A new threat to honey bees, the parasitic phorid fly Apocephalus borealis

Honey bee colonies are subject to numerous pathogens and parasites. Interaction among multiple pathogens and parasites is the proposed cause for Colony Collapse Disorder (CCD), a syndrome characterized by worker bees abandoning their hive. Here we provide 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, we confirmed that phorids that emerged from honey bees and bumble bees were the same species. Microarray analyses of honey bees from infected hives revealed that these bees are often infected with deformed wing virus and Nosema ceranae. Larvae and adult phorids also tested positive for these pathogens, implicating the fly as a potential vector or reservoir of these honey bee pathogens. 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. Understanding details of phorid infection may shed light on similar hive abandonment behaviors seen in CCD.     

Multiple routes of pesticide exposure for honey bees living near agricultural fields

Populations of honey bees and other pollinators have declined worldwide in recent years. A variety of stressors have been implicated as potential causes, including agricultural pesticides. Neonicotinoid insecticides, which are widely used and highly toxic to honey bees, have been found in previous analyses of honey bee pollen and comb material. However, the routes of exposure have remained largely undefined. We used LC/MS-MS to analyze samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. Our results demonstrate that bees are exposed to these compounds and several other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. We 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, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear. We 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. These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments.     

Competition between honey bees and wild bees and the role of nesting resources in a nature reserve

The European honey bee exploits floral resources efficiently and may therefore compete with solitary wild bees. Hence, conservationists and bee keepers are debating about the consequences of beekeeping for the conservation of wild bees in nature reserves. We observed flower-visiting bees on flowers of Calluna vulgaris in sites differing in the distance to the next honey-bee hive and in sites with hives present and absent in the Lüneburger Heath, Germany. Additionally, we counted wild bee ground nests in sites that differ in their distance to the next hive and wild bee stem nests and stem-nesting bee species in sites with hives present and absent. We did not observe fewer honey bees or higher wild bee flower visits in sites with different distances to the next hive (up to 1,229 m). However, wild bees visited fewer flowers and honey bee visits increased in sites containing honey-bee hives and in sites containing honey-bee hives we found fewer stem-nesting bee species. The reproductive success, measured as number of nests, was not affected by distance to honey-bee hives or their presence but by availability and characteristics of nesting resources. Our results suggest that beekeeping in the Lüneburg Heath can affect the conservation of stem-nesting bee species richness but not the overall reproduction either of stem-nesting or of ground-nesting bees. Future experiments need control sites with larger distances than 500 m to hives. Until more information is available, conservation efforts should forgo to enhance honey bee stocking rates but enhance the availability of nesting resources.     

Olfactory responses of Aethina tumida murray (Coleoptera: Nitidulidae) to some major volatile compounds from hive materials and workers of Apis mellifera

The small hive beetle (Aethina tumida Murray) is an invasive pest affecting honey bee colonies. The beetles are known to be attracted to volatiles from hive products and honey bees like Apis mellifera L. Previously we reported the presence of five major compounds from the volatile extracts of hive materials; ethyl linolenate and ethyl palmitate from pollen dough, oleamide and tetracosane in fermenting honey, and oleamide and 5-methyl-2-phenyl-1H-indole from A. mellifera worker bees. This study tested the attractiveness of the aforementioned five volatile organic compounds to small hive beetles (SHB) by Y-tube olfactometric bioassay. Ethyl linolenate was highly attractive to both male and female adults of SHB. Ethyl palmitate was attractive to SHB only at higher concentration (0.01–01 mg/ml). Interestingly, tetracosane, 5-methyl-2-phenyl-1H-indole and oleamide were repellent for SHB of both sexes, but ethyl linolenate and ethyl palmitate as components of honey bee brood pheromone attracted SHB. The results highlight that SHB differentially utilizes volatile chemicals from hive materials and honey bees as cues to locate honey bee hives.     

Genetics,Synergists, and Age Affect Insecticide Sensitivity of the Honey Bee,Apis mellifera

The number of honey bee colonies in the United States has declined to half of its peak level in the 1940s, and colonies lost over the winter have reached levels that are becoming economically unstable. While the causes of these losses are numerous and the interaction between them is very complex, the role of insecticides has garnered much attention. As a result, there is a need to better understand the risk of insecticides to bees, leading to more studies on both toxicity and exposure. While much research has been conducted on insecticides and bees, there have been very limited studies to elucidate the role that bee genotype and age has on the toxicity of these insecticides. The goal of this study was to determine if there are differences in insecticide sensitivity between honey bees of different genetic backgrounds (Carniolan, Italian, and Russian stocks) and assess if insecticide sensitivity varies with age. We found that Italian bees were the most sensitive of these stocks to insecticides, but variation was largely dependent on the class of insecticide tested. There were almost no differences in organophosphate bioassays between honey bee stocks (<1-fold), moderate differences in pyrethroid bioassays (1.5 to 3-fold), and dramatic differences in neonicotinoid bioassays (3.4 to 33.3-fold). Synergism bioassays with piperonyl butoxide, amitraz, and coumaphos showed increased phenothrin sensitivity in all stocks and also demonstrated further physiological differences between stocks. In addition, as bees aged, the sensitivity to phenothrin significantly decreased, but the sensitivity to naled significantly increased. These results demonstrate the variation arising from the genetic background and physiological transitions in honey bees as they age. This information can be used to determine risk assessment, as well as establishing baseline data for future comparisons to explain the variation in toxicity differences for honey bees reported in the literature.     

Learning and Task Interference by Corpse-removal Specialists in Honey Bee Colonies

Undertakers are considered to be among the most specialized of pre-foraging honey bee (Apis mellifera L.) workers. In this study we examined a possible benefit and a cost of the corpse-rem oval specialty, the improvement in performance with experience, and interference by individuals attempting to perform the same task in the same location, respectively. Experienced bees removed corpses significantly faster than less experienced bees and also were less likely to drop corpses while exiting the hive (5.5% vs. 14.3% of attempts). Superior performance by experienced undertakers might occur as a consequence of learning, or by greater ability from the outset. Because active undertakers (≥ 3 corpse removals) did not improve with experience over their own careers, learning was not demonstrated. An extreme specialist, Yellow 54, removed a total of 114 corpses (33.8% of experimentally introduced dead bees) from the hive over a 13-day period. This is the longest recorded tenure of undertaking to date and demonstrates how a few individuals can dominate this task in a honey bee colony-Yellow 54 removed corpses significantly faster than other active bees, but she demonstrated no obvious improvement in performance over her undertaking career. This suggests the possibility that active undertakers were more talented than less active undertakers, irrespective of learning. When two undertakers worked together to remove a corpse from the hive, they took longer to complete the task than did single individuals. When multiple undertakers flew together from the hive, they were less likely to clear a nearby obstruction than single undertakers and were more likely to drop the corpse within 1 m of the hive. Thus, mutual interference exacted a measurable cost as a result of the undertaking specialization while learning provided few benefits.     

A Locomotor Deficit Induced by Sublethal Doses of Pyrethroid and Neonicotinoid Insecticides in the Honeybee Apis mellifera

The toxicity of pesticides used in agriculture towards non-targeted organisms and especially pollinators has recently drawn the attention from a broad scientific community. Increased honeybee mortality observed worldwide certainly contributes to this interest. The potential role of several neurotoxic insecticides in triggering or potentiating honeybee mortality was considered, in particular phenylpyrazoles and neonicotinoids, given that they are widely used and highly toxic for insects. Along with their ability to kill insects at lethal doses, they can compromise survival at sublethal doses by producing subtle deleterious effects. In this study, we compared the bee’s locomotor ability, which is crucial for many tasks within the hive (e.g. cleaning brood cells, feeding larvae…), before and after an acute sublethal exposure to one insecticide belonging to the two insecticide classes, fipronil and thiamethoxam. Additionally, we examined the locomotor ability after exposure to pyrethroids, an older chemical insecticide class still widely used and known to be highly toxic to bees as well. Our study focused on young bees (day 1 after emergence) since (i) few studies are available on locomotion at this stage and (ii) in recent years, pesticides have been reported to accumulate in different hive matrices, where young bees undergo their early development. At sublethal doses (SLD_48h, i.e. causing no mortality at 48h), three pyrethroids, namely cypermethrin (2.5 ng/bee), tetramethrin (70 ng/bee), tau-fluvalinate (33 ng/bee) and the neonicotinoid thiamethoxam (3.8 ng/bee) caused a locomotor deficit in honeybees. While the SLD_48h of fipronil (a phenylpyrazole, 0.5 ng/bee) had no measurable effect on locomotion, we observed high mortality several days after exposure, an effect that was not observed with the other insecticides. Although locomotor deficits observed in the sublethal range of pyrethroids and thiamethoxam would suggest deleterious effects in the field, the case of fipronil demonstrates that toxicity evaluation requires information on multiple endpoints (e.g. long term survival) to fully address pesticides risks for honeybees. Pyrethroid-induced locomotor deficits are discussed in light of recent advances regarding their mode of action on honeybee ion channels and current structure-function studies.     

Unique Honey Bee (Apis mellifera) Hive Component-Based Communities as Detected by a Hybrid of Phospholipid Fatty-Acid and Fatty-Acid Methyl Ester Analyses

Microbial communities (microbiomes) are associated with almost all metazoans, including the honey bee Apis mellifera. Honey bees are social insects, maintaining complex hive systems composed of a variety of integral components including bees, comb, propolis, honey, and stored pollen. Given that the different components within hives can be physically separated and are nutritionally variable, we hypothesize that unique microbial communities may occur within the different microenvironments of honey bee colonies. To explore this hypothesis and to provide further insights into the microbiome of honey bees, we use a hybrid of fatty acid methyl ester (FAME) and phospholipid-derived fatty acid (PLFA) analysis to produce broad, lipid-based microbial community profiles of stored pollen, adults, pupae, honey, empty comb, and propolis for 11 honey bee hives. Averaging component lipid profiles by hive, we show that, in decreasing order, lipid markers representing fungi, Gram-negative bacteria, and Gram-positive bacteria have the highest relative abundances within honey bee colonies. Our lipid profiles reveal the presence of viable microbial communities in each of the six hive components sampled, with overall microbial community richness varying from lowest to highest in honey, comb, pupae, pollen, adults and propolis, respectively. Finally, microbial community lipid profiles were more similar when compared by component than by hive, location, or sampling year. Specifically, we found that individual hive components typically exhibited several dominant lipids and that these dominant lipids differ between components. Principal component and two-way clustering analyses both support significant grouping of lipids by hive component. Our findings indicate that in addition to the microbial communities present in individual workers, honey bee hives have resident microbial communities associated with different colony components.     

Nonsusceptibility of the Honey Bee,Apis mellifera (Hymenoptera: Apidae), to Steinernematid and Heterorhabditid Nematodes

We exposed honey bee workers and brood to four entomopathogenic nematode species under conditions normally encountered in the hive by spraying nematodes onto combs. Mortality of adult bees exposed to any of the nematode species was less than 10%, and there was no evidence of nematode infection when dead adults were dissected. To assess the impact of nematodes on brood, we used smaller-size honey combs placed in the second story (super) of a hive and large brood combs placed in the main section of the hive. Our results were inconsistent between these two experimental designs. The smaller honey combs sprayed with Steinernema carpocapsae contained the largest number of uncapped ceils, those sprayed with Heterorhabditis baeteriophora or S. riobravis contained an intermediate number of uncapped cells, and control combs and those sprayed with S. glaseri contained the fewest nmnber of uncapped cells. Large combs sprayed with S. riobravis contained more uncapped ceils than controls or those sprayed with S. carpocapsae, although the differences were not significant. Our results do not support the hypothesis that high-temperature-tolerant species of nematodes are necessarily more infective to honey bees.     

Field-Level Sublethal Effects of Approved Bee Hive Chemicals on Honey Bees (Apis mellifera L)

In a study replicated across two states and two years, we tested the sublethal effects on honey bees of the miticides Apistan (tau fluvalinate) and Check Mite+ (coumaphos) and the wood preservative copper naphthenate applied at label rates in field conditions. A continuous covariate, a colony Varroa mite index, helped us disambiguate the effects of the chemicals on bees while adjusting for a presumed benefit of controlling mites. Mite levels in colonies treated with Apistan or Check Mite+ were not different from levels in non-treated controls. Experimental chemicals significantly decreased 3-day brood survivorship and increased construction of queen supercedure cells compared to non-treated controls. Bees exposed to Check Mite+ as immatures had higher legacy mortality as adults relative to non-treated controls, whereas bees exposed to Apistan had improved legacy mortality relative to non-treated controls. Relative to non-treated controls, Check Mite+ increased adult emergence weight. Although there was a treatment effect on a test of associative learning, it was not possible to statistically separate the treatment means, but bees treated with Apistan performed comparatively well. And finally, there were no detected effects of bee hive chemical on colony bee population, amount of brood, amount of honey, foraging rate, time required for marked released bees to return to their nest, percentage of released bees that return to the nest, and colony Nosema spore loads. To our knowledge, this is the first study to examine sublethal effects of bee hive chemicals applied at label rates under field conditions while disambiguating the results from mite control benefits realized from the chemicals. Given the poor performance of the miticides at reducing mites and their inconsistent effects on the host, these results defend the use of bee health management practices that minimize use of exotic hive chemicals.     

Evaluation of an upper hive entrance for control of Aethina tumida (Coleoptera: Nitidulidae) in colonies of honey bees (Hymenoptera: Apidae)

This investigation was conducted to test whether an upper hive entrance may result in reduced Aethina tumida Murray (Coleoptera: Nitidulidae) population buildup in newly established honey bee, Apis mellifera L., colonies over an 8-mo period. The upper hive entrance consisted of a 3.5-cm-i.d. polyvinyl chloride pipe positioned 20 cm above the hive bottom. Sixteen bee colonies were established using five-frame nucleus hives with a 0.9-kg (2-1b) package of bees with queen. Eight colonies were placed in each apiary, and each colony received one of two treatments: 1) conventional hive lower entrance and 2) modified upper hive entrance. This investigation was conducted in two distant apiaries where A. tumida had been a major problem to local beekeepers for a minimum of 2 yr. Results showed no overall differences between treatment effects on A. tumida counts over the test period, but there was a reduction in bee brood measured in colonies having an upper hive entrance. We conclude that the upper pipe entrance is not recommended in areas where A. tumida are well established and have become problematic. The expected reduction of brood in colonies as a result of using an upper hive entrance will lead to less productive units for honey production and pollination activities. Other control measures will be necessary to maintain tolerable levels of A. tumida in honey bee colonies at high pest densities.     

Evaluation of spring organic treatments against Varroa destructor (Acari: Varroidae) in honey bee Apis mellifera (Hymenoptera: Apidae) colonies in eastern Canada

The objective of this study was to measure the efficacy of two organic acid treatments, formic acid (FA) and oxalic acid (OA) for the spring control of Varroa destructor (Anderson and Trueman) in honey bee (Apis mellifera L.) colonies. Forty-eight varroa-infested colonies were randomly distributed amongst six experimental groups (n = 8 colonies per group): one control group (G1); two groups tested applications of different dosages of a 40 g OA/l sugar solution 1:1 trickled on bees (G2 and G3); three groups tested different applications of FA: 35 ml of 65% FA in an absorbent Dri-Loc^? pad (G4); 35 ml of 65% FA poured directly on the hive bottom board (G5) and MiteAwayII™ (G6). The efficacy of treatments (varroa drop), colony development, honey yield and hive survival were monitored from May until September. Five honey bee queens died during this research, all of which were in the FA treated colonies (G4, G5 and G6). G6 colonies had significantly lower brood build-up during the beekeeping season. Brood populations at the end of summer were significantly higher in G2 colonies. Spring honey yield per colony was significantly lower in G6 and higher in G1. Summer honey flow was significantly lower in G6 and higher in G3 and G5. During the treatment period, there was an increase of mite drop in all the treated colonies. Varroa daily drop at the end of the beekeeping season (September) was significantly higher in G1 and significantly lower in G6. The average number of dead bees found in front of hives during treatment was significantly lower in G1, G2 and G3 versus G4, G5 and G6. Results suggest that varroa control is obtained from all spring treatment options. However, all groups treated with FA showed slower summer hive population build-up resulting in reduced honey flow and weaker hives at the end of summer. FA had an immediate toxic effect on bees that resulted in queen death in five colonies. The OA treatments that were tested have minimal toxic impacts on the honey bee colonies.     

Mechanism of biological effects observed in honey bees (apis mellifera,L.) hived under extra-high-voltage transmission lines: Implications derived from bee exposure to simulated intense electric fields and shocks

This work explores mechanisms for disturbance of honey bee colonies under a 765 kV, 60-Hz transmission line [electric (E) field = 7 kV/m] observed in previous studies. Proposed mechanisms fell into two categories: direct bee perception of enhanced in-hive E fields and perception of shock from induced currents. The adverse biological effects could be reproduced in simulations where only the worker bees were exposed to shock or to E field in elongated hive entranceways (=tunnels). We now report the results of full-scale experiments using the tunnel exposure scheme, which assesses the contribution of shock and intense E field to colony disturbance. Exposure of worker bees (1,400 h) to 60-Hz E fields including 100 kV/m under moisture-free conditions within a nonconductive tunnel causes no deleterious affect on colony behavior. Exposure of bees in conductive (e.g., wet) tunnels produces bee disturbance, increased mortality, abnormal propolization, and possible impairment of colony growth. We propose that this substrate dependence of bee disturbance is the result of perception of shock from coupled body currents and enhanced current densities postulated to exist in the legs and thorax of bees on conductors. Similarly, disturbance occurs when bees are exposed to step-potential-induced currents. At 275–350 nA single bees are disturbed; at 600 nA bees begin abnormal propolization behavior; and stinging occurs at 900 nA. We conclude that biological effects seen in bee colonies under a transmission line are primarily the result of electric shock from induced hive currents. This evaluation is based on the limited effects of E-field exposure in tunnels, the observed disturbance thresholds caused by shocks in tunnels, and the ability of hives exposed under a transmission line to source currents 100–1,000 times the shock thresholds.     

Exposure scheme separates effects of electric shock and electric field for honey bees, Apis mellifera L

Mechanisms to explain disturbance of honey bee colonies under a 765-kV, 60-Hz transmission line [electric (E) field = 7 kV/m] fall into two categories: direct bee perception of enhanced in-hive E fields, and perception of shock from induced currents. The same adverse biological effects previously observed in honey bee colonies exposed under a 765-kV transmission line can be reproduced by exposing worker bees to shock or E field within elongated hive entranceways (= tunnels). Exposure to intense E field caused disturbance only if bees were in contact with a conductive substrate. E-field and shock exposure can be separated and precisely defined within tunnels, eliminating dosimetric vagaries that occur when entire hives are exposed to E field.     

Resource overlap and possible competition between honey bees and wild bees in central Europe

Evidence for interspecific competition between honey bees and wild bees was studied on 15 calcareous grasslands with respect to: (1) foraging radius of honey bees, (2) overlap in resource use, and (3) possible honey bee effects on species richness and abundance of flower-visiting, ground-nesting and trap-nesting wild bees. The grasslands greatly differed in the number of honey bee colonies within a radius of 2 km and were surrounded by agricultural habitats. The number of flower-visiting honey bees on both potted mustard plants and small grassland patches declined with increasing distance from the nearest apiary and was almost zero at a distance of 1.5–2.0 km. Wild bees were observed visiting 57 plant species, whereas honey bees visited only 24 plant species. Percentage resource overlap between honey bees and wild bees was 45.5%, and Hurlbert’s index of niche overlap was 3.1. In total, 1849 wild bees from 98 species were recorded on the calcareous grasslands. Neither species richness nor abundance of wild bees were negatively correlated with the density of honey bee colonies (within a radius of 2 km) or the density of flower-visiting honey bees per site. Abundance of flower- visiting wild bees was correlated only with the percentage cover of flowering plants. In 240 trap nests, 1292 bee nests with 6066 brood cells were found. Neither the number of bee species nor the number of brood cells per grassland was significantly correlated with the density of honey bees. Significant correlations were found only between the number of brood cells and the percentage cover of shrubs. The number of nest entrances of ground-nesting bees per square metre was not correlated with the density of honey bees but was negatively correlated with the cover of vegetation. Interspecific competition by honey bees for food resources was not shown to be a significant factor determining abundance and species richness of wild bees. Received: 22 March 1999 / Accepted: 24 September 1999     

Behavioral responses of the small hive beetle,Aethina tumida,to odors of three meliponine bee species and honey bees,Apis mellifera scutellata

Recent studies have shown that honey bees, bumble bees, and some meliponine bee species of the genera Trigona, Meliponula, and Dactylurina are hosts of the small hive beetle (SHB) Aethina tumidaMurray (Coleoptera: Nitidulidae), a pest of honey bee colonies in various regions of the world. Olfaction has been implicated in SHB infestations of honey bee and bumble bee colonies. We used olfactometer bioassays to investigate responses of adult male and female SHBs to odors from intact colonies and separate hive components (pot honey, pot pollen, cerumen, and propolis) of three African meliponine bee species, Meliponula ferruginea (Lepeletier) (black morphospecies), M. ferruginea (reddish brown morphospecies), and Meliponula bocandei (Spinola) (Hymenoptera: Apidae). Although both sexes of the beetle strongly preferred intact colony, pot honey, and pot pollen odors, there was no evidence of attraction to propolis and cerumen odors from the three meliponine bee species. Both sexes of SHB also strongly preferred odors from honey bees, Apis mellifera L. (Hymenoptera: Apidae), over odors from the three meliponine bee species. Our results provide substantial evidence of the host potential of African meliponine bees for the SHB, and we discuss this complex association of the SHB with species within the Apidae family.     

How Hives Collapse: Allee Effects,Ecological Resilience,and the Honey Bee

We construct a mathematical model to quantify the loss of resilience in collapsing honey bee colonies due to the presence of a strong Allee effect. In the model, recruitment and mortality of adult bees have substantial social components, with recruitment enhanced and mortality reduced by additional adult bee numbers. The result is an Allee effect, a net per-individual rate of hive increase that increases as a function of adult bee numbers. The Allee effect creates a critical minimum size in adult bee numbers, below which mortality is greater than recruitment, with ensuing loss of viability of the hive. Under ordinary and favorable environmental circumstances, the critical size is low, and hives remain large, sending off viably-sized swarms (naturally or through beekeeping management) when hive numbers approach an upper stable equilibrium size (carrying capacity). However, both the lower critical size and the upper stable size depend on many parameters related to demographic rates and their enhancement by bee sociality. Any environmental factors that increase mortality, decrease recruitment, or interfere with the social moderation of these rates has the effect of exacerbating the Allee effect by increasing the lower critical size and substantially decreasing the upper stable size. As well, the basin of attraction to the upper stable size, defined by the model potential function, becomes narrower and shallower, indicating the loss of resilience as the hive becomes subjected to increased risk of falling below the critical size. Environmental effects of greater severity can cause the two equilibria to merge and the basin of attraction to the upper stable size to disappear, resulting in collapse of the hive from any initial size. The model suggests that multiple proximate causes, among them pesticides, mites, pathogens, and climate change, working singly or in combinations, could trigger hive collapse.     

Distribution of Paenibacillus larvae spores inside honey bee colonies and its relevance for diagnosis

One of the most important factors affecting the development of honey bee colonies is infectious diseases such as American foulbrood (AFB) caused by the spore forming Gram-positive bacterium Paenibacillus larvae. Colony inspections for AFB clinical symptoms are time consuming. Moreover, diseased cells in the early stages of the infection may easily be overlooked. In this study, we investigated whether it is possible to determine the sanitary status of a colony based on analyses of different materials collected from the hive. We analysed 237 bee samples and 67 honey samples originating from 71 colonies situated in 13 apiaries with clinical AFB occurrences. We tested whether a difference in spore load among bees inside the whole hive exists and which sample material related to its location inside the hive was the most appropriate for an early AFB diagnosis based on the culture method. Results indicated that diagnostics based on analysis of honey samples and bees collected at the hive entrance are of limited value as only 86% and 83%, respectively, of samples from AFB-symptomatic colonies were positive. Analysis of bee samples collected from the brood nest, honey chamber, and edge frame allowed the detection of all colonies showing AFB clinical symptoms. Microbiological analysis showed that more than one quarter of samples collected from colonies without AFB clinical symptoms were positive for P. larvae. Based on these results, we recommend investigating colonies by testing bee samples from the brood nest, edge frame or honey chamber for P. larvae spores.     

A Four-Year Field Program Investigating Long-Term Effects of Repeated Exposure of Honey Bee Colonies to Flowering Crops Treated with Thiamethoxam

Neonicotinoid residues in nectar and pollen from crop plants have been implicated as one of the potential factors causing the declines of honey bee populations. Median residues of thiamethoxam in pollen collected from honey bees after foraging on flowering seed treated maize were found to be between 1 and 7 µg/kg, median residues of the metabolite CGA322704 (clothianidin) in the pollen were between 1 and 4 µg/kg. In oilseed rape, median residues of thiamethoxam found in pollen collected from bees were between <1 and 3.5 µg/kg and in nectar from foraging bees were between 0.65 and 2.4 µg/kg. Median residues of CGA322704 in pollen and nectar in the oilseed rape trials were all below the limit of quantification (1 µg/kg). Residues in the hive were even lower in both the maize and oilseed rape trials, being at or below the level of detection of 1 µg/kg for bee bread in the hive and at or below the level of detection of 0.5 µg/kg for hive nectar, honey and royal jelly samples. The long-term risk to honey bee colonies in the field was also investigated, including the sensitive overwintering stage, from four years consecutive single treatment crop exposures to flowering maize and oilseed rape grown from thiamethoxam treated seeds at rates recommended for insect control. Throughout the study, mortality, foraging behavior, colony strength, colony weight, brood development and food storage levels were similar between treatment and control colonies. Detailed examination of brood development throughout the year demonstrated that colonies exposed to the treated crop were able to successfully overwinter and had a similar health status to the control colonies in the following spring. We conclude that these data demonstrate there is a low risk to honey bees from systemic residues in nectar and pollen following the use of thiamethoxam as a seed treatment on oilseed rape and maize.     

Hierarchy of Attractants for Honey Bee Swarms

Chemical signals influence the selection of potential nest cavities by honey bee reproductive swarms. Attractants for swarms include the odors of old dark honey bee brood combs, odors from noncomb hive materials and propolis, and Nasonov pheromone, the odor released from the Nasonov glands of worker bees. Based on crossover and choice test experiments, swarms were shown to prefer, among otherwise identical cavities, those cavities containing Nasonov pheromone over cavities with only comb or other hive odors, cavities containing old comb over those with only noncomb odors or propolis, and cavities containing noncomb odors or propolis over those without bee or hive odor. Synergy between odors was not observed; that is, comb and/or noncomb hive odors did not enhance the attractiveness of Nasonov pheromone. The data support a model based on a hierarchy of olfactory attractants used by honey bee swarms, in order of highest to lowest: Nasonov pheromone, comb odor, noncomb and propolis odors, and, finally, absence of bee- or hive-produced odor.