Imidacloprid Treatment Research Articles

Sublethal and transgenerational effects of acetamiprid and imidacloprid on the predatory bug Orius sauteri (Poppius) (Hemiptera: Anthocoridae)

The predatory bug Orius sauteri (Poppius) is currently one of the most important beneficial arthropods in Northeast Asia and used as a biological control agent of several small pest arthropods including Frankliniella occidentalis (Pergande). Two neonicotinoid chemical insecticides, acetamiprid and imidacloprid, mainly used in China as chemical control on F. occidentalis, although applied at sublethal concentrations in the field or greenhouse to protect beneficial arthropods, still may affect the predator O. sauteri. The objective of present work is to assess the long-term effects of 24-h exposure time to these two insecticides on the life-cycle of O. sauteri at application rates similar to the laboratory 24-h LC10, LC20 and LC30 of O. sauteri. Results showed that acetamiprid and imidacloprid at all tested concentrations significantly decreased the fecundity of O. sauteri females, while the effect of acetamiprid was higher than that of imidacloprid. Moreover, the oviposition period and longevity of O. sauteri to both insecticides shortened. The sublethal effects on the first progeny (F1 generation) were also found to increase nymphal mortality, shorten adult longevity and reduce fecundity. However, all treatments of acetamiprid and imidacloprid at the concentration of LC10, LC20 and LC30 caused no significant effect on the developmental time of different nymphal stages and sex ratio of the F1 generation. This paper is the first one that assesses the compatibility between neonicotinoid insecticides and O. sauteri, and shows that the application of acetamiprid and imidacloprid likely interferes with the population dynamic of O. sauteri.

Neonicotinoids caused oxidative stress and DNA damage in juvenile Chinese rare minnows (Gobiocypris rarus).

To assess the effects of neonicotinoid insecticides on fish, juvenile Chinese rare minnows (Gobiocypris rarus) were exposed to 0.1, 0.5, or 2.0mg/L neonicotinoid insecticides (imidacloprid, nitenpyram, and dinotefuran) for 60 days. The endpoints, including oxidative stress and DNA damage, were determined. The results of oxidative stress assays showed that SOD activities were significantly increased in the 2.0mg/L imidacloprid and 0.5mg/L nitenpyram and dinotefuran treatments (p<0.05). CAT activity was significantly increased with 0.1mg/L nitenpyram (p<0.05), whereas it was significantly decreased in the 0.1 and 2.0mg/L dinotefuran treatment groups (p<0.05). Moreover, MDA content was significantly decreased in all imidacloprid treatments and in the 0.5 and 2.0mg/L dinotefuran treatments (p<0.05); however, it was significantly increased in the 0.1mg/L nitenpyram treatment (p<0.05). GSH content was significantly increased at all treatments except for the 0.5mg/L dinotefuran treatment (p<0.05). The transcript expression results showed that gstm mRNA expression was significantly inhibited by 0.5 and 2.0mg/L imidacloprid, and gstp1 mRNA expression was significantly inhibited by all nitenpyram treatments (p<0.05). In addition, ugt1a mRNA expression was significantly inhibited in the 0.5mg/L nitenpyram treatment (p<0.05). The results of the DNA damage assay showed that tail moments were significantly increased by the 2.0mg/L imidacloprid treatment (p<0.01), while tail DNA was significantly increased by 0.5 and 2.0mg/L imidacloprid, 2.0mg/L nitenpyram and all dinotefuran treatments (p<0.01). Moreover, olive tail moments were significantly increased by the 0.5 and 2.0mg/L imidacloprid and 2.0mg/L dinotefuran treatments (p<0.01). Therefore, our oxidative stress and DNA damage findings demonstrated that imidacloprid and nitenpyram could cause adverse effects on juvenile rare minnows.

Bio-efficacy of newer insecticides and bio-pesticides against sucking insect pest aphid (Aphis craccivora Koch) of groundnut

To evaluate efficacy of newer insecticides and biopesticide against aphid, Aphis craccivora Koch experiment were carried out during Kharif 2018 at Agronomy farm, S.K.N. College of Agriculture, Jobner (Rajasthan). The experiment was laid out in Randomized Block Design (RBD) with nine treatments including untreated control on groundnut variety RG-382. All the insecticidal treatments were found significantly superior over the untreated control in aphid population in both the sprays. On the basis of mean per cent reduction in aphid population in two successive sprays the treatment of imidacloprid (81.94%) was found most effective against aphids, followed by thiamethoxam (79.87%) and acetamiprid (77.99%). The methyl demeton (72.79%), fipronil (70.54%) and acephate (68.60%) falls under moderately effective group and were differed significantly to each other. Biopesticides Metarhizium anisopliae (32.56%) and NSKE (47.97%) were proved least effective.

Evaluation and phytotoxicity of Imidacloprid (600FS) on Chilli thrips as seed treatment

Imidacloprid, an insecticide belonging to chloronicotinyl group was applied as seed treatment for the management of thrips on chilies. Seed treatment of imidacloprid 600 FS and 70 WS at 7, 9, 12, 15 and 30 ml kg−1 protected the seedlings in the nursery up to 35 days. Imidacloprid @ 12 ml was most effective followed by imidacloprid @ 9 ml and @ 30 ml/litre. The seed treatment of imidacloprid reduced the thrips population significantly and also recorded higher yield of chilli fruits. There was no phytotoxicity in the chilli plants due to the treatment of imidacloprid as seed treatment even at highest dose.

The Inducible CYP4C71 Can Metabolize Imidacloprid in Laodelphax striatellus (Hemiptera: Delphacidae).

Laodelphax striatellus (Fallén) is an important rice pest species which has developed high resistance to imidacloprid. Previous studies have demonstrated that CYP6AY3v2 and CYP353D1v2 were constitutively overexpressed in a imidacloprid resistant strain and can metabolize imidacloprid to mediated metabolic resistance. Further studies still needed to explore whether there are other L. striatellus P450 enzymes that can also metabolize imidacloprid. In this study, the expression level of L. striatellus CYP4C71 was significantly upregulated both in laboratory strains and field strains of L. striatellus after imidacloprid treatment for 4 h. The capability of CYP4C71 to metabolize imidacloprid was investigated. The full-length CYP4C71 was cloned, and its open reading frame was 1,515 bp with an enzyme estimated to be 505 amino acid residues in size. Furthermore, CYP4C71 was heterologously expressed along with L. striatellus cytochrome P450 reductase (CPR) in insect cells. A carbon monoxide difference spectra analysis confirmed the successful expression of CYP4C71. The recombinant CYP4C71 showed high P450 O-demethylation activity with PNP as a substrate. In vitro metabolism studies showed that recombinant CYP4C71 can metabolize imidacloprid to an easily excreted hydroxy-form. The rate of imidacloprid depletion in response to imidacloprid concentration revealed Michaelis Menten kinetics (R2 fitted curve = 0.99) with a relative low affinity: Kcat = 0.032 ± 0.009 pmol depleted imidacloprid/min/pmol P450 and Km=85.19 ± 2.93 μM. A relative big Km (85.19 ± 2.93 μM) indicated relative low imidacloprid's affinity for the CYP4C71 enzyme. In conclusion, CYP4C71 was another P450 enzyme that can metabolize imidacloprid with a relatively low affinity.

Transcriptome Analysis and Identification of Insecticide Tolerance-Related Genes after Exposure to Insecticide in Sitobion avenae.

Aphids cause serious losses to the production of wheat. The grain aphid, Sitobion avenae, which is the dominant species of aphid in all wheat regions of China, is resistant to a variety of insecticides, including imidacloprid and chlorpyrifos. However, the resistance and mechanism of insecticide tolerance of S. avenae are still unclear. Therefore, this study employed transcriptome analysis to compare the expression patterns of stress response genes under imidacloprid and chlorpyrifos treatment for 15 min, 3 h, and 36 h of exposure. S. avenae adult transcriptome was assembled and characterized first, after which samples treated with insecticides for different lengths of time were compared with control samples, which revealed 60–2267 differentially expressed unigenes (DEUs). Among these DEUs, 31–790 unigenes were classified into 66–786 categories of gene ontology (GO) functional groups, and 24–760 DEUs could be mapped into 54–268 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Finally, 11 insecticide-tolerance-related unigenes were chosen to confirm the relative expression by quantitative real-time polymerase chain reaction (qRT-PCR) in each treatment. Most of the results between qRT-PCR and RNA sequencing (RNA-Seq) are well-established. The results presented herein will facilitate molecular research investigating insecticide resistance in S. avenae, as well as in other wheat aphids.

Multiple down-regulated cytochrome P450 monooxygenase genes contributed to synergistic interaction between chlorpyrifos and imidacloprid against Nilaparvata lugens

Abstract Insecticide mixtures are an effective strategy in pest resistance management. The synergistic chlorpyrifos and imidacloprid mixture could significantly increase toxicity against rice pest, Nilaparvata lugens, despite their high levels of resistance. However, synergism mechanisms to explain this phenomenon remain unknown. Chlorpyrifos and imidacloprid at a 1:0.5 ratio showed significant synergism on N. lugens with a combination index value of 0.18 after topical exposure. We constructed a genetic database of the genes expressed in individual and synergistic chlorpyrifos and imidacloprid treatments of N. lugens using Illumina Hiseq™ X Ten, and 17 co-downregulated genes putatively involved in synergism were detected by comparative transcriptome analyses. Expression patterns of the 17 candidate synergistic genes matched with transcriptome sequencing data by quantitative real-time PCR analyses. Feeding of dsRNAs further reduced the expression levels of 10 of these candidate synergistic genes (from 1.68 to 4.13-fold). Nymphs fed with only dsRNAs of CYP4DE1, CYP6AY1v2, CYP353D1, and CYP439A1 experienced more high mortality rates (81.45–90.34%) to improve synergism between chlorpyrifos and imidacloprid. Multiple reductive expressed P450 genes were potentially associated with synergism of a mixture of chlorpyrifos and imidacloprid, as confirmed by comparative transcriptome analyses and RNAi assays. Our findings suggested that synergistic interactions between chlorpyrifos and imidacloprid might be controlled by P450s.

Impact of Imidacloprid Soil Drenching on Survival, Longevity, and Reproduction of the Zoophytophagous Predator Podisus maculiventris (Hemiptera: Pentatomidae: Asopinae)

Systemic insecticides when applied as seed treatments or soil drenches are often more toxicologically selective for natural enemies than target pests. This may not be the case, however, for omnivorous predators, which are at risk of extended exposure to systemically applied pesticides through ingestion while feeding on treated plants for nutrients or water. Such exposure may kill or have sublethal consequences for these natural enemies, compromising their role as biocontrol agents of agricultural pest species. The spined soldier bug, Podisus maculiventris (Say) (Hemiptera: Pentatomidae: Asopinae), is an important zoophytophagous biocontrol agent (i.e., able to substitute zoophagy by phytophagy for survival) that may be exposed to systemic insecticides in many agricultural systems. We, therefore, examined effects on P. maculiventris following exposure to cabbage plants subject to soil-drench treatments with imidacloprid, a systemic neonicotinoid insecticide. Predator survival, development, body weight, and reproduction were recorded. Imidacloprid significantly affected nymph survival and adult emergence, but not duration of the nymphal period or adult body weight. At one-twentieth the recommended field rate for whitefly and aphid management, imidacloprid treatments reduced longevity, fecundity, and fertility of female predators. These findings demonstrate that soil treatments with systemic insecticide can negatively impact zoophytophagous natural enemies.

Repellent effects of insecticides on Stephanitis pyrioides Scott (Hemiptera: Tingidae) under laboratory conditions

Stephanitis pyrioides Scott (Hemiptera: Tingidae) is an important insect pest of azalea plants (Rhododendron L. spp.) in the USA. The use of neonicotinoids in landscapes has been reduced because of consumer perceptions that they are not pollinator friendly. The reductions are due mostly to changes in the labels that restrict times these materials can be applied to ornamental plants based on plant phenology and bloom period. Pest management can be improved by using insecticides that repel S. pyrioides. A series of non-contact and contact laboratory assays were conducted with adult S. pyrioides to determine the repellency of insecticides. Insecticides with various modes of action were included in the assays. During the non-contact assay, significantly more S. pyrioides individuals were collected away from the insecticide source than closer to the source when cyfluthrin, bifenthrin, dinotefuran, clothianidin, cyclaniliprole and novaluron were used. During the contact assay, the number of visits was significantly lower for thiamethoxam, lambda-cyhalothrin + bifenthrin + imidacloprid, permethrin, tebufenozide and spinosad treatments than for dinotefuran, azadirachtin, spirotetramat and Chromobacterium subtsugae strain PRAA4-1 T. The adults spent significantly less time on leaves treated with cyfluthrin, permethrin and pyriproxyfen than the other treatments. In a mortality assay performed after 4 h of exposure, significantly more dead adults were found associated with acetamiprid, dinotefuran, thiamethoxam and flupyradifurone compared to chlorantraniliprole, cyantraniliprole, cyclaniliprole, azadirachtin, afidopyropen and flonicamid. After 24 h of exposure, a significantly lower number of fecal spots was observed in the acetamiprid, dinotefuran, thiamethoxam, flupyradifurone, lambda-cyhalothrin, cyantraniliprole, cyclaniliprole, pyrifluquinazon and afidopyropen treatments than chlorantraniliprole and azadirachtin.

Development of bio-rational management approach against mango hopper, Idioscopus nagpurensis (Pruthi) in Bangladesh

A field experiment was conducted during the 2016-17 mango cropping season in farmers’ fields of Gazipur, Rajshahi and Chapainawabgonj districts of Bangladesh to find an effective bio-rational management option for controlling the mango hopper, Idioscopus nagpurensis (Pruthi) (Hemiptera: Cicadellidae). Randomized Complete Block Design was used incorporating 8 treatments with 3 replications. The treatments were pruning of overcrowded and overlapping branches, spraying of azadirachtin, Beauveria bassiana (Lycomax, Russel IPM), imidacloprid insecticide, installation of yellow sticky grey and blue sticky trap and untreated control. Lowest leafhopper population was recorded in B. bassiana (3.0 hoppers/sweep/tree) followed by imidacloprid (3.7 leafhoppers/sweep/tree) treatments. Highest number of fruit retention was recorded in imidacloprid (40.00 fruits/20 inflorescence/tree) followed B. bassiana (32.67 fruits/20 inflorescence/tree) and azadirachtin (24.00 fruits/20 inflorescence/tree). Imidacloprid treatment offered maximum marginal benefit cost ratio (5.60). Increasing trend of hopper population was recorded in control. Considering health and environment issues, spraying of B. bassiana @ 5.0g/L of water at flower initiation stage, flowering stage and pea stage may be recommended for controlling mango hopper.

Influence of Oilseed Rape Seed Treatment with Imidacloprid on Survival, Feeding Behavior, and Detoxifying Enzymes of Mustard Aphid, Lipaphis erysimi.

Imidacloprid application, as a seed coating agent on oilseed rape, is recommended to control mustard aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae). In this study, responses of L. erysimi were investigated, including survival, feeding behavior, and detoxifying enzymes, on the oilseed rape seedlings grown from seeds coated with imidacloprid at rates of 6, 12, or 18 g active ingredient (a.i.)/kg seed. The results showed that the aphids’ survival rate, together with that of the progeny of the survivors, on the seed-treated seedlings significantly decreased. This indicates that the aphid population in fields can be suppressed effectively. The electrical penetration graph (EPG) technique was used to record aphid feeding behaviors on two-, four-, and six-leaf stages of oilseed rape seedlings that had been seed-coated with imidacloprid, and individual responses were revealed during the aphid feeding behavior. On the plants at the two-leaf stage, aphid feeding behaviors were influenced, showing decreased frequency of stylet penetration into the leaf (probe) or into the mesophyll cells (potential drops, pds for short), and shortened duration of stylet event in the leaf (probe) or in the phloem. On the plants at the four- and six-leaf stages, these impacts of imidacloprid were weakened; however, the saliva secretion duration in phloem was shortened to less than 5 min in all imidacloprid treatments. The activity of mixed-function oxidase in aphids maintained on the treated seedlings with imidacloprid was elevated. In conclusion, imidacloprid could be used as a seed coating agent for aphid control, but chemical resistance in aphids should not be ignored.

Long-term dynamics of honey bee colonies following exposure to chemical stress

Pesticide residues have been linked to reduced bee health and increased honey bee colony failure. Most research to date has investigated the role of pesticides on individual honey bees, and it is still unclear how trace levels of pesticides change colony viability and productivity over seasonal time scales. To address this question we exposed standard bee colonies to chemical stressors known to have negative effects on individual bees, and measured the productivity of bee colonies across a whole year in two environments: near Tucson Arizona and Sydney Australia. We exposed hives to a trace amount of the neonicotinoid imidacloprid and to the acaricide thymol, and measured capped brood, bee and honey production, as well as the temperature and foraging force of the colonies. The effect of imidacloprid on colony dynamics differed between the two environments. In Tucson we recorded a positive effect of imidacloprid treatment on bee and brood numbers. Thymol was associated with short-term negative effects on bee numbers at both locations, and may have affected colony survival at one location. The overall benefits of thymol for the colonies were unclear. We conclude that long-term and colony-level measures of the effects of agrochemicals are needed to properly understand risks to bees.

Integrated Management of Tomato Yellow Leaf Curl Virus and its Whitefly Vector in Tomato.

Whitefly-transmitted Tomato yellow leaf curl virus (Family Geminiviridae; Genus Begomovirus) severely restricts tomato production in the Southeastern United States. Whitefly and tomato yellow leaf curl virus management studies typically investigate control tactics individually, but successful management of this pest complex more often relies on a combination of tactics. This study examined the individual and combined effects of tomato yellow leaf curl virus-resistant cultivars, insecticides, and metallic reflective mulch on whiteflies, tomato yellow leaf curl virus disease incidence, and marketable tomato yields using split-split plot trials over 3 yr. Reflective mulch significantly reduced whitefly adults and nymphs and tomato yellow leaf curl virus symptom severity in all 3 yr of the study. Reflective mulch treatments also provided greater marketable tomato yield in 2 out of 3 yr. Imidacloprid and cyantraniliprole treatments reduced whitefly adults and nymphs' establishment and marginally increased yields, but there was no significant insecticide effect on tomato yellow leaf curl virus incidence/symptom severity compared with the non-treated check. Virus-resistant tomato cultivars did not influence whitefly populations, but provided consistent reduction in virus disease incidence. Interactions between host plant resistance and insecticide treatments ranged from strongly additive in the standard white plastic mulch treatment to only marginally additive in the reflective mulch treatments in terms of enhancing tomato yields. tomato yellow leaf curl virus-resistant tomato cultivars and reflective mulch provided the bulk of the protection against tomato yellow leaf curl virus disease incidence. However, it was the combination of all the best tactics (reflective mulch, cyantraniliprole, 'Security' hyb. tomato yellow leaf curl virus-resistant) that provided the maximum increase in marketable tomato yield (2.8-fold) over the least effective combination (white mulch, no whitefly insecticide, 'FL47' hyb. tomato yellow leaf curl virus-susceptible).

Brain transcriptome of honey bees (Apis mellifera) exhibiting impaired olfactory learning induced by a sublethal dose of imidacloprid

Declines in honey bee populations represent a worldwide concern. The widespread use of neonicotinoid insecticides has been one of the factors linked to these declines. Sublethal doses of a neonicotinoid insecticide, imidacloprid, has been reported to cause olfactory learning deficits in honey bees via impairment of the target organ, the brain. In the present study, olfactory learning of honey bees was compared between controls and imidacloprid-treated bees. The brains of imidacloprid-treated and control bees were used for comparative transcriptome analysis by RNA-Seq to elucidate the effects of imidacloprid on honey bee learning capacity. The results showed that the learning performance of imidacloprid-treated bees was significantly impaired in comparison with control bees after chronic oral exposure to imidacloprid (0.02 ng/μl) for 11 days. Gene expression profiles between imidacloprid treatment and the control revealed that 131 genes were differentially expressed, of which 130 were downregulated in imidacloprid-treated bees. Validation of the RNA-Seq data using qRT-PCR showed that the results of qRT-PCR and RNA-Seq exhibited a high level of agreement. Gene ontology annotation indicated that the oxidation-reduction imbalance might exist in the brain of honey bees due to oxidative stress induced by imidacloprid exposure. KEGG and ingenuity pathway analysis revealed that transient receptor potential and Arrestin 2 in the phototransduction pathway were significantly downregulated in imidacloprid-treated bees, and that five downregulated genes have causal effects on behavioral response inhibition in imidacloprid-treated bees. Our results suggest that downregulation of brain genes involved in immune, detoxification and chemosensory responses may result in decreased olfactory learning capabilities in imidacloprid-treated bees.

The neonicotinoids acetamiprid and imidacloprid impair neurogenesis and alter the microglial profile in the hippocampal dentate gyrus of mouse neonates.

Acetamiprid (ACE) and imidacloprid (IMI) are widely used neonicotinoid pesticides. They bind selectively to insect nicotinic acetylcholine receptors (nAChRs) and are considered non-hazardous to mammals. Few studies have assessed the activation of vertebrate nAChRs and the neurodevelopmental toxicity following in utero or neonatal exposure to neonicotinoids; therefore, we evaluated the effects of ACE or IMI exposure on neurogenesis and microglial profiles in the developing hippocampal dentate gyrus (DG) of mouse neonates. Mice were exposed to ACE, IMI (both 5mg/kg/day) or nicotine (0.5mg/kg/day) from postnatal day (P)12 to P26 by oral gavage. On P27, brains were removed, and neurogenesis and microglial activation in the hippocampal DG were examined via immunohistochemistry. A reduction in neurogenesis in the hippocampal DG of neonates following ACE, IMI and nicotine treatment was found. Additionally, neonicotinoid-exposed newborns showed an increase in the number of amoeboid-type and activated M1-type microglia. These results suggest that exposure to ACE and IMI impairs neurogenesis and alters microglial profiles in the developing hippocampal DG following oral dosing in an early postnatal period. A better understanding of the potential effects of these pesticides on human infant health is an important goal of our research.

Effects of Chemical Insecticide Imidacloprid on the Release of C6 Green Leaf Volatiles in Tea Plants (Camellia sinensis)

Chemical insecticides are widely used for pest control worldwide. However, the impact of insecticides on indirect plant defense is seldom reported. Here, using tea plants and the pesticide imidacloprid, effects of chemical insecticides on C6-green leaf volatiles (GLVs) anabolism and release were investigated first time. Compared with the non-treated control plants, the treatment of imidacloprid resulted in the lower release amount of key GLVs: (Z)-3-hexenal, n-hexenal, (Z)-3-hexene-1-ol and (Z)-3-Hexenyl acetate. The qPCR analysis revealed a slight higher transcript level of the CsLOX3 gene but a significantly lower transcript level of CsHPL gene. Our results suggest that imidacloprid treatment can have a negative effect on the emission of GLVs due to suppressing the critical GLVs synthesis-related gene, consequently affecting plant indirect defense.

Differential expression of genes in greenbug (Schizaphis graminum Rondani) treated by imidacloprid and RNA interference.

Insecticides act as toxins, inhibitors of digestion and deterrents, and affect the expression of many genes in insects. To assess key genes associated with the detoxification or regulation of imidacloprid in greenbug, Schizaphis graminum (Rondani), the transcriptome and digital gene expression (DGE) profile were analyzed using Illumina sequencing. In total, 48 763 494 clean reads were obtained by sequencing. Expression profile analysis showed that 2782 unigenes were differently expressed between the imidacloprid treatment and control groups. After exposure to imidacloprid, the expression levels of 1846 unigenes were upregulated and 936 were downregulated in comparison with controls. Expression patterns of the top 20 highly expressed genes show that they could be involved in the detoxification of imidacloprid. Silencing of multidrug resistance-associated gene (MRA), GATA-binding gene (GAT) and takeout-like precursor gene (TLP) resulted in increasing susceptibility to imidacloprid. The differentially expressed genes in S. graminum have potential regulatory or detoxification roles in response to imidacloprid. These results should be useful in understanding the molecular mechanisms of greenbug adaption to imidacloprid. © 2018 Society of Chemical Industry.

RNA-seq reveals disruption of gene regulation when honey bees are caged and deprived of hive conditions.

In this study, we present phenotypic and genetic data characterizing the impact of imidacloprid and caging stress on honey bee Apis mellifera physiological responses and regulation of 45 genes using targeted-RNA seq. The term 'caging stress' characterizes the effects of depriving honey bees of all hive aspects and conditions. Two cohorts of 1day old sister bees were subjected to different conditions. One cohort was caged and fed different imidacloprid-tainted sugar solutions and the second was marked and introduced back to its natal hive. Physiological bee parameters and diet behavior were monitored daily for caged bees over several weeks. Bee samples from both cohorts were sampled weekly for RNA sequencing and oxidative stress analyses. Imidacloprid induced significant protein damage and post-ingestive aversion responses in caged bees, leading to lower tainted syrup consumption and higher water intake compared with the controls. No differentially expressed genes were observed among caged bees in regards to imidacloprid treatment. However, significant upregulation in antioxidant genes was recorded in caged bees as compared with hive bees, with overwhelming downregulation in all gene categories in caged bees at week 4. We identified two sets of genes that were constantly regulated in caged bees, including Rsod with unknown function in insects that could potentially characterize caging stress in honey bees.

Chronic exposure of bumblebees to neonicotinoid imidacloprid suppresses the entire mevalonate pathway and fatty acid synthesis

Determining the side effects of pesticides on pollinators is an important topic due to the increasing loss of pollinators. We aimed to determine the effects of chronic sublethal exposure of the neonicotinoid pesticide imidacloprid on the bumblebee Bombus terrestris under laboratory conditions. The analytical standard of imidacloprid in sugar solution was used for the treatment. Verification of pesticides using UHPLC-QqQ-MS/MS in the experimental bumblebees showed the presence of only two compounds, imidacloprid and imidacloprid-olefin, which were found in quantities of 0.57 ± 0.22 and 1.95 ± 0.43 ng/g, respectively. Thus, the level of the dangerous metabolite imidacloprid-olefin was 3.4-fold higher than that of imidacloprid. Label-free nanoLC-MS/MS quantitative proteomics of bumblebee heads enabled quantitative comparison of 2883 proteins, and 206 proteins were significantly influenced by the imidacloprid treatment. The next analysis revealed that the highly downregulated markers are members of the terpenoid backbone biosynthesis pathway (KEGG: bter00900) and that imidacloprid treatment suppressed the entire mevalonate pathway, fatty acid synthesis and associated markers. The proteomics results indicate that the consequences of imidacloprid treatment are complex, and the marker changes are associated with metabolic and neurological diseases and olfaction disruption. This study provides important markers and can help to explain the widely held assumptions from biological observations. SignificanceThe major finding is that all markers of the mevalonate pathway were substantially downregulated due to the chronic imidacloprid exposure. The disbalance of mevalonate pathway has many important consequences. We suggest the mechanism associated with the novel toxicogenic effect of imidacloprid. The results are helpful to explain that imidacloprid impairs the cognitive functions and possesses the delayed and time cumulative effect.

Multi-level ecotoxicological effects of imidacloprid on earthworm (Eisenia fetida)

As a neurotoxic insecticide, imidacloprid (IMI) has been widely used for crop protection. However, continuous application of such pesticide in the environment may damage the non-target organisms in soil. In the present study, we aimed to investigate the effects of IMI on earthworms in terms of survival, avoidance behavior, reproduction, detoxification enzyme activity and gene expression using a systematic experimental approach. The results showed that the 14-day LC50 value of IMI was 2.26 (2.09–2.43) mg a.i. kg−1, and the 2-day AC50 value (concentration inducing an avoidance rate of 50%) of IMI was 1.34 (1.02–1.91) mg a.i. kg−1 to E. fetida. For reproduction, the 56-day EC50 value of IMI was 0.87 (0.66–1.33) mg a.i. kg−1 to E. fetida, and there was a positive correlation between the growth rate of earthworms and the number of juveniles in IMI treatments. Activities of carboxylesterase (CarE) and glutathione-S-transferases (GST) in earthworms were disturbed by IMI exposure. Moreover, effects of IMI on the CarE activity in earthworms were more severe and sensitive compared with the GST activity. The expressions of annetocin (ann) and calreticulin (crt) at the transcriptional level were decreased upon IMI exposure, reaching the lowest levels of 0.09 fold and 0.16 fold on day 7 and day 14, respectively. Transcriptionally controlled tumor protein (tctp), heat shock protein 70 (hsp70) and gst exhibited relatively obvious variations (up-regulation or down-regulation) when the exposure duration was extended. Taken together, these results comprehensively contributed to further understandings of the impacts of IMI on earthworms.