Agricultural Insecticides Research Articles

Safety of Natural Insecticides: Toxic Effects on Experimental Animals.

Long-term application and extensive use of synthetic insecticides have resulted in accumulating their residues in food, milk, water, and soil and cause adverse health effects to human and ecosystems. Therefore, application of natural insecticides in agriculture and public health sectors has been increased as alternative to synthetic insecticides. The question here is, are all natural insecticides safe. Therefore, the review presented here focuses on the safety of natural insecticides. Natural insecticides contain chemical, mineral, and biological materials and some products are available commercially, e.g., pyrethrum, neem, spinosad, rotenone, abamectin, Bacillus thuringiensis (Bt), garlic, cinnamon, pepper, and essential oil products. It can induce hepatotoxicity, renal toxicity, hematotoxicity, reproductive toxicity, neurotoxicity, and oxidative stress. It can induce mutagenicity, genotoxicity, and carcinogenicity in mammals. Some natural insecticides and active compounds from essential oils are classified in categories Ib (Highly hazardous) to U (unlikely toxic). Therefore, the selectivity and safety of natural insecticides not absolute and some natural compounds are toxic and induce adverse effects to experimental animals. In concussion, all natural insecticides are not safe and the term “natural” does not mean that compounds are safe. In this respect, the term “natural” is not synonymous with “organic” and not all-natural insecticide products are acceptable in organic farmers.

Activity Improvement of Organophosphorus Hydrolase Enzyme by Error Prone PCR Method

Introduction: Organophosphorus compounds are frequently used as pesticides and insecticides in agriculture, livestock and home. Because of the high toxicity, it seems is very important its removal from the environment. An enzyme called organophosphorus hydrolase (OPH) is responsible for the decomposition of organophosphorus compounds in most of the strains. Production of enzymes and strains with more efficiency is frequently performed by genetic engineering techniques. Materials and Methods: In this study, we used PCR-based method for quick and easy improvement in activity of OPH enzyme. We selected 5.5 mM Mg2+ and 0.2 mM and Mn2+ concentrations for high PCR product. Results: After one round of error prone PCR (epPCR), The 5 number of screened strains (29%) were shown more ability than the native strains to degrade of diazinon, with more than 25% raising ratio. The E6 strain was found to have highest improvement degradation, with 29.3% improvement. At 48-hour time point, the E6 strains were able to completely remove of diazinon. Conclusions: The epPCR method has the low complexity than other methods and can provide a diverse library include efficient mutants.

Chromosome Missegregation and Aneuploidy Induction in Human Peripheral Blood Lymphocytes In vitro by Low Concentrations of Chlorpyrifos, Imidacloprid and α-Cypermethrin.

Chlorpyrifos, imidacloprid, and α-cypermethrin are some of the most widely used insecticides in contemporary agriculture. However, their low-dose, nontarget genotoxic effects have not been extensively assayed. As one of the most relevant cancer biomarkers, we aimed to assess the aneuploidy due to chromosome missegregation during mitosis. To aim it we treated human lymphocytes in vitro with three concentrations of insecticides equivalents relevant for real scenario exposure assessed by regulatory agencies. We focused on chlorpyrifos as conventional and imidacloprid and α-cypermethrin as sustainable use insecticides. Cytokinesis-blocked micronucleus assay was performed coupled with fluorescence in situ hybridization (FISH) with directly labeled pancentromeric probes for chromosomes 9, 18, X and Y. None of the insecticides induced significant secondary DNA damage in terms of micronuclei (MN), nuclear buds (NB), or nucleoplasmic bridges (NPB). However, significant disbalances in chromosomes 9, 18, X and Y, and in insecticide-treated cells has been observed. According to recent studies, these disbalances in chromosome numbers may be atributted to defect sister chromatid cohesion which contribute to the increase of chromosome missegregation but not to micronuclei incidence. We conclude that tested insecticidal active substances exert chromosome missegregation effects at low concentrations, possibly by mechanism of sister chromatid cohesion. These findings may contribute to future risk assesments and understanding of insecticide mode of action on human genome. Environ. Mol. Mutagen. 60:72-84, 2019. © 2018 Wiley Periodicals, Inc.

Determination of ultra-trace amounts of neonicotinoid insecticide imidacloprid by cyclic and square wave voltammetric methods using pretreated glassy carbon electrode

<p>Pesticide production and application have progressively increased worldwide during recent decades. Among these compounds, imidacloprid (IMD) is a widely used insecticide in agriculture, and more particularly to control sucking insects in crops. The aim of this work is to develop rapid, simple and sufficiently sensitive cyclic voltammetry (CV) and square wave voltammetry (SWV) for the detection and quantification of this insecticide in water and agriculture samples. Pretreated glassy carbon electrode (PGC) was employed as working electrode. Aqueous solutions were prepared with Confidor 200-SL commercial formulation of IMD. Each voltammogram was characterized by a well-defined single irreversible cathodic peak at approximately -1.38 V/SCE. The electrode reaction is mainly a diffusion controlled process. The optimization of experimental parameters such as IMD initial concentration, potential scan rate, pH and temperature was carried out by CV, and then a comparative study was conducted by SWV. For the detection and quantification of IMD, the results obtained by SWV showed higher sensibility and accuracy than that by CV. The developed methods were successfully used to determine IMD in real samples, namely plum and peach juice.</p>

Long‐term risk assessment on noneffective and effective toxic doses of imidacloprid to honeybee workers

AbstractImidacloprid is the most widely used insecticide in agriculture. Its impact on honeybees has received worldwide attention. Foliar sprays are commonly and frequently used for piercing insect control, particularly on cotton in southern USA. To simulate field exposures of formulated imidacloprid (Advise® 2Fl), we used a modified spray tower to treat honeybee workers and monitored five enzyme activities and survival for up to 52 days. Results indicated that spray treatments twice a week for 52 days with 0.001 and 1 mg/L and once a week for three weeks with 4.3 mg/L Advise showed no adverse effect on bee survival, where imidacloprid‐treated bees could live as long as untreated bees. Concentration ≥80 mg/L significantly reduced bee survival, and substantial number of bees continued to die after 48‐hr of post‐treatment period which was commonly used for measuring insecticide toxicity. The body weight of imidacloprid‐treated bees (at LC20 and LC50) was also significantly reduced. Enzymatic data showed that activities of detoxification enzymes esterase and glutathione S‐transferase (GST), insecticide‐target enzyme acetylcholinesterase (AChE) and honey enzyme invertase in imidacloprid‐treated survivors were mostly similar to those found in untreated bees. The immunity‐related phenoloxidase (PO) activity in imidacloprid‐treated survivors was also mostly similar to that of untreated control, but higher PO activity was detected in bees treated with higher concentrations for 3 weeks. By using both bioassays and enzymatic assays, this study revealed long‐term noneffective and effective concentrations of imidacloprid that may be useful for accurate assessment of toxicity risk of neonicotinoids to bees.

Celastrol inhibits glucocorticoid‑induced osteoporosis in rat via the PI3K/AKT and Wnt signaling pathways.

Modern pharmacological studies revealed that Celastrol exhibits anti‑inflammation, anti‑bacteria, anti‑virus, anti‑fertility, insect‑resistance functions and has been used for the treatment of rheumatism, rheumatoid arthritis, blood diseases, skin diseases and agricultural insecticide. The present study aimed to investigate the effects of Celastrol on glucocorticoid‑induced osteoporosis (GIOP) and the underlying molecular mechanisms. The findings of the current study revealed that Celastrol reduced body weight, urine calcium/creatinine, tartrate‑resistant acid phosphatase5b, C‑terminal telopeptide of typeI collagen, and induced osteocalcin in GIOP rats. In addition, alkaline phosphatase, triiodothyronine receptor auxiliary protein and cathepsinK mRNA expression levels were effectively suppressed, and osteocalcin, bone morphogenetic protein 2, typeI collagen and runt‑related transcription factor 2mRNA expression levels were effectively induced in osteoporosis rats treated with Celastrol. Celastrol inhibited prostaglandin E2 and caspase‑3 protein expression levels, and induced phosphoinositol 3‑kinase (PI3K), phosphorylated‑protein kinase B(AKT) and glycogen synthase kinase‑3 phosphorylation, Wnt and β‑catenin protein expression in GIOP rats. The present study demonstrated that Celastrol may inhibit GIOP in rats via the PI3K/AKT and Wnt signaling pathways.

Botanical insecticides effectively control chickpea weevil, Callosobruchus maculatus

Health hazards associated with the excess use of chemical insecticides used for the post-harvest preservation of food grains has prompted the emphasis on the use of natural insecticides in agriculture. In this regards, botanical insecticides have emerged as one of the best, safer, green, eco-friendly, promising and sustainable alternatives for controlling insect pests. Therefore, present study was aimed to evaluate the insecticidal and repellent activities of extracts of various plants such as Azadirachta indica (kernel), Allium sativum (bulb), Curcuma longa (rhizome), Citrus sinensis (peel), Citrus limon (peel), Murraya koenigii (leaves) and Eucalyptus sp. (leaves) against the chickpea weevil, Callosobruchus maculatus (Coleoptera: Chrysomelidae). These extracts exhibited potent insecticidal and repellent effects on C. maculatus. After 5 days treatment, all these extracts showed varying degree of insecticidal and repellent activity against C. maculatus; A. indica produced highest mortality (58%) followed by A. sativum (52.66% mortality) and C. longa (49.33% mortality) whereas C. sinensis exerted the lowest mortality (12.45%) against C. maculatus. All these extracts also showed good repellent activity, A. indica showed the highest index of repellency (IR) (0.53) followed by A. sativum (IR = 0.66), C. longa (IR = 0.73) and M. koenigii (IR = 0.86). These plant extracts also protected the chickpea grains from damage due to the beetle, A. indica provided 95.63% protection to chickpea grains against damage. Among the various extracts, extracts of A. indica (kernel), A. sativum (bulb) and C. longa (rhizome) proved to be promising insecticides and repellent against chickpea insect pest and can be used as effective, safer and green insecticides and repellents to preserve and protect chickpea grains against coleopteran pest.

Effects of short-term, sublethal fipronil and its metabolite on dragonfly feeding activity.

Dragonflies, Sympetrum spp., are indispensable to agriculture and are a central element of culture in Japan. However, S. frequens populations in rice paddy fields have declined in recent decades. Dragonfly larvae are predatory aquatic insects that feed on other organisms found in habitats with slow-moving or standing water. The increasing use of fipronil and neonicotinoid insecticides in agriculture is also increasing exposure to Sympetrum spp. in larval stages through paddy soil and water. The role of fipronil insecticides in the decline of dragonflies is of concern, and we here examine the sublethal effects of this insecticide on the feeding behaviors of two Sympetrum spp. Based on the quantity of prey items consumed and the time to capture prey items, feeding inhibition was determined to be a potential mechanism of the decline of Sympetrum spp. following 48-h exposure to fipronil and fipronil sulfone. Prey consumption by S. infuscatum was significantly reduced for fipronil sulfone at all concentrations (0.01–1000 μg/L). S. frequens exposed to 1, 10, 100 and 1000 μg/L fipronil sulfone had significantly longer prey capture times. Fipronil sulfone was 2.8, 9.7 and 10.5 times more toxic to S. infuscatum than fipronil in terms of acute toxicity, feeding inhibition and delayed toxicity, respectively. In addition, fipronil sulfone was 6.6, 2.9 and 9.1 times more toxic, respectively, to S. frequens than fipronil. Our findings suggest that sublethal effects on feeding inhibition lead to severe mortality at realistic paddy soil and water concentrations. Our results provide the first demonstration that short-term exposure to fipronil and fipronil sulfone can consequently cause significant harm to dragonfly larvae survival due to feeding inhibition. These findings have implications for current pesticide risk assessment and dragonfly protection.

Molecular and Biochemical Evidences for Beneficial Effects of Zinc Oxide Nanoparticles in Modulation of Chlorpyrifos Toxicity in Human Lymphocytes.

Chlorpyrifos (CP), an acetylcholinesterase (AChE) inhibitor, is used throughout the world as an insecticide in agriculture and an eradicating agent for termites around homes. In the present study, we examined the protective role of zinc oxide nanoparticles (ZnO NPs) in human CP-treated lymphocytes. Lymphocytes isolated by Ficoll and exposed to 75 µg/mL CP either alone or in combination with logarithmic doses of ZnO NPs (0/1, 1, 10, 100 µg/mL). After a 3-day incubation period, the viability and oxidative stress markers were determined. Then, the levels of tumor necrosis factor-α (TNF-α), as an inflammatory index along with AChE activity and cell death were evaluated. Our results showed that incubation with CP significantly increases the percent of cell death, activities of caspase-3 and -9, level of TNF-α and also promotes the levels of biomarkers which play important role in oxidative stress. On the other hand, the activity of AChE and levels of the total antioxidant power (TAP) decreased in CP-treated lymphocytes. In contrast, lymphocytes treated with different concentrations of ZnO NPs showed a significant decrease in the percent of mortality as well as the levels of TNF-α, as compared with CP-treated lymphocytes. Besides, ZnO NPs increased the levels of AChE and TAP at 1 µg/mL. In conclusion, the results indicate the protective effects of ZnO NPs in the prevention of cytotoxic activity of CP in the lymphocytes.

Monitoring and spatiotemporal variations of pyrethroid insecticides in surface water, sediment, and fish of the river Chenab Pakistan.

There is a serious concern regarding freshwater resources of Pakistan which have been mismanaged and now are depleting extensively due to other reasons like intensive application of agricultural pesticides and insecticides. The present study was conducted to determine the concentrations of cypermethrin, deltamethrin, permethrin, and bifenthrin in the samples of water, sediments, and fish collected from various locations of River Chenab, Pakistan, during summer and winter seasons. These locations include namely Marala, Khanki, Qadirabad, and Trimu Headworks. High-performance liquid chromatography (HPLC) was deployed for analysis and determination of pyrethroid concentrations in these samples. The analytics show the order of pyrethroid concentrations in river as fish> sediment>water. Whereas maximum concentrations of 0.472μgg-1 found in fish and minimum concentrations were determined in water, i.e., 0.087μgL-1 at the sampling locations of Trimu and Marala headworks, respectively. Moreover, highest mean concentrations of pyrethroid, i.e., 1.248μgg-1 in fish were detected in winter season as compared to summers, i.e., 0.087μgL-1. However, all the values of pyrethroid were found to be lower than the maximum permissible levels specified by EU and WHO-FAO. Whereas the levels of deltamethrin and permethrin in water were found much higher than the specific limits set by EU.

Organophosphate insecticide exposure: A clinical consideration of chlorpyrifos regulation.

In March 2017, the Environmental Protection Agency (EPA) reversed course on a proposal to ban the agricultural use of the organophosphate (OP) insecticide chlorpyrifos (CPF). The purpose of this article is to examine the evidence leading to this controversial decision and provide clinically applicable health promotion guidance for nurse practitioners on CPF exposure and risk reduction measures. Environmental Protection Agency documents on CPF regulation and corresponding research referenced within the EPA reports are reviewed. Evidence-based health promotion strategies obtained through PubMed, CINAHL, Center for Disease Control and Prevention, and National Institutes of Health sources are summarized. Available data suggest a potential association between CPF exposure and adverse neurodevelopmental outcomes. Particularly vulnerable populations are pregnant women, children younger than two years, and agricultural workers. There may be genetic variability in susceptibility to environmental toxins. Because of the extensive use of the OP CPF in agriculture and other community-based settings throughout the United States, nurse practitioners should be knowledgeable of the evidence regarding CPF exposure and be prepared to provide health promotion guidance to patients in clinical practice. Nurse practitioners should also consider their role in advocacy for healthy environments and the protection of vulnerable populations as it relates to agricultural insecticide exposure.

Neonicotinoid detection in wild turkeys (Meleagris gallopavo silvestris) in Ontario, Canada

The use of neonicotinoid insecticides in agriculture is now recognized for the health risks it poses to non-target wildlife, with associated honey bee mortality especially concerning. Research directed toward the presence and effects of these pesticides on terrestrial vertebrates that consume neonicotinoid-coated seeds, such as wild turkeys (Meleagris gallopavo silvestris), is lacking. This study used liquid chromatography attached to a tandem mass spectrometer to assess the liver from 40 wild turkeys for neonicotinoid and other pesticide residues and compared detected levels of these contaminants across the southern Ontario, Canada. Nine (22.5%) wild turkeys had detectible levels of neonicotinoid residues—clothianidin in eight, and thiamethoxam in three. Two (5.0%) of these turkeys had detectable levels of both clothianidin and thiamethoxam. Fuberidazole was detected in two (5.0%) wild turkeys. The highest level of thiamethoxam detected was 0.16 ppm, while clothianidin was detected at 0.12 ppm, and fuberidazole at 0.0094 ppm. Knowledge of exposure in free-ranging wildlife is critical for better understanding the effects of neonicotinoids on wildlife health; thus, these data help establish baseline data for southern Ontario wild turkeys and provide context for reference values in future analyses.

Impaired associative learning after chronic exposure to pesticides in young adult honey bees.

Neonicotinoids are the most widespread insecticides in agriculture, preferred for their low toxicity to mammals and their systemic nature. Nevertheless, there have been increasing concerns regarding their impact on non-target organisms. Glyphosate is also widely used in crops and, therefore, traces of this pesticide are likely to be found together with neonicotinoids. Although glyphosate is considered a herbicide, adverse effects have been found on animal species, including honey bees. Apis mellifera is one of the most important pollinators in agroecosystems and is exposed to both these pesticides. Traces can be found in nectar and pollen of flowers that honey bees visit, but also in honey stores inside the hive. Young workers, which perform in-hive tasks that are crucial for colony maintenance, are potentially exposed to both these contaminated resources. These workers present high plasticity and are susceptible to stimuli that can modulate their behaviour and impact on colony state. Therefore, by performing standardised assays to study sublethal effects of these pesticides, these bees can be used as bioindicators. We studied the effect of chronic joint exposure to field-realistic concentrations of the neonicotinoid imidacloprid and glyphosate on gustatory perception and olfactory learning. Both pesticides reduced sucrose responsiveness and had a negative effect on olfactory learning. Glyphosate also reduced food uptake during rearing. The results indicate differential susceptibility according to honey bee age. The two agrochemicals had adverse effects on different aspects of honey bee appetitive behaviour, which could have repercussions for food distribution, propagation of olfactory information and task coordination within the nest.

Prospects of botanical pesticides for the future in pest management.

IN THIS STUDY, three plant oils (fenugreek, ginseng and marjoram) and the bio-insecticide abamectin were used as agricultural insecticides. Effects of these materials on cowpea weevil (Callosobruchus maculatus) and on Vicia faba plant cells were examined. Results showed that the mortality percentage of C. maculatus adult increased with the increase of dose treatments (ml/kg) and by increasing the time of exposure. The residual activity of the tested materials on cowpea seeds at storage periods (3 months) showed that 2LC95 of tested oils have a reduction effect on Callosobruchus maculatus progeny (F1 ); which decreased gradually till the 6th week while, LC95 of abamectin decrease the number of F1 to zero (100% reduction) in all times of treatment until storage periods. The percentage of C. maculatus emergence in cowpea seed treated with the tested mixtures (oils- abamectin) showed that mixture 2 is the most effective which recorded 100% at the initial time up to 12th week.On the other hand, the cytotoxic effects using root tips of Vicia faba assay showed reduction in MI in all treatments applied which increased with the increase of the concentration. It recorded 2.42, 2.01, 1.64 and 0.91% in roots treated with the highest concentration of fenugreek, ginseng, marjoram and abamectin respectively, as compared with negative control (4.18%) or with the positive control (1.83%). All the mixtures (oils- abamectin) applied recorded significant decrease in MI values. Different types of chromosome abnormalities were recorded such as stickiness, disturbance in metaphase and anaphase, C-metaphase, chromosome bridges, lagging chromosome and micronuclei at interphase.

Chlorpyrifos interacts with other agricultural stressors to alter stream communities in laboratory microcosms.

Chlorpyrifos is one of the most widely used agricultural insecticides in the world, but to date there is limited empirical information about its potential to interact with other common agricultural stressors. We conducted a 15-d, community-level, microcosm experiment evaluating individual and combined effects of chlorpyrifos, nutrient enrichment, and sedimentation on stream invertebrate communities (abundance, biomass, richness, size structure, composition) and ecosystem processes (primary productivity and leaf decomposition). We found that sedimentation was the most detrimental stressor, with significant negative impacts on most invertebrate community and ecosystem function variables. Even though chlorpyrifos did not cause significant invertebrate mortality in the microcosms, it still altered ecosystem function by lowering leaf decomposition rates, probably through sublethal inhibition of invertebrate shredders. Furthermore, we observed a significant reversal interaction between chlorpyrifos and sediment for small-sized invertebrates collected in gravel (abundance in sediment×insecticide microcosms was 2.4 times lower than predicted by additivity), as well as an antagonistic interaction with nutrients on invertebrate richness in the same microhabitat (richness in nutrient×insecticide microcosms was 1.6 times higher than predicted by additivity). Our results suggest that chlorpyrifos has the potential to alter freshwater ecosystem function and interact non-additively with other common agricultural stressors. These findings are in keeping with a growing body of research highlighting that multiple stressor interactions and ecosystem processes should be considered when evaluating the impacts of organic toxicants on freshwater ecosystems.

Intraperitoneal fipronil effects on liver histopathological, biochemistry and morphology in Caspian kutum, Rutilus frisii kutum (Kamenskii, 1901)

Fipronil is a relatively new insecticide in agriculture with health and environmental effects. This is the first report studying effect of fipronil on fish administered via intraperitoneal route. Intraperitoneal LD50 of fipronil in 16.3 g Caspian kutum, Rutilus frisii kutum, fingerlings was determined using a total of 133 fish in 19 tanks (7 fish/tank) including one control and 6 treatment groups (300, 450, 550, 650, 750, 850 mg/kg). Fish were injected intraperitoneally and monitored at 96 h. The LD50 of fipronil was 632 mg/kg in Caspian kutum. Sub-lethal test doses of 10, 20, and 30% of the LD50 at 96 h were used to assess the effect of fipronil on the fish’s liver. The blood plasma of 90 fish were used (18 at each test dose and in controls) on days 7 and 14 for biochemistry. The hepatosomatic index (HSI) of the livers were obtained and histopathology done on the same days. Pyknosis, sinusoid dilation and vacuolization were common histological changes, and these changes became more severe in a time and dose dependent manner. This dependence was also observed for HSI and the liver biochemical test (alanine and aspartate transaminase). Liver histological alterations showed that fipronil can be a potential factor in liver carcinoma.

RDL mutations predict multiple insecticide resistance in Anopheles sinensis in Guangxi, China

BackgroundAnopheles sinensis is a major vector of malaria in China. The gamma-aminobutyric acid (GABA)-gated chloride channel, encoded by the RDL (Resistant to dieldrin) gene, is the important target for insecticides of widely varied structures. The use of various insecticides in agriculture and vector control has inevitably led to the development of insecticide resistance, which may reduce the control effectiveness. Therefore, it is important to investigate the presence and distribution frequency of the resistance related mutation(s) in An. sinensis RDL to predict resistance to both the withdrawn cyclodienes (e.g. dieldrin) and currently used insecticides, such as fipronil.MethodsTwo hundred and forty adults of An. sinensis collected from nine locations across Guangxi Zhuang Autonomous Region were used. Two fragments of An. sinensis RDL (AsRDL) gene, covering the putative insecticide resistance related sites, were sequenced respectively. The haplotypes of each individual were reconstructed by the PHASE2.1 software, and confirmed by clone sequencing. The phylogenetic tree was built using maximum-likelihood and Bayesian inference methods. Genealogical relations among different haplotypes were also analysed using Network 5.0.ResultsThe coding region of AsRDL gene was 1674 bp long, encoding a protein of 557 amino acids. AsRDL had 98.0% amino acid identity to that from Anopheles funestus, and shared common structural features of Cys-loop ligand-gated ion channels. Three resistance-related amino acid substitutions (A296S, V327I and T345S) were detected in all the nine populations of An. sinensis in Guangxi, with the 296S mutation being the most abundant (77–100%), followed by 345S (22–47%) and 327I (8–60%). 38 AsRDL haplotypes were identified from 240 individuals at frequencies ranging from 0.2 to 34.8%. Genealogical analysis suggested multiple origins of the 345S mutation in AsRDL.ConclusionsThe near fixation of the 296S mutation and the occurrence of the 327I and 345S mutations in addition to 296S, in all the nine tested An. sinensis populations in Guangxi, strongly indicate a risk of multiple insecticide resistance. The haplotype diversity plus genetic heterogeneities in the geographical distribution, and multiple origins of AsRDL alleles call for a location-customized strategy for monitoring and management of insecticide resistance.

Adaptation of Gammarus pulex to agricultural insecticide contamination in streams

Exposure to pesticides affects non-target aquatic communities, with substantial consequences on ecosystem services. Adaptation of exposed populations may reduce the effects of pesticides. However, it is not known under which conditions adaptation occurs when only a low toxic pressure from pesticides is present. Here, we show that Gammarus pulex, a dominant macroinvertebrate species in many agricultural streams, acquires increased tolerance to pesticides when recolonization from non-contaminated refuge areas is low. Populations in the field that were exposed to pesticides at concentrations several orders of magnitude below considerable acute effects showed almost 3-fold higher tolerance to the neonicotinoid insecticide clothianidin (mean EC50 218μgL−1) compared with non-exposed populations (mean EC50 81μgL−1). This tolerance of exposed populations increased from 2- to 4-fold with increasing distance to the next refuge area (0 to 10km). We conclude that the development of tolerance for non-target species may occur at very low concentrations, much below those affecting sensitive test organisms and also lower than those predicted to be safe by governmental risk assessment frameworks.

Honeybees, poster insects for pollinators

ENVIRONMENT Honeybees, poster insects for pollinators ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2017, 95 (46), p 32November 20, 2017Cite this:C&EN 95, 46, 32(Credit: CSIRO)Figure1of2Figure1of2Honeybees (Apis mellifera) are one of nature’s often underappreciated heroes. While they busily go about their business of foraging, collecting pollen, and producing honey, they also serve as unwitting pollinators to help humans produce much of the food we eat. Because bees are often managed by beekeepers and moved around, they would normally make poor sentinel species. But they still qualify as valuable sentinels by virtue of contaminants that show up in the honey they produce.Honeybees and other pollinators such as bumblebees and monarch butterflies are under threats from dangers that include loss of habitat and the use of agricultural insecticides. In particular, neonicotinoids used to kill crop-damaging insects have unintended effects on bee neurological function and are one of the prime suspects for causing recent declines in bee populations. Exposure to neonicotinoids affects honeybee olfactory learning, memory, and navigation, which together impair their foraging efficiency and could lead to problems for people by affecting food availability, quality, and cost.Although emerging studies on the effects of neonicotinoids in vertebrates show some impaired immune functioning, it’s not clear whether the problems bees and other insects have with neonicotinoids are also human health problems. To help monitor bee health scientists have started using microsensing devices fitted to their backs (shown), which identify individual bees and record their movements around hives to analyze their ability to pollinate.Sources:Christopher N. Connolly, University of Dundee; Edward A. D. Mitchell and Alexandre Aebi, University of Neuchâtel; Paulo de Souza, Commonwealth Scientific & Industrial Research Organisation Did you know? Honeybees are the only insects that produce food for humans.“The decline in bee abundances is particularly alarming given their role in pollination—bee losses are a major threat to human food security and ecosystem stability.”—Christopher N. Connolly, University of Dundee Data bite A recent study of nearly 200 honey samples from around the world found traces of at least one of the five main neonicotinoids in 75% of the samples and two or more neonicotinoids in 45% of the samples. The measured concentrations fell below the residue levels typically permitted for human consumption in the European Union, but about one-third of the samples had high enough concentrations to harm bees (Science 2017, DOI: 10.1126/science.aan3684).

Imidacloprid and chlorpyrifos insecticides impair migratory ability in a seed-eating songbird

Birds that travel long distances between their wintering and breeding grounds may be particularly susceptible to neurotoxic insecticides, but the influence of insecticides on migration ability is poorly understood. Following acute exposure to two widely used agricultural insecticides, imidacloprid (neonicotinoid) and chlorpyrifos (organophosphate), we compared effects on body mass, migratory activity and orientation in a seed-eating bird, the white-crowned sparrow (Zonotrichia leucophrys). During spring migration, sparrows were captured, held and dosed by gavage daily for 3 days with either the vehicle control, low (10% LD50) or high (25% LD50) doses of imidacloprid or chlorpyrifos and tested in migratory orientation trials pre-exposure, post-exposure and during recovery. Control birds maintained body mass and a seasonally appropriate northward orientation throughout the experiment. Imidacloprid dosed birds exhibited significant declines in fat stores and body mass (mean loss: −17% low, −25% high dose) and failed to orient correctly. Chlorpyrifos had no overt effects on mass but significantly impaired orientation. These results suggest that wild songbirds consuming the equivalent of just four imidacloprid-treated canola seeds or eight chlorpyrifos granules per day over 3 days could suffer impaired condition, migration delays and improper migratory direction, which could lead to increased risk of mortality or lost breeding opportunity.