Agricultural Insect Pests Research Articles

Pyriproxyfen exposure compromises cocoon spinning and damages the Malpighian tubules of the nontarget predator Ceraeochrysa claveri (Neuroptera: Chrysopidae)

Pyriproxyfen has been extensively employed in the Neotropical region for agricultural pest management and insect vectors. However, measuring the sublethal and indirect effects of this active ingredient on nontarget organisms, such as lacewings, is important. Using morphological tools on target organs, we can evaluate these effects and use them as biomarkers for future ecotoxicological studies. Here, we investigated the effects of pyriproxyfen exposure on cocoon spinning and Malpighian tubules in Ceraeochrysa claveri adults. For this purpose, first-instar C. claveri larvae were orally exposed to Diatraea saccharalis egg clusters treated with pyriproxyfen in a solution of 50 or 100 mg a.i. L-1 throughout the larval stage. Insecticide exposure decreases predator survival, mainly in the prepupal and pupal stages, along with changes in the internal and external surfaces and thickness of the cocoon wall. Histopathological and ultrastructural injuries, including cytoplasmic vacuolization, loss of microvilli and a reduction in neutral glycoconjugates, were observed in Malphigian tubule cells of adults (≤ 24 h old). These changes indicate toxicological effects on Malpighian tubules that in lacewing involve cocoon spinning during metamorphosis and, in the adult stage, act in physiological processes of excretion and osmoregulation. Furthermore, it can affect the efficiency of the cocoon in protecting the specimen during metamorphosis against natural enemies and environmental factors. This organ has demonstrated its applicability as a biomarker for assessing the multisystemic effects of insecticides, thereby assisting in future risk assessments aimed at conserving nontargeted specimens.

Entomopathogenic nematode detection and counting model developed based on A-star algorithm

Entomopathogenic nematodes are soil-dwelling living organisms widely employed in the biological control of agricultural insect pests, serving as a significant alternative to pesticides. In laboratory procedures, the counting process remains the most common, labor-intensive, time-consuming, and approximate aspect of studies related to entomopathogenic nematodes. In this context, a novel method has been proposed for the detection and quantification of Steinernema feltiae isolate using computer vision on microscope images. The proposed method involves two primary algorithmic steps: framing and isolation. Compared to YOLO-V5m, YOLO-V7m, and YOLO-V8m, the A-star-based developed network demonstrates significantly improved detection accuracy compared to other networks. The novel method is particularly effective in facilitating the detection of overlapping nematodes. The developed algorithm excludes processes that increase space and time complexity, such as the weight document, which contains the learned parameters of the deep learning model, model integration, and prediction time, resulting in more efficient operation. The results indicate the feasibility of the proposed method for detecting and counting entomopathogenic nematodes.

A scaffold protein manages the biosynthesis of steroidal defense metabolites in plants.

Solanaceae plants produce two major classes of valuable sterol derived natural products-steroidal glycoalkaloids and steroidal saponins-from a common cholesterol precursor. Attempts to heterologously produce these molecules have consistently failed, although the genes responsible for each biosynthetic step have been identified. Here we identify a cellulose synthase like protein, an unexpected biosynthetic component that interacts with the early pathway enzymes, enabling steroidal scaffolds production in plants. Moreover, knockout of this gene in black nightshade, Solanum nigrum resulted in plants lacking both steroidal alkaloids and saponins. Unexpectedly, these knockout plants also revealed that steroidal saponins deter serious agricultural insect pests. This discovery provides the missing link to engineer these high value steroidal molecules, and also pinpoints the ecological role for the steroidal saponins.

Side effects of semi-synthetic insecticide spinetoram on the whitefly parasitoid Encarsia formosa.

Insecticide risk assessment for biological control agents is essential for implementing integrated pest management (IPM) programs. Spinetoram is a naturally derived insecticide used to control a variety of agricultural sap-sucking insect pests, and Encarsia formosa Gahan (Hymenoptera: Aphelinidae) plays a key role in the biocontrol of greenhouse whiteflies. Despite its presumed safe ecotoxicological profile, the side effects of spinetoram on E. formosa are partially unknown, especially at sublethal doses. In the laboratory, we estimated the lethal concentrations (LC) of spinetoram on E. formosa by topical exposure of pupae and 48 h residual contact exposure of emerged adults. Afterwards, we assessed the impact of spinetoram LCs on the life history traits (juvenile development, adult longevity, parasitism, adult emergence) and population growth parameter (the instantaneous rate of increase, ri) of the parasitoid. Probit analysis allowed the estimation of LC10 = 0.10 mg/L, LC50 = 0.56 mg/L, and LC90 = 3.28 mg/L. Spinetoram at LC10 had no impact on the observed parameters of E. formosa. Conversely, spinetoram at LC50 and LC90 significantly reduced adult longevity by 19.2% and 40.6%, total parasitism by 33.4% and 38.7%, and total adult emergence by 29.6% and 39.1%, respectively. Also, the ri of E. formosa was significantly affected by spinetoram LC50 and LC90 with a reduction of 8.17 and 29.83%, respectively. Our results suggested that spinetoram significantly threatens the effectiveness of E. formosa when applied at the field recommended rate. However, further validation of spinetoram under greenhouse conditions is required for a comprehensive risk assessment for E. formosa in IPM programs. © 2024 Society of Chemical Industry.

Symbiont community assembly shaped by insecticide exposure and feedback on insecticide resistance of Spodoptera frugiperda

Exploring the mechanism of microbiota assembly and its ecological consequences is crucial for connecting microbiome variation to ecosystem function. However, the influencing factors underlying microbiota assembly in the host-microbe system and their impact on the host phenotype remain unclear. Through investigating the prevalent and worsening ecological phenomenon of insecticide resistance in global agriculture, we found that insecticide exposure significantly changed the gut microbiota assembly patterns of a major agricultural invasive insect pest, Spodoptera frugiperda. The relative importance of various microbiota assembly processes significantly varied with habitat heterogeneity and heterogeneous selection serving as a potential predictor of the host’s insecticide resistance in field populations. Moreover, disturbance of the gut microbiota assembly through antibiotics was revealed to significantly affect the rate and heritability of insecticide resistance evolution, leading to a delay in insecticide resistance evolution in this insect pest. These findings indicate that the gut microbiota assembly process of the insect host is influenced by persistent exposure to habitat conditions, particularly insecticides. This variation in insecticide exposure-related community assembly process subsequently influences the insect host’s insecticide resistance phenotype. This study provides insights into gut microbiota assembly processes from a symbiotic perspective and underscores the significant impact of symbiotic community changes on host phenotypic variation.

Environmental exposure to cadmium induces olfactory neurotoxicity in fire ants and the molecular basis

Cadmium (Cd) exhibits widely olfactory toxicity to animals. We previously reported that Cd exposure induces the transcriptional dysregulation of olfactory marker proteins (OMPs) of the red imported fire ant Solenopsis invicta. However, it is still unclear how environmental Cd exposure-induced deregulation of OMPs affects the olfactory signal transduction and olfaction-driven social behavior of S. invicta. Here, we showed that S. invicta displayed dull sensory perception on bait in Cd-contaminated areas and dietary Cd ingestion by S. invicta reduced the bait search efficiency. We hypothesize that deregulation of OMPs by Cd exposure blocks the olfactory signal transduction in fire ants. Our results indicated the odor binding protein 14 (SiOBP14) was consistently inhibited in antennal sensilla of fire ants across Cd exposure at 0.5, 5 and 50 mg/kg. Function analysis in vitro and in vivo demonstrated that SiOBP14 is essential in perception of S. invicta to bait odorants. Cd-exposed fire ants showed weak odorant receptor neurons (ORNs) chemosensory signaling and electroantennogram (EAG) response. Moreover, Cd exposure repeals the preference of S. invicta to the active bait odorants, including 2-methyltetrahydrofuran-3-one, 2-methyl-3-furanthiol and 4,5-dimethylthiazole, and even triggers a behavioral transition from preference to repellence. These results indicate that Cd exposure inhibits the specific OMP expression and disrupts olfactory signal transduction, thereby inducing dull sensory perception of S. invicta to bait odorants. The findings provide new implications for monitoring and control of agricultural insect pests in heavy metal polluted areas.

Ecological aspects of three strains of entomopathogenic nematodes from the department of Lambayeque-Peru

BackgroundEntomopathogenic nematodes (EPN) are used as a biological control agent for different insect pests in agriculture. The genera Heterorhabditis and Steinernema are the most used commercially. For an EPN species to be used as a biological controller, it is necessary to know its ecological aspects, including reproductive potential, movement capacity, and mean lethal concentration (LC50). These aspects were evaluated in three EPN strains isolated in Galleria mellonella larvae collected in the Lambayeque-Peru region, to determine if they are promising as biological controllers. The strains of EPN studied are Heterorhabditis sp. (PC9 strain), H. bacteriophora Poinar (PM10 strain), and Steinernema diaprepesi Nguyen y Duncan (SV19 strain).ResultsHeterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) had high production of infective juveniles (IJs): 217.750 and 186.800, respectively, while S. diaprepesi (SV19 strain) only reached 84.150 IJs. The movement capacity of Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) reached a depth of 15 cm to parasitize G. mellonella larvae, while S. diaprepesi (SV19 strain) only reached 10 cm. In decreasing order, the LC50 value of S. diaprepesi (SV19 strain), Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) were: 24.03, 13.74, and 8.19 IJs/ml, respectively.ConclusionsHeterorhabditis sp. PC9 and H. bacteriophora PM10 are promising a biological control agent because they present great production of IJs, great displacement capacity, and high pathogenicity against G. mellonella. Additionally, both strains present a mixed search strategy or seeker-hunter (seeker-browser).

Understanding pyrethrin biosynthesis: toward and beyond natural pesticide overproduction.

Pyrethrins are natural insecticides biosynthesised by Asteraceae plants, such as Tanacetum cinerariifolium and have a long history, dating back to ancient times. Pyrethrins are often used as low-persistence and safe insecticides to control household, horticultural, and agricultural insect pests. Despite its long history of use, pyrethrin biosynthesis remains a mystery, presenting a significant opportunity to improve yields and meet the growing demand for organic agriculture. To achieve this, both genetic modification and non-genetic methods, such as chemical activation and priming, are indispensable. Plants use pyrethrins as a defence against herbivores, but pyrethrin biosynthesis pathways are shared with plant hormones and signal molecules. Hence, the insight that pyrethrins may play broader roles than those traditionally expected is invaluable to advance the basic and applied sciences of pyrethrins.

RNAi targeting Nav and CPR via leaf delivery reduces adult emergence and increases the susceptibility to λ-cyholthin in Tuta absoluta (Meyrick)

The tomato leafminer, Tuta absoluta (Meyrick), one of the most economically destructive pests of tomato, causes severe yields losses of tomato production globally. Rapid evolution of insecticide resistance requires the development of alternative control strategy for this pest. RNA interference (RNAi) represents a promising, innovative control strategy against key agricultural insect pests, which has recently been licensed for Colorado Potato Beetle control. Here two essential genes, voltage-gated sodium channel (Nav) and NADPH-cytochrome P450 reductase (CPR) were evaluated as targets for RNAi using an ex vivo tomato leaf delivery system. Developmental stage-dependent expression profiles showed TaNav was most abundant in adult stages, whereas TaCPR was highly expressed in larval and adult stages. T. absoluta larvae feeding on tomato leaflets treated with dsRNA targeting TaNav and TaCPR showed significant knockdown of gene expression, leading to reduction in adult emergence. Additionally, tomato leaves treated with dsRNA targeting these two genes were significantly less damaged by larval feeding and mining. Furthermore, bioassay with LC30 doses of λ-cyholthin showed that silencing TaNav and TaCPR increased T. absoluta mortality about 32.2 and 17.4%, respectively, thus indicating that RNAi targeting TaNav and TaCPR could increase the susceptibility to λ-cyholthin in T. absoluta. This study demonstrates the potential of using RNAi targeting key genes, like TaNav and TaCPR, as an alternative technology for the control of this most destructive tomato pests in the future.

Neonicotinoid Residues on Filter Paper Lack Insecticidal Activity.

Neonicotinoid insecticides are used against agricultural, forest, and urban insect pests. Evaluation of dry neonicotinoid residues on treated filter paper is a commonly used method to determine the toxicity of active ingredients towards target and non-target organisms. Dry residues of four neonicotinoids, acetamiprid, dinotefuran, imidacloprid, and thiamethoxam, on filter paper did not cause significant levels of mortality in Hippodamia convergens (Guérin-Méneville) (Coleoptera: Coccinellidae) and Nezara viridula (L.) (Hemiptera: Pentatomidae) when compared to paired untreated groups. Conversely, nearly 100% mortality was observed when test insects were exposed to dry neonicotinoid residues on leaf discs and glass plate surfaces. On the other hand, dry residues of the pyrethroid bifenthrin on filter paper, leaf disks, and glass plates killed significantly more test insects when compared to untreated groups. Additional bioassays tested the toxicity of acetamiprid and thiamethoxam by evaluating the toxicity of dry residues on (1) the upper and (2) lower surfaces of treated filter paper, (3) on a glass plate underneath treated filter paper, (4) on the upper surface of treated filter paper treated with insecticide and adjuvant, and (5) dried residues on a glass plate after dipping treated filter paper in water and letting the solvent dry on the inert test surface. The results indicated that neonicotinoid insecticides applied to filter paper were adsorbed. Toxic compounds possibly move in between and binding to paper fibers so that no toxic residues were left on treated surfaces. However, adsorbed insecticides were still biologically active when washed out of filter paper and dried on an inert glass surface. The results reported here clearly demonstrate that the toxicity of neonicotinoid insecticides should not be evaluated using filter paper as a test surface.

Composition of Parasitoid Wasps in Insect Pests of Rice (Rice Leaffolder, Cnaphalocrocis Medinalis Guenée)

Biological control is one aspect of Integrated Pest Management (IPM). The method focusses on natural enemies; beneficial insects are applied for biological control of agricultural insect pests and also provide an environmentally friendly approach. For the rice pests including Rice Leaf Folder (RLF), several parasitoids tend to be natural enemies that could be used to control the pest from the egg stage to pupa. This study was conducted with two varieties of rice, namely “Sen Kra Oub” and “Sro Ngea” at Battambang Province of Cambodia. Parasitoid wasps were collected from egg to pupa stages of RLF and rice yellow stem borer by rearing method, and stored in 70% of alcohol solution before sending for identification in Vietnam’s Institute of Ecology and Biological Resources (IEBR) Laboratory. The outcomes revealed that five hymenopteran parasitic wasps of three different families were found, viz. Apanteles cypris Nixon, Bracon onukii Watanabe and Pentatermus striatus (Szepligeti) (Braconidae), Xanthopimla flavolineata Cameron (Ichneumonidae), and Telenomus rowani Gahan (Scelionidae) and being the primary parasitoids of rice leaffolder, Cnaphalocrocis medinalis Guenee; stemborer Scirpophaga incertulas Walker (Pyralidae) and black branded swift Pelopidas mathias (Hesperiidae). Parasitism was not found at the vegetative phase with Sen Kra Ob varieties but in reproductive phase. parasitism proportion was 16.66% and 28.57% to 50% in ripening phase, different from Sro Ngea variety where a proportion was found in vegetative phase 27.27%, reproductive phase at 28.57% to 40% and 28.57% to 43% in ripening phase. All the hymenopteran parasitoids were initially recorded in Cambodia, whereby all the parasitoids were potential agents for biological control for important rice insect pests. The outcome of this research suggests that the Government should invest more in the research and development for biological control in Cambodia.

Role of cuticular genes in the insect antimicrobial immune response.

Insects are established models for understanding host-pathogen interactions and innate immune mechanisms. The innate immune system in insects is highly efficient in recognizing and opposing pathogens that cause detrimental effects during infection. The cuticular layer which covers the superficial layer of the insect body participates in host defense and wound healing by inducing innate immune responses. Previous studies have started to address the involvement of cuticular genes in conferring resistance to insect pathogens, particularly those that infect by disrupting the insect cuticle. For example, the cuticular gene Transglutaminase (TG) in Drosophila melanogaster plays a structural role in cuticle formation and blood coagulation and also possesses immune properties against pathogenic infection. However, more information is becoming available about the immune function of other cuticular gene families in insects. In this review, we aim to highlight the recent advances in insect cuticular immunity and address the necessity of pursuing further research to fill the existing gaps in this important field of insect immunology. This information will lead to novel strategies for the efficient management of agricultural insect pests and vectors of plant and human disease.

Actinobacteria mediated synthesis of silver nanoparticles using Streptomyces diastaticus and their biological efficacy against human vector mosquitoes and agricultural insect pests

Mosquitoes and agricultural insects were harmful to both public health and crops. Prolonged use of synthetic chemical pesticides for insect pest control was associated with resistance development and negative human and ecological effects. This study investigates the larvicidal activity of Ag-NPs produced using Streptomyces diastaticus against Culex quinquefasciatus, Anopheles stephensi, Aedes aegypti, Spodoptera litura, and Plutella xylostella. UV-Vis spectroscopy, XRD, SEM-EDX, FT-IR, TEM, DLS, and Zeta potential analysis were used to characterize the biosynthesized Ag-NPs. The results showed that biosynthesized Ag-NPs were more toxic to, A. stephensi, C. quinquefasciatus, and A. aegypti with LC50 values of 15.70, 11.10, and 17.53 µg/mL, respectively. Biosynthesized Ag-NPs exhibited the highest antifeedant effects against S. litura (88.73 %) and P. xylostella (92.36 %) at 50 µg/mL concentration. The mortality bioassay revealed considerable larvicidal activity against S. litura and P. xylostella larvae at greater doses of 50 µg/mL, 80.67 and 84.05 %, respectively. Morphogenetic variations were observed on treated larvae of C. quinquefasciatus, A. aegypti, and A. stephensi, S. litura, and P. xylostella with Ag-NPs. In the present investigation the impact of Ag-NPs on the antioxidant enzymes (SOD, CAT, and GPx), the activity of each enzyme were dramatically increased with higher concentrations resulting in significant differences. The study also found that Ag-NPs inhibited the detoxifying enzyme (GST and AChE) activity of target organisms. The histological structure of the treated and untreated larvae revealed structural changes between the midgut epithelial cells. As a consequence of these findings, the S. diastaticus-mediated Ag-NPs serve as a possible, eco-friendly biopesticide and alternative to synthetic chemicals for the control of human vector mosquitoes and destructive arthropod insect pests.

The Activin Branch Ligand Daw Regulates the Drosophila melanogaster Immune Response and Lipid Metabolism against the Heterorhabditis bacteriophora Serine Carboxypeptidase.

Despite impressive advances in the broad field of innate immunity, our understanding of the molecules and signaling pathways that control the host immune response to nematode infection remains incomplete. We have shown recently that Transforming Growth Factor-β (TGF-β) signaling in the fruit fly Drosophila melanogaster is activated by nematode infection and certain TGF-β superfamily members regulate the D. melanogaster anti-nematode immune response. Here, we investigate the effect of an entomopathogenic nematode infection factor on host TGF-β pathway regulation and immune function. We find that Heterorhabditis bacteriophora serine carboxypeptidase activates the Activin branch in D. melanogaster adults and the immune deficiency pathway in Activin-deficient flies, it affects hemocyte numbers and survival in flies deficient for Activin signaling, and causes increased intestinal steatosis in Activin-deficient flies. Thus, insights into the D. melanogaster signaling pathways and metabolic processes interacting with H. bacteriophora pathogenicity factors will be applicable to entomopathogenic nematode infection of important agricultural insect pests and vectors of disease.

Oxidative Stress Evaluation of Lambda-Cyhalothrin and Antioxidant (Vitamin E) on Male Rats

Abstract Background: Lambda-cyhalothrin (LCT) is a widely used pyrethroid to control insect pests in agriculture, public health, and homes. Objectives: The aim of this study was to evaluate the oxidative stress evaluation of LCT pesticides and and antioxidants (vitamin E) in male rats. Materials and Methods: Thirty adult male rats were separated evenly into three groups after 3 weeks of acclimatization as follows: For 12 weeks, group-normal C’s feed and water were given to 10 rats. Group T was given LCT at a dose of 0.5 mL per 100 g of body weight for 12 weeks (n = 10 rats) and group E was given (LC + vitamin E) at a dose of 0.5 mL per 100 g of body weight. Results: At a results significant increase in malondialdehyde (MDA) level in the T group compared with the E group and C group. Significant decrease of glutathione (GSH) levels in the T group compared with the E group and C group. Macroscopic and microscopic lesions demonstrated atrophy of the kidney in the T group and congestion in the G group while the C group was normal the microscopic lesion of the kidney in the T group multiplied the area of the renal cast at renal tubules with degenerative changes and multiply the area of hemorrhage at the interstitial area but E group show mild degenerative changes in the structure of the renal tubule. It is interesting to note that every modification showed how detrimental LTC is to the kidneys and how vitamin E’s antioxidant capacity benefits them. Conclusions: Exposure to pesticides continuously creates a health concern, particularly in the agricultural working environment where animal and human life are intertwined. Thus, the study findings demonstrate the impact of LCT on oxidative stress and renal function as well as the antioxidant role of vitamin E.

Modified snake optimizer based multi-level thresholding for color image segmentation of agricultural diseases

Image segmentation is crucial for early identification and diagnosis of crop diseases in agriculture. It helps identify disease areas and characteristics, laying the groundwork for disease diagnosis and treatment. However, color image thresholding segmentation method faces challenges in finding the optimal threshold as the number of thresholds increases, which affects segmentation quality. In this paper, a modified snake optimizer (MSO) is proposed to address the color image thresholding segmentation problem using Kapur’s entropy as the objective function. MSO incorporates a dynamic adaptive parameter adjustment method. The improved global position update formula introduces guidance from the optimal individual and disturbance from random individuals, effectively achieving a balance between global and local search capabilities. A dynamic parameter adjustment method is added to accelerate convergence speed during snake movement to food. Lévy flight is introduced to the Flight mode to help the algorithm escape local extremums. A balancing strategy is implemented in the Mating mode, incorporating guidance from the optimal individual and information exchange between sub-populations, enabling balanced exploration and local exploitation capabilities. The hill-climbing jump operation for the optimal individual is added to help the algorithm overcome local stagnation. The proposed MSO is evaluated on CEC 2017 test functions and color test images, and the obtained results are compared with other segmentation methods and other intelligent optimization algorithms. The results demonstrate that MSO exhibits stable and excellent performance in both complex global optimization problems and color image thresholding segmentation problems. Finally, MSO is applied to segment rice disease images, and the results reveal significantly better segmentation performance compared to other algorithms. MSO shows great potential in solving the thresholding segmentation problem for agricultural disease images, thereby assisting in the accurate identification, diagnosis, and treatment of agricultural diseases and insect pests.

Insecticide Efficacy of Green Synthesis Silver Nanoparticles on Diaphorina citri Kuwayama (Hemiptera: Liviidae).

Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a vector of Liberibacter asiaticus Jagoueix et al. and Liberibacter americanus Teixeira et al., causal agents of the critical yellow dragon disease or Huanglongbing (HLB), which affects citrus production worldwide. Recently, green synthetic nanoparticles have emerged as a potential alternative to control of agricultural insect pests. The insecticide effect of silver nanoparticles (AgNPs) on 2nd instar nymphs of D. citri under laboratory and greenhouse conditions was evaluated. Mortality was recorded 24, 48, and 72 h after application on D. citri nymphs under both laboratory and greenhouse conditions. The laboratory results showed that AgNPs caused 97.84 and 100% mortality at 32 and 64 ppm, respectively, 72 h after treatment. In the greenhouse, AgNPs caused 78.69 and 80.14% mortality using 64 and 128 ppm 72 h after application. This research is the first to evaluate the green synthesis AgNPs on D. citri and are a promising strategy to control the pest.

Baseline of susceptibility, risk assessment, biochemical mechanism, and fitness cost of resistance to dimpropyridaz, a novel pyridazine pyrazolecarboxamide insecticide, in Bemisia tabaci from China

Bemisia tabaci is one of the most destructive agricultural insect pests around the world, and it has developed high levels of resistance to most pesticides. Dimpropyridaz, a novel insecticide developed by BASF, displays excellent activity against piercing-sucking insect pests. In this study, baseline of susceptibility showed all tested field populations of B. tabaci are susceptible to dimpropyridaz. After continuous selection with dimpropyridaz in the lab, a B. tabaci strain (F12) developed 2.2-fold higher level of resistance compared with a susceptible MED-S strain, and the realized heritability (h2) was estimated as 0.0518. The F12 strain displayed little cross-resistance to afidopyropen, cyantraniliprole, sulfoxaflor, or abamectin, and significantly increased activity of cytochrome P450 monooxygenase (P450). The fitness cost of dimpropyridaz resistance was evident in F12 strain, which had a relative fitness of 0.95 and significantly lower fecundity per female compared with MED-S strain. Taken together, B. tabaci displays high susceptibility to dimpropyridaz in the field, and low risk of developing resistance to dimpropyridaz under successive selection pressure. Little cross-resistance to popular insecticides was found, and fitness cost associated dimpropyridaz resistance was observed. Higher activity of cytochrome P450 in the F12 strain, may be involved in the process of detoxifying dimpropyridaz in whitefly.

ROLE OF SOIL MICROBES IN MODULATION OF PLANT DEFENSE AGAINST INSECT PESTS: A REVIEW

A vital role of soil microbes is to keep plants healthy and productive. There is growing interest in the role of soil microbes in plant defense against insect pests. Soil microbes can influence plant resistance to insect pests by interacting with plants. They produce compounds that can degrade insect toxins and make plants resistant to pests. By understanding the complex interactions between soil microbes, plants, and insect pests, strategies could be developed to enhance crop resilience and reduce reliance on chemical inputs. They can improve plant defense by generating secondary metabolites, breaking down insecticidal substances, and promoting systemic resistance. Using soil microbes for pest management has significant implications for the environment, human health, and the economy. However, further research is needed to fully understand the interactions between soil microbes and plants and develop standardized protocols for their use in pest management. Overall, the use of soil microbes has the potential to provide a sustainable and eco-friendly solution to the problem of insect pests in agriculture. This review discusses this interaction, its implications in insect pest management, and the challenges of their use in plant defense.. KEYWORDS :Insect pests, Microbial interaction, Pest management, Plant defense, Soil microbes

Enhancing toxicity of pyrethroids by oxidase and esterase inhibitors in Spodoptera littoralis (Boisd.) larvae

Although pyrethroids are increasingly being used to control a number of agricultural insect pests, especially the cotton leafworm, Spodoptera littoralis (Boisd.), pyrethroid resistance is a major obstacle limiting effective control. With the aim of maintaining the effectiveness of pyrethroids in managing pests, a study was undertaken to evaluated the effectiveness of oxidase and esterase inhibitors for synergizing pyrethroids in S. littoralis larvae. Compared with the insecticide-susceptible strain (L-SS) of S. littoralis, the resistance ratio (RR) in the field population (F-RS) was 271.43–fold to cypermethrin. The use of profenofos as an esterase inhibitor significantly increased larval susceptibility to cypermethrin in the F-RS strain, with a synergy ratio (SR) of up to 192.57–fold. Significant inhibition of esterase by profenofos in the F-RS strain was found in vivo. Also, piperonyl butoxide (PB) as an oxidase inhibitor had slight effect of cypermethrin toxicity, so its addition is not a solution for pyrethroid resistance. Thus, modifying the toxicity of cypermethrin by mixing it with organophosphorus compounds (OPs) increased its toxicity and decreased the population of S. littoralis, which is a successful strategy for managing pyrethroid resistance.