Sublethal Concentrations Of Imidacloprid Research Articles

Mating behavior and responses to sublethal concentrations of imidacloprid in the predator Cyrtorhinus lividipennis.

Mating is an essential factor that governs the size of insect populations that reproduce sexually. The extensive application of insecticides has both lethal and sublethal effects on the physiology and mating behavior of insect natural enemies. The predatory bug Cyrtorhinus lividipennis is a natural enemy of planthopper and leafhopper populations in the rice ecosystem. Unfortunately, the effects of insecticides on the mating behavior of C. lividipennis are not well-understood. The mating behavior of C. livdipennis consisted of mounting, antennal touch and mating attempts, genital insertion, adjustment of posture, and separation of the mating pair. Approximately 82.5% of the C. lividipennis mating pairs displayed their first mating at 12-36 h postemergence. Mating activity occurred throughout a 24-h period, with peak activity at 12:00-14:00 h, and the mean duration of mating was 48.75 min. Sublethal exposure to imidacloprid increased mating latency. Compared with the controls, the duration of courtship, pre-mating and adjusting posture for males treated with imidacloprid were prolonged. The duration of mating for females treated with imidacloprid was prolonged relative to untreated controls. The fecundity and daily spawning capacity of females treated with imidacloprid were higher than the untreated controls. Our results provide insight into the mating process of C. lividipennis. Imidacloprid prolonged the duration of mating, which may explain the enhanced reproductive output in C. lividipennis females treated with imidacloprid. These findings will be useful in both rearing C. lividipennis and deploying this natural enemy in rice fields. © 2024 Society of Chemical Industry.

Novel Reproduction Toxicity Test Method for Hyalella azteca Using Sexually Mature Amphipods Provides More Robust Data Than Standard Methods in Exposures to Imidacloprid.

Hyalella azteca is an epibenthic crustacean used in ecotoxicology, but there are challenges associated with standard methods using reproduction as an endpoint. A novel, 28-day reproduction toxicity test method for H. azteca was created to address these issues by initiating tests with sexually mature amphipods to eliminate the confounding effects of growth, using a sex ratio of seven females to three males to reduce reproductive variability, and conducting tests in water-only conditions to make recovery of juveniles easier and expand testing capabilities to water-soluble compounds. In the present study, we evaluated the 28-day novel method by comparing it with the 42-day standard test method in duplicate and parallel water-only, static-renewal exposures to sublethal concentrations of imidacloprid (0.5-8 µg/L). Both methods showed similar effects on survival, with survival approaching 50% in the highest test concentration (8 µg/L). However, the 42-day median effect concentrations (EC50s) for growth were more sensitive in the standard method (1.5-3.2 µg/L) compared with the 28-day EC50s generated by the novel method (>8 µg/L). Reproduction endpoints (juveniles/female) produced similar EC50s between methods, but the data were less variable in novel tests (smaller coefficients of variation); therefore, fewer replicates would be required to detect effects on reproduction compared with the standard method. In addition, novel tests generated 28 days of reproduction data compared with 14 days using standard tests and allowed survival and growth of sexes to be assessed independently. Thus, the novel method shows promise to improve the use of reproduction as an endpoint in water-only toxicity tests with H. azteca. Environ Toxicol Chem 2024;43:723-735. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Exposure to Imidacloprid under variable conditions disturbs the muscle fatty acid profile of a fresh water non target fish: Labeo rohita

Economy of Pakistan is heavily dependent upon agriculture and extensive use of pesticide is quiet common to enhance the crop yield. Imidacloprid is among the first choice pesticides in Pakistan and it has been reported that through run off along with water it ends up in water bodies affecting non target aquatic fauna. Through the present investigation, we are reporting the effects of Imidacloprid on the fatty acids composition of a non-target, commercially important carp: Labeo rohita. Fish were exposed to sub lethal concentration of Imidacloprid (120 mgL1) for 2, 4 and 8 days (short term) as well as for 16, 32 and 64 days (long term experimental conditions). Pesticide untreated controls were also maintained for each treatment. Following the specific Imidacloprid exposure, fatty acid composition (%) was determined in the muscle of all experimental groups by using gas chromatography. Fish exposed to Imidacloprid for 8 days had reduced Palmitic acid (p = 0.02) and elevated muscle Arachidic acid (p < 0.001) than control group. Labeo rohita exposed to the pesticide for 32 days had elevated muscle Oleic (p = 0.02) and Linoleic acid (p = 0.02) while fish exposed to Imidacloprid to 64 days had reduced muscle Palmitic (p = 0.04) and Oleic acid (p = 0.03). In conclusion, we are reporting that the exposure to sub lethal concentration of Imidacloprid disturb the muscle fatty acid composition of Labeo rohita that may affect its food quality. The effects were more pronounced under long term experimental conditions and were probably due to potentiating lipid peroxidation and disturbed fish metabolism upon Imidacloprid exposure.

Feeding behavior and hormoligosis associated with imidacloprid resistance in Asian citrus psyllid, Diaphorina citri

AbstractImidacloprid is a neonicotinoid insecticide used for managing the Asian citrus psyllid, Diaphorina citri Kuwayama, which serves as vector of phytopathogens causing citrus greening. However, development of resistance to neonicotinoids among populations of D. citri has coincided with occasional control failures in the field. The objectives of this research were to (1) survey current levels of imidacloprid resistance in Florida citrus; (2) compare feeding behavior between imidacloprid‐resistant and susceptible D. citri using electrical penetration graph recordings, and (3) investigate the possible amplification of insecticide hormoligosis associated with resistance. Field surveys confirmed that the susceptibility of D. citri populations to imidacloprid has decreased in commercial Florida citrus groves compared with a laboratory‐susceptible population. Following 12 generations of selection, resistance to imidacloprid increased by 438 fold compared with the susceptible strain. Imidacloprid‐susceptible D. citri feeding on citrus exhibited significantly more bouts associated with intercellular pathway (C), phloem penetration (D), phloem salivation (E1), and nonprobing (Np) activities than imidacloprid‐resistant counterparts. However, there were no differences observed in the frequency or duration of phloem ingestion or xylem feeding between susceptible and resistant D. citri. There was no statistical difference in fecundity between resistant and susceptible strains. However, the fecundity of imidacloprid‐susceptible female D. citri treated with a sublethal concentration of imidacloprid (LC25) increased significantly compared with controls, while such hormoligosis was less pronounced among imidacloprid‐resistant psyllids. Our results suggest that imidacloprid‐resistant psyllids may cease feeding sooner than susceptible counterparts following sublethal exposure to this insecticide, indicative of a behavioral resistance mechanism.

Exposure to sublethal concentrations of imidacloprid, pyraclostrobin, and glyphosate harm the behavior and fat body cells of the stingless bee Scaptotrigona postica

Pesticide use in agriculture threatens non-target insects such as bees. Considering the ecological and economic relevance of native bees, such as Scaptotrigona postica, and the insufficient studies on the effects of pesticides on their behavior and physiology, improving the current knowledge on this issue is essential. Therefore, this study investigated the sublethal effects of imidacloprid, pyraclostrobin, and glyphosate on the behavior and fat body cells of S. postica. Pesticide ingestion decreased the walking distance and mean velocity of bees compared to the control and solvent control groups. The oenocytes of the control groups were spherical, with central nuclei containing decondensed chromatin, and the trophocytes presented irregular morphology, with cells varying in shape and the cytoplasm filled with vacuoles and granules. However, bees exposed to pesticides showed extensive cytoarchitectural disruption in the fat body, such as vacuolization and shape changes in oenocytes and altered nuclei morphology in trophocytes. Moreover, pesticide exposure increased the number of atypical oenocytes and altered trophocytes, except for the PYR group, which showed a lower number of atypical oenocytes. Caspase-positive labeling significantly increased in all exposed bee groups. Alternatively, TLR4 labeling was significantly decreased in the exposed groups compared to the control groups. There was a significant increase in HSP90 immunolabeling in all exposed groups compared to the control. These findings reinforce the importance of research on the sublethal effects of low pesticide concentrations on key neotropical pollinators and prove that these toxic substances can impair their detoxification and immune defense.

Assessment of imidacloprid induced genotoxicity in Pethia conchonius (Rosy barb), a common freshwater fish of India

Imidacloprid is one of the highly efficient, globally used neonicotinoid groups of insecticides. The indiscriminate use of imidacloprid is contaminating large water bodies affecting not only the target organisms but also non-target organisms including fish. The present study aimed to assess the extent of nuclear DNA damage by imidacloprid in Pethia conchonius a freshwater fish in India using comet and micronucleus assays. The LC50 value of imidacloprid was estimated to be 227.33 mg L−1. Based on the LC50-96 h value, three sub-lethal concentrations of imidacloprid, SLC I −18.94 mg L−1, SLC II −28.41 mg L−1 and SLC III −56.83 mg L−1 were used to detect its genotoxic effect at DNA and cellular level. The imidacloprid exposed fishes exhibited higher DNA damage and nuclear abnormalities (p < 0.05) than the control. The %head DNA, %tail DNA, tail length and the frequency of micronuclei with other nuclear abnormalities like blebbed and notched nuclei were significantly higher than the control in a time and concentration-dependent manner. The DNA damage parameters such as %head DNA (29.107 ± 1.843), %tail DNA (70.893 ± 1.843), tail length (361.431 ± 8.455) micronucleus (1.300 ± 0.019), notched (0.844 ± 0.011) and blebbed (0.811 ± 0.011) nuclei were found to be highest for SLC III (56.83 mg L−1) at 96 h. The findings indicate that IMI is highly genotoxic in fish and other vertebrates leading to mutagenic/clastogenic effects. The study will be helpful in optimization of the imidacloprid use.

Sensitivity to imidacloprid insecticide varies among some social and solitary bee species of agricultural value.

Pollinator health risks from long-lasting neonicotinoid insecticides like imidacloprid has primarily focused on commercially managed, cavity-nesting bees in the genera Apis, Bombus, and Osmia. We expand these assessments to include 12 species of native and non-native crop pollinators of differing levels of body size, sociality, and floral specialization. Bees were collected throughout 2016 and 2017 from flowering blueberry, squash, pumpkin, sunflower and okra in south Mississippi, USA. Within 30-60 minutes of capture, bees were installed in bioassay cages made from transparent plastic cups and dark amber jars. Bees were fed via dental wicks saturated with 27% (1.25 M) sugar syrup containing a realistic range of sublethal concentrations of imidacloprid (0, 5, 20, or 100 ppb) that are often found in nectar. Bees displayed no visible tremors or convulsions except for a small sweat bee, Halictus ligatus, and only at 100ppb syrup. Imidacloprid shortened the captive longevities of the solitary bees. Tolerant bee species lived ~10 to 12 days in the bioassays and included two social and one solitary species: Halictus ligatus, Apis mellifera and Ptilothrix bombiformis (rose mallow bees), respectively. No other bee species tolerated imidacloprid as well as honey bees did, which exhibited no appreciable mortality and only modest paralysis across concentration. In contrast, native bees either lived shorter lives, experienced longer paralysis, or endured both. Overall, longevity decreased with concentration linearly for social bees and non-linearly for solitary species. The percentage of a bee's captive lifespan spent paralyzed increased logarithmically with concentration for all species, although bumble bees suffered longest. Of greatest concern was comparable debilitation of agriculturally valuable solitary bees at both low and high sublethal rates of imidacloprid.

Effects of imidacloprid-induced hormesis on the development and reproduction of the rose-grain aphid Metopolophium dirhodum (Hemiptera: Aphididae).

Field populations of insect pests are affected by sub-lethal doses of insecticides, leading to hormesis. Imidacloprid is a neonicotinoid insecticide widely used to control various sucking insect pests, including aphids. In this study, the effects of sub-lethal concentrations of imidacloprid on the life table traits of the rose-grain aphid Metopolophium dirhodum (Walker) were evaluated on parental and first filial generations. The results showed that sub-lethal concentrations of imidacloprid significantly reduced the fecundity, adult longevity, and reproductive period of M. dirhodum in parental generation (F0). However, the imidacloprid-induced hormetic effects on development and reproduction were detected in the F1 generation. These hormetic effects were indicated by significantly higher adult longevity, fecundity, survival rate, intrinsic and finite rates of increase, and net reproductive rate of first filial generation (F1) of M. dirhodum. Our finding indicated that the application of sub-lethal concentrations of imidacloprid inhibited parental generation (F0), but it significantly stimulated the population growth of filial generation (F1) in the M. dirhodum. The results support the inclusion of insecticides in integrated pest management programs for managing wheat aphids.

Behavioural Response of Oreochromis niloticus Fingerlings Exposed to Sub-Lethal Concentrations of Imidacloprid

Imidacloprid, a neonicotinoid pesticide that was once thought to be a solution to environmental pollution caused by previous pesticides like organophosphates and organochlorines has raised global concern recently. The present study aimed at assessing the effect of Imidacloprid on the behaviour of a commercially important fish species, Oreochromis niloticus. The study involved a 48 h sub-lethal toxicity test which was carried out with 0, 5, 10, 20, and 40 ppm of Imidacloprid. Fingerlings of O. niloticus weighing between 18 and 32g were exposed to these concentrations in a static bioassay with continuous aeration. Regular observation of the clinical signs revealed that fish exposed to higher concentrations of Imidacloprid displayed behavioural abnormalities such as erratic behaviour, respiratory stress, and irregular nervousness. The findings of this study revealed that Imidacloprid is toxic and causes behavioural distress on O. niloticus fingerlings. Therefore, there is urgent need for further studies to determine safe limit of Imidacloprid and other pesticides in the environment. Unregulated disposal of toxic pesticides should be avoided, to ensure human safety and environmental sustainability.

Sublethal effects of imidacloprid and clothianidin on the biological traits of predatory lacewing Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae)

Imidacloprid and clothianidin are widely used insecticides for controlling piercing-sucking pests. However, their effects on non-targets insects are a major concern. Here, we evaluated the effects of sublethal concentrations of imidacloprid and clothianidin on Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae), an important pest predator on many crops. Our data showed that imidacloprid and clothianidin at LD10 (0.71 and 1.42 ng active ingredient [a.i.] per insect, respectively) and LD30 (1.31 and 2.49 ng a.i. per insect, respectively) significantly increased the duration of the second instar larval stage of C. pallens. However, the duration of the third instar was prolonged only by clothianidin at LD30. At LD10, imidacloprid and clothianidin significantly increased the length of pupal stage. In addition, imidacloprid at LD30 significantly prolonged the mean generation time (T). Our results showed that imidacloprid and clothianidin prolong C. pallens developmental but had limited effects on population growth parameters. These results are expected to guide the development of integrated pest management strategies.

Evidence of diet supplementation with vitamin C protecting honeybees from Imidacloprid induced peroxidative damage: a study with Apis cerana indica

Neonicotinoids are one of the major stresses contributing to the decline in the population of honeybees. Worker bees are prone to various stress factors during foraging and are susceptible to Imidacloprid due to the reduction in the number of genes encoding for the major enzyme families responsible for the detoxification of toxins. The present study worked on the hypothesis that the dietary supplementation of Ascorbic acid (VIT C) could reduce the peroxidative damage in the worker bees of Apis cerana indica exposed to sub-lethal concentration of imidacloprid (IMD). Furthermore, we also evaluated the role and efficacy of VIT C supplementation on the cytoarchitecture of midgut tissues on exposure to IMD. Colonies of honeybees were maintained by providing sugar syrup to the control group and sugar syrup supplemented with 0.2% VIT C for the experimental group for six months. Worker bees from both groups were randomly collected and exposed to 0.001 mg/mL IMD. To study the peroxidative damage, the activities of various enzymes were analyzed. The activities of antioxidant enzymes including Catalase, Superoxide Dismutase, Glutathione S Transferase, and Glutathione Peroxidase in the hemolymph and midgut tissues of worker bees were significantly decreased due to exposure to IMD as a single agent. However, their activities showed a significant elevation under diet supplementation with VIT C. Histological examination revealed midgut tissue damage and the rupture of peritrophic membrane among the workers exposed to IMD as compared with the control group. The damage to the midgut was alleviated and the peritrophic membrane was found to be intact in the worker bees supplemented with VIT C. Our results indicated that the dietary supplementation of VIT C has the potential to maintain the redox status and thereby can offer protective potential against the peroxidative damages induced by the sub-lethal concentration of IMD.

Multigenerational Insecticide Hormesis Enhances Fitness Traits in a Key Egg Parasitoid, Trichogramma chilonis Ishii

Hormesis for the intractable pests can be dreadful, but for natural enemies of pests, it is a puissant strategy in optimizing their mass rearing. We report multigenerational stimulatory effects of widely used insecticide, imidacloprid, on the demographic traits of an important egg parasitoid Trichogramma chilonis Ishii. The study investigated the consequences of sublethal (LC5), low lethal (LC30), and median lethal (LC50) concentrations, as well as a control, for five continuous generations (F1 to F5). The initial bioassay experiments revealed imidacloprid exhibiting the highest toxicity for the parasitoid with a LC50 of 2 µg·L−1, whereas LC5 and LC30 were 0.07 µg·L−1 and 0.6 µg·L−1, respectively. Among biological traits, compared to the F1 individuals, a substantial increase in the fecundity of T. chilonis was observed in the F5 individuals by 54.92% and 46.81% when exposed to LC5 and LC30, respectively (p &lt; 0.00001). Further, there was a significant enhancement in the adult longevity as well as oviposition days of the F5 individuals at both these concentrations. Considering the population traits, along with gross reproductive rate (GRR), net reproductive rate (R0) was also enhanced by both LC5 and LC30 in F5 individuals than F1; whereas the intrinsic rate of increase (r) and finite rate of increase (λ) were enhanced only at LC30 upon comparing with control. On the other hand, LC50 exposure to T. chilonis did not result in notable differences in biological or population traits when compared across generations (F1 and F5). Low and sublethal concentrations of imidacloprid did not have a major influence on demographic traits of T. chilonis at initial generations of exposure but can induce hormetic effects in the subsequent generations. Overall, imidacloprid-induced hormesis stimulating the development of T. chilonis might be helpful under circumstances of mild exposure of imidacloprid in fields and could be leveraged for its mass rearing.

Sublethal Effects of Imidacloprid on Fecundity, Apoptosis and Virus Transmission in the Small Brown Planthopper Laodelphax striatellus.

Simple SummaryThe small brown planthopper (SBPH) Laodelphax striatellus is an economically important pest in Asia, especially in China. Imidacloprid, a neonicotinoid insecticide, is commonly applied in rice fields to control the planthoppers. However, the widespread application of imidacloprid also has led to the development of resistance and to other potentially negative effects on crop protection. The sublethal effects of imidacloprid have been reported in many insects. Here, we investigated the potential effects of different sublethal concentrations of imidacloprid on SBPH and found that imidacloprid could affect the fecundity, apoptosis and virus transmission in the viruliferous SBPH. The results indicated that sublethal concentrations of imidacloprid may increase the fecundity of SBPH and the impact of insecticides on the transmission of plant viruses by insects should be considered when insecticides are applied to manage insect pests.Laodelphax striatellus damages plants directly through sucking plant sap and indirectly as a vector of rice stripe virus (RSV), resulting in serious losses of rice yield. It is one of the most destructive insects of rice in East Asia. Insecticides are primarily used for pest management, but the sublethal concentrations of insecticides may benefit several insects. The present research attempted to explore the effects of sublethal concentrations of imidacloprid on the fecundity, apoptosis and RSV transmission in the viruliferous SBPH. The results showed that the fecundity of SBPH was significantly increased after treatment with the LC10 dose of imidacloprid, while the LC30 dose of imidacloprid reduced the fecundity compared with the control. To further investigate the underlying mechanism of increased fecundity after exposure to the LC10 dose of imidacloprid, we examined the expression levels of vitellogenin (Vg), Vg receptor (VgR) and caspases in the ovaries of SBPH, and observed the apoptosis by terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL). qRT-PCR results indicated that the expression levels of Vg, VgR and four caspase genes were all significantly increased by the LC10 dose of imidacloprid, and TUNEL assays suggested that the frequency of apoptosis was significantly higher in the SBPH treated by the LC10 dose of imidacloprid, suggesting a potential correlation between the increased fecundity and the apoptosis of SBPH ovarioles. Additionally, the expression levels of RNA3 and capsid protein (CP) were both increased significantly by the LC10 dose of imidacloprid, whereas were decreased by the LC30 dose of imidacloprid compared to the control. Therefore, this study clarifies the mechanisms of sublethal effects of imidacloprid on viruliferous SBPH and could be used to optimize pest control strategies.

Effects of Imidacloprid on Histology and mRNA Levels of HSP70 and CYP1A Gene to a Standard Non-targeted Test Animal, Cyprinus carpio

Background: Imidacloprid (IMI) belongs to the class of neuro active insecticides, used to control pest and insects in agricultural crops. Reports suggest that IMI has highly toxic consequences on bees, humans and non-targeted aquatic animals. Hence the present study aims to investigate the toxicity effects of commercial-grade Imidacloprid (IMI) (Premise, 30.5%, a.i) using histological and transcriptional changes in heat shock protein 70 (HSP70) and cytochrome P4501A(CYP1A) genes in liver and gills of non-targeted aquatic animal, Cyprinus carpio. Methods: Three different sublethal concentrations of IMI (T1=26.04 mg/L, T2= 20.38 mg/L, T3=17.36 mg/L) were selected and common carp fingerlings were exposed for 28 days where histological alterations and expression study of HSP70 and CYP1A in gills and liver of exposed fishes being studied on 7, 14, 21 and 28 days interval using standard procedure. Result: Marked histological alteration like hydropic degeneration and cellular infiltration in liver; telangiectasis in secondary lamellae, epithelial lifting and oedema in gills were recorded. Moreover, significant upregulation of HSP70 and CYP1A gene in the gills and liver in a dose and time dependent manner was observed (P less than 0.05). As a result of the current investigation, it is obvious that IMI could be a possible toxicant that affects fish at the tissue and gene level in dosage and time dependent ways, potentially influencing other physiological processes in the long term.

Acute Application of Imidacloprid Alters the Sensitivity of Direction Selective Motion Detecting Neurons in an Insect Pollinator.

Cholinergic pesticides, such as the neonicotinoid imidacloprid, are the most important insecticides used for plant protection worldwide. In recent decades, concerns have been raised about side effects on non-target insect species, including altered foraging behavior and navigation. Although pollinators rely on visual cues to forage and navigate their environment, the effects of neonicotinoids on visual processing have been largely overlooked. To test the effect of acute treatment with imidacloprid at known concentrations in the brain, we developed a modified electrophysiological setup that allows recordings of visually evoked responses while perfusing the brain in vivo. We obtained long-lasting recordings from direction selective wide-field, motion sensitive neurons of the hoverfly pollinator, Eristalis tenax. Neurons were treated with imidacloprid (3.9 μM, 0.39 μM or a sham control treatment using the solvent (dimethylsulfoxide) only. Exposure to a high, yet sub-lethal concentration of imidacloprid significantly alters their physiological response to motion stimuli. We observed a general effect of imidacloprid (3.9 μM) increasing spontaneous activity, reducing contrast sensitivity and giving weaker directional tuning to wide-field moving stimuli, with likely implications for errors in flight control, hovering and routing. Our electrophysiological approach reveals the robustness of the fly visual pathway against cholinergic perturbance (i.e., at 0.39 μM) but also potential threatening effects of cholinergic pesticides (i.e., evident at 3.9 μM) for the visual motion detecting system of an important pollinator.

Neonicotinoid Exposures that Stimulate Predatory Stink Bug, Podisus maculiventris (Hemiptera: Pentatomidae), Reproduction Do Not Inhibit Its Behavior.

Exposure to sublethal amounts of pesticide can compromise life-history traits and behavior of natural enemies thereby reducing their effectiveness as predators. However, sublethal exposures to pesticides and other stressors may also stimulate insects, a dose-response phenomenon known as hormesis. We previously reported stimulatory effects on reproduction in the beneficial insect predator Podisus maculiventris (Say) (Hemiptera: Pentatomidae) following exposure to sublethal concentrations of imidacloprid. Here we examined whether these same treatments stimulated behavior and/or predation of P. maculiventris. Stimulation of some behaviors occurred at a reproductively hormetic concentration and two additional sublethal concentrations, depending upon bioassay design and sex. We observed no substantial inhibition of behavior or predation at a reproductively hormetic concentration, demonstrating that reproductive fitness in P. maculiventris may be stimulated without compromising behaviors important in its effectiveness as a natural enemy.

Neonicotinoid-contaminated diet causes behavior changes in forager honey bees (Apis mellifera) that may reduce colony survival during late fall

Neonicotinoid insecticides are often detected in pollen and nectar, which are the main food resources for honey bees. Sub-lethal and chronic exposure to these insecticides may have a prolonged effect on honey bees who are solely dependent on the stored food inside of the hive during cold weather. Our study investigated the effects of sub-lethal concentrations of imidacloprid on late fall forager honey bees’ behavior by accessing their activity levels and walking performance after being fed ad libitum with six different concentrations (2—125 μg/kg) of imidacloprid-dosed syrup for up to 48 h in the laboratory. Numbers of honey bees that walked after being released into a UV light illuminated tunnel decreased significantly as dosages of neonicotinoid in their diet increased. However, their walking speeds were not significantly affected by imidacloprid. The behavioral changes we observed in honey bees chronically exposed to neonicotinoid via diet could negatively affect individual honey bee performance of hive duties and consequently, colony survival during cold weather.

Chemosensory proteins participate in insecticide susceptibility in Rhopalosiphum padi, a serious pest on wheat crops.

Rhopalosiphum padi is a worldwide agricultural pest. Chemosensory proteins (CSPs) are considered to be a type of transporters which can bind chemicals from external environments. Previous research showed that the expression of some insect CSPs were significantly increased after exposure to insecticides, and CSPs were involved in insecticide resistance or susceptibility. However, the role of CSPs in the susceptibility and response of R. padi to insecticides is still unknown. In this study, we identified eight CSP (RpCSP) from R. padi by genome-wide investigation. Seven RpCSP genes had two exons, while RpCSP7 had three exons. qPCR analyses showed that the mRNA levels of the eight RpCSP genes were significantly affected by imidacloprid and beta-cypermethrin in different post-treatment periods. Molecular docking predicted that there were hydrogen bonding sites which played key roles in binding of RpCSP4, RpCSP5, RpCSP6, RpCSP7 and RpCSP10 with imidacloprid and beta-cypermethrin. Knockdown of RpCSP4, RpCSP5, RpCSP6 and RpCSP10 by RNA interference significantly increased the aphid mortality under two sublethal concentrations of imidacloprid. Mortalities under two sublethal concentrations of beta-cypermethrin conditions were significantly higher after injection of R. padi with dsCSP4 and dsCSP6. The results indicate that some RpCSP genes are involved in the insecticide susceptibility of R. padi.

SUBLETHAL EFFECTS OF IMIDACLOPRID ON HAEMATOLOGICAL AND BIOCHEMICAL PROFILE OF FRESHWATER FISH, CYPRINUS CARPIO

Imidacloprid is a commercialized Neonicotinoid pesticide, widely used to kill piercing and sucking types of insect pests in agriculture field. Due to its systemic nature and high water solubility, imidacloprid gradually reach and contaminate surrounding water bodies. The present study was planned to investigate the sublethal toxic impacts of pesticide imidacloprid on haematological and biochemical profile of freshwater fish, Cyprinus carpio. The fingerlings of Cyprinus carpio were exposed to three different sublethal concentrations of imidacloprid (7.8 ppm, 15.6 ppm and 23.4 ppm) for 30 days. Blood samples from all treatments were collected and used for hematological as well as biochemical diagnosis. During the trial period, haematological parameters like TEC, Hb and Hct were decreased significantly (P&lt;0.05), whereas TLC count was found to be increased in imidacloprid treated fish. Similarly MCH count was lower but MCV was higher significantly as compared to control. In the biochemical analysis, plasma protein levels were significantly decreased in all the treatment groups when compared to control. Similar trends of significant decrease in the values of albumin and globulin was also reported. Thus, results of present study show that imidacloprid can cause remarkable alterations in the haematological and biochemical parameters of Cyprinus carpio.

Hormesis in the Brown Citrus Aphid, Toxoptera citricida (Kirkaldy) (Hemiptera: Aphididae) Exposed to Sublethal Doses of Imidacloprid

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a major pest that transmits phloem-limited, gram negative bacteria including ‘Candidatus’ liberibacter asiaticus (Clas), causing huanglongbing. Management of this pest relies primarily on insecticides, such as the neonicotinoid imidacloprid, that may affect secondary pests including the brown citrus aphid, Toxoptera citricida (Kirkaldy) (Hemiptera: Aphididae). Here, we report on direct toxicity and sublethal dose effects of imidacloprid on T. citricida nymphs and adults following direct contact and ingestion. We also examined transgenerational dose-response and hormetic effects following exposure of T. citricida to a sublethal concentration of imidacloprid. Toxicity of imidacloprid was similar for nymphs (0.6 ng per µL) and adults (1 ng per µL) at 72 h. Fecundity and finite rate of increase were greater for populations exposed to systemic and foliar treatments at a sublethal concentration (0.1 ng per µL) compared with untreated controls. Development times of first instar nymphs in the F1 generation and third instar nymphs in the F2 generation were significantly greater for individuals treated with the sublethal dose than an untreated control. Survival of second instar T. citricida on plants treated with a sublethal concentration also was significantly greater than controls. There also was a significant increase in fecundity of F1 and F2 individuals after sublethal treatment compared with controls. Our results indicated that a sublethal concentration of imidacloprid increased the reproductive performance and induced possible physiologically stimulative (hormetic) effects in T. citricida. Hormesis in secondary pests should be considered when developing a management program for pathogen vectors such as D. citri.