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Neonicotinoids: Trying to make sense of the science

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... The fatal agrochemical incidents are not limited to target pests, but also affects beneficial insects like the honeybee and its products. Continuous contamination by insecticides and herbicides caused the low quality of honey (Oliver, 2012). Some of the negative impacts of agrochemicals or pesticides on honeybees and their products discussed here as follows. ...
... Honeybee face agrochemical related problems during the collection of pollen, nectar, and water or moisture from their natural environment after applied. Because of its drifts in the air, water, and soil (Oliver, 2012). ...
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Abstract: Beekeeping is important for securing food, poverty reduction, health, envir- onmental protection and plant pollination. These important practices are challenged by many biotic and abiotic factors in recent years. These factors affect honeybees and their valuable products either in combination or alone. The climatic factors like extreme temperature, relative humidity, shortage of water, deforestation of floral plants, human factors like poor apicultural practices, synthetic pesticides, diseases, and arthropod pests led to the decline of honeybee colonies and their products. But the world market demand for honey and other hive products has increased tremendously in recent decades since it is important for a wide variety of uses and applications. This review paper, therefore, was aimed at exploring these major constraints in beekeeping. It also outlines the most important cultural methods with emphasis on sanitation, maintaining bee colony vigor and some other management practices. Furthermore, from the conclusion of the review, it became important to recommend establishing specific laws and legislations that might be issued by decision makers to prevent honey adulteration. It also requires organizing honey marketing channels and raising awareness on limiting the use of pesticides in agriculture to protect the bees and the environment as well. The renovations and application of improved beekeeping technologies not only benefits beekeepers but also
... The fatal agrochemical incidents are not limited to target pests, but also affects beneficial insects like the honeybee and its products. Continuous contamination by insecticides and herbicides caused the low quality of honey (Oliver, 2012). Some of the negative impacts of agrochemicals or pesticides on honeybees and their products discussed here as follows. ...
... Honeybee face agrochemical related problems during the collection of pollen, nectar, and water or moisture from their natural environment after applied. Because of its drifts in the air, water, and soil (Oliver, 2012). ...
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Honeybee is a beneficial insect for human beings. However, their valuable products and colonies became decline from time to time. For instance, in the USA alone it declined from 60% to 26% from 1947 to 2008. However, the demand increased since it is important for a wide variety of uses. This review paper is, therefore, aimed to explore the major constraints of honeybee productions that were sourced from both abiotic and biotic factors and their management. Most of the constraints were extreme temperatures, relative humidity, drought, deforestation, poor apicultural practices, unsafe pesticide utilization, and pests. The constraints managed by different methods. For instance, foulbrood disease managed by destructing the infected comb, avoiding spore contaminations, drying the combs, ventilating, sanitation, and feed honeybees with sugar-syrup. The Varroa destructor is also managed by removing the infested combs, splitting colony, ventilating, and applying organic acids (e.g., lactic, oxalic, and formic like Mite-Away Quick Strips®), ethereal oils, synthetic pyrethroids, fluvalinate, flumethrin, and predatory mites. The tetracycline antibiotics, chemotherapeutics, and sodium sulfathiazole used for antagonizing the honeybee pathogens while feeding the antibiotic fumagillin with 25 mg/1Litre sugar-syrup manages nosema. Chalkbrood managed by improving the genetic resistance of honeybees. The parasitoids (Bracon hebetor and Apanteles galleries) have potential against wax moths. Application of Coumaphos, permethrin, and irradiation used to manage the small hive beetles. Reforestations played a great role to cope with the drought and deforestations of honey bee floras. In the future, the government should have to establish specific laws to reduce honeybee decline.
... A factor that has received a lot of attention has been the use of pesticides in agriculture, particularly insecticides. Insecticide sprays were responsible for a number of fatal incidents with honeybees and the introduction of new insecticides must reduce (Oliver, 2012). The application of agrochemical is occurring in the summer season and usually due to agricultural misuse of certain pesticide products (AFSSA, 2009). ...
... A factor that has received a lot of attention has been the use of pesticides in agriculture, particularly insecticides. Insecticide sprays were responsible for a number of fatal incidents with honeybees and the introduction of new insecticides must reduce (Oliver, 2012). The application of agrochemical is occurring in the summer season and usually due to agricultural misuse of certain pesticide products (AFSSA, 2009). ...
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The study was conducted in selected district of East Wollega Zone, Oromia Regional State, Ethiopia, to determine the prevalence of honeybee disease and varroa mite. Questionnaire survey and laboratory diagnostic methods were used for the study. The questionnaire was administered to 146 beekeepers (97.1% males) and two honeybee colony samples from each beekeeper, totally (292 honeybee colonies) were collected from transitional and frame box hives for laboratory diagnosis. The honeybee samples collected were examined in laboratory for the prevalence of honeybee disease pathogens and varroa mite. From honeybee pests, Varroa and bee lice, from pathogens; Nosema, Amoeba and chalk brood disease were confirmed while tracheal mite, stone brood, American and European foul brood pathogen did not confirmed during the study period. The prevalence of varroa destructor was higher in active season, while the prevalence of Nosema and chalk brood disease was limited during dry season. Amoeba disease was distributed in both seasons.
... A factor that has received a lot of attention has been the use of pesticides in agriculture, particularly insecticides. Insecticide sprays were responsible for a number of fatal incidents with honeybees and the introduction of new insecticides must reduce (Oliver, 2012). The application of agrochemical is occurring in the summer season and usually due to agricultural misuse of certain pesticide products (AFSSA, 2009). ...
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The study was conducted in Diga and Wayu Tuka Districts to determine the constraints and opportunities of beekeeping. Questionnaire surveys was administered to 146 beekeepers (97.1% males). Majority of the respondents started beekeeping after 2010 (28.03%) by catching colonies as honey bee colony source (54.8%). The major dearth period of the area was late march to early may. The trend of bee keeping in the study area was shifting from traditional to modern beekeeping and the trend of honeybee colony and its yield was decreasing due to honeybee health problem of the area (pests, predators, pathogenic disease, high cost of bee equipment and agrochemical application). In the study area the major pests and predators considered as challenges were ants, beetles, wax moth, varroa destructor and some predators like honey badgers, honeybee eater birds, dead head hawks moth, lizards, wasps and birds respectively. For the reason of time restraint in this study area, farther study on the driving force of challenge and opportunity of beekeeping is suggested by monitoring throughout the year.
... It is worth noting that in a subsequent laboratory study, when newly emerged (one-day old) adult bees from the very same field study colonies were experimentally inoculated with Nosema, a common gut pathogen, bees from the field-relevant dosage group were significantly more vulnerable to infection than bees from untreated hives [27]. However, EPA officials [28] and [29] have questioned of this latter laboratory result to bee colonies under natural conditions with the EPA deeming it ([28]: p. 1213, my emphasis), since there was no observed correlation in the field experiment between colony-wide levels of Nosema and the varying dosages of imidacloprid that would have been predicted by the lab study ([27]: p.156). Such field experiments to investigate the links between honey bee health and the newer systemic insecticides are designed to isolate individual factors and their direct, causal roles. ...
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Amidst ongoing declines in honey bee health, the contributory role of the newer systemic insecticides continues to be intensely debated. Scores of toxicological field experiments, which bee scientists and regulators in the United States have looked to for definitive causal evidence, indicate a lack of support. This paper analyzes the methodological norms that shape the design and interpretation of field toxicological studies. I argue that contemporary field studies of honey bees and pesticides are underpinned by a “control-oriented” approach, which precludes a serious investigation of the indirect and multifactorial ways in which pesticides could drive declines in honey bee health. I trace the historical rise to prominence of this approach in honey bee toxicology to the development of entomology as a science of insecticide development in the United States. Drawing on “complexity-oriented” knowledge practices in ecology, epidemiology, beekeeping and sociology, I suggest an alternative socio-ecological systems approach, which would entail in situ studies that are less concerned with isolating individual factors and more attentive to the interactive and place-based mix of factors affecting honey bee health.
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Participated in translation of Nature Magazine
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Honeybee Colony Collapse Disorder (HCCD or CCD) is an epidemic in which worker bees mysteriously disappear from hives, despite the presence of a living queen and immature brood—the care and feeding of both being their ordinary preoccupation—and sometimes even despite the presence of ample supplies of stored honey that would sustain them. While it understandably has a great impact on honey production, the greatest significance of HCCD is its effects on tens of billions of dollars’ worth of crops that depend on bees to pollinate their flowers so as to have higher rates of seed or fruit set. A review of the literature done in 2008, covering journal articles up through 2007, disclosed a wide variety of potential causes for HCCD being put forth, largely in articles confined to the literature of entomology and apiology. This update, which covers 2008–2013, suggests that the number of factors still seriously implicated has actually diminished and that the majority of papers today favor multifactorial explanations, which now appear in much higher visibility journals in science, especially multiscience and microbiology.
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PurposePolicy objectives and government interventions about sustainability resulting from social debates forces business models to adapt and determines the kind of innovation that is required and the ways in which it can be achieved. Yet, governments' role in defining sustainability and innovation is often overlooked, and new ways of managing the government dimension of sustainability is required as well as the development of corporate strategies encompassing inclusive visions of the corporations' role in society.Design/methodology/approachThis article aims to examine the issue from various perspectives in view of doing further research.FindingsThe management of innovation for sustainability requires increased collaboration and mentoring by public governance systems and the elaboration of coherent and inclusive strategic visions also serving the public interest when setting corporate strategies.Originality/valueThe article is based on political and economic writings and on practical experience in the public and private sectors. Copyright © 2014 John Wiley & Sons, Ltd.
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Neonicotinoid insecticides have been the target of much scrutiny as possible causes of recent declines observed in pollinator populations. Although neonicotinoids have been implicated in honey bee pesticide incidents, there has been little examination of incident report data. Here we summarize honey bee incident report data obtained from the Canadian Pest Management Regulatory Agency (PMRA). In Canada, there were very few honey bee incidents reported 2007-2011 and data were not collected prior to 2007. In 2012, a significant number of incidents were reported in the province of Ontario, where exposure to neonicotinoid dust during planting of corn was suspected to have caused the incident in up to 70% of cases. Most of these incidents were classified as "minor" by PMRA, and only six cases were considered "moderate" or "major". In that same year, there were over three times as many moderate or major incidents due to older non-neonicotinoid pesticides, involving numbers of hives or bees far greater than those suspected to be due to neonicotinoid poisoning. These data emphasize that, while exposure of honey bees to neonicotinoid-contaminated dust during corn planting needs to be mitigated, other pesticides also pose a risk.
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The effects of imidacloprid and the entomopathogen Metarhizium anisopliae (Metsch.) Sorokin on the eastern subterranean termite, Reticulitermes flavipes (Kollar), were evaluated in a 4 × 3 factorial experiment in both sterile and nonsterile loam soil. Termites were not susceptible to M. anisopliae when assays were conducted in nonsterile soil but were highly susceptible in sterile soil. Termite mortality after 21 d of continuous exposure to 104 conidia per gram of soil was zero and 41.6% in nonsterile and sterile soil, respectively. Termites were significantly more susceptible to sterile soil containing 107 conidia per gram than to the same soil containing 104 conidia per gram. In continuous exposure assays, termites were highly susceptible to imidacloprid-treated (5, 10, and 20 ppm) nonsterile and sterile soil containing no experimentally introduced M. anisopliae. Exposure of termites to imidacloprid enhanced their susceptibility to introduced M. anisopliae in nonsterile and sterile soil. Native entomopathogens recovered from termites exposed to imidacloprid-treated, nonsterile soil (i.e., no introduced M. anisopliae) included Conidiobolus coronatus (Constantin) Batko, Cunninghamella echinulata Thaxter, Fusarium spp., Aspergillus spp., and a naturally occurring strain of M. anisopliae variety majus.
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Nonlethal exposure of honey bees to thiamethoxam (neonicotinoid systemic pesticide) causes high mortality due to homing failure at levels that could put a colony at risk of collapse. Simulated exposure events on free-ranging foragers labeled with a radio-frequency identification tag suggest that homing is impaired by thiamethoxam intoxication. These experiments offer new insights into the consequences of common neonicotinoid pesticides used worldwide.
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Background: The honeybee, Apis mellifera, is undergoing a worldwide decline whose origin is still in debate. Studies performed for twenty years suggest that this decline may involve both infectious diseases and exposure to pesticides. Joint action of pathogens and chemicals are known to threaten several organisms but the combined effects of these stressors were poorly investigated in honeybees. Our study was designed to explore the effect of Nosema ceranae infection on honeybee sensitivity to sublethal doses of the insecticides fipronil and thiacloprid. Methodology/finding: Five days after their emergence, honeybees were divided in 6 experimental groups: (i) uninfected controls, (ii) infected with N. ceranae, (iii) uninfected and exposed to fipronil, (iv) uninfected and exposed to thiacloprid, (v) infected with N. ceranae and exposed 10 days post-infection (p.i.) to fipronil, and (vi) infected with N. ceranae and exposed 10 days p.i. to thiacloprid. Honeybee mortality and insecticide consumption were analyzed daily and the intestinal spore content was evaluated 20 days after infection. A significant increase in honeybee mortality was observed when N. ceranae-infected honeybees were exposed to sublethal doses of insecticides. Surprisingly, exposures to fipronil and thiacloprid had opposite effects on microsporidian spore production. Analysis of the honeybee detoxification system 10 days p.i. showed that N. ceranae infection induced an increase in glutathione-S-transferase activity in midgut and fat body but not in 7-ethoxycoumarin-O-deethylase activity. Conclusions/significance: After exposure to sublethal doses of fipronil or thiacloprid a higher mortality was observed in N. ceranae-infected honeybees than in uninfected ones. The synergistic effect of N. ceranae and insecticide on honeybee mortality, however, did not appear strongly linked to a decrease of the insect detoxification system. These data support the hypothesis that the combination of the increasing prevalence of N. ceranae with high pesticide content in beehives may contribute to colony depopulation.
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Laboratory bioassays were conducted to evaluate the effects on honeybee behavior of sublethal doses of insecticides chronically administered orally or by contact. Emergent honeybees received a daily dose of insecticide ranging from one-fifth to one-five-hundredth of the median lethal dose (LD50) during 11 d. After exposure to fipronil (0.1 and 0.01 ng/bee), acetamiprid (1 and 0.1 microg/bee), or thiamethoxam (1 and 0.1 ng/bee), behavioral functions of honeybees were tested on day 12. Fipronil, used at the dose of 0.1 ng/bee, induced mortality of all honeybees after one week of treatment. As a result of contact treatment at 0.01 ng/bee, honeybees spent significantly more time immobile in an open-field apparatus and ingested significantly more water. In the olfactory conditioning paradigm, fipronil-treated honeybees failed to discriminate between a known and an unknown odorant. Thiamethoxam by contact induced either a significant decrease of olfactory memory 24 h after learning at 0.1 ng/bee or a significant impairment of learning performance with no effect on memory at 1 ng/bee. Responsiveness to antennal sucrose stimulation was significantly decreased for high sucrose concentrations in honeybees treated orally with thiamethoxam (1 ng/bee). The only significant effect of acetamiprid (administered orally, 0.1 microg/bee) was an increase in responsiveness to water. The neonicotinoids acetamiprid and thiamethoxam tested at the highest dose (one-tenth and one-fifth of their oral LD50, respectively) and fipronil at one-five-hundredth of LD50 have limited effects on the motor, sensory, and cognitive functions of the honeybee. Our data on the intrinsic toxicity of the compounds after chronic exposure have to be taken into account for evaluation of risk to honeybees in field conditions.
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To investigate the possible consequences of brood-temperature regulation in honey bee colonies on the quality of behavioral performance of adults, we placed honey bee pupae in incubators and allowed them to develop at temperatures held constant at 32 degrees C, 34.5 degrees C, and 36 degrees C. This temperature range occurs naturally within hives. On emergence, the young adult bees were marked and introduced into foster colonies housed in normal and observation hives and allowed to live out their lives. No obvious difference in within-hive behavior was noted between the temperature-treated bees and the foster-colony bees. However, when the temperature-treated bees became foragers and were trained to visit a feeder 200 m from the hive, they exhibited clear differences in dance performance that could be correlated with the temperatures at which they had been raised: bees raised at 32 degrees C completed only approximately 20% of the dance circuits when compared with bees of the higher-temperature group. Also, the variance in the duration of the waggle phase is larger in 32 degrees C-raised bees compared with 36 degrees C-raised bees. All other parameters compared across all groups were not significantly different. One-trial learning and memory consolidation in the bees raised at different temperatures was investigated 1 and 10 min after conditioning the proboscis-extension reflex. Bees raised at 36 degrees C performed as expected for bees typically classified as "good learners," whereas bees raised at 32 degrees C and 34.5 degrees C performed significantly less well. We propose that the temperature at which pupae are raised will influence their behavioral performance as adults and may determine the tasks they carry out best inside and outside the hive.
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Biotransformation of imidacloprid and the appearance of olefin and 5-hydroxyimidacloprid metabolites in the honeybee were studied by HPLC-MS/MS analysis. Honeybees were treated orally with imidacloprid at 20 and 50 microg kg(-1) bee. Imidacloprid was metabolised relatively quickly and thoroughly. Twenty minutes after the beginning of imidacloprid ingestion, the sum of the residues from the three compounds amounted to only 70% of the actual given dose. Imidacloprid, 5-hydroxyimidacloprid and olefin represented, respectively, 50%, 9% and 8% of the actual ingested dose. Six and 24 h, respectively, after ingestion of imidacloprid at 20 and 50 microg kg(-1) bee, imidacloprid could no longer be detected in the honeybee. Imidacloprid had a half-life ranging between 4.5 and 5 h and was rapidly metabolised into 5-hydroxyimidacloprid and olefin. Except 5-hydroxyimidacloprid in the 20 microg kg(-1) treatment, these two metabolites presented a peak value 4 h after ingestion of the 20 and 50 microg kg(-1) doses. This time fully coincided with the appearance of mortality induced by imidacloprid after acute oral intoxication. These results suggested that the immediate neurotoxicity symptoms are due to the action of imidacloprid, whereas 5-hydroxyimidacloprid and/or olefin are involved in honeybee mortality. In addition, it was likely that the 30% of residues undetected 20 min after intoxication were imidacloprid metabolites, although not 5-hydroxyimidacloprid or olefin. Thus, 5-hydroxyimidacloprid and olefin could not be the major metabolites in the worker bees.
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In vivo distribution of the neonicotinoid insecticide, imidacloprid, was followed during 72 h in six biological compartments of Apis mellifera L: head, thorax, abdomen, haemolymph, midgut and rectum. Honeybees were treated orally with 100 microg of 14C-imidacloprid per kg of bee, a dose close to the median lethal dose. Elimination half-life of total radioactivity in honeybee was 25 h. Haemolymph was the compartment with the lowest and rectum that with the highest level of total radioactivity during the whole study, with a maximum 24h after treatment. Elimination half-life of imidacloprid in whole honeybee was 5 h. Imidacloprid was readily distributed and metabolised only by Phase I enzymes into five metabolites: 4/5-hydroxy-imidacloprid, 4,5-dihydroxy-imidacloprid, 6-chloronicotinic acid, and olefin and urea derivatives. The guanidine derivative was not detected. The urea derivative and 6-chloronicotinic acid were the main metabolites and appeared particularly in midgut and rectum. The olefin derivative and 4/5-hydroxy-imidacloprid preferentially occurred in head, thorax and abdomen, which are nicotinic acetylcholine receptor-rich tissues. Moreover, they presented a peak value around 4 h after imidacloprid ingestion. These results explain the prolongation of imidacloprid action in bees, and particularly the differences between rapid intoxication symptoms and late mortality.
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Short exposure of less than 2 min to pure CO2 or 3 min to −20°C did not alter the orientation and successful return of released forager honey bees to colonies. Narcosis for 15 sec with CO2 and 3 min at −20°C did not affect survival or pollen foraging behavior, but CO2 treatments of 30, 60, and 120 sec reduced survival and pollen gathering behavior. Narcosis with pure CO2 should not exceed 15 sec to reduce the risks of inducing abnormal physiological and behavioral changes in worker bees.
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Growing evidence for declines in bee populations has caused great concern because of the valuable ecosystem services they provide. Neonicotinoid insecticides have been implicated in these declines because they occur at trace levels in the nectar and pollen of crop plants. We exposed colonies of the bumble bee Bombus terrestris in the laboratory to field-realistic levels of the neonicotinoid imidacloprid, then allowed them to develop naturally under field conditions. Treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared with control colonies. Given the scale of use of neonicotinoids, we suggest that they may be having a considerable negative impact on wild bumble bee populations across the developed world.
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In addition to human error and variation in laboratory conditions, there are numerous factors that can complicate comparisons among studies. Furthermore, differences in how experimental methods are executed can make it difficult to distinguish between effects of focal versus extraneous variables. Insect neural function is commonly evaluated using Pavlovian conditioning techniques; learning and memory in many species can be assessed using the proboscis extension reflex (PER). However, there are significant inconsistencies in methods used to immobilize insects prior to PER tests. We compared responses of honeybees immobilized in a refrigerator, on ice, and in a freezer, and evaluated influence of recovery interval before testing. Ice-chilling weakly decreased learning (response to an originally neutral odor) more so than refrigeration or freezing, but not 24-h recall of odor. We found no significant differences in responsiveness to sucrose relative to cooling method, but responsiveness was significantly lower among honeybees left to recover for only 0.75h versus 1.5 or 3h. Finally, we observed increased responsiveness to sucrose and geraniol between June and August. Our results suggest that inconsistencies in cold immobilization methods could confound interpretation and comparison of results from a large body of work on honeybee learning and memory.
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Honey bees provide important pollination services to crops and wild plants. The agricultural use of systemic insecticides, such as neonicotinoids, may harm bees through their presence in pollen and nectar, which bees consume. Many studies have tested the effects on honey bees of imidacloprid, a neonicotinoid, but a clear picture of the risk it poses to bees has not previously emerged, because investigations are methodologically varied and inconsistent in outcome. In a meta-analysis of fourteen published studies of the effects of imidacloprid on honey bees under laboratory and semi-field conditions that comprised measurements on 7073 adult individuals and 36 colonies, fitted dose-response relationships estimate that trace dietary imidacloprid at field-realistic levels in nectar will have no lethal effects, but will reduce expected performance in honey bees by between 6 and 20%. Statistical power analysis showed that published field trials that have reported no effects on honey bees from neonicotinoids were incapable of detecting these predicted sublethal effects with conventionally accepted levels of certainty. These findings raise renewed concern about the impact on honey bees of dietary imidacloprid, but because questions remain over the environmental relevance of predominantly laboratory-based results, I identify targets for research and provide procedural recommendations for future studies.
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The essence of the Druckrey-Küpfmüller equation dtn = constant (where d = daily dose and t = exposure time-to-effect, with n > 1) for chemical carcinogens is that the total dose required to produce the same effect decreases with decreasing exposure levels, even though the exposure times required to produce the same effect increase with decreasing exposure levels. Druckrey and Küpfmüller inferred that if both receptor binding and the effect are irreversible, exposure time would reinforce the effect. The Druckrey-Küpfmüller equation explains why toxicity may occur after prolonged exposure to very low toxicant levels. Recently, similar dose-response characteristics have been established for the toxicity of the neonicotinoid insecticides imidacloprid and thiacloprid to arthropods. This observation is highly relevant for environmental risk assessment. Traditional approaches that consider toxic effects at fixed exposure times are unable to allow extrapolation from measured endpoints to effects that may occur at other times of exposure. Time-to-effect approaches that provide information on the doses and exposure times needed to produce toxic effects on tested organisms are required for prediction of toxic effects for any combination of concentration and time in the environment.
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Elucidating the mechanisms by which honey bees process pollen vs. protein supplements are important in the generation of artificial diets needed to sustain managed honeybees. We measured the effects of diet on protein concentration, hypopharyngeal gland development and virus titers in worker honey bees fed either pollen, a protein supplement (MegaBee), or a protein-free diet of sugar syrup. Workers consumed more pollen than protein supplement, but protein amounts and size of hypopharyngeal gland acini did not differ between the two feeding treatments. Bees fed sugar syrup alone had lower protein concentrations and smaller hypopharyngeal glands compared with the other feeding treatments especially as the bees aged. Deformed wing virus was detected in workers at the start of a trial. The virus concentrations increased as bees aged and were highest in those fed sugar syrup and lowest in bees fed pollen. Overall results suggest a connection between diet, protein levels and immune response and indicate that colony losses might be reduced by alleviating protein stress through supplemental feeding.
Article
To establish the sublethal concentrations domain, acute and chronic oral tests were conducted on caged honeybee workers (Apis mellifera L) using imidacloprid and a metabolite, 5-OH-imidacloprid, under laboratory conditions. The latter showed a 48-h oral LD50 value (153 ng per bee) five times higher than that of imidacloprid (30 ng per bee). Chronic feeding tests indicated that the lowest observed effect concentrations (LOEC) of imidacloprid and of 5-OH-imidacloprid on mortality of winter bees were 24 and 120 microg kg(-1) respectively. Behavioural effects of imidacloprid and 5-OH-imidacloprid were studied using the olfactory conditioning of proboscis extension response at two periods of the year. Winter bees surviving chronic treatment with imidacloprid and 5-OH-imidacloprid had reduced learning performances. The LOEC of imidacloprid was lower in summer bees (12 microg kg(-1)) than in winter bees (48 microg kg(-1)), which points to a greater sensitivity of honeybees behaviour in summer bees, compared to winter bees.
Article
Previous studies have shown that imidacloprid and insecticidally active imidacloprid plant metabolites are rapidly metabolized by honeybees. Accordingly, no striking differences were expected between the acute and the chronic dietary toxicity of imidacloprid to honeybees. More recently, however, an unexpectedly high chronic dietary toxicity to honeybees was reported for imidacloprid and imidacloprid plant metabolites, and a novel pharmacologic mechanism unrelated to the parent toxophor was postulated. In an extensive literature survey, no further evidence was found for the reported high difference between the acute and the chronic dietary toxicity of imidacloprid and its plant metabolites to honeybees. The majority of data indicated a dietary no observed lethal-effect concentration >0.04 and 0.02 mg/L 50% sucrose solution, respectively, for an acute and a chronic dietary exposure of honeybees to either imidacloprid or its plant metabolites. Findings of chronic feeding studies with those plant metabolites where the toxophor had already been cleaved did not support the hypotheses of a novel pharmacologic mechanism unrelated to the parent toxophor. No increased treatment-related mortality or behavioral abnormalities were recorded in four independent research facilities during a 10-day dietary exposure of honeybees of different ages to sucrose solutions spiked with the respective metabolites at 0.0001, 0.001, and 0.010 mg/L 50% sucrose solution.
Article
Behavior was altered and survivorship was reduced when parasitoids, Anagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae), were fed flowers from buckwheat, Fagopyrum esculentum L. (Polygonaceae), treated with soil applications of imidacloprid (Marathon 1% G). Parasitoids at 1 d had significantly reduced survivorship of 38 +/- 6.7% on label rate and 17 +/- 4.2% on twice label rate compared with 98 +/- 1.2% on untreated flowers. Parasitoids trembled 88% on label rate and 94% on twice label rate compared with 0% on untreated flowers. Residue analysis on a composite sample of 425 flowers showed that imidacloprid concentration was 6.6 +/- 1.0 ppm (16 ppb/flower) in label rate, 12.3 +/- 2.7 ppm (29 ppb/flower) in twice label rate, and 0 ppb in untreated flowers. The hydroxy metabolite concentration was 1.1 ppm (2.4 ppb/flower) in label rate, 1.9 ppm (4.4 ppb/flower) in twice label rate, and 0 ppm in untreated flowers. The olefin metabolite concentration was 0.2 ppm (0.5 ppb/flower) in label rate, 0.5 ppm (1.1 ppb/flower) in twice label rate, and 0 ppm in untreated flowers. Soil-applied imidacloprid used at flowering may be translocated to nectar in higher concentration compared with the imidacloprid seed treatment Gaucho. Considerable research has studied effects of Gaucho-treated canola, sunflower, and maize on behavior and mortality of Apis mellifera L. In our laboratory, we showed that translocation of imidacloprid to flowers reduced survivorship and altered behavior of pink lady beetle, Coleomegilla maculata DeGeer (Smith and Krischik 1999) and green lacewing, Chrysoperla carnea Stephens (Rogers et al. 2007).