LC50 Concentration Research Articles

Toxicity, antifeedant and physiological effects of trans-anethole against Hyphantria cunea Drury (Lep: Arctiidae)

Plant secondary metabolites are currently known to interfere with basic metabolic, behavioral and physiological processes of insects. In the current study, the biological and physiological effects of trans-anethole were investigated against Hyphantria cunea Drury. The bioassay data demonstrated the high toxicity of trans-anethole against the fourth-instar larvae with the LC30, LC50 and LC90 values of 0.72, 1.41 and 7.20 μL/mL, respectively. Also the concentrations of LC30 and LC50 showed 53 and 87% feeding deterrency against the larvae. The biochemical experiments revealed that oral exposure of trans-anethole decreased the activities of digestive enzymes, acetylcholinesterase and the contents of energy reserves while, it induced the activities of detoxifying and antioxidant enzymes compared to control. In fact, trans-anethole induced the inhibition of digestion and AChE activities accompanied by imbalance in metabolic and oxidative processes so it may be recommended as a potent biopesticide in control of H. cunea populations.

Sublethal Effects of Three Insecticides on Development and Reproduction of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Spodoptera frugiperda is a serious invasive pest, which has attracted attention globally in recent years. Research on the sublethal effects of common insecticides on S. frugiperda is important for its comprehensive management in the field. In this paper, the sublethal effects have been studied for S. frugiperda exposed to the LC30 concentration of three insecticides, chlorantraniliprole, dinotefuran, and beta-cypermethrin. The results showed that the pupation rates of the treatment groups were significantly lower than that of control group, but there were no significant differences in the eclosion rate. Chlorantraniliprole and beta-cypermethrin significantly inhibited fecundity of the F0 and F1 generations, and the number of eggs laid per female decreased by 67.4% and 43.1%, respectively, and that of the F1 generation decreased by 28.0% and 21.7%, respectively. The intrinsic growth rate (rm), net growth rate (R0), and weekly growth rate (λ) of the F0 generation in the chlorantraniliprole and beta-cypermethrin treatment groups were significantly lower than those in the control group. Additionally, dinotefuran had a certain role in promoting oviposition in the F0 and F1 generations, which may stimulate the growth of offspring population and cause the resurgence of pests. The results provide a reference for the effective implementation of the IPM plan in the field to control S. frugiperda.

Differences in the Sublethal Effects of Sulfoxaflor and Acetamiprid on the Aphis gossypii Glover (Homoptera: Aphididae) Are Related to Its Basic Sensitivity Level.

Simple SummaryThe sublethal effects of insecticides are not only environmentally risky to arthropods but may also promote resistance evolution. Sublethal effects are influenced by factors such as the type of insecticide, sublethal concentration, and type of pest. This study evaluated the sublethal effects of sulfoxaflor and acetamiprid on two field cotton aphid (Aphis gossypii) populations with different genetic backgrounds. For acetamiprid, a significant negative sublethal effect of an LC25 concentration of acetamiprid on longevity and fecundity was observed in the F0 generation of Jinghe, and a significant negative sublethal effect occurred in the F1 and F2 generations of Yarkant, some biological traits of which were significantly degraded. However, in terms of biological traits, significant stimulative sublethal effects of an LC25 concentration of sulfoxaflor were observed in the F0 generation of Jinghe and the F1 generation of Yarkant. These experimental results demonstrate that sulfoxaflor and acetamiprid have different sublethal effects on A. gossypii that vary depending on the generation. Moreover, the sublethal effects of an insecticide may be influenced by the genetic background and resistance levels of A. gossypii. Our findings are useful for assessing the overall effects of sulfoxaflor and acetamiprid on A. gossypii.The cotton aphid, Aphis gossypii, is an important insect pest of many crops around the world, and it has developed resistance to a large number of frequently used insecticides. The sublethal effects of insecticides not only have an environmental risk to arthropods but also have the potential to promote resistance evolution. The sublethal effects (inhibitory or stimulatory) are influenced by many factors, such as the type of insecticide, sublethal concentrations, pest species, and others. In this study, the sublethal effects of sulfoxaflor and acetamiprid on A. gossypii were compared using two field-collected populations. The results show that sulfoxaflor was more toxic than acetamiprid against A. gossypii in both populations, the LC50 concentrations of acetamiprid and sulfoxaflor were 6.35 and 3.26 times higher, respectively, for the Jinghe population than for Yarkant. The LC25 concentration of acetamiprid significantly reduced adult longevity and fecundity in exposed adults (F0) of the Jinghe population, but it had no significant effects on these factors in Yarkant. Similar inhibitory effects were found in the F1 and F2 generations, but the biological traits in the Yarkant population were significantly reduced when the parents (F0) were exposed to LC25 of acetamiprid, whereas the changes in the Jinghe population were not significant. However, sublethal sulfoxaflor showed a stimulatory effect on A. gossypii in the F0 and F1 generation; the adult fecundity and longevity of the F0 generation were significantly higher in Jinghe, while the biological traits of the F1 generation were obviously higher in Yarkant. In the F2 generation, the r and λ were significantly higher in Jinghe; meanwhile, these biological traits were reduced in Yarkant. These results indicate that sulfoxaflor and acetamiprid had different sublethal effects on A. gossypii that varied by generation. In addition, we speculate that the genetic background and the resistance levels of A. gossypii may also influence the sublethal effects. Our findings are useful for assessing the overall effects of sulfoxaflor and acetamiprid on A. gossypii.

Evaluation of oxidative stress biomarkers in Pila virens exposed to spinel Co3O4 nanoparticles

Cobalt oxide nanoparticles (Co3O4NPs) are used in various devices including magnetic and energy storage, sensors, pigments, and catalysts, thereby imparting enhanced production and use. The current work aims to investigate on the toxicity of Co3O4NPs on fresh water edible snail Pila virens (P. virens). A total of ten P. virens were chosen for acute toxicity studies (96 h) and the lethal concentration (LC50) for Co3O4NPs was found to be 509.45 µg/L. Based on the LC50 value P. virens was exposed to ½ (254 µg/L) and ¼ (127 µg/L) of LC50 concentration for 24 h. The current findings revealed that an increase in lipid peroxidation, catalase, glutathione sulfotransferase, and reduction in reduced glutathione and glutathione peroxidase activity in P. virens upon exposure to 127 and 254 µg/L concentration of Co3O4NPs for 24 h. The Co3O4NPs induced toxicity in fresh water snail P. virens via oxidative stress. P. virens fits as the best organism for the toxicological assessment of Co3O4NPs contaminating the environment.

To each their own: Disparate abilities of Nrf2 activators to protect against various electrophilic and oxidative insults

Electrophilic and oxidative stress contribute to major diseases such as cancer and diabetes. Small‐molecule activators of the Nrf2 cytoprotective pathway show significant promise for prevention and amelioration of chronic diseases by combating these stressors through upregulation of detoxification and antioxidant enzymes. An understudied area is whether distinct small molecular Nrf2 activators can protect cells from all electrophilic and oxidative stressors, or whether certain molecules are better suited to protect against a particular type of stress.In this study, human keratinocyte HaCaT cells were preincubated for 24 h with one of four Nrf2 activators before different stressors were added for an additional 24 h and cell death was assessed. Three electrophiles were tested: sulforaphane (SFN), the subject of over 70 clinical trials, the multiple sclerosis drug Tecfidera (dimethyl fumarate, DMF), and bardoxolone methyl (BARD), in clinical trials for treatment of chronic kidney diseases and other conditions including COVID‐19. SFN, DMF, and BARD target C151 of the Keap1 protein, a negative regulator of Nrf2. Also tested was KI696, an inhibitor of the Keap1‐Nrf2 interaction. Three chemically distinct stressors—hydrogen peroxide, menadione (a quinone that rapidly generates ROS through one‐electron redox cycling), or chlorambucil (an alkylating chemotherapy agent)—were tested. Stressors were added to the cells at their LC50 concentration after pretreatment with a range of cytoprotective compound concentrations. Unexpectedly, SFN pretreatment showed little to no rescue for all stressors. However, DMF rescued the viability of cells stressed with hydrogen peroxide, menadione, and chlorambucil. BARD showed no rescue for hydrogen peroxide‐treated cells. KI696 improved the cell’s ability to survive chlorambucil. The ability of a given Nrf2 activator (or lack thereof) to protect against a given stressor points to a need to better understand the cytoprotective environment (specific enzymes upregulated, glutathione levels, etc.) that best protect against specific stressors.

Bio-efficacy of Karu Nochi, Vitex negundo L. (Lamiaceae) against the dengue vector, Aedes aegypti (L.)

The dengue vector, Aedes aegypti (L.) is one of the world's deadliest species and it spreads diseases like Zika, chikungunya, dengue, and yellow fever. In this present investigation, we attempt to evaluate the larvicidal toxicity of different solvent extracts and essential oil of Karunochi, Vitex negundo (L.) on third instar larvae of the dengue vector, A. aegypti. The crude extracts were prepared by using soxhlet apparatus and rotary vacuum evaporator technique. The highest mortality was observed in essential oil and ethanolic extract followed by hexane and acetone extracts, the lethal concentrations LC50 (LC90) values were obtained from noticed, for Vn-EO- 218.46 (517.10), Vn-EE 268.37 (592.56), Vn-HE 309.59 (667.33), and Vn-AE 327.88 (748.47), respectively and nil mortality observed in the control treatment. Karunochi, V. negundo essential oil, and ethanolic extract (Vn-EE) were more efficient against A. aegypti than crude extracts of Vn-AE (acetone) and Vn-HE (hexane). Therefore, from our studies the formulations are promising for a low-cost larvicide without isolating an active ingredient, EO’s were tested. The goal of this study is to promote the use of plant-based larvicides in public health programmes.

Effects of the extract and the essential oil of Allium sativum on tea mealy bug, Pseudococcus viburni Sigornet (Hemiptera: Pseudococcidae)

The effects of methanolic extract (ME) and essential oil (EO) of garlic were studied on the third-instar nymphs of Pseudococcus viburni Signoret to elucidate whether garlic essential oil and extract may cause mortality on tea mealybug and physiological disorders. The nymphs exposed to ME showed the LC50 values of 0.33 and 0.12% after 24 and 48 h while those were 0.42 and 0.31% in case of EO. The ED50 values of ME and EO were calculated to be 0.31 and 0.22%, respectively. The LC50 concentrations of Garlic ME and EO significantly increased the activities of general esterase and glutathione S-transferase. Meanwhile, treating P. viburni nymphs by ME and EO significantly increased the activities of aspartate- and alanine aminotransferases as well as ɤ-glutamyl transferase compared to control. The lower activity of lactate dehydrogenase was recorded in the nymphs treated by ME and EO compared to control but the significant increase of acid- and alkaline phosphatase activities was found in the nymphs treated by ME and EO, respectively. Finally, garlic ME and EO significantly decreased the content of protein and glycogen as storage macromolecules compared to control. Our results demonstrated garlic metabolites imposed significant mortality on the nymphs of P. viburni and prominently caused discrepancies in the physiological processes.

Efficacy of cumin ( Cuminum cyminum ) and lavender ( Lavandula angustifolia ) essential oils as anaesthesics in common carp ( Cyprinus carpio L.1758)

In this study, anaesthetic effects of cumin and lavender essential oils by comparing with clove oil were determined on common carp. Fish (mean weight of 10 g) were exposed to nine concentrations of essential oils (5–500 mg L−1). Anaesthesia induction, recovery times and mean lethal dose of essential oils (10 min LC50 concentration) were evaluated separately for each fish. In addition, histopathological effects of essential oils on the fish tissues including hepatopancreas, gill and skin were investigated. The results showed that when the dose of essential oils increased, the time to anaesthesia induction was shortened and the time to recovery from anaesthesia was prolonged. Cumin essential oil at 300 mg L−1 dose and lavender oil at 400 mg L−1 dose on common carp showed similar anaesthetic effects (sedative and deep anaesthesia) to clove oil (p > .05). At these concentrations, sedative (Stage 2) and deep anaesthesia (Stage 4) induction times were 105 and 187.5 s for cumin and 94 and 194 s for lavender respectively. Recovery times at these concentrations were 415 s for cumin and 477.5 s for lavender. Mean lethal dose of essential oils for carp were found as 450 mg L−1 for cumin oil and 500 mg L−1 for lavender oil. Histopathological examination revealed no lesion in gill, skin and hepatopancreas in essential oils group. In the light of these findings, it was determined that lavender and cumin oils can be used as effective and safe anaesthetic in common carp.

Assessment of the impact of green synthesized copper nanoparticles on freshwater snails (Indoplanorbis exustus) in comparison with field-control and lab-control snails

BackgroundNanomaterials are used extensively because of their optical, electrical, catalytic, and mechanical properties. To understand the biological processes in an experimental organism, we aimed to highlight the comparative results obtained in the field-control, lab-control, and experimental freshwater snails (Indoplanorbis exustus). Terminalia arjuna bark extract was used for the synthesis of CuNPs and for characterization SEM, XRD, and FTIR techniques were used.ResultsThe estimated LC50 concentration for 96 h was to be 9.97 mg/L, thereafter animals were exposed further for 14 days to sub-lethal concentrations: 1/7th (1.42 mg/L), 1/5th (1.99 mg/L), 1/3rd (3.32 mg/L), and 1/2nd (4.98 mg/L). The data collected after conducting experiments on snails in the laboratory varied from the field-control snails. For comparison, the protein profile of field-control, lab-control, and experimental animals were displayed using sodium dodecyl sulfate–polyacrylamide gel electrophoresis and then compared based on molecular masses. The bacterial isolates obtained were all belonging to streptococcus family. All isolates were Gram-positive and catalase-negative. A significant increase in bioaccumulation of CuNPs and dose-dependent necrosis was observed after 14 days.ConclusionsThe results obtained from the field control animals were different from those obtained in the lab control and experimental groups upon exposure to increasing concentration of CuNPs for 14 days.

Cytotoxic Effect of Cypermethrin and Neem Extract on Human Lymphocytes

There is a need to increase our agricultural production of food grains and other crops to feed a continuously increasing population. To achieve this food security, use of insecticides/pesticides has become necessary. Cypermethrin is a pyrethroid insecticide used for control of pests of cereals, fruits, vegetables and cotton etc. but it has several toxic effects on human beings. Apart from being neurotoxic, it has harmful effects on lymphocytes also. Neem is also a potent insecticide of herbal and indigenous origin. In this investigation the cytotoxicity of cypermethrin (dissolved in DMSO) and aqueous extract of neem leaves to human lymphocytes was studied by MTT assay. It was found that after an exposure of two hours to LC50 concentration of cypermethrin viability of lymphocytes fell to 87.83%; however at lower concentration the viability fell further because of the increase in the DMSO concentration, proving the toxicity of DMSO. Treatment of lymphocytes with 45% of neem extract increased the viability by 196% but at lower concentrations lesser increase was noted due to the increase in concentration of PBS. Thus apart from being a safe insecticide neem extract can be used to promote viability and proliferation of cells of animal origin also.

Effects of pyroligneous acid on life history and physiology of two pyralid pests of stored products

Natural products derived from plant materials, such as wood vinegar (pyroligneous acid; PA), have shown toxicity to insects in previous studies; however, the impact of this substance on physiology and life history of stored product insects is unknown. Thus, the current study aimed to determine the effects of PA on two prominent stored product moths, Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). LC50/24h values of PA were determined for both species and first instar larvae were fed on an artificial diet containing LC50 concentrations of PA for their entire life cycle. Final instar larvae were selected for biochemical analysis while life history parameters were assayed in female adults that emerged from treated larvae. In both species, significantly lower activities of digestive enzymes (α-amylase, protease, and lipase) and detoxifying enzymes (carboxylesterase, monooxygenase cytochrome P450, and glutathione S-transferase) were observed in treated larvae relative to untreated larvae. In contrast, antioxidant enzyme activities (superoxide dismutase, phenoloxidase, and ascorbate peroxidase) were significantly elevated in treated larvae compare to controls in both species. Moreover, larvae of both species tended to have lower levels of energy reserves, such as proteins, lipids, and carbohydrates, and adults exhibited reduced longevity, fecundity, and oviposition periods in comparison to untreated larvae. Finally, GC-MS analysis of the PA used for this study demonstrated that phenolic compounds and organic acids were the largest constituents. These results indicate that consumption of PA leads to the induction of to the antioxidant system, the inhibition of detoxification and digestion enzyme activities as well as reduced levels of energy reserves. Cumulatively, these effects resulted in reduced longevity and fecundity compared to control insects. This study expands our knowledge of the impacts of PA on physiology and life history for two prominent pests of stored products.

PENGARUH EKSTRAK DAUN BINTARO (CERBERA ODOLLAM GAERTN) TERHADAP MORTALITAS LALAT RUMAH (MUSCA DOMESTICA LINNAEUS)

House flies are a species that can be found in the environment and play a role in health problems. The use of plant-based insecticide is an alternative to reduce the negative impact of chemical insecticides. One of them is by using bintaro leaf extract. This study aims to determine the effect of giving various concentrations of bintaro leaf extract on the mortality of house flies. This type of research is experimental research design with Posttest Only Control Group Design. The parameter observed was the LC50 mortality of house flies with probit regression analysis. The sample in this study were as many as 1200 adult-stage house flies caught from TPA Jatibarang Semarang The results showed that the LC50 concentration of Bintaro leaf extract was 86%. Based on the one-way Anova test, it is known that p value = 0.001 (p <0.05) means that there is a significant difference between the mortality of flies for each concentration of Bintaro leaf extract From this research it can be concluded that Bintaro leaf extract has the power to kill house flies as adults. Researchers suggest that further research is needed on the use of Bintaro leaf extract using other methods, as well as on other vectors that act as vectors of disease.

Evaluation of toxic effect of insecticide, herbicide and fungicide as single and mixture on Gammarus lacustris using biochemical markers

ABSTRACT In the present study, the acute toxic effects of single, double, and triple mixtures of imidacloprid, azoxystrobin, and glyphosate on Gammarus lacustris were investigated. Initially, the 96-hour median lethal dose (LC50) values for imidacloprid, azoxystrobin, and glyphosate were determined as 157, 1.92, and 4.33 mg L−1, respectively. The animals were exposed to one-fiftieth of the 96-h LC50 concentration for 24 or 96 h. The activity of glutathione S-transferase (GST), glutathione reductase, acetylcholinesterase, carboxylesterase (CaE), and superoxide dismutase enzymes as biological markers were examined to determine the non-lethal effects of the pesticides tested. Significant changes were observed in GST and CaE activities especially in detoxification compared to control and between different applications. The results of this study show the potential for increased toxicity in organisms exposed to pesticide mixtures.

Respiratory response of Cirrhinus mrigala (Hamilton, 1822) fingerlings exposed to sub lethal concentration of Fenvalerate

Pesticides are toxic to aquatic fauna, which form significant components of the food chain. In this study to estimate, the lethal concentration LC50 of fenvalerate and sub-lethal concentration of Fenvalerate on the respiratory metabolism of Cirrhinus mrigala fingerlings was recorded in laboratory condition. The median lethal concentration of fenvalerate was estimated, by exposing different concentration such as 0.01, 0.05, 0.1, 0.15 and 0.2 ppm of fenvalerate. The profit analysis, it was estimated that the LC50 value for 96 hrs for the pesticide fenvalerate was calculated as 0.025 ppm. The rate of oxygen consumption increased from 0.44 mg/g/hrs to 0.67 mg/g/hrs. When the partial pressure increase from 80 to 100 (mm/hg) in the exposed to 0.00083 ppm. The rate of oxygen consumption shoots us in 0.00083 and 0.00125 ppm concentration of fenvalarate, when compared with control. In the present investigation, the decline of oxygen consumption was observed in the subsequence exposure of Fenvalerate.

Evaluating the effect of acute ammonia toxicity in a freshwater ecological environment on the growth and hematological functioning of Clarias gariepinus

Abstract This study was carried out to evaluate the effect of ammonia toxicity on the growth and hematology of Clarias gariepinus. The mean weight gain of fish 1.52 ± 0.3 g was investigated under laboratory conditions at static bioassay for 96 h and 14 days, respectively. Five treatments of 96 h median lethal concentration LC50 were used, namely, T0 (0.00 g·l−1), T1 (0.40 g·l−1), T2 (0.60 g·l−1), T3 (0.80 g·l−1) and T4 (1.00 g·l−1), and each of these treatment concentrations was replicated three times for both toxicity exposures. The results clearly revealed that 96 h median lethal concentration (LC50) at treatments T4 (4.00), T3 (3.00), T2 (2.00) and T0 (0.00) g·l−1 gave an average mean value of 3.02 ± 0.02 g·l−1 with upper and lower limits of 6.28 and 1.42 g·l−1, respectively. The overall percentage mortality showed more than 71% of fish mortality at T4. Values for the 14-day sub-acute exposures to ammonia concentrations of T4 (1.00), T3 (0.80), T2 (0.60) and control (0.00) g·l−1 were also obtained. Growth indices indicated significant decreases (P<0.05) in the total feed intake (TFI), specific growth rate (SGR), mean weight gain and food conversion ratio (FCR) compared with the control.

Persistent susceptibility of Aedes aegypti to eugenol

Botanical insecticides are preferred for their environment and user-friendly nature. Eugenol is a plant-based monoterpene having multifarious biocidal activities. To understand whether eugenol would persistently work against Aedes aegypti, we performed larvicidal bioassays on thirty successive generations and determined median lethal concentration (LC50) on each generation. Results showed no apparent differences between LC50 at F0 (63.48 ppm) and F30 (64.50 ppm) indicating no alteration of susceptibility toward eugenol. To analyze, if eugenol has any effect on metabolic detoxification-associated enzymes, we measured esterases (alpha and beta), cytochrome P450, and GST activities from the survived larvae exposed to LC50 concentration from F0–F30. Results revealed a decrease of esterases, GST, and cytochrome P450 activities at the initial 4–8 generations and then a gradual increase as the generations progressed. GST activity remained significantly below the control groups. Synergists (TPP, DEM, and PBO) were applied along with eugenol at F30 and LC50 concentration, and the said enzyme activities were recorded. Results showed a noticeable decrease in LC50 and enzyme activities indicating effective inhibitions of the respective enzymes. Overall, present results inferred that eugenol would effectively work as a larvicide for a longer period in successive generations without initiating rapid resistance and therefore could be advocated for controlling A. aegypti.

Ultrastructural studies of photoreceptor cell degeneration with organophosphate and its regeneration in Cyprinus carpio communis L.

Organophosphates are highly neurotoxic to aquatic fauna if they enter the water bodies as runoff, thus affecting the nervous system of the fishes. The present study was undertaken to investigate the vision changes, especially on the photoreceptor layer of the retina, of Cyprinus carpio communis L. when exposed to monocrotophos, an organophosphate. Fish were exposed to three sub-lethal concentrations of LC50, i.e. 0.038 ppm (1/10 LC50), 0.062 ppm (1/6 LC50), and 0.126 ppm (1/3 LC50), to observe the changes in the photoreceptor cells at the behavioral, histopathological and ultrastructural levels. Further, acetylcholinesterase activity was also evaluated. Behavioral changes, such as long resting period, inactivity, increase in air gulps and decrease in opercular and fin movements, were observed. A semi-quantitative analysis of the histological sections showed shrinkage in retinal layers at 0.038 ppm concentration of monocrotophos. At 0.062 ppm, the disappearance of the outer nuclear layer was observed and at the highest concentration of 0.126 ppm, damage in all retinal layers involving necrosis of the outer segment of the photoreceptor cells was observed. Further, at the ultrastructural level, detachment of photoreceptor cells and damage in the inner and outer segments of the photoreceptors were observed in an increasing dose-dependent manner. A reduction in the acetylcholinesterase level was observed in the treated groups. The treated fish were then transferred to toxicant-free water for 60 days to study self-regeneration, but no regeneration was observed in photoreceptor cells of the fish retina. This study shows that exposure to of monocrotophos effectively damages and disturbs the functioning of photoreceptor cells of retina of C. carpio communis L., thus affecting its vision.

Spinosyns Delivered in Sugar Meals to Aedes aegypti and Aedes albopictus (Diptera: Culicidae): Acute Toxicity and Subacute Effects on Survival, Fecundity, and Fertility.

Sugar is an essential source of nutrition for adult mosquitoes to acquire energy. Toxic sugar bait (TSB) provides a promising method for mosquito control by incorporating toxins into artificial sources of sugar (i.e., toxic baits) presented to wild populations. Spinosyns comprise a family of bacterial secondary metabolites with a unique mode of action against the insect nervous system, an appealing environmental safety profile, and potential for incorporation into sugar baits. This research evaluated acute and subacute effects of spinosad (spinosyns A and D) and spinetoram (spinosyns J and L) in sugar meals on survival, fecundity, and fertility of Aedes aegypti and Aedes albopictus. Acute toxicity of spinosyns doubled from 24 to 48 h of assessment, revealing a relatively slow and cumulative action of the formulated spinosyns. Median lethal concentrations at 48 h were lower for spinetoram than for spinosad, lower for Ae. albopictus than Ae. aegypti, and lower for males than females. When exposed to subacute LC50 concentrations of spinosad and spinetoram for 24 h, survival of males and females of both species was diminished compared with controls, fecundity of females was increased, but fertility as measured by hatch rate of eggs was decreased. The formulations may have increased the nutritive value of the sugar meals thereby boosting fecundity, while toxifying embryos, reducing fertility. The inclusion of subacute effects of spinosyns allows assessment of the broader consequences of TSB for adult mosquito control.

Effect of Entamopathogenic fungus, Nomuraea rileyi on the Larval Protein Patterns and Proteases Activity of Helicoverpa armigera (Hubner)

The Helicoverpa armigera is one of the most serious polyphagus pest of many economically important crops. Nomuraea rileyi is an effective entomopathogenic fungus for the control of H. armigera has several advantages over other synthetic insecticide. N. rileyi LC50 concentration of 1.97×106 spores/ml was applied to the 4 th larval instar of H. armigera to investigate their impacts on the total protein and protease activity of body homogenate. Moreover, qualitative analysis of proteins in healthy developmental stages of H. armigera larvae and in N. rileyi treated larvae was detected using SDS-PAGE. The present investigation reported that there was difference in SDS-protein bands of control untreated and treated groups. The SDS-PAGE analysis of total body homogenate demonstrated that the few of proteins get under regulated upon treatment with N. rileyi. The quantitative analysis of total protein content and proteolytic activity was done. The H. armigera larvae upon treatment with N. rileyi produced significant decrease (p<0.05) in the total protein content of larval body while the proteases activity increased (p<0.05) significantly in N. rileyi treated larvae than the control larvae. The data of present findings help to understand a part how N. rileyi be effective in controlling H. armigera.

Isolation and evaluation of Heterorhabditis bacteriophora strain-s26 as biocontrol agents against Pieris brassicae L. under laboratory conditions

Entomopathogenic nematodes (EPNs) as bio-control have been reported as conventional and intensified method in insect pest management. In the present investigation, a survey was carried out in district Sirmaur to detect the presence of EPNs. In total, 110 soil samples were collected from the rhizospheric soil of fruit plantations and among them 35 samples possess EPNs. Based on morphological analysis, all the isolated EPNs were identified as Heterorhabditis bacteriophora. The insecticidal potential of local isolate of EPN H. bacteriophora strain EUPT-S26 was evaluated against two different larval instars (3rd and 4th instars) of Pieris brassicae (cabbage butterfly) under the laboratory conditions. Different concentrations of nematode inoculums @ 30 infective juveniles (IJs), 60 IJs, 90 IJs, 120 IJs and 150 IJs/ml along with control were applied against both the instars. The rate of pathogenicity was recorded upto 96 h. It was observed that both the instars of P. brassicae were highly susceptible for H. bacteriophora strain EUPT-S26 infection. The inoculum level of 150 IJs was causing highest mortality to both 3rd and 4th larval instars at 96 h of exposure. The data recorded from the present study shows lethal concentration LC50=29.13 IJs (95% FL=21.92–38.71) in 3rd instars and LC50=21.62 IJs (95% FL=16.06–29.10) against 4th instar larvae after 96 h of nematodes exposure. It was concluded from the present investigation, that the local isolates of H. bacteriophora strain EUPT-S26 showed significant mortality among both the larval instars that keeps on enhanced with the increase in nematode inoculum concentration and exposure time. Further studies are required to explore their insecticidal potential against other insect pests in the field condition also.