What the Science Shows

Since 2007, researchers have increased their efforts to find a cause for the CCD phenomena. The issue is diverse and complex, with many factors potentially contributing to the cause including parasites, pesticides and stress. However, pesticides have consistently been implicated as a key issue in pollinator declines, not only through immediate bee deaths, but also through sublethal exposure causing changes in bee reproduction, navigation and foraging. These chemicals have implications for bees, other pollinators like bumblebees and hummingbirds, as well as organisms that are beneficial to the environment. The research below seeks to highlight the impact of pesticides on these organisms and their role in exacerbating susceptibility to parasites and viruses.

• Pesticide impacts on bees
• Pesticide impacts on other pollinators
• Pesticide impacts on beneficial organisms
• Parasites and Viruses

Pesticide impacts on bees

• Reduction of homing flights in the honey bee Apis mellifera after a sublethal dose of neonicotinoid insecticides
  Researchers dosed honey bees with sublethal doses four pesticides and released them in the field to determine their success in returning to their hives. The bees were treated with two neonicotinoids (clothianidin and dinotefuran), one pyrethroid (etofenprox) and one organophosphate (fenitrothion) at five different doses. Then the bees were released 500 m from their hives in the field. The proportion of successful homing flights by bees exposed to neonicotinoids and pyrethroid decreased with doses one tenth of their median lethal dose (LD50) or more and one-fourth of their LD50 or more respectively, though the bees exposed to organophosphate did not seem to respond with any declines in homing. The research has implications for the survival of honey bee hives after worker bee exposures.
• European Food Safety Authority Report on Neonicotinoids & Risk Assessment for Bees
  The report presented by the European Food Safety Authority (EFSA) finds that the neonicotinoid class of insecticides poses unacceptable hazards to bees. They concluded that certain crops treated with neonicotinoid chemicals -imidacloprid, clothianidin and thiamethoxam- are of “critical concern” for bee health. The report prompted the European Commission to push EU nations to impose a two year suspension on crops that are attractive to bees, particularly, sunflowers, rapeseed, corn, cotton, and cereal crops.
• Sublethal doses of imidacloprid decreased size of hypopharyngeal glands and respiratory rhythm of honeybees in vivo
  This report documents significant ~40-50% reduction in beneficial predator insects in cotton crops.
• Neonicotinoids Cause Neuronal Inactivation in Honeybees
  This study shows that honeybee exposure to two widely used classes of pesticide, neonicotinoid and organophosphate miticides, leads to a shut down of neurons so that the lobes of the brain fail to communicate with eachother These effects are observed at
  concentrations that are encountered by foraging honeybees and within the hive, and are additive with combined application.
• Exposure to multiple pesticides impairs olfactory learning and memory in honeybees
  Bees exposed to imidacloprid were less likely to form a long-term memory, whereas bees exposed to coumaphos were only less likely to respond during the short-term memory test after massed conditioning. Both imidacloprid, coumaphos and a combination of the two compounds impaired the bees’ ability to differentiate the conditioned odor from a novel odor during the memory test. The results demonstrate that exposure to sublethal doses of combined cholinergic pesticides significantly impairs important behaviors involved in foraging, implying that pollinator population decline could be the result of a failure of neural function of bees exposed to pesticides in agricultural landscapes.
• Bee Health: The Role of Pesticides
  This study, developed by the Congressional Research Service, provides information regarding: 1. Changes to managed and wild bee populations (they indicate information is limited); 2. Factors that are documented to impact bee health including pesticides, pests and diseases, diet and nutrition, genetics, habitat loss, and beekeeper issues, highlighting that there are multiple exposure pathways that may work synergistically; 3. Scientific research on the role of pesticides; and finally 4. Current research and regulatory activity regarding neonicotinoids, a highly controversial neurotoxin impacting bees.
• Dr. Christian Krupke's and Dr. James Frazier's criticism of Bayer Crop Science's unpublished memo entitled "Overview of recent publications on neonicotinoids and pollinators,"as submitted to EPA
• Combined pesticide exposure severely affects individual and colony level traits in bees
  This study indicates that multiple pesticides are working with synergistic effects on bees.
• Imidacloprid Depresses Honey Bee Feeding and Communication
  University of California at San Diego biologists found in their experiments that honey bees treated with a small, single dose of imidacloprid, comparable to what they would receive in nectar, became “picky eaters.” The researchers point out that honey bees that prefer only very sweet foods can dramatically reduce the amount of resources brought back to the colony. Further reductions in their food stores can occur when bees no longer communicate to their kin the location of the food source.
• Common Pesticide Decreases Foraging Success and Survival in Honey Bees
  In their study, the researchers used Radio-frequency identification (RFID) to test the hypothesis that a sublethal exposure to a neonicotinoid indirectly increases hive death rate through homing failure in foraging honey bees. When exposed to sublethal doses of thiamethoxam, at levels present in the environment, honey bees were less likely to return to the hive after foraging than control bees that were tracked with RFID, but not intentionally dosed with pesticides. Higher risks are observed when the homing task is more challenging. The survival rate is even lower when exposed bees are placed in foraging areas with which they are less familiar.
• Bee Exposure to Treated Seed Dust During Planting Confirmed
  The findings of an Italian Research team  confirm that high amounts of neonicotinoids are present in the exhaust of corn seed planters and that bees are exposed to these potentially lethal concentrations of the chemical simply by flying through the area during planting. In analyzing bees that were induced to fly through planter exhaust in a field that was being planted, the team found that there were high concentrations of clothianidin and thiamethoxam in and on the bees themselves. These concentrations were “significantly higher” than known lethal doses of the chemicals for honeybees, according to the researchers.
• Multiple routes of pesticide exposure for honey bees living near agricultural fields.
  The study analyzed samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. Study also found neonicotinoids in the soil of each field we sampled, including unplanted fields. Plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well. Study also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in our field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in our study readily collected maize pollen. These findings clarify some of the mechanisms by which honey bees may be exposed to agricultural pesticides throughout the growing season.
• See lead researcher's response to a critique of this study by Bayer scientists. Additional response by Jim Frazier, PhD, entomologist at Pennsylvania State University.
• RFID Tracking of Sublethal Effects of Two Neonicotinoid Insecticides on the Foraging Behavior of Apis mellifera.
  Study tested an experimental design using the radiofrequency identification (RFID) method to monitor the influence of sublethal doses of insecticides on individual honeybee foragers on an automated basis. In this experimental approach the authors monitored the acute effects of sublethal doses of the neonicotinoids imidacloprid and clothianidin under field-like circumstances. At field-relevant doses for nectar and pollen no adverse effects were observed for either substance. Both substances led to a significant reduction of foraging activity and to longer foraging flights during the first three hours after treatment.
• Exposure to Sublethal Doses of Fipronil and Thiacloprid Highly Increases Mortality of Honeybees Previously Infected by Nosema ceranae
  This study explores the effect of Nosema ceranae infection on honeybee sensitivity to sublethal doses of the insecticides fipronil and 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. 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.
• Fatal powdering of bees in flight with particulates of neonicotinoids seed coating and humidity implication
  The effect of direct aerial powdering was tested on foragers in free flight near the drilling machine. Bees were conditioned to visit a dispenser of sugar solution whilst a drilling machine was sowing corn along the flight path. Samples of bees were captured on the dispenser, caged and held in the laboratory. Chemical analysis showed some hundred nanograms of insecticide per bee. Nevertheless, caged bees, previously contaminated in flight, died only if kept in conditions of high humidity. After the sowing, an increase in bee mortality in front of the hives was also observed. Spring bee losses, which corresponded with the sowing of corn-coated seed, seemed to be related to the casual encountering of drilling machine during foraging flight across the ploughed fields.
• Neonicotinoid insecticides translocated in guttated droplets of seed-treated maize and wheat: a threat to honeybees?
  This experiment demonstrates that guttated water of plants germinated from seeds dressed with neonicotinoids contains neonicotinoids. Maize seeds treated with clothianidin (Poncho® 0.5mg/seed and Poncho® Pro 1.25mg/seed) resulted in neonicotinoid concentrations up to 8,000ngmL−1 in the guttated fluid. This concentration decreases rapidly, but remained detectable over several weeks. Seeds treated with Poncho® Pro did not result in higher concentrations in guttated droplets in the first stages of plant development, but the concentration decreased more slowly. Triticale seed treated with imidacloprid contained small quantities of this active agent (up to 13ngmL−1) in the guttated fluid the following spring after overwintering.
• Sub-Lethal Effects of Pesticide Residues in Brood Comb on Worker Honey Bee (Apis mellifera) Development and Longevity
  Synopsis: Researchers conducted studies to examine possible direct and indirect effects of pesticide exposure from contaminated brood comb on developing worker bees and adult worker lifespan. Results demonstrate sub-lethal effects on worker honey bees from pesticide residue exposure from contaminated brood comb. Sub-lethal effects, including delayed larval development and adult emergence or shortened adult longevity, can have indirect effects on the colony such as premature shifts in hive roles and foraging activity.
• Rapid analysis of neonicotinoid insecticides in guttation drops of corn seedlings obtained from coated seeds
  Synopsis: In the present study, guttation drops of corn plants obtained from commercial seeds coated with thiamethoxam, clothianidin, imidacloprid and fipronil have been analyzed. The young plants grown both in pots – in greenhouse – and in open field from coated seeds, produced guttation solutions containing high levels of the neonicotinoid insecticides (up to 346 mg L-1 for imidacloprid, 102 mg L-1 for clothianidin and 146 mg L-1 for thiamethoxam). These concentration levels may represent lethal doses for bees that use guttation drops as a source of water. The neonicotinoid concentrations in guttation drops progressively decrease during the first 10–15 days after the emergence of the plant from the soil. Otherwise fipronil, which is a non-systemic phenylpyrazole insecticide, was never detected into guttation drops. Current results confirm that the physiological fluids of the corn plant can effectively transfer neonicotinoid insecticides from the seed onto the surface of the leaves, where guttation drops may expose bees and other insects to elevated doses of neurotoxic insecticides.
• Abnormal Foraging Behavior Induced by Sublethal Dosage of Imidacloprid in the Honey Bee (Hymenoptera: Apidae)
  Synopsis: Although sublethal dosages of insecticide to nontarget insects have never been an important issue, they are attracting more and more attention lately. It has been demonstrated that low dosages of the neonicotinoid insecticide imidacloprid may affect honey bee, Apis mellifera L., behavior. In this article, the foraging behavior of the honey bee workers was investigated to show the effects of imidacloprid. Results demonstrated that sublethal dosages of imidacloprid were able to affect foraging behavior of honey bees.
• Pesticides and honey bee toxicity – USA
  Synopsis: This review examines pesticides applied to crops, pesticides used in apiculture and pesticide residues in hive products. Authors discuss the role that pesticides and their residues in hive products may play in colony collapse disorder and other colony problems. Although no single pesticide has been shown to cause colony collapse disorder, the additive and synergistic effects of multiple pesticide exposures may contribute to declining honey bee health.
• High Levels of Miticides and Agrochemicals in North American Apiaries: Implications for Honey Bee Health
  Synopsis: Recent declines in honey bees for crop pollination threaten fruit, nut, vegetable and seed production in the United States. A broad survey of pesticide residues was conducted on samples from migratory and other beekeepers across 23 states, one Canadian province and several agricultural cropping systems during the 2007–08 growing seasons. The 98 pesticides and metabolites detected in mixtures up to 214 ppm in bee pollen alone represents a remarkably high level for toxicants in the brood and adult food of this primary pollinator. This represents over half of the maximum individual pesticide incidences ever reported for apiaries. While exposure to many of these neurotoxicants elicits acute and sublethal reductions in honey bee fitness, the effects of these materials in combinations and their direct association with CCD or declining bee health remains to be determined. See: Daily News Blog.
• Effects of sublethal concentrations of bifenthrin and deltamethrin on fecundity, growth, and development of the honeybee Apis mellifera ligustica
  Synopsis: Bifenthrin and deltamethrin have been widely used as pesticides in agriculture and forestry and are becoming an increasing risk to honeybees. The honeybee, Apis mellifera ligustica, is widely recognized as a beneficial insect of agronomic, ecological, and scientific importance. It is important to understand what effects these chemicals have on bees. Effects of two pesticides at sublethal concentrations on fecundity, growth, and development of honeybees were examined with the feeding method for a three-year period (2006–2008). It was shown that both bifenthrin and deltamethrin significantly reduced bee fecundity, decreased the rate at which bees develop to adulthood, and increased their immature periods. The toxicity of bifenthrin and deltamethrin on workers of Apis mellifera ligustica was also assessed, and the results from the present study showed that the median lethal effects of bifenthrin and deltamethrin were 16.7 and 62.8?mg/L, respectively. See Daily News Blog.
• Synergistic Interactions Between In-Hive Miticides in Apis mellifera
  Synopsis : The varroa mite, Varroa destructor Anderson & Trueman, is a devastating pest of honey bees, Apis mellifera L., that has been primarily controlled over the last 15 yr with two in-hive miticides: the organophosphate coumaphos (Checkmite+), and the pyrethroid tau-fluvalinate (Apistan). In this laboratory study, the authors observed a large increase in the toxicity of tau-fluvalinate to 3-day-old bees that had been treated previously with coumaphos, and a moderate increase in the toxicity of coumpahos in bees treated previously with tau-fluvalinate. The observed synergism may result from competition between miticides. These results suggest that honey bee mortality may occur with the application of otherwise sublethal doses of miticide when tau-fluvalinate and coumaphos are simultaneously present in the hive.
• Translocation of Neonicotinoid Insecticides From Coated Seeds to Seedling Guttation Drops: A Novel Way of Intoxication for Bees
  Synopsis: The death of honey bees, Apis mellifera L., and the consequent colony collapse disorder causes major losses in agriculture and plant pollination worldwide. The phenomenon showed increasing rates in the past years, although its causes are still awaiting a clear answer. Here, we show that leaf guttation drops of all the corn plants germinated from neonicotinoid-coated seeds contained amounts of insecticide constantly higher than 10 mg/l, with maxima up to 100 mg/l for thiamethoxam and clothianidin, and up to 200 mg/l for imidacloprid. The concentration of neonicotinoids in guttation drops can be near those of active ingredients commonly applied in field sprays for pest control, or even higher. When bees consume guttation drops, collected from plants grown from neonicotinoid-coated seeds, they encounter death within few minutes.
• Interactions between Nosema microspores and a neonicotinoid weaken honeybees (Apis mellifera) Synopsis: Global pollinators, like honeybees, are declining in abundance and diversity, which can adversely affect natural ecosystems and agriculture. The authors tested the current hypotheses describing honeybee losses as a multifactorial syndrome, by investigating integrative effects of an infectious organism and an insecticide on honeybee health. Study demonstrated that the interaction between the microsporidia Nosema and a neonicotinoid (imidacloprid) significantly weakened honeybees. In the short term, the combination of both agents caused the highest individual mortality rates and energetic stress. This provides the first evidences that interaction between an infectious organism and a chemical can also threaten pollinators, interactions that are widely used to eliminate insect pests in integrative pest management.
• Toxicities of fipronil enantiomers to the honeybee Apis mellifera L. and enantiomeric compositions of fipronil in honey plant flowers.
  Synopsis: Fipronil is a chiral phenylpyrazole insecticide that is effective for control of a wide range of agricultural and domestic pests at low application rates. Wide application of fipronil also causes poisoning of some nontarget insects, such as honeybees. In the present study, toxicities of fipronil enantiomers and racemate to the honeybee Apis mellifera L. were determined to examine whether using formulations of single or enriched fipronil enantiomer is a possible option to reduce risks to bees. The results indicate that it is unlikely that use of formulations with single or enriched fipronil enantiomer would reduce the risk that fipronil poses to honeybees. Improved fipronil application practices (based on safest timing and bloom conditions) and reduction of overall fipronil usage seem to be more realistic options.
• Is Apis mellifera more sensitive to insecticides than other insects?
  Synopsis: The goal of this review was to summarize insecticide toxicity data between A. mellifera and other insects to determine the relative sensitivity of honey bees to insecticides. It was found that, in general, honey bees were no more sensitive than other insect species across the 62 insecticides examined. In addition, honey bees were not more sensitive to any of the six classes of insecticides (carbamates, nicotinoids, organochlorines, organophosphates, pyrethroids and miscellaneous) examined. While honey bees can be sensitive to individual insecticides, they are not a highly sensitive species to insecticides overall, or even to specific classes of insecticides. However, all pesticides should be used in a way that minimizes honey bee exposure, so as to minimize possible declines in the number of bees and/or honey contamination.
• Exposure to pesticides at sublethal level and their distribution within a honey bee (Apis mellifera) colony.
  Synopsis: Honey bee colonies were exposed to pesticides used in agriculture or within bee hives by beekeepers: coumaphos; diazinon; amitraz or fluvalinate. Samples of bee workers, larvae and royal jelly were analysed. Amitraz residues in all sampled material were below the level of detection of 10 ng/g. Diazinon was not detected in any of the analysed samples. The large quantities of fluvalinate found in bee heads and larvae, the coumaphos residues in royal jelly, and additional potential sub-lethal effects on individual honey bees or brood are discussed.
• The relevance of sublethal effects in honey bee testing for pesticide risk assessment.
  This paper considers whether and if sublethal effects should be incorporated into risk assessment, by addressing a number of questions: The authors conclude that sublethal studies may be helpful as an optional test to address particular, compound-specific concerns, as a lower-tier alternative to semi-field or field testing, if the effects are shown to be ecologically relevant. However, available higher-tier data (semi-field, field tests) should make any additional sublethal testing unnecessary, and higher-tier data should always override data of lower-tier trials on sublethal effects.
• Is it possible to use the honey bee adult as a bioindicator for the detection of pesticide residues in plants?
  Synopsis: Pesticide residues are usually determined by physical, chemical and biological methods. Theoretically, any organism that is susceptible to a pesticide may be used for its bioassay in any environmental sample. This means that such organism may serve as a bioindicator for the detection of certain pollutants. The susceptibility of honey bees (Apis melifera L.) to many insecticides commonly used in crop protection led to an attempt to use it as a bioindicator for the determination of residues of some insecticides in plant materials, as well as to detect toxicity hazards to honey bees of some commonly used insecticides. Results of this work which have been recently published may suggest "Yes" to answer the question posed in the title of this subject.
• Subchronic exposure of honeybees to sublethal doses of pesticides: effects on behavior.
  Synopsis: Laboratory bioassays were conducted to evaluate the effects on honeybee behavior of sublethal doses of insecticides chronically administered orally or by contact. After exposure to fipronil, acetamiprid or thiamethoxam, 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. 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. The only significant effect of acetamiprid (administered orally, 0.1 microg/bee) was an increase in responsiveness to water. 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.
• Comparative sublethal toxicity of nine pesticides on olfactory learning performances of the honeybee Apis mellifera.
  Synopsis: Using a conditioned proboscis extension response (PER) assay, honeybees (Apis mellifera L.) can be trained to associate an odor stimulus with a sucrose reward. In the present study, the effects of sublethal concentrations of nine pesticides on learning performances of worker bees subjected to the PER assay were estimated and compared. Reduced learning performances were observed for bees surviving treatment with fipronil, deltamethrin, endosulfan, and prochloraz. A lack of behavioral effects after treatment with lambda-cyalothrin, cypermethrin, tau-fluvalinate, triazamate, and dimethoate was recorded.
• Residues of Pesticides in honeybee (Apis mellifera carnica) bee bread and in pollen loads from treated apple orchards.
  Synopsis: Honey bee (Apis mellifera carnica) colonies were placed in two apple orchards treated with the insecticides diazinon and thiacloprid and the fungicide difenoconazole in accordance with a Protection Treatment Plan in the spring of 2007. Possible sub-lethal effects on individual honey bees and brood are discussed.

Pesticide impacts on other pollinators

• Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production
  Researchers exposed colonies of the bumble bees to levels of imidacloprid, treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared to unexposed control colonies.
• Brain morphophysiology of Africanized Bee Apis mellifera Exposed to Sublethal Doses of Imidacloprid
  The results of this study show that imidacloprid causes changes to the brain in Africanized bees, particularly to the optic lobes of the brain, disrupting their visual system and impairing their learning capacity. These changes could lead to abnormal behavior and possibly to the death of affected bees.
• Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees
  “To determine whether environmentally realistic levels of imidacloprid are capable of making a demographic impact on bumble bees, we exposed queenless microcolonies of worker bumble bees, Bombus terrestris, to a range of dosages of dietary imidacloprid between zero and 125μgL(-1) and examined the effects on ovary development and fecundity… Imidacloprid reduced feeding on both syrup and pollen but, after controlling statistically for dosage, microcolonies that consumed more syrup and pollen produced more brood. We therefore speculate that the detrimental effects of imidacloprid on fecundity emerge principally from nutrient limitation imposed by the failure of individuals to feed. "
• The impact of neonicotinoid insecticides on bumblebees, Honey bees and other non-target invertebrates
  Synopsis: This report reviews existing approvals research and independent research on the effects of neonicotinoid pesticides on Honey bees, bumblebees and other non-target invertebrates, and investigates the current approvals mechanism and its standards.
• Risk assessment for side-effects of neonicotinoids against bumblebees with and without impairing foraging behavior.
  Synopsis: Bombus terrestris bumblebees are important pollinators of wild flowers, and in modern agriculture they are used to guarantee pollination of vegetables and fruits. In the field it is likely that worker bees are exposed to pesticides during foraging. Within the context of ecotoxicology and insect physiology, study reports the development of a new bioassay to assess the impact of sublethal concentrations on the bumblebee foraging behavior under laboratory conditions. In general, the experiments showed that concentrations that may be considered safe for bumblebees can have a negative influence on their foraging behavior. Therefore it is recommended that behavior tests should be included in risk assessment tests for highly toxic pesticides because impairment of the foraging behavior can result in a decreased pollination, lower reproduction and finally in colony mortality due to a lack of food.

Pesticide impacts on beneficial organism

• Water polluted with imidacloprid linked to low numbers of aquatic insects
  The study found 70% fewer invertebrate species in water polluted with imidacloprid compared to clean water in the Netherlands. Mayflies, midges and molluscs, were all severely impacted with potential harm to their predators like birds. Researchers compiled and analyzed information from 700 sites between 1998 and 2009 to determine the impacts of water quality on wildlife. For highly polluted waters that exceeded the Dutch pollution limits, only 17 species were found on average in comparison to 52 species in clean water.
• Effects of Aldicarb and Neonicotinoid Seed Treatments on Twospotted Spider Mite on Cotton
  This is an interesting new Bayer study indicating that neonicotinoid seed treatments increase infestation of pest species in cotton crops. While the application of neonicotinoids to seeds did not increase the fecundity of mites, foliar application of thiamethoxam elevated average fecundity.
• Lethal and Sublethal Effects of Imidacloprid and Buprofezin on the Sweetpotato Whitefly Parasitoid
  This results of this study showed that the longevity and fecundity of the parasitoid, E.mundus, were reduced significantly by the two insecticides, though the sex ratio of E.mundus offspring was not affected. Population parameters of the parasitoid such as R₀, r_m and T were also significantly reduced by the insecticides. Our results indicated that, in addition to lethal effects, sublethal effects should also be considered when these insecticides are applied.
• Environmental Impact of Imidacloprid on Soil Fertility
  This study focused on imidacloprid, one of the major components of many widely used insecticides and is relatively persistent in soils. Earthworms are used as indicator species for ecotoxicological evaluation and risk assessment. The effect of Imidacloprid on mortality of a dominant crop field earthworm (Drawida willsi, Michaelsen) was studied under ideal laboratory conditions to rice field soil. The concluded that although the doses were sometimes low, that imidacloprid could affect the soil biota by altering its vita rates and metabolism.
• The Significance of the Druckrey-Küpfmüller Equation for Risk Assessment - The Toxicity of Neonicotinoid Insecticides to Arthropods is Reinforced by Exposure Time
  Synopsis: 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. See: Daily News Blog.

 

Parasites and Viruses

• Pesticide exposure in honey bees results in increased levels of the gut pathogen Nosema.
  Study exposed honey bee colonies during three brood generations to sub-lethal doses of a widely used pesticide, imidacloprid, and then subsequently challenged newly emerged bees with the gut parasite, Nosema spp. The pesticide dosages used were below levels demonstrated to cause effects on longevity or foraging in adult honey bees. Nosema infections increased significantly in the bees from pesticide-treated hives when compared to bees from control hives demonstrating an indirect effect of pesticides on pathogen growth in honey bees. Interactions between pesticides and pathogens could be a major contributor to increased mortality of honey bee colonies, including colony collapse disorder, and other pollinator declines worldwide.
  
  
• A New Threat to Honey Bees, the Parasitic Phorid Fly Apocephalus borealis.
  Study provides the first documentation that the phorid fly Apocephalus borealis, previously known to parasitize bumble bees, also infects and eventually kills honey bees and may pose an emerging threat to North American apiculture. Parasitized honey bees show hive abandonment behavior, leaving their hives at night and dying shortly thereafter. On average, seven days later up to 13 phorid larvae emerge from each dead bee and pupate away from the bee. Using DNA barcoding, study confirmed that phorids that emerged from honey bees and bumble bees were the same species. Phorid parasitism may affect hive viability since 77% of sites sampled in the San Francisco Bay Area were infected by the fly and microarray analyses detected phorids in commercial hives in South Dakota and California's Central Valley. Study concludes that understanding details of phorid infection may shed light on similar hive abandonment behaviors seen in CCD.
  
  
• Iridovirus and Microsporidian Linked to Honey Bee Colony Decline
  Synopsis: In 2010 Colony Collapse Disorder (CCD), again devastated honey bee colonies in the USA, indicating that the problem is neither diminishing nor has it been resolved. Many CCD investigations, using sensitive genome-based methods, have found small RNA bee viruses and the microsporidia, Nosema apis and N. ceranae in healthy and collapsing colonies alike with no single pathogen firmly linked to honey bee losses. These findings implicate co-infection by invertebrate iridescent virus (IIV) (Iridoviridae) and Nosema with honey bee colony decline, giving credence to older research pointing to IIV, interacting with Nosema and mites, as probable cause of bee losses in the USA, Europe, and Asia. See: Daily News Blog.
  
  
• Nosema ceranae, a newly identified pathogen of Apis mellifera in the U.S. and Asia
  Synopsis: Nosemosis (Nosema disease) is one of the most serious and prevalent adult honey bee diseases worldwide. For years, Nosema apis was thought to be the only microsporidia infecting domestic bee colonies. However, recently it was discovered that N. ceranae could jump from Asian honey bees (Apis cerana) to European honey bees (Apis mellifera) that are widely used for crop pollination. The data presented in the studies demonstrated that N. ceranae infection is widespread in the U.S., China and Australia and that infection with N. ceranae was more common than infection with N. apis in European honey bees. The finding about the prevalence of N. ceranae in the U.S. and Asian bee populations in conjunction with findings in other parts of the world invites further research of the evolutionary history of N. ceranae infection in European honey bees.
  
  
• Winter losses of honeybee colonies (Apis mellifera): The role of infestations with Aethina tumida and Varroa destructor
  Synopsis: Multiple infections and infestations of honeybee colonies with pathogens and parasites are inevitable due to the ubiquitous ectoparasitic mite Varroa destructor and might be one of the mechanisms underlying winter losses. Here the authors investigated the role of adult small hive beetles, Aethina tumida, alone and in combination with V. destructor for winter losses and infections with the microsporidian endoparasite Nosema ceranae. High losses occurred in all groups highly infested with V. destructor, supporting the central role of this mite in colony losses. Data suggest that A. tumida alone is unlikely to contribute to losses of overwintering honeybee colonies.
  
  
• Changes in Gene Expression Relating to Colony Collapse Disorder in honey bees, Apis mellifera
  Synopsis: Colony collapse disorder (CCD) is a mysterious disappearance of honey bees that has beset beekeepers in the United States since late in 2006. Pathogens and other environmental stresses, including pesticides, have been linked to CCD, but a causal relationship has not yet been demonstrated. Considerable variation in gene expression was associated with the geographical origin of bees, but a consensus list of 65 transcripts was identified as potential genetic markers for CCD status. Reduced expression of two genes associated with detoxification and a mixed response from genes involved in immune function were observed. Unusual ribosomal RNA fragments were also conspicuously more abundant in CCD bee guts. The presence of these fragments may be a possible consequence of picornavirus infection. Ribosomal fragment abundance and viral presence may prove useful as diagnostic markers for colonies afflicted with CCD.
  
  
• Honeybee Sacbrood virus infects adult small hive beetles, Aethina tumida (Coleoptera: Nitidulidae)
  Synopsis: The Small Hive Beetle (SHB) is a recently discovered pest that invades honey bee colonies and causes damage to comb, stored honey and pollen. A laboratory experiment was conducted to investigate whether SHB could harbor honey bee virus(es) via feeding on virus infected brood and thereby serving as a vector of viruses in honey bee colonies. Study demonstrated for the first time that SHB could become infected with honey bee Sacbrood virus (SBV) via the food-borne transmission route. This study should raise awareness among scientists, beekeepers, and regulatory personnel to the threats of SHB not only for its directly negative impact on bee health but also for its ability to transmit viral diseases in bee colonies.
  
  
• Entombed pollen: A new condition in honey bee colonies associated with increased risk of colony mortality
  Synopsis: Here we describe a new phenomenon, entombed pollen, which is highly associated with increased colony mortality. Entombed pollen appears as sunken, wax-covered cells amidst "normal", uncapped cells of stored pollen, and the pollen contained within these cells is brick red in color. The increased incidence of entombed pollen in reused wax comb suggests that there is a transmittable factor common to the phenomenon and colony mortality. In addition, there were elevated pesticide levels, notably of the fungicide chlorothalonil, in entombed pollen. Additional studies are needed to determine if there is a causal relationship between entombed pollen, chemical residues, and colony mortality.
  
  
• Differential gene expression of the honey bee Apis mellifera associated with Varroa destructor infection.
  Synopsis: The parasitic mite, Varroa destructor, is the most serious pest of the western honey bee, Apis mellifera, and has caused the death of millions of colonies worldwide. Authors investigated whether Varroa infestation induces changes in Apis mellifera gene expression, and whether there are genotypic differences in the bee’s tolerance, as first steps toward unraveling mechanisms of host response and differences in susceptibility to Varroa parasitism. Results suggest that differences in behavior, rather than in the immune system, underlie Varroa tolerance in honey bees. They provide a first step toward better understanding molecular pathways involved in this particular host-parasite relationship.
  
  
• A metagenomic survey of microbes in honey bee colony collapse disorder
  Synopsis: In Colony Collapse Disorder (CCD), honey bee colonies inexplicably lose all of their workers. CCD has resulted in a loss of 50-90% of colonies in beekeeping operations across the United States. The observation that irradiated combs from affected colonies can be repopulated with naïve bees suggests an infectious basis for CCD. One organism, Israeli acute paralysis virus (IAPV) of bees, was strongly correlated with CCD. The prevalence of IAPV sequences in CCD operations, as well as the temporal and geographic overlap of CCD and importation of IAPV infected bees from Australia, indicates that IAPV is a significant marker for CCD.
  
  
• Honeybee colony collapse due to Nosema ceranae in professional apiaries
  Synopsis Honeybee colony collapse is a sanitary and ecological worldwide problem. To date there has not been a consensus about its origins. This report describes the clinical features of two professional bee-keepers affecting by this syndrome. Anamnesis, clinical examination and analyses support that the depopulation in both cases was due to the infection by Nosema ceranae (Microsporidia), an emerging pathogen of Apis mellifera. No other significant pathogens or pesticides (neonicotinoids) were detected and the bees had not been foraging in corn or sunflower crops. The treatment with fumagillin avoided the loss of surviving weak colonies. This is the first case report of honeybee colony collapse due to N. ceranae in professional apiaries in field conditions reported worldwide.
  
  
• Recent Honey Bee Colony Declines
  Synopsis : In 2006, commercial migratory beekeepers along the East Coast of the United States began reporting sharp declines in their honey bee colonies. Current reports indicate that beekeepers in 35 states have been affected. Recent surveys indicate that about one-half of surveyed beekeepers have experienced "abnormal" or "severe" colony losses. To date, the potential causes of CCD, as reported by the scientists who are researching this phenomenon, include but may not be limited to the following: parasites, mites, and disease loads in the bees and brood; emergence of new or newly more virulent pathogens; poor nutrition among adult bees; lack of genetic diversity and lineage of bees; level of stress in adult bees (e.g., transportation and confinement of bees, or other environmental or biological stressors); chemical residue/contamination in the wax, food stores, and/or bees; and a combination of these and/or other factors.
  
  
• IAPV, a bee-affecting virus associated with Colony Collapse Disorder can be silenced by dsRNA ingestion
  Synopsis: Colony Collapse Disorder (CCD) has been associated with Israeli acute paralysis virus (IAPV). CCD poses a serious threat to apiculture and agriculture as a whole, due to the consequent inability to provide the necessary amount of bees for pollination of critical crops. Here we report on RNAi-silencing of IAPV infection by feeding bees with double-stranded RNA, as an efficient and feasible way of controlling this viral disease. The association of CCD with IAPV is discussed, as well as the potential of controlling CCD.
  
  
• Behavioral attributes and parental care of Varroa mites parasitizing honeybee brood
  Synopsis: Varroa jacobsoni, an ectoparasite of the Asian honeybee Apis cerana, has been introduced world-wide, and is currently decimating colonies of the European honeybee Apis mellifera. Study describes here how a single fertilized female, infesting a brood cell, can produce two to four adult fertilized females within the limited time span of bee development (270 h in worker and 330 h in drone cells), despite the disturbance caused by cocoon spinning and subsequent morphological changes of the bee.
  
  
• Nutritional stress due to habitat loss may explain recent honeybee colony collapses
  Synopsis: In spite of the tremendous public interest in the recent large honeybee losses attributed to colony collapse disorder, there is still no definitive explanation for the phenomenon. With the hypothesis that nutritional stress due to habitat loss has played an important role in honeybee colony collapse, study analyzes the land use data in United States to show that the colony loss suffered by each state is significantly predicted by the extent of its open land relative to its developed land area. Study also discusses how increasing loss of foraging resources could be synergistically acting with emerging diseases to stress honeybee populations and the importance therefore for preserving natural areas that act as important pollinator habitats.
  
  
• Effects of neonicotinoid pesticide pollution of Dutch surface water on non-target species abundance
  MSc Thesis by Teresa C. van Dijk, 2010.
  Sustainable Development Track Land use, Environment and Biodiversity (SD: LEB), Utrecht University

Special Interest

• Global Bee Colony Disorders and other Threats to Insect Pollinators United Nations Environment Programme (UNEP).
  Scientists working for the United Nations (UN) reveal in a report published March 10, 2011 that the collapse of honeybee colonies is now a global phenomenon that could have devastating consequences. Declines in managed bee colonies, seen increasingly in Europe and the US in the past decade, are now being observed in China, Japan and Egypt according to the report.