellence responses in M. gallinae compared to M. ginglymura. The toxicities of these NEOFs were comparably effective against both parasites, showing no significant difference compared with chemical insecticide treatment. Therefore, further research will explore the practicality of using clove and cinnamon-derived NEOFs under farm conditions.

Effective delivery and selective insecticidal activity of double-stranded RNA via complexation with diblock copolymer varies with polymer block composition.

Chemical insecticides are an important tool to control damaging pest infestations. However, lack of species specificity, the rise of resistance and the demand for biological alternatives with improved ecotoxicity profiles means that chemicals with new modes of action are required. RNA interference (RNAi)-based strategies using double-stranded RNA (dsRNA) as a species-specific bio-insecticide offer an exquisite solution that addresses these issues. Many species, such as the fruit pest Drosophila suzukii, do not exhibit RNAi when dsRNA is orally administered due to degradation by gut nucleases and slow cellular uptake pathways. Thus, delivery vehicles that protect and deliver dsRNA are highly desirable. In this work, we demonstrate the complexation of D. suzukii-specific dsRNA for degradation of vha26 mRNA with bespoke diblock copolymers. We study the ex vivo protection of dsRNA against enzymatic degradation by gut enzymes, which demonstrates the efficiency of this system. Flow cytometry then investigates the cellular uptake of Cy3-labelled dsRNA, showing a 10-fold increase in the mean fluorescence intensity of cells treated with polyplexes. The polymer/dsRNA polyplexes induced a significant 87% decrease in the odds of survival of D. suzukii larvae following oral feeding only when formed with a diblock copolymer containing a long neutral block length (1:2 cationic block/neutral block). However, there was no toxicity when fed to the closely related Drosophila melanogaster. We provide evidence that dsRNA complexation with diblock copolymers is a promising strategy for RNAi-based species-specific pest control, but optimisation of polymer composition is essential for RNAi success. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Overexpression of cytochrome P450 and esterase genes involved in permethrin resistance in larvae and adults of Culex quinquefasciatus.

Mosquitoes are important vectors of several arthropod-borne diseases, which remain a priority for epidemiological research. Mosquito vector control strategies have traditionally relied on chemical insecticides such as synthetic pyrethroids. However, the indiscriminate use of pesticides has resulted in the development of resistance in many mosquito species. In insects, resistance evolves primarily through the overexpression of one or more gene products from the cytochrome P450, carboxylesterase, and glutathione superfamilies. The current study examined the expression of cytochrome P450 CYP6M2, CYP6AA7, CYP6Z2, CYP9J34, α-Esterase, Esterase B1, and neuroactin genes in larvae and adults of a permethrin-resistant (PerRes) and susceptible (Sus) Culex quinquefasciatus strains. The results showed that the CYP6AA7 gene was overexpressed (10-fold) in larvae and adults with PerRes (p < 0.01) followed by CYPJ34 (9.0-fold) and CYP6Z2 (5.0-fold) compared to the Sus, whereas fewer changes in CYP6M gene expression were observed in PerRes adults (p < 0.05), and no expression was found in larvae. The esterase gene was overexpressed in PerRes larvae (9.0-fold) followed by adults (2.5-fold) compared to the susceptible strain. Based on data, the present study suggests that cytochrome P450, CYP6AA7, CYP6Z2, CYP9J34, α-Esterase, Esterase B1, and neuroactin genes were involved in permethrin resistance in larval and adult Cx. quinquefasciatus.

Efficacy of metarhizium anisopliae and beauveria bassiana as biological control agents of African Rice Gall Midge (AfRGM), Orseolia oryzivora Harris & Gagné

African rice gall midge (AfRGM), Orseolia oryzivora (Diptera: Cecidomyiidae) is a significant pest of rainfed and lowland rice that causes about 25% to 100% yield loss. The effectiveness of chemical insecticides has been compromised due to insecticide resistance and concerns over their environmental impact, which necessitated an alternative approach that is safe and more sustainable. The study aimed to determine the effectiveness of Entomopathogenic fungi (EPF), Metarhizium anisopliae and Beauveria bassiana in controlling AfRGM on four popular rice cultivars under screenhouse conditions at AfricaRice/IITA, Ibadan, Nigeria. The experiment was laid out in a 4 x 3 factorial fitted in a completely randomized design (CRD) in three replications. Results showed that although both fungi significantly reduced AfRGM tiller infestation, the degree of reduction varied with the specific fungus and rice variety grown. Beauveria bassiana exhibited better control of AfRGM on FARO 37 and FARO 44 varieties, while M. anisopliae was more effective on FARO 66 and FARO 67 varieties. Tiller infestation had a significant negative correlation with grain yield (r= − 0.87, R2 = 77). The study also indicated that the two fungi strains had no harmful effect on the chlorophyll content and positively influenced agronomic traits and grain yield.