Systemic insecticides are applied to plants using a wide variety of methods, ranging from foliar sprays to seed treatments and soil drenches. Neonicotinoids and fipronil are among the most widely ...used pesticides in the world. Their popularity is largely due to their high toxicity to invertebrates, the ease and flexibility with which they can be applied, their long persistence, and their systemic nature, which ensures that they spread to all parts of the target crop. However, these properties also increase the probability of environmental contamination and exposure of nontarget organisms. Environmental contamination occurs via a number of routes including dust generated during drilling of dressed seeds, contamination and accumulation in arable soils and soil water, runoff into waterways, and uptake of pesticides by nontarget plants via their roots or dust deposition on leaves. Persistence in soils, waterways, and nontarget plants is variable but can be prolonged; for example, the half-lives of neonicotinoids in soils can exceed 1,000 days, so they can accumulate when used repeatedly. Similarly, they can persist in woody plants for periods exceeding 1 year. Breakdown results in toxic metabolites, though concentrations of these in the environment are rarely measured. Overall, there is strong evidence that soils, waterways, and plants in agricultural environments and neighboring areas are contaminated with variable levels of neonicotinoids or fipronil mixtures and their metabolites (soil, parts per billion (ppb)-parts per million (ppm) range; water, parts per trillion (ppt)-ppb range; and plants, ppb-ppm range). This provides multiple routes for chronic (and acute in some cases) exposure of nontarget animals. For example, pollinators are exposed through direct contact with dust during drilling; consumption of pollen, nectar, or guttation drops from seed-treated crops, water, and consumption of contaminated pollen and nectar from wild flowers and trees growing near-treated crops. Studies of food stores in honeybee colonies from across the globe demonstrate that colonies are routinely and chronically exposed to neonicotinoids, fipronil, and their metabolites (generally in the 1–100 ppb range), mixed with other pesticides some of which are known to act synergistically with neonicotinoids. Other nontarget organisms, particularly those inhabiting soils, aquatic habitats, or herbivorous insects feeding on noncrop plants in farmland, will also inevitably receive exposure, although data are generally lacking for these groups. We summarize the current state of knowledge regarding the environmental fate of these compounds by outlining what is known about the chemical properties of these compounds, and placing these properties in the context of modern agricultural practices.
We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine ...environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earthworms), Apoidae sensu lato (bumblebees, solitary bees) and the section “other invertebrates” review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large-scale and wide ranging negative biological and ecological impacts on a wide range of non-target invertebrates in terrestrial, aquatic, marine and benthic habitats.
Since their discovery in the late 1980s, neonicotinoid pesticides have become the most widely used class of insecticides worldwide, with large-scale applications ranging from plant protection (crops, ...vegetables, fruits), veterinary products, and biocides to invertebrate pest control in fish farming. In this review, we address the phenyl-pyrazole fipronil together with neonicotinoids because of similarities in their toxicity, physicochemical profiles, and presence in the environment. Neonicotinoids and fipronil currently account for approximately one third of the world insecticide market; the annual world production of the archetype neonicotinoid, imidacloprid, was estimated to be ca. 20,000 tonnes active substance in 2010. There were several reasons for the initial success of neonicotinoids and fipronil: (1) there was no known pesticide resistance in target pests, mainly because of their recent development, (2) their physicochemical properties included many advantages over previous generations of insecticides (i.e., organophosphates, carbamates, pyrethroids, etc.), and (3) they shared an assumed reduced operator and consumer risk. Due to their systemic nature, they are taken up by the roots or leaves and translocated to all parts of the plant, which, in turn, makes them effectively toxic to herbivorous insects. The toxicity persists for a variable period of time—depending on the plant, its growth stage, and the amount of pesticide applied. A wide variety of applications are available, including the most common prophylactic non-Good Agricultural Practices (GAP) application by seed coating. As a result of their extensive use and physicochemical properties, these substances can be found in all environmental compartments including soil, water, and air. Neonicotinoids and fipronil operate by disrupting neural transmission in the central nervous system of invertebrates. Neonicotinoids mimic the action of neurotransmitters, while fipronil inhibits neuronal receptors. In doing so, they continuously stimulate neurons leading ultimately to death of target invertebrates. Like virtually all insecticides, they can also have lethal and sublethal impacts on non-target organisms, including insect predators and vertebrates. Furthermore, a range of synergistic effects with other stressors have been documented. Here, we review extensively their metabolic pathways, showing how they form both compound-specific and common metabolites which can themselves be toxic. These may result in prolonged toxicity. Considering their wide commercial expansion, mode of action, the systemic properties in plants, persistence and environmental fate, coupled with limited information about the toxicity profiles of these compounds and their metabolites, neonicotinoids and fipronil may entail significant risks to the environment. A global evaluation of the potential collateral effects of their use is therefore timely. The present paper and subsequent chapters in this review of the global literature explore these risks and show a growing body of evidence that persistent, low concentrations of these insecticides pose serious risks of undesirable environmental impacts.
The name surfactin refers to a bacterial cyclic lipopeptide, primarily renowned for its exceptional surfactant power since it lowers the surface tension of water from 72 mN m-1 to 27 mN m-1 at a ...concentration as low as 20 microM. Although surfactin was discovered about 30 years ago, there has been a revival of interest in this compound over the past decade, triggered by an increasing demand for effective biosurfactants for difficult contemporary ecological problems. This simple molecule also looks very promising as an antitumoral, antiviral and anti-Mycoplasma agent. Structural characteristics show the presence of a heptapeptide with an LLDLLDL chiral sequence linked, via a lactone bond, to a beta-hydroxy fatty acid with 13-15 C atoms. In solution, the molecule exhibits a characteristic "horse saddle" conformation that accounts for its large spectrum of biological activity, making it very attractive for both industrial applications and academic studies. Surfactin biosynthesis is catalysed non-ribosomally by the action of a large multienzyme complex consisting of four modular building blocks, called the surfactin synthetase. The biosynthetic activity involves the multicarrier thiotemplate mechanism and the enzyme is organized in structural domains that place it in the family of peptide synthetases, a class of enzymes involved in peptidic secondary-metabolite synthesis. The srfA operon, the sfp gene encoding a 4'-phosphopantetheinyltransferase and the comA regulatory gene work together for surfactin biosynthesis, while the gene encoding the acyltransferase remains to be isolated. Concerning surfactin production, there is no indication whether the genetic regulation, involving a quorum-sensing mechanism, overrides other regulation factors promoted by the fermentation conditions. Knowledge of the modular arrangement of the peptide synthetases is of the utmost relevance to combinatorial biosynthetic approaches and has been successfully used at the gene level to modify the surfactin template. Biosynthetic and genetic rationales have been described for building variants. A fine study of the structure/function relationships associated with the three-dimensional structure has led to the recognition of the specific residues required for activity. These studies will assist researchers in the selection of molecules with improved and/or refined properties useful in oil and biomedical industries.
Aggregations of 27 nm virus-like particles were observed in electron microscopy images of sectioned Varroa destructor mite tissue. The scattered occurrence of individual particles and accumulation of ...the virions in lattices in the cytoplasm gave an apparent indication that the virus replicates in the mite. Sequence analysis of the RNA of the purified virus revealed a genome organization with high similarity to that of members of the genus Iflavirus. Phylogenetic analysis of the polymerase showed that the virus was related most closely to Deformed wing virus (DWV) and Kakugo virus (KV) of bees. The virus has a genome of 10 112 nt without the poly(A) tail, with an overall RNA genome identity of 84 % to those of DWV and KV and has one large ORF, translated into a 2893 aa polyprotein with an amino acid identity of 95 % to those of DWV and KV. The first 1455 nt of the ORF encoding the lower molecular mass structural proteins shows the greatest diversion from those of DWV and KV, with an RNA identity of 79 %, and translates to a polypeptide of 485 aa with an identity of 90 %. The name proposed for this virus is Varroa destructor virus 1 (VDV-1). To determine whether VDV-1 replicates in mites, a selective RT-PCR was done to detect the presence of the negative-sense RNA strand. The virus isolate and the closely related DWV could be discriminated by two primer sets, each specific to one virus. Both viruses replicated in the population of the mite species studied.
Imidacloprid, the most used systemic insecticide, is suspected of having harmful effects on honeybees at nanogram per bee or at microgram per kilogram levels. However, there is a lack of methodology ...to detect imidacloprid and its metabolites at such low levels. We developed a method for the determination of low amounts of imidacloprid in soils, plants (leaves and flowers), and pollens by using HPLC coupled to tandem mass spectrometry (APCI-MS/MS). Extraction, separation, and detection were performed according to quality assurance criteria, to Good Laboratory Practice, and to criteria from the directive 96/23/EC, which is designed for banned substances. The linear range of application is 0.5−20 μg/kg imidacloprid in soils, in plants, and in pollens, with a relative standard deviation of 2.9% at 1 μg/kg. The limits of detection and of quantification are LOD = 0.1 μg/kg and LOQ = 1 μg/kg, respectively. For the first time, this study permitted us to follow the fate of imidacloprid in the environment. When treated, flowers of sunflower and maize contain average values of ∼10 μg/kg imidacloprid. This explains that pollens from these crops are contaminated at levels of a few micrograms per kilogram, suggesting probable deleterious effects on honeybees.
The assessment of agropharmaceuticals' side effects requires more realistic simulations of field conditions than those deduced from the dose-lethality relation obtained under laboratory conditions. ...Because the presence of sublethal doses or concentrations may also alter the behavior of foraging insects, we attempted to devise a quantifiable and accurate protocol for evidencing various alterations in free-flying bees. Such a protocol was illustrated by testing new classes of systemic insecticides. The protocol focused on video recording to quantify the foraging activity of small colonies of honey bees confined in insect-proof tunnels. The basis of the protocol was not the colony itself but the change in each colony on a specific day and between days. First, the paradigms of attendance at a safe feeding source were established by observing 8 control colonies at different times of the season during 5 days after the necessary forager training was accomplished. Second, on three different colonies we considered the paradigms on the control day before contamination and during 4 days after the feeding source was contaminated. During the same period, one more colony was exclusively fed with safe food to serve as control. Two plant-systemic insecticides were tested at contamination levels 70 times lower than the 50% of the lethal concentration. Imidacloprid, at 6 microg/kg, clearly induced a decrease in the proportion of active bees. Fipronil, at 2 microg/kg, induced an additional decrease in attendance at the feeder. Such levels are still higher than the corresponding lowest observable effect concentration (LOEC). Our protocol, which provided intermediate conditions between field and laboratory conditions, allowed the quantification, with an enhanced level of sensitivity, of sublethal effects on foraging bees.
The systemic imidacloprid is one of the most used insecticides in the world for field and horticultural crops. This neurotoxicant is often used as seed-dressing, especially for maize, sunflower, and ...rape. Using a LC/MS/MS technique (LOQ = 1 μg/kg and LOD = 0.1 μg/kg), the presence of imidacloprid has been measured in maize from field samples at the time of pollen shed, from less than 0.1 μg/kg up to 33.6 μg/kg. Numerous random samples were collected throughout France from 2000 to 2003. The average levels of imidacloprid measured are 4.1 μg/kg in stems and leaves, 6.6 μg/kg in male flowers (panicles), and 2.1 μg/kg in pollen. These values are similar to those found previously in sunflower and rape. These results permit evaluation of the risk to honeybees by using the PEC/PNEC ratios (probable exposition concentrations/predicted no effect concentration). PEC/PNEC risk ratios were determined and ranged between 500 and 600 for honeybees foraging on maize treated with imidacloprid by seed dressing. Such a high risk factor can be related to one of the main causes of honeybee colony losses. Keywords: Imidacloprid; maize; corn; pollen; flowers; systemic insecticide; honeybees
The One Health approach acknowledges that human health is firmly linked to animal and environmental health. It involves using animals such as bees and other pollinators as sentinels for environmental ...contamination or biological indicators. Beekeepers noticed intoxications of apiaries located in the vicinity of sheep and cattle farms, which led to the suspicion of bees' intoxication by the products used for livestock: veterinary medicinal products (VMPs) and Biocides, confirmed by laboratory analysis. We review the legal context of VMPs and Biocidal products considering Europe as a case study, and identify shortcomings at the environmental level. We describe the possible ways these products could intoxicate bees in the vicinity of livestock farms. We also illustrate the way they may impact non-target species. The cases of ivermectin and abamectin as VMPs, deltamethrin and permethrin as Biocides are considered as case studies. We show bees can be exposed to new and unrecognized routes of exposure to these chemicals, and demonstrate that their application in livestock farming can affect the survival of pollinators, such as bees. We conclude that: (1) figures on the marketing/use of these chemicals should be harmonized, centralized and publicly available, (2) research should be devoted to clarifying how pollinators are exposed to VMPs and Biocides, (3) toxicity studies on bees should be carried out, and (4) pollinators should be considered as non-targeted species concerning the environmental risk assessment before their marketing authorization. We propose the term “Multi-use substances” for active ingredients with versatile use.
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•We evaluate the impact that VMPs and Biocides have on bees using the One Health concept.•We show that VMPs and Biocides involve health risks to pollinators, which remain unconsidered.•Lack of data and knowledge gaps should be filled regarding exposure and toxicity to pollinators of VPMs and Biocides•Bees ought to be included in environmental risk assessment of VMPs and Biocides•Term “Multi-use substances”, for referring to a product with versatile usage: VMPs, Biocides, and pesticides.
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