Activity Of Detoxifying Enzymes Research Articles

Varied response of detoxification enzyme activities against lethal and sublethal exposures of phosphine in Tribolium castaneum populations

Varied response of detoxification enzyme activities against lethal and sublethal exposures of phosphine in Tribolium castaneum populations

Effects of fungicides propiconazole and Trichoderma spp. on the mortality and the physiological status of larvae and adult worker honey bees (Apis mellifera L.)

Exposure to pesticides may affect the survival and normal physiological functions of the honey bee (Apis mellifera L.). The fungicide propiconazole (PRO) and the biofungicide Trichoderma are widely used in agroecosystems, and their effects on the physiology of the honey bee have been largely neglected in risk assessment procedures. We investigated the mortality and variations in physiological biomarkers of honey bee larvae and newly emerged workers exposed to PRO and Trichoderma. Exceeding the field-recommended concentrations of Trichoderma decreased the survival of newly emerged bee workers significantly through oral exposure. PRO, however, showed no significant lethal effects. Contact or oral exposure to field-realistic concentrations of PRO and Trichoderma profoundly altered the activities of detoxification, antioxidative, and digestive enzymes along with energy reserve concentrations of honey bee larvae and adult workers. Integrated biological index (IBRv2) values suggested potential risks of PRO and Trichoderma to honey bees by impairing the physiological status of larvae and newly emerged workers.

In situ polymerization of sodium alginate and polyethylene glycol nano-formulations of acetamiprid against khapra beetle, Trogoderma granarium (Everts) (Coleoptera: Dermestidae)

Nano-formulations have been identified as a novel method of integrated pest management due to their increased effectiveness. Acetamiprid is an insecticide belonging to the group of neonicotinoids that selectively binds and interacts with the insect nicotinic acetylcholine receptor site, causing convulsions, paralysis, and ultimately death. Our research describes nano-formulated acetamiprid in situ polymerized using sodium alginate (AL) and polyethylene glycol (PEG). Third instar larvae of the Trogoderma granarium were sprayed using a potter tower for bioassays. LC50 for bulk formulation was 1.48 μg/cm2 and for AL and PEG were 0.85 μg/cm2 and 0.93 μg/cm2, respectively. Data analysis demonstrated that AL was 1.76-fold and PEG was 1.57-fold more toxic than bulk acetamiprid. LT50 for bulk formulation, AL, and PEG were 2104, 9, and 23 min, respectively. The results indicated that AL and PEG were more active and rapidly induced toxicity than bulk acetamiprid, viz., 224.18-fold and 92.58-fold, respectively. In vitro experiments revealed that protein, carbohydrate, glycogen, and lipid contents of treated larvae were significantly decreased. Detoxifying enzymes activities (glutathione S-transferases) were also reduced by AL and PEG-nano-encapsulated formulations but the activity of α-β-esterase were significantly increased. Based on outcomes, nano-formulation can enhance effectiveness of acetamiprid in terms of toxicity.

Sulfoxaflor influences the biochemical and histological changes on honeybees (Apis mellifera L.)

Pesticide application can have an adverse effect on pollinator honey bees, Apis mellifera L., ranging from mortality to sublethal effects. Therefore, it is necessary to understand any potential effects of pesticides. The present study reports the acute toxicity and adverse effects of sulfoxaflor insecticide on the biochemical activity and histological changes on A. mellifera. The results showed that after 48 h post-treatment, the LD25 and LD50 values were 0.078 and 0.162 µg/bee, respectively, of sulfoxaflor on A. mellifera. The detoxification enzyme activity shows an increase of glutathione-S-transferase (GST) enzyme on A. mellifera in response to sulfoxaflor at LD50 value. Conversely, no significant differences were found in mixed-function oxidation (MFO) activity. In addition, after 4 h of sulfoxaflor exposure, the brains of treated bees showed nuclear pyknosis and degeneration in some cells, which evolved to mushroom shaped tissue losses, mainly neurons replaced by vacuoles after 48 h. There was a slight effect on secretory vesicles in the hypopharyngeal gland after 4 h of exposure. After 48 h, the vacuolar cytoplasm and basophilic pyknotic nuclei were lost in the atrophied acini. After exposure to sulfoxaflor, the midgut of A. mellifera workers showed histological changes in epithelial cells. These findings of the present study showed that sulfoxaflor could have an adverse effect on A. mellifera.

Insights into the toxicity, biochemical activity, and molecular docking of Cymbopogon citratus essential oils and citral on Spodoptera littoralis (Lepidoptera: Noctuidae).

Insecticide resistance is a significant problem in insect management that can result from several processes including target-site change and increased activity of detoxifying enzymes. Spodoptera littoralis is one of the most resistant insect pests. For more effective insect management, alternatives to synthetic pesticides are encouraged. One of these alternatives is essential oils (EOs). Cymbopogon citratus EO and its main constituent citral were, therefore, considered in this study. The results revealed that C. citratus EO and citral exhibited significant larvicidal activity against S. littoralis, and the former was insignificantly more toxic than the latter. Additionally, treatments significantly affected the activity of detoxification enzymes. Cytochrome P-450 and glutathione-S-transferase were inhibited, while carboxylesterases, a-esterase and β-esterase, were induced. The molecular docking study indicated that citral bonded with the amino acids cysteine (CYS 345) and histidine (HIS 343) of cytochrome P-450. This result suggests that interaction with cytochrome P-450 enzyme is one key mechanism by which C. citratus EO and citral act in S. littoralis. The results of our study are hoped to contribute to a better understanding of the mechanism of action of essential oils at the biochemical and molecular levels and provide safer and more efficient pest management solutions for S. littoralis.

The mechanisms of metabolic resistance to pyrethroids and neonicotinoids fade away without selection pressure in the tarnished plant bug Lygus lineolaris.

Heavy selection pressure prompted the development of resistance in a serious cotton pest tarnished plant bug (TPB), Lygus Lineolaris in the mid-southern USA. Conversely, a laboratory resistant TPB strain lost its resistance to five pyrethroids and two neonicotinoids after 36 generations without exposure to any insecticide. It is worthwhile to examine why the resistance diminished in this population and determine whether the resistance fade away has practical value for insecticide resistance management in TPB populations. A field-collected resistant TPB population in July (Field-R1) exhibited 3.90-14.37-fold resistance to five pyrethroids and two neonicotinoids, while another field-collected TPB population in April (Field-R2) showed much lower levels of resistance (0.84-3.78-fold) due to the absence of selection pressure. Interestingly, after 36 generations without exposure to insecticide, the resistance levels in the same population (lab-R) significantly decreased to 0.80-2.09-fold. The use of detoxification enzyme inhibitors had synergistic effects on permethrin, bifenthrin and imidacloprid in resistant populations of L. lineolaris. The synergism was more pronounced in field-R2 than lab-S and lab-R TPB population. Moreover, esterase, GST, and P450 enzyme activities increased significantly by approximately 1.92-, 1.43-, and 1.44- fold in field-R1, respectively, and 1.38-fold increased P450 enzyme activities in field-R2 TPB population, compared to the lab susceptible (lab-S) TPB. In contrast, the three enzyme activities in the lab-R strain were not significantly elevated anymore relative to the lab-S population. Additionally, field-R1 TPB showed elevated expression levels of certain esterase, GST and P450 genes, respectively, while field-R2 TPB overexpressed only P450 genes. The elevation of these gene expression levels in lab-R expectedly diminished to levels close to those of the lab susceptible (lab-S) TPB populations. Our results indicated that the major mechanism of resistance in TPB populations was metabolic detoxification, and the resistance development was likely conferred by increased gene expressions of esterase, GST, and P450 genes, the fadeaway of the resistance may be caused by reversing the overexpression of esterase, GST and P450. Without pesticide selection, resistant gene (esterase, GST, P450s) frequencies declined, and detoxification enzyme activities returned to lab-S level, which resulted in the recovery of the susceptibility in the resistant TPB populations. Therefore, pest's self-purging of insecticide resistance becomes strategically desirable for managing resistance in pest populations. This article is protected by copyright. All rights reserved.

The influence of ocean acidification and warming on responses of Scylla serrata to oil pollution: An integrated biomarker approach.

Anthropogenic activities primarily combustion of fossil fuel is the prime cause behind the increased concentration of CO2 into the atmosphere. As a consequence, marine environments are anticipated to experience shift towards lower pH and elevated temperatures. Moreover, since the industrial revolution the growing demand for petroleum-based products has been mounting up worldwide leading to severe oil pollution. Sundarbans estuarine system (SES) is experiencing ocean warming, acidification as well as oil pollution from the last couple of decades. Scylla serrata is one of the most commercially significant species for aquaculture in coastal areas of Sundarbans. Thus, the prime objective of this study is to delineate whether exposure under ocean warming and acidification exacerbates effect of oil spill on oxidative stress of an estuarine crab S. serrata. Animals were separately exposed under current and projected climate change scenario for 30days. After this half animals of each treatment were exposed to oil spill conditions for 24h. Oxidative stress status superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), lipid peroxidation (LPO level) and DNA damage (Comet assay) were measured. Augmented antioxidant and detoxification enzyme activity was noted except for SOD but failed to counteract LPO and DNA damage. The present results clearly highlighted the detrimental combined effect of OWA and pollution on oxidative stress status of crabs that might potentially reduce its population and affect the coastal aquaculture in impending years.

Cyantraniliprole seed treatment effectively controls wireworms (Pleonomus canaliculatus Faldermann) and white grubs (Anomala corpulenta Motschulsky) in maize fields

Wireworms and white grubs are destructive underground pests in maize fields in China. Cyantraniliprole has good control effect on coleoptera pests. Here, we evaluated the toxicity of cyantraniliprole to the second instar larvae of Anomala corpulenta Motschulsky and third-instar of larvae of Pleonomus canaliculatus Faldermann and the effects of sublethal concentrations on the activity of antioxidant and detoxification enzymes. We also explored the efficacy of cyantraniliprole on underground pests under indoor and field conditions. The LC50 of cyantraniliprole for the third instar larvae of P. canaliculatus was 23.3712 mg/L, and that for the second instar larvae of A. corpulenta was 5.9715 mg/L. Cyantraniliprole can activate the activity of superoxide dismutase (SOD), peroxidase (POD), and glutathione S-transferase (GST) to different degrees at a sublethal dose. According to the pot experiment and the control efficacy test in the field, the indoor control effect of cyantraniliprole seed treatment on P. canaliculatus and white grubs was approximately 80%, and the maximum increase in yield achieved through cyantraniliprole application was approximately 15% in the field efficacy test. Cyantraniliprole has a strong control effect on wireworms and white grubs, so it can be used to treat seeds to control underground pests in maize fields.

Evaluation of Afidopyropen Toxicity at Environmentally Relevant Doses to the Asian Honeybee (Apis cerana) Using Physiological and Transcriptome Analysis.

Afidopyropen is a novel biogenic pesticide widely applied to control sap-feeding pests, and a few studies have evaluated the side effects of afidopyropen on pollinators, excluding the Asian honeybee. Thus, we estimated the physiological influences of afidopyropen in Apis cerana, which could cause significant death and nutritional deficiency in bees after continuous dietary intake (14 days) at the field recommended dose. Moreover, we found afidopyropen ingestion-induced changes in the activity of detoxification enzymes (AChE, GR, CarE) and expression of genes critical for the central nervous system and chemosensory function in the antennae, brain, midgut, and malpighian tubule of exposed bees. However, there was no evidence that there was a long-term impact on foraging activity when observing foragers treated with apfidopyropen as newly emerged workers. Overall, our study provides vital information to improve bee health, which will improve outcomes for beekeepers, increase pollination services, and strengthen pollinator communities.

Insecticide Resistance Development and Detoxification Enzyme Activities of Spodoptera litura (Fabricius) in Soybean from Kumaon Himalayas

Background: Soybean is an important crop of Uttarakhand both in hills as well as in plains and Spodoptera litura is an important pest of soybean in Uttarakhand. Several insecticides have been in use for its management and resistance has been observed against different group of insecticides. Thus, to study the level of infestation and insecticide resistance from soybean fields of hill farmers of Kumaon Himalaya, survey and experiments were conducted. Methods: Survey was conducted and scale of infestation was determined. Chemical and biochemical assay were conducted to study insecticide resistance. For chemical assay IRAC Method No. 7 using insecticides indoxacarb 14.5% SC, chlorantraniliprole 18.5% Sc, fipronil 5% SC, chlorpyriphos 50%+cypermethrin 5% EC and profenofos 40%+cypermethrin 4% EC and for biochemical assay the specific activity of Carboxylesterase, Acetyl choline esterase, Mono-oxygenase and Glutathione-S-transferase was studied. Result: The infestation level from different regions showed the presence of S. litura, ranging from mild to severe infestation. The resistance ratio of different insecticides used ranged from a low to an extremely high resistance level with LC50 ranging from 0.37 µg/ml to 1648.84 µg/ml. The biochemical analysis of carboxylesterase, acetylcholinesterase, monooxygenase and gluthione-s-transferase showed an overproduction of these detoxification enzymes in the resistant population.

The effect of pollution on the competitive dynamics of Anopheles arabiensis Patton, 1905 and Culex quinquefasciatus Say, 1823 (Diptera: Culicidae)

Culex quinquefasciatus Say, 1823 and Anopheles arabiensis Patton, 1905 (Diptera: Culicidae) are often found breeding in the same water sources and engage in interspecific competition. Although Cx. quinquefasciatus is known to proliferate in a range of polluted environments, the ability of An. arabiensis to proliferate in polluted water has only been reported relatively recently. The effects of pollution and insecticide resistance on this competitive interaction are unknown. This study examined the effect of pollution on the dynamics of the interspecific competition. Three laboratory strains were used in this study: an insecticide susceptible and an insecticide resistant An. arabiensis, and an insecticide resistant Cx. quinquefasciatus. Larval pollutant tolerances of each strain were assessed and compared by determining the lethal concentration at 50% mortality (LC50). The larvae from each strain were exposed to either inorganic fertiliser or copper nitrate, following which eclosion success was assessed. The results showed that the insecticide resistant strains had higher emergence rates when reared in polluted conditions without competition, with the Cx. quinquefasciatus strain showing the highest rate of eclosion. This species also had a higher tolerance for metal pollution than the An. arabiensis strains. The effects of pollutants on oviposition choice were examined. Pollution altered adult oviposition choice. The effect of larval metal exposure had variable effects on the activity of metabolic detoxification enzymes. An insecticide resistant phenotype had greater tolerance to pollutants and possibly developmental advantages based on a variable detoxification response to the pollutant. Pollution can therefore alter interspecific competition dynamics between the malaria vector An. arabiensis and Cx. quinquefasciatus.

Ameliorating the drought stress tolerance of a susceptible soybean cultivar, MAUS 2 through dual inoculation with selected rhizobia and AM fungus

BackgroundDrought stress is currently the primary abiotic stress factor for crop loss worldwide. Although drought stress reduces the crop yield significantly, species and genotypes differ in their stress response; some tolerate the stress effect while others not. In several systems, it has been shown that, some of the beneficial soil microbes ameliorate the stress effect and thereby, minimizing yield losses under stress conditions. Realizing the importance of beneficial soil microbes, a field experiment was conducted to study the effect of selected microbial inoculants namely, N-fixing bacteria, Bradyrhizobium liaoningense and P-supplying arbuscular mycorrhizal fungus, Ambispora leptoticha on growth and performance of a drought susceptible and high yielding soybean cultivar, MAUS 2 under drought condition.ResultsDrought stress imposed during flowering and pod filling stages showed that, dual inoculation consisting of B. liaoningense and A. leptoticha improved the physiological and biometric characteristics including nutrient uptake and yield under drought conditions. Inoculated plants showed an increased number of pods and pod weight per plant by 19% and 34% respectively, while the number of seeds and seed weight per plant increased by 17% and 32% respectively over un-inoculated plants under drought stress condition. Further, the inoculated plants showed higher chlorophyll and osmolyte content, higher detoxifying enzyme activity, and higher cell viability because of less membrane damage compared to un-inoculated plants under stress condition. In addition, they also showed higher water use efficiency coupled with more nutrients accumulation besides exhibiting higher load of beneficial microbes.ConclusionDual inoculation of soybean plants with beneficial microbes would alleviate the drought stress effects, thereby allowing normal plants’ growth under stress condition. The study therefore, infers that AM fungal and rhizobia inoculation seems to be necessary when soybean is to be cultivated under drought or water limiting conditions.

Host-Plant Switching Impacts Susceptibility and Biochemical Responses of Cnaphalocrocis medinalis to Abamectin and Chlorpyrifos

Insect tolerance to insecticides is closely related to the host plant. Migratory insects flying downwind and landing randomly may face host-plant switching after migration. However, it is not clear whether host-plant switching affects the tolerance of migratory insects to insecticides. In the present work, Cnaphalocrocis medinalis, a migratory pest destructive to rice, was studied to explore this issue. The results show that the host-plant switch reduced the susceptibility of rice and wheat larvae populations to abamectin but increased that of wheat larvae populations to chlorpyrifos, indicating that host switching resulted in different tolerance to different insecticides. Enzyme activity determination showed that, although abamectin and chlorpyrifos affect the activities of detoxification enzymes (carboxylesterase, multifunctional oxidase, and glutathione S-transferases), antioxidant enzymes (superoxide dismutase, peroxidase, and catalase), and acetylcholinesterase at sublethal dosages, the effect depends on the host plant and insecticide species. Overall, our findings show that the induction of C. medinalis by host switching affects its susceptibility and biochemical responses to abamectin and chlorpyrifos. Insecticides against C. medinalis should be used with consideration of the potential impact of host switching. Reasonable selection and usages of insecticides can help in the resistance management and control of migratory insects.

Bioinsecticide spinosad poses multiple harmful effects on foragers of Apis mellifera.

There are multifactorial causes for the recent decline in bee populations, which has resulted in compromised pollination and reduced biodiversity. Bees are considered one of the most important non-target insects affected by insecticides used in crop production. In the present study, we investigated the effects of acute oral exposure to spinosad on the survival, food consumption, flight behavior, respiration rate, activity of detoxification enzymes, total antioxidant capacity (TAC), brain morphology, and hemocyte count of Apis mellifera foragers. We tested six different concentrations of spinosad for the first two analyses, followed by LC50 (7.7mg L-1) for other assays. Spinosad ingestion decreased survival and food consumption. Exposure to spinosad LC50 reduced flight capacity, respiration rate, and superoxide dismutase activity. Furthermore, this concentration increased glutathione S-transferase activity and the TAC of the brain. Notably, exposure to LC50 damaged mushroom bodies, reduced the total hemocyte count and granulocyte number, and increased the number of prohemocytes. These findings imply that the neurotoxin spinosad affects various crucial functions and tissues important for bee performance and that the toxic effects are complex and detrimental to individual homeostasis.

Hormetic effects of neonicotinoid insecticides on Rhizoglyphus robini (Acari: Acaridae)

The stimulation of biological processes by sublethal doses of insecticides or other stressors is known as hormesis. Here, we have evaluated whether exposure to field-relevant or low concentrations of neonicotinoids induce changes in the reproductive capacity of the bulb mite Rhizoglyphus robini (Acari: Acaridae). Among the tested neonicotinoids imidacloprid, thiamethoxam, and dinotefuran, the highest hormetic effect on the reproduction of R. robini occurred 24 h after the 48 h exposure period to imidacloprid at concentrations of 70 and 140 mg a.i./L. Despite the stimulating effects of imidacloprid on mite reproduction, no significant differences were observed in the offspring (F1) for biological aspects including egg hatch rate, embryonic period and sex ratio, while an increase was found in the duration of development time from egg to adult. Evaluation of the detoxification enzyme activities of treated adults showed that the highest activity of carboxyl/cholinesterases, cytochrome P450s, and glutathione S-transferases was obtained when exposed to 70, 140 and 70 mg a.i./L imidacloprid, immediately after the exposure period, respectively. Also, an increase in the activity of the antioxidant enzyme catalase was observed compared to that of the control. After imidacloprid pretreatment (140 mg a.i./L), the tolerance of adult mites to diazinon was increased about two-fold. This study shows that exposure to imidacloprid can induce hormetic effects on R. robini and could severely complicate its control due to a higher reproduction, enhanced detoxification enzyme activities, and increased tolerance against other pesticides.

Tenuazonic acid alters immune and physiological reactions and susceptibility to pathogens in Galleria mellonella larvae.

Tenuazonic acid (TeA) is synthesized by phytopathogenic and opportunistic fungi and is detected in a broad range of foods. This natural compound is of interest in terms of toxicity to animals, but its mechanisms of action on insects are poorly understood. We administered TeA orally at different concentrations (0.2-5.0mg/[gram of a growth medium]) to the model insect Galleria mellonella, with subsequent estimation of physiological, histological, and immunological parameters in different tissues (midgut, fat body, and hemolymph). Susceptibility of the TeA-treated larvae to pathogenic microorganisms Beauveria bassiana and Bacillus thuringiensis was also analyzed. The feeding of TeA to the larvae led to a substation delay of larval growth, apoptosis-like changes in midgut cells, and an increase in midgut bacterial load. A decrease in activities of detoxification enzymes and downregulation of genes Nox, lysozyme, and cecropin in the midgut and/or hemocoel tissues were detected. By contrast, genes gloverin, gallerimycin, and galiomycin and phenoloxidase activity proved to be upregulated in the studied tissues. Hemocyte density did not change under the influence of TeA. TeA administration increased susceptibility of the larvae to B. bassiana but diminished their susceptibility to B. thuringiensis. The results indicate that TeA disturbs wax moth gut physiology and immunity and also exerts a systemic action on this insect. Mechanisms underlying the observed changes in wax moth susceptibility to the pathogens are discussed.

The gut symbiont Sphingomonas mediates imidacloprid resistance in the important agricultural insect pest Aphis gossypii Glover

BackgroundNeonicotinoid insecticides are applied worldwide for the control of agricultural insect pests. The evolution of neonicotinoid resistance has led to the failure of pest control in the field. The enhanced detoxifying enzyme activity and target mutations play important roles in the resistance of insects to neonicotinoid resistance. Emerging evidence indicates a central role of the gut symbiont in insect pest resistance to pesticides. Existing reports suggest that symbiotic microorganisms could mediate pesticide resistance by degrading pesticides in insect pests.ResultsThe 16S rDNA sequencing results showed that the richness and diversity of the gut community between the imidacloprid-resistant (IMI-R) and imidacloprid-susceptible (IMI-S) strains of the cotton aphid Aphis gossypii showed no significant difference, while the abundance of the gut symbiont Sphingomonas was significantly higher in the IMI-R strain. Antibiotic treatment deprived Sphingomonas of the gut, followed by an increase in susceptibility to imidacloprid in the IMI-R strain. The susceptibility of the IMI-S strain to imidacloprid was significantly decreased as expected after supplementation with Sphingomonas. In addition, the imidacloprid susceptibility in nine field populations, which were all infected with Sphingomonas, increased to different degrees after treatment with antibiotics. Then, we demonstrated that Sphingomonas isolated from the gut of the IMI-R strain could subsist only with imidacloprid as a carbon source. The metabolic efficiency of imidacloprid by Sphingomonas reached 56% by HPLC detection. This further proved that Sphingomonas could mediate A. gossypii resistance to imidacloprid by hydroxylation and nitroreduction.ConclusionsOur findings suggest that the gut symbiont Sphingomonas, with detoxification properties, could offer an opportunity for insect pests to metabolize imidacloprid. These findings enriched our knowledge of mechanisms of insecticide resistance and provided new symbiont-based strategies for control of insecticide-resistant insect pests with high Sphingomonas abundance.

Ecotoxicological impacts of metals in single and co-exposure on mussels: Comparison of observable and predicted results

Used in high-tech and everyday products, mercury (Hg), cobalt (Co), and nickel (Ni) are known to be persistent and potentially toxic elements that pose a serious threat to the most vulnerable ecosystems. Despite being on the Priority Hazardous Substances List, existing studies have only assessed the individual toxicity of Co, Ni and Hg in aquatic organisms, with a focus on the latter, ignoring potential synergistic effects that may occur in real-world contamination scenarios. The present study evaluated the responses of the mussel Mytilus galloprovincialis, recognized as a good bioindicator of pollution, after exposure to Hg (25 μg/L), Co (200 μg/L) and Ni (200 μg/L) individually, and to the mixture of the three metals at the same concentration. The exposure lasted 28 days at 17 ± 1 °C, after which metal accumulation and a set of biomarkers related to organisms' metabolic capacity and oxidative status were measured. The results showed that the mussels could accumulate metals in both single- and co-exposure conditions (bioconcentration factors between 115 and 808) and that exposure to metals induced the activation of antioxidant enzymes. Although Hg concentration in organisms in the mixture decreased significantly compared to single exposure (9.4 ± 0.8 vs 21 ± 0.7 mg/kg), the negative effects increased in the mixture of the three elements, resulting in depletion of energy reserves, activation of antioxidants and detoxification enzymes, and cellular damage, with a hormesis response pattern. This study underscores the importance of risk assessment studies that include the effects of the combination of pollutants and demonstrates the limitations of applying models to predict metal mixture toxicity, especially when a hormesis response is given by the organisms.

Effects of Honeysuckle Varieties on Protective and Detoxifying Enzyme Activities in Heterolocha Jinyinhuaphaga Chu (Lepidoptera: Geometridae) Larvae.

Investigating the effects of various host plants on protective and detoxifying enzyme activities in insects could provide insights into the adaptation mechanisms of insects to host plants. In the present study, we measured superoxide dismutase (SOD), peroxidase (POD), catalase(CAT), carboxylesterase(CarE), acetylcholinesterase (AchE), and glutathione S-transferase (GST) activity levels in Heterolocha jinyinhuaphaga Chu (Lepidoptera: Geometridae) larvae fed on four honeysuckle varieties (wild variety, Jiufeng 1, Xiangshui 1, and Xiangshui 2). The results showed that levels of SOD, POD, CAT, CarE, AchE, and GST activities in H. jinyinhuaphaga larvae fed on the four honeysuckle varieties differed. The enzyme activity levels were the highest when larvae were fed on the wild variety, followed by Jiufeng 1 and Xiangshui 2, and the lowest when fed on Xiangshui 1. Furthermore, the enzyme activity levels increased with an increase in larval age. According to the results of two - way analysis of variance, the interaction between host plants and larval age had no significant effect on SOD, POD, CAT, CarE, AchE, and GST activities in H. jinyinhuaphaga larvae (p ˃0.05).

Monitoring Resistance and Biochemical Studies of Three Egyptian Field Strains of Spodoptera littoralis (Lepidoptera: Noctuidae) to Six Insecticides

Spodoptera littoralis (Boisd.) is a prominent agricultural insect pest that has developed resistance to a variety of insecticide classes. In this study, the resistance of three field strains of S. littoralis, collected over three consecutive seasons (2018 to 2020) from three Egyptian Governorates (El-Fayoum, Behera and Kafr El-Shiekh), to six insecticides was monitored. Laboratory bioassays were carried out using the leaf-dipping method to examine the susceptibility of the laboratory and field strains to the tested insecticides. Activities of detoxification enzymes were determined in an attempt to identify resistance mechanisms. The results showed that LC50 values of the field strains ranged from 0.0089 to 132.24 mg/L, and the corresponding resistance ratio (RR) ranged from 0.17 to 4.13-fold compared with the susceptible strain. Notably, low resistance developed to spinosad in all field strains, and very low resistance developed to alpha-cypermethrin and chlorpyrifos. On the other hand, no resistance developed to methomyl, hexaflumeron or Bacillus thuringiensis. The determination of detoxification enzymes, including carboxylesterases (α- and β-esterase), mixed function oxidase (MFO) and glutathione-S-transferase (GST), or the target site of acetylcholinesterase (AChE), revealed that the three field strains had significantly different activity levels compared with the susceptible strain. Our findings, along with other tactics, are expected to help with the resistance management of S. littoralis in Egypt.