Concentrations Of Imidacloprid Research Articles

Lethal and sublethal toxicity of neonicotinoid and butenolide insecticides to the mayfly, Hexagenia spp.

Neonicotinoid insecticides are environmentally persistent and highly water-soluble, and thus are prone to leaching into surface waters where they may negatively affect non-target aquatic insects. Most of the research to date has focused on imidacloprid, and few data are available regarding the effects of other neonicotinoids or their proposed replacements (butenolide insecticides). The objective of this study was to assess the toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to Hexagenia spp. (mayfly larvae). Acute (96-h), water-only tests were conducted, and survival and behaviour (number of surviving mayflies inhabiting artificial burrows) were assessed. Acute sublethal tests were also conducted with imidacloprid, acetamiprid, and thiacloprid, and in addition to survival and behaviour, mobility (ability to burrow into sediment) and recovery (survival and growth following 21 d in clean sediment) were measured. Sublethal effects occurred at much lower concentrations than survival: 96-h LC50s ranged from 780 μg/L (acetamiprid) to >10,000 μg/L (dinotefuran), whereas 96-h EC50s ranged from 4.0 μg/L (acetamiprid) to 630 μg/L (thiamethoxam). Flupyradifurone was intermediate in toxicity, with a 96-h LC50 of 2000 μg/L and a 96-h EC50 of 81 μg/L. Behaviour and mobility were impaired significantly and to a similar degree in sublethal exposures to 10 μg/L imidacloprid, acetamiprid, and thiacloprid, and survival and growth following the recovery period were significantly lower in mayflies exposed to 10 μg/L acetamiprid and thiacloprid, respectively. A suite of effects on mayfly swimming behaviour/ability and respiration were also observed, but not quantified, following exposures to imidacloprid, acetamiprid, and thiacloprid at 1 μg/L and higher. Imidacloprid concentrations measured in North American surface waters have been found to meet or exceed those causing toxicity to Hexagenia, indicating that environmental concentrations may adversely affect Hexagenia and similarly sensitive non-target aquatic species.

Imidacloprid soil movement under micro-sprinkler irrigation and soil-drench applications to control Asian citrus psyllid (ACP) and citrus leafminer (CLM)

Imidacloprid (IM) is used to control the Asian Citrus Psyllid (ACP) and citrus leafminer (CLM), which are related to the spread of huanglongbing (HLB or citrus greening) and citrus canker diseases, respectively. In Florida citrus, imidacloprid is mainly soil-drenched around the trees for proper root uptake and translocation into plant canopy to impact ACP and CLM. The objective of this study was to determine the effect of imidacloprid rate, and irrigate amount on concentration of imidacloprid in the soil following drench application to citrus trees in three age classes. The plots were established at the Southwest Florida Research and Education Center, Immokalee, using a randomized complete-block design for three age classes of trees: one-year-old trees (B1), three to five-year-old trees (B2), and eight-year-old trees (B3). The treatments were a combination of two rates each of imidacloprid (1D, 2D) and micro-sprinkling irrigation (1I, 2I). Imidacloprid and bromide (Br-) used as tracer were applied simultaneously. Soil moisture and concentrations of imidacloprid and Br were monitored using soil cores from hand held augers. Soil moisture content (θV) did not differ under two irrigation rates at any given observation day or depth, except following heavy rainfall events. Br- was lost from the observation depths (0–45 cm) about two weeks after soil-drench. Contrarily, imidacloprid persisted for a much longer time (4–8 weeks) at all soil depths, regardless of treatment combinations. The higher retardation of imidacloprid was related to the predominantly unsaturated conditions of the soil (which in turn reduced soil hydraulic conductivities by orders of magnitude), the imidacloprid sorption on soil organic matter, and the citrus root uptake.Findings of this study are important for citrus growers coping with the citrus greening and citrus canker diseases because they suggest that imidacloprid soil drenches can still be an effective control measure of ACP and CLM, and the potential for imidacloprid leaching to groundwater is minimal.

Effects of Spinosad, Imidacloprid, and Lambda-cyhalothrin on Survival, Parasitism, and Reproduction of the Aphid Parasitoid Aphidius colemani.

Insecticides can affect biological control by parasitoids. Here, we examined the lethal and sublethal effects of two conventional insecticides, imidacloprid and lambda-cyhalothrin, and a reduced-risk bioinsecticide, spinosad, on the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae). Concentration-mortality curves generated from insecticide residue bioassays found that wasps were nearly 20-fold more susceptible to spinosad than imidacloprid and lambda-cyhalothrin. Imidacloprid and lambda-cyhalothrin compromised adult parasitoid longevity, but not as dramatically as spinosad: concentrations >200 ng spinosad/cm2 reduced wasp longevity by half. Imidacloprid and lambda-cyhalothrin also compromised aphid parasitism by wasps. Although increasing imidacloprid concentrations led to increased host viability and reduced progeny production, lambda-cyhalothrin did not affect viability of parasitized hosts or parasitoid progeny production in a dose-dependent manner. Our results demonstrate that reduced risk bioinsecticide products like spinosad can be more toxic to biological control agents than certain conventional insecticides.

Effects of imidacloprid on the ecology of sub-tropical freshwater microcosms.

The neonicotinoid insecticide imidacloprid is used in Bangladesh for a variety of crop protection purposes. Imidacloprid may contaminate aquatic ecosystems via spray drift, surface runoff and ground water leaching. The present study aimed at assessing the fate and effects of imidacloprid on structural (phytoplankton, zooplankton, macroinvertebrates and periphyton) and functional (organic matter decomposition) endpoints of freshwater, sub-tropical ecosystems in Bangladesh. Imidacloprid was applied weekly to 16 freshwater microcosms (PVC tanks containing 400 L de-chlorinated tap water) at nominal concentrations of 0, 30, 300, 3000 ng/L over a period of 4 weeks. Results indicated that imidacloprid concentrations from the microcosm water column declined rapidly. Univariate and multivariate analysis showed significant effects of imidacloprid on the zooplankton and macroinvertebrate community, some individual phytoplankton taxa, and water quality variables (i.e. DO, alkalinity, ammonia and nitrate), with Cloeon sp., Diaptomus sp. and Keratella sp. being the most affected species, i.e. showing lower abundance values in all treatments compared to the control. The observed high sensitivity of Cloeon sp. and Diaptomus sp. was confirmed by the results of single species tests. No significant effects were observed on the species composition of the phytoplankton, periphyton biomass and organic matter decomposition for any of the sampling days. Our study indicates that (sub-)tropical aquatic ecosystems can be much more sensitive to imidacloprid compared to temperate ones.

Concentrations of imidacloprid and thiamethoxam in pollen, nectar and leaves from seed-dressed cotton crops and their potential risk to honeybees (Apis mellifera L.)

Neonicotinoid insecticides (NIs) have recently been recognized as co-factors in the decline of honeybee colonies because most neonicotinoids are systemic and can transfer into the pollen and nectar of many pollinated crops. In this study, we collected pollen, nectar and leaves from a cotton crop treated with imidacloprid and thiamethoxam to measure the residue levels of these two NIs at different application doses during the flowering period. Then, the residual data were used to assess the risk posed by the systemic insecticides to honeybees following mandated methods published by the European Food Safety Authority (EFSA), and a highly toxic risk to honeybees was highlighted. Imidacloprid was found in both pollen and nectar samples, whereas thiamethoxam was found in 90% of pollen samples and over 60% of nectar samples. Analysis of the pollen and nectar revealed residual amounts of imidacloprid ranging from 1.61 to 64.58 ng g−1 in the pollen and from not detected (ND) to 1.769 ng g−1 in the nectar. By comparison, the thiamethoxam concentrations in pollen and nectar ranged from ND to 14.521 ng g−1 and from ND to 4.285 ng g−1, respectively. The results of this study provide information on the transfer of two NIs from seed treatment to areas of the plant and provides an understanding of the potential exposure of the bee and other pollinators to systemic insecticides.

Cholinesterase activity in the cup oyster Saccostrea sp. exposed to chlorpyrifos, imidacloprid, cadmium and copper

In the present study, the sensitivity and concentration dependence of three functionally-defined components of cholinesterase activity (total: T-ChE; eserine-sensitive: Es-ChE; and eserine-resistant: Er-ChE) were quantified in the gill, digestive gland and adductor muscle of the tropical cup oyster Saccostrea sp., following acute (96h) aqueous exposure to commercial formulations of the organophosphate (OP) insecticide chlorpyrifos and the neonicotinoid (NN) imidacloprid (concentration range: 0.1–100mg/L), as well as to dissolved cadmium and copper (concentration range: 1–1000μg/L). Oysters (1.5–5.0cm shell length), field-collected from a boating marina in Santa Marta, Colombia (Caribbean Sea) were exposed in the laboratory to each substance at five concentrations. T-ChE, Es-ChE, and Er-ChE activity were quantified in the three tissues in pools of 5 individuals (3 replicates per concentration), before and after inhibition with the total cholinesterase inhibitor eserine (physostigmine, 100µM). Oysters exposed to chlorpyrifos, imidacloprid and Cd showed reduced T-ChE and Es-ChE activity in gills at highest exposure concentrations, with Es-ChE activity being inhibited proportionally more so than T-ChE, whereas Er-ChE activity showed no significant concentration-response. Digestive gland also showed diminished T-ChE, Es-ChE and Er-ChE activity for highest chlorpyrifos and Cd concentrations relative to controls, but an increase of T-ChE and Er-ChE activity at the highest imidacloprid concentration (100mg/L). For Cu, T-ChE, Es-ChE and Er-ChE activities in gills and digestive gland were elevated relative to controls in oysters exposed to Cu concentrations > 100µg/L. In adductor muscle, T-ChE, Es-ChE and Er-ChE activity showed no apparent pattern for any of the four xenobiotics and concentration levels tested. Although this study confirms acute (96h) concentration-dependent reduction of tissue T-ChE and Es-ChE activity in gills and digestive glands of Saccostrea sp. exposed to high concentrations of chlorpyrifos (100mg/L), significant changes in T-ChE, Es-ChE and Er-ChE were also caused by exposure to Cd and Cu at concentrations > 100µg/L and by exposure to imidacloprid (100mg/L), indicating that cholinesterase activity is not a specific biomarker of organophosphate exposure in this species, but, rather, a biomarker of diverse xenobiotic exposure.

Uptake and dissipation of neonicotinoid residues in nectar and foliage of systemically treated woody landscape plants

Systemic neonicotinoid insecticides used in urban arboriculture could pose a risk to bees and other pollinators foraging on treated plants. We measured uptake and dissipation of soil-applied imidacloprid and dinotefuran in nectar and leaves of 2 woody plant species, a broadleaf evergreen tree (Ilex × attenuata) and a deciduous shrub (Clethra alnifolia), to assess concentrations to which pollinators and pests might be exposed in landscape settings. Three application timings, autumn (postbloom), spring (prebloom), and summer (early postbloom), were evaluated to see if taking advantage of differences in the neonicotinoids' systemic mobility and persistence might enable pest control while minimizing transference into nectar. Nectar and tissue samples were collected from in-ground plants and analyzed for residues by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) in 2 successive years. Concentrations found in nectar following autumn or spring applications ranged from 166 to 515 ng/g for imidacloprid and from 70 to 1235 ng/gg for dinotefuran, depending on plant and timing. These residues exceed concentrations shown to adversely affect individual- and colony-level traits of bees. Summer application mitigated concentrations of imidacloprid (8-31 ng/g), but not dinotefuran (235-1191 ng/g), in nectar. Our data suggest that dinotefuran may be more persistent than is generally believed. Implications for integrated pest and pollinator management in urban landscapes are discussed. Environ Toxicol Chem 2018;37:860-870. © 2017 SETAC.

Silver@ graphene oxide nanocomposite: synthesize and application in removal of imidacloprid from contaminated waters.

Silver@graphene oxide nanocomposite was synthesized through an efficient approach, characterized by FTIR, EDX, and TEM instruments and then was used as adsorbent for imidacloprid removal from water in batch procedure. Effective variants such as contact time, pH, adsorbent dosage, and initial concentration of imidacloprid on procedure by two methods, one at a time and experimental design methods, were studied. Results in optimum conditions based on one at a time experiments is removal of 63% of the pesticide from 50mL water containing 10mg/L of imidacloprid by 0.03g of the adsorbent at pH = 6.6 after 60min while, experimental design method predict similarity results, 66% uptake of the poison by 0.06g of the adsorbent in pH = 8. Kinetics and isotherm for adsorption processes follows Freundlich and pseudo-second-order models. Results confirm that Ag@graphene oxide nanocomposite can be applicable for removal of imidacloprid from real polluted water.

DNA damage and oxidative stress induced by imidacloprid exposure in different tissues of the Neotropical fish Prochilodus lineatus

Imidacloprid (IMI), a systemic neonicotinoid insecticide widely used in worldwide scale, is reported in freshwater bodies. Nevertheless, there is a lack of information about IMI sublethal effects on freshwater fish. Thus, the aim of this study was to identify the potential hazard of this insecticide to the South American fish Prochilodus lineatus exposed for 120 h to four IMI concentrations (1.25, 12.5, 125, and 1250 μg L−1). A set of biochemical, genotoxic and physiological biomarkers were evaluated in different organs of the fish. IMI exposure induced significant changes in the enzymatic profiles of P. lineatus, with alterations in the activity of biotransformation and antioxidant enzymes in different tissues. Redox balance of the tissues was affected, since oxidative damage such as lipoperoxidation (LPO) and protein carbonylation (PCC) were evidenced in the liver, gills, kidney and brain of fish exposed to different IMI concentrations. Fish exposed to all IMI concentrations showed decreased blood glucose indicating an increase of energetic demand. DNA damage was evidenced by the comet test, in the erythrocytes of fish all the concentrations evaluated. We integrated these results in the Integrated Biomarker Response (IBR) index, which evidenced that the organs most affected by IMI exposure were the liver and kidney, followed by the gills. Our results highlight the importance of investigating different target tissues after IMI exposure and show the sublethal effects of IMI in some of them; they also warn to the possible consequences that fish living in freshwater ecosystems can suffer due to IMI exposure.

The impacts of modern-use pesticides on shrimp aquaculture: An assessment for north eastern Australia

The use of pyrethroid and neonicotinoid insecticides has increased in Australia over the last decade, and as a consequence, increased concentrations of the neonicotinoid insecticide imidacloprid have been measured in Australian rivers. Previous studies have shown that non-target crustaceans, including commercially important species, can be extremely sensitive to these pesticides. Most shrimp farms in Australia are predominantly located adjacent to estuaries so they can obtain their required saline water, which support multiple land uses upstream (e.g. sugar-cane farming, banana farming, beef cattle and urbanisation). Larval and post-larval shrimp may be most susceptible to the impacts of these pesticides because of their high surface area to volume ratio and rapid growth requirements. However, given the uncertainties in the levels of insecticides in farm intake water and regarding the impacts of insecticide exposure on shrimp larvae, the risks that the increased use of new classes of pesticide pose towards survival of post-larval phase shrimp cannot be adequately predicted. To assess the potential for risk, toxicity in 20day past hatch post-larval Black Tiger shrimp (Penaeus monodon) to modern use insecticides, imidacloprid, bifenthin, and fipronil was measured as decreased survival and feeding inhibition. Post-larval phase shrimp were sensitive to fipronil, bifenthrin, and imidacloprid, in that order, at concentrations that were comparable to those that cause mortality other crustaceans. Bifenthrin and imidacloprid exposure reduced the ability of post-larval shrimp to capture live prey at environmentally realistic concentrations. Concentrations of a broad suite of pesticides were also measured in shrimp farm intake waters. Some pesticides were detected in every sample. Most of the pesticides detected were measured below concentrations that are toxic to post-larval shrimp as used in this study, although pesticides exceed guideline values, suggesting the possibility of indirect or mixture-related impacts. However, at two study sites, the concentrations of insecticides were sufficient to cause toxicity in shrimp post larvae, based on the risk assessment undertaken in this study.

Sublethal effects of imidacloprid on targeting muscle and ribosomal protein related genes in the honey bee Apis mellifera L.

A sublethal concentration of imidacloprid can cause chronic toxicity in bees and can impact the behavior of honey bees. The nectar- and water-collecting, and climbing abilities of bees are crucial to the survival of the bees and the execution of responsibilities in bee colonies. Besides behavioral impact, data on the molecular mechanisms underlying the toxicity of imidacloprid, especially by the way of RNA-seq at the transcriptomic level, are limited. We treated Apis mellifera L. with sublethal concentrations of imidacloprid (0.1, 1 and 10 ppb) and determined the effect on behaviors and the transcriptomic changes. The sublethal concentrations of imidacloprid had a limited impact on the survival and syrup consumption of bees, but caused a significant increase in water consumption. Moreover, the climbing ability was significantly impaired by 10 ppb imidacloprid at 8 d. In the RNA-seq analysis, gene ontology (GO) term enrichment indicated a significant down-regulation of muscle-related genes, which might contribute to the impairment in climbing ability of bees. The enriched GO terms were attributed to the up-regulated ribosomal protein genes. Considering the ribosomal and extra-ribosomal functions of the ribosomal proteins, we hypothesized that imidacloprid also causes cell dysfunction. Our findings further enhance the understanding of imidacloprid sublethal toxicity.

Exposure to a sublethal concentration of imidacloprid and the side effects on target and nontarget organs of Apis mellifera (Hymenoptera, Apidae).

The use of insecticides has become increasingly frequent, and studies indicate that these compounds are involved in the intoxication of bees. Imidacloprid is a widely used neonicotinoid; thus, we have highlighted the importance of assessing its oral toxicity to Africanized bees and used transmission electron microscopy to investigate the sublethal effects in the brain, the target organ, and the midgut, responsible for the digestion/absorption of food. In addition, the distribution of proteins involved in important biological processes in the brain were evaluated on the 1st day of exposure by MALDI-imaging analysis. Bioassays were performed to determine the Median Lethal Concentration (LC50) of imidacloprid to bees, and the value obtained was 1.4651 ng imidacloprid/μL diet. Based on this result, the sublethal concentration to be administered at 1, 4 and 8 days was established as a hundredth (1/100) of the LC50. The results obtained from the ultrastructural analysis showed alterations in the midgut cells of bees as nuclear and mitochondrial damage and an increase of vacuoles. The insecticide caused spacing among the Kenyon cells in the mushroom bodies, chromatin condensation and loss of mitochondrial cristae. The MALDI-imaging analysis showed an increase in the expression of such proteins as vascular endothelial growth factor receptor, amyloid protein precursor and protein kinase C, which are related to oxygen supply, neuronal degeneration and memory/learning, and a decrease in the expression of the nicotinic acetylcholine receptor alpha 1, which is fundamental to the synapses. These alterations demonstrated that imidacloprid could compromise the viability of the midgut epithelium, as well as inhibiting important cognitive processes in individuals, and may be reflected in losses of the colony.

Does multigenerational exposure to hormetic concentrations of imidacloprid precondition aphids for increased insecticide tolerance?

Hormetic preconditioning, whereby exposure to mild stress primes an organism to better tolerate subsequent stress, is well documented. It is unknown if exposure to hormetic concentrations of insecticide can trans-generationally prime insects to better tolerate insecticide exposure, or whether exposure to hormetic concentrations of insecticide can induce mutations in genes responsible for insecticide resistance. Using the aphid Myzus persicae (Sulzer) and the insecticide imidacloprid as a model, we examined if exposure to mildly toxic and hormetic concentrations of imidacloprid reduced aphid susceptibility to insecticides across four generations, and whether such exposures induced mutations in the imidacloprid binding site in post-synaptic nicotinic acetylcholine receptors. Chronic, multigenerational exposure of aphids to hormetic concentrations of imidacloprid primed offspring to better survive exposure to certain concentrations of imidacloprid, but not exposure to spirotetramat, an insecticide with a different mode of action. Exposure to hormetic and mildly toxic concentrations of imidacloprid did not result in mutations in any of the examined nicotinic acetylcholine receptor subunits. Our findings demonstrate that exposure to hormetic concentrations of insecticide can prime insects to better withstand subsequent chemical stress, but this is dependent upon the insecticide exposure scenario, and may be subtle over generations. © 2017 Society of Chemical Industry.

Research on characterization and modeling for ultraviolet degradation of imidacloprid based on absorbance change

Absorption spectrum of imidacloprid was measured using spectrophotometer and the most intensive characteristic peak (269nm) was found. The function relationship between imidacloprid concentration and absorbance was obtained with a good linear relationship(R >0.99). The hardware platform for pesticide degradation was designed and built based on ultraviolet light technology, and imidacloprid degradation experiments were conducted based on the platform. It was proposed to describe degradation effect using absorbance change, and prediction model of pesticide residues degradation was obtained according to the relationship between degradation time and absorbance. The results showed that it was feasible to characterize ultraviolet degradation effect according to absorbance change, degradation rate was 4.71% after ultraviolet irradiation for 1minute, and it was 98.43% after 10minutes.

Effect of imidacloprid (insecticide) on Serum Biochemical Parameters and degenerative Lesions In Male Rat's Liver

Imidacloprid is one of the most widely used insecticides in the world. Present study is indicating the effects of orally administered imidacloprid on biochemical blood profile and histological parameters on male rat’s liver. Dose response with respect to different time intervals was evaluated on different groups of rats. Signs of acute/sub-acute poisoning were observed and severity of these findings in the imidacloprid treated rats was found to be dose dependent. Higher concentrations of imidacloprid increased the amount of cholesterol in all the treated groups, the HDLlevel decreased and the Level of LDLin treated group was higher when these were compared with control rats. The toxicity of the pesticide leads to higher levels of AST and ALTin time and dose dependent manner as compared to the control rats. Moreover, a high concentration of imidacloprid dose transiently increased and then slightly decreased the concentration of total serum proteins, globulins and serum albumin. Additionally, histopathological examination of liver revealed bile duct hyperplasia along with degenerative changes in hepatocytes and the severity was found to be dose dependent.

Biodegradation of imidacloprid in liquid media by an isolated wastewater fungus Aspergillus terreus YESM3

ABSTRACTIn the present study, a new fungal strain capable of imidacloprid degradation was isolated from agricultural wastewater drain. The fungal strain of YESM3 was identified as Aspergillus terreus based on ITS1-5.8S rDNA-ITS2 gene sequence by PCR amplification of a 500 bp sequence. Screening of A. terreus YESM3 to the insecticide imidacloprid tolerance was achieved by growing fungus in Czapek Dox agar for 6 days at 28°C. High values (1.13 and 0.94 cm cm−1) of tolerance index (TI) were recorded at 25 and 50 mg L−1 of imidacloprid, respectively in the presence and absence of sucrose. However, at 400 mg L−1 the fungus did not grow. Effects of the imidacloprid concentration, pH, and inoculum size on the biodegradation percentage were tested using Box–Behnken statistical design and the biodegradation was monitored by HPLC analysis at different time intervals. Box–Behnken results indicated that optimal conditions for biodegradation were at pH 4 and two fungal discs (10 mm diameter) in the presence of 61.2 mg L−1 of imidacloprid. A. terreus YESM3 strain was capable of degrading 85% of imidacloprid 25 mg L−1 in Czapek Dox broth medium at pH 4 and 28°C for 6 days under static conditions. In addition, after 20 days of inoculation, biodegradation recorded 96.23% of 25 mg L−1 imidacloprid. Degradation kinetics showed that the imidacloprid followed the first order kinetics with half-life (t50) of 1.532 day. Intermediate product identified as 6-chloronicotinic acid (6CNA) as one of the major metabolites during degradation of imidacloprid by using HPLC. Thus, A. terreus YESM3 showed a potential to reduce pollution by pesticides and toxicity in the effected environment. However, further studies should be conducted to understand the biodegradation mechanism of this pesticide in liquid media.

Effects of imidacloprid on Rana catesbeiana immune and nervous system

Imidacloprid (IMD), a neonicotinoid, is generally considered to be of low toxicity in vertebrates. However, the inhibition of acetylcholine (ACh) receptors can have a profound effect on both the immune and nervous system due to the anti-inflammatory effects of ACh. Vertebrates, such as amphibians, might be affected by IMD because they breed in wetlands where the concentration of IMD is high. In our study, we experimentally exposed Rana catesbeiana tadpoles to environmentally relevant IMD and then quantified the ACh and antibody to non-replicating antigens. We hypothesized that IMD exposure would result in higher AChE and antibody levels. We completed a factorial experiment in which tadpoles were divided into four groups, two of which were exposed to 100 ng/L of IMD. After five weeks, two groups were injected with the novel antigen keyhole limpet hemocyanin (KLH) and two injected with a control. Three weeks later, tadpoles were euthanized and blood samples collected. At 100 ng/L, IMD exposure did not cause a significant difference in AChE levels or KLH-specific IgY antibodies. However, tadpoles injected with KLH had slightly higher levels of AChE. In addition, we saw a trend in total IgM with higher levels in tadpoles exposed to IMD. While we found no effect of IMD at 100 ng/L on antibody response to a novel, non-replicating antigen nor on ACh production, further research is needed to determine if higher concentrations of IMD or parasite infection can influence development of R. catesbeiana.

Complex mixtures of dissolved pesticides show potential aquatic toxicity in a synoptic study of Midwestern U.S. streams

Aquatic organisms in streams are exposed to pesticide mixtures that vary in composition over time in response to changes in flow conditions, pesticide inputs to the stream, and pesticide fate and degradation within the stream. To characterize mixtures of dissolved-phase pesticides and degradates in Midwestern streams, a synoptic study was conducted at 100 streams during May–August 2013. In weekly water samples, 94 pesticides and 89 degradates were detected, with a median of 25 compounds detected per sample and 54 detected per site. In a screening-level assessment using aquatic-life benchmarks and the Pesticide Toxicity Index (PTI), potential effects on fish were unlikely in most streams. For invertebrates, potential chronic toxicity was predicted in 53% of streams, punctuated in 12% of streams by acutely toxic exposures. For aquatic plants, acute but likely reversible effects on biomass were predicted in 75% of streams, with potential longer-term effects on plant communities in 9% of streams. Relatively few pesticides in water—atrazine, acetochlor, metolachlor, imidacloprid, fipronil, organophosphate insecticides, and carbendazim—were predicted to be major contributors to potential toxicity. Agricultural streams had the highest potential for effects on plants, especially in May–June, corresponding to high spring-flush herbicide concentrations. Urban streams had higher detection frequencies and concentrations of insecticides and most fungicides than in agricultural streams, and higher potential for invertebrate toxicity, which peaked during July–August. Toxicity-screening predictions for invertebrates were supported by quantile regressions showing significant associations for the Benthic Invertebrate-PTI and imidacloprid concentrations with invertebrate community metrics for MSQA streams, and by mesocosm toxicity testing with imidacloprid showing effects on invertebrate communities at environmentally relevant concentrations. This study documents the most complex pesticide mixtures yet reported in discrete water samples in the U.S. and, using multiple lines of evidence, predicts that pesticides were potentially toxic to nontarget aquatic life in about half of the sampled streams.

Influence of imidacloprid treatment on Protein Profiling of soil isolate Bacillus weihenstephanensis

Imidacloprid has gained great attention as a synthetic insecticide that acts in a similar manner as nicotine and is now widely used for the control of pests. Bacteria react to environmental or chemical stress by synthesizing specific sets of proteins and these can be analyzed by protein profiling using SDS PAGE. The present investigation was undertaken to reveal protein profile changes and differentially expressed proteins in soil isolate Bacillus weihenstephanensis on dose and durational exposure to imidacloprid. Protein profiling of Bacillus weihenstephanensis treated with different (10-7 to 10-3 M) concentrations of imidacloprid observed regularly at the duration of 24 hrs for a period of 96 hours, showed the over expressions of certain protein, expression of stress proteins and novel proteins. The proteins expressed were observed to be dose and durational dependent. The present investigation proves that imidacloprid exposure induces the expression of stress and novel proteins in soil isolate Bacillus weihenstephanensis. The expression of these proteins may be necessary for the protection of the Bacillus weihenstephanensis from toxic effects of imidacloprid. The specific protein profiles that are expressed in response to the stress induced by imidacloprid can be used to monitor the environmental samples for the presence of similar pollutants.

Sublethal effects of imidacloprid on the development, reproduction, and susceptibility of the white-backed planthopper, Sogatella furcifera (Hemiptera: Delphacidae)

Sogatella furcifera (Horváth) (white-backed planthopper, WBPH) is one of the most important pests on rice in Asia. It seriously impacts rice production by sucking phloem from the rice plant and transmitting southern rice black-streaked dwarf virus (SRBSDV). In the current study, we examined the sublethal effects of imidacloprid on the development, reproduction, and susceptibility of S. furcifera in the laboratory using the rice stem dipping method. The results showed that exposure of third-instar S. furcifera nymphs to sublethal concentrations (LC10 and LC25) of imidacloprid inhibited the rate of nymphal development in the F0 and F1 generations, and there was a significant difference between the LC25 treated group and the control group. The fecundity (eggs per female) of the F1 generation showed significant declines of 22.05% and 38.56% following exposure to LC10 and LC25, respectively compared with the control group. Emergence rate, copulation rate, and hatchability were significantly lower in the LC25-treated group. The relative fitness of S. furcifera treated with LC10 and LC25 imidacloprid was 0.46 and 0.22, respectively. These results showed that exposure to imidacloprid impacted the next generation of S. furcifera, thus affecting the population growth of this species. After third-instar S. furcifera nymphs were exposed to sublethal concentrations of imidacloprid LC10 and LC25, S. furcifera showed reduced susceptibility to treatment with thiamethoxam and buprofezin. Although the susceptibility of S. furcifera to chlorpyrifos was decreased after the exposure of third-instar nymphs to imidacloprid LC25, S. furcifera populations that had been exposed to imidacloprid LC10 showed enhanced susceptibility to chlorpyrifos. These results provided a reference point for the application of insecticides to control S. furcifera.