Affect Honey Bee Health Research Articles

Detection of deformed wing virus in the greenhouse for possible horizontal transmission of virus in honey bee colony

AbstractThe honey bee Apis mellifera L. is a crucial insect in the agricultural industry and natural ecosystem by being a major pollinator. Nevertheless, honey bee population has been recently facing a decline. Among the several factors responsible for this decline, deformed wing virus (DWV) is considered a primary cause that negatively affects honey bee health. DWV is a cosmopolitan honey bee pathogen and causes morphological disadvantages in individual honey bees and colony collapse. Regarding the horizontal transmission of DWV, in addition to Varroa destructor, a well‐known major vector of DWV, flowers have recently been implied as a transmission route. Therefore, in this study, we detected DWV from various substances, including flowers, honey bee feces, pupa, larva, nurse bee, surface of nurse bee, pollen collected by forager bee, and forager bee samples in four strawberry greenhouses, which could suggest the potential for the horizontal transmission of DWV in the semi‐field condition. We also detected DWV in pollen collected by DWV‐negative forager bees, implying that flowers can serve as a potential source of virus infection. These findings suggest that the surrounding environment such as shared floral sources affects the spread of DWV.

Pesticide exposure and forage shortage in rice cropping system prevents honey bee colony establishment

As one of the key stable crops to feed half of the world's population, how rice cropping system affects honey bee health regarding pesticide exposure and forage availability is under investigated. We predicted honey bees were stressed by high pesticide exposure and forage dearth in monoculture rice systems. Providing access to natural habitats is a typical approach to mitigate the negative impact of intensive agriculture on honey bees. We aimed to determine if bee colonies located in landscapes with more cover of forest habitat would collect more forage and be exposed to less pesticides. We selected beekeeping locations in rice dominated landscapes (as control), mosaic landscapes of rice and medium woodland (MW) cover, and landscapes of high woodland (HW) cover, respectively, in July when rice starts bloom and pesticides are commonly used. Colonies were inspected at a biweekly frequency from July to October with population growth and forage (nectar and pollen) availability estimated. Pollen and bees were collected in middle August for pesticide exposure analysis. We did not observe enhancement in forage availability and reduction in pesticide exposure in landscapes with increased forest habitat (i.e., MW or HW cover), and all colonies failed in the end. Other natural habitats that can supplement flower shortage periods in forest can be considered for supporting bee health. Our results suggest that forest should be carefully assessed for being incorporated into beekeeping management or pollinator conservation when forest phenology can be a factor to affect its impact as a natural habitat.

Effects of Two Commercial Protein Diets on the Health of Two Imago Ages of Apis mellifera L. Reared in Laboratory.

Simple SummaryBeekeepers often feed their bees with supplemented artificial diets. The formulation of an integrative diet for honey bee colonies able to prevent nutritional deficiencies is yet to be found. In this work, the effects of pollen diet substitution with commercial protein diets in newly emerged bees (that still feed a little on pollen) and in forager bees (that usually do not feed on pollen) were tested. Results obtained suggest that commercial protein diets do not compensate pollen diets in newly emerged bees and do not determine an increase in life span or immunity in forager bees. Further investigations on the effect of concentration and quality of proteins are desirable in order to provide beekeepers with scientific evidence on protein-based feeding.Protein-supplemented artificial diets are widely used by beekeepers during winter and whenever food availability is low, yet no data are available concerning their effects on bees’ health. In this work, the effects of two commercial diets enriched with 1.7% and 7.7% protein concentration on feed intake, survival rate, glucose oxidase, phenoloxidase and glutathione S-transferase in newly emerged and forager bees were tested. Administration of a 7.7% protein-enriched diet significantly reduced the lifespan of both newly emerged and forager bees, while only in foragers a significantly higher feed intake was recorded. In newly emerged bees, administration of a high-protein-enriched diet stimulated glucose oxidase production at the 10th day of feeding, determined a reduction of phenoloxidase and did not affect glutathione S-transferase activity. In forager bees, a high level of protein inclusion did not determine any significant variation in either glucose oxidase, phenoloxidase or glutathione S-transferase activity. Therefore, the results obtained in this investigation suggest that administration of commercial protein diets negatively affect honey bee health, determining an increase in mortality. Further investigations on the effect of concentration and quality of proteins are desirable to provide beekeepers with scientific evidence on protein feeding.

Nano-La2O3 Induces Honeybee (Apis mellifera) Death and Enriches for Pathogens in Honeybee Gut Bacterial Communities.

Honeybees (Apis mellifera) can be exposed via numerous potential pathways to ambient nanoparticles (NPs), including rare earth oxide (REO) NPs that are increasingly used and released into the environment. Gut microorganisms are pivotal in mediating honeybee health, but how REO NPs may affect honeybee health and gut microbiota remains poorly understood. To address this knowledge gap, honeybees were fed pollen and sucrose syrup containing 0, 1, 10, 100, and 1000mgkg−1 of nano-La2O3 for 12days. Nano-La2O3 exerted detrimental effects on honeybee physiology, as reflected by dose-dependent adverse effects of nano-La2O3 on survival, pollen consumption, and body weight (p<0.05). Nano-La2O3 caused the dysbiosis of honeybee gut bacterial communities, as evidenced by the change of gut bacterial community composition, the enrichment of pathogenic Serratia and Frischella, and the alteration of digestion-related taxa Bombella (p<0.05). There were significant correlations between honeybee physiological parameters and the relative abundances of pathogenic Serratia and Frischella (p<0.05), underscoring linkages between honeybee health and gut bacterial communities. Taken together, this study demonstrates that nano-La2O3 can cause detrimental effects on honeybee health, potentially by disordering gut bacterial communities. This study thus reveals a previously overlooked effect of nano-La2O3 on the ecologically and economically important honeybee species Apis mellifera.

Developmental environment shapes honeybee worker response to virus infection

The consequences of early-life experiences are far reaching. In particular, the social and nutritional environments that developing animals experience can shape their adult phenotypes. In honeybees, larval nutrition determines the eventual social roles of adults as reproductive queens or sterile workers. However, little is known about the effects of developmental nutrition on important adult worker phenotypes such as disease resilience. In this study, we manipulated worker developmental nutrition in two distinct ways under semi-natural field conditions. In the first experiment, we restricted access to nutrition via social isolation by temporarily preventing alloparental care. In the second experiment, we altered the diet quality experienced by the entire colony, leading to adult bees that had developed entirely in a nutritionally restricted environment. When bees from these two experiments reached the adult stage, we challenged them with a common bee virus, Israeli acute paralysis virus (IAPV) and compared mortality, body condition, and the expression of immune genes across diet and viral inoculation treatments. Our findings show that both forms of early life nutritional stress, whether induced by lack of alloparental care or diet quality restriction, significantly reduced bees’ resilience to virus infection and affected the expression of several key genes related to immune function. These results extend our understanding of how early life nutritional environment can affect phenotypes relevant to health and highlight the importance of considering how nutritional stress can be profound even when filtered through a social group. These results also provide important insights into how nutritional stress can affect honeybee health on a longer time scale and its potential to interact with other forms of stress (i.e. disease).

A small scale survey in Morocco revealed the presence of four honey bee viruses

A small-scale survey was conducted on 12 beehives located in the Gharb region of Morocco in order to assess for the first time the presence of honey bee-infecting viruses in the country. A total of 240 individual bee samples were screened for seven honey bee viruses using reverse transcription (RT)-PCR. Among the infected samples, 41.7% contained one virus, 15% showed mixed infection with two viruses while 3.3% contained three. Deformed wing virus (DWV), was the most prevalent one, detected in 38.3% of the samples, followed by acute bee paralysis virus (ABPV), sacbrood virus (SBV) and chronic bee paralysis virus (CBPV) (20%, 14.2% and 9.2% of infection rate, respectively). Israeli acute paralysis virus (IAPV), Kashmir bee virus (KBV) and black queen cell virus (BQCV) were not detected. Nucleotide sequences of PCR amplicons obtained from detected viruses shared 98.5-99.4% identity with isolates reported in the GenBank. Although bee viruses usually persist as asymptomatic infections and persist in the colonies as covert infections, they can dramatically affect honey bee health and shorten the lives of infected bees under certain conditions. To the best of our knowledge, this study represents the first detection of ABPV, CBPV and SBV in honey bees in Morocco.

A combination of Tropilaelaps mercedesae and imidacloprid negatively affects survival, pollen consumption and midgut bacterial composition of honey bee

Tropilaelaps mercedesae is not only a major threat to honey bees in Asia but also a potential risk to global apiculture due to trade. Imidacloprid is a systemic insecticide that negatively affects individual bees. Moreover, the health of honey bees may be threatened by imidacloprid exposure and T. mercedesae infestation. We studied the effects of T. mercedesae and imidacloprid on the survival, food consumption and midgut bacterial diversity of Apis mellifera in the laboratory. Illumina 16S rRNA gene sequencing was used to determine the bacterial composition in the honey bee midgut. T. mercedesae decreased survival in parasitized honey bees compared with nonparasitized honey bees, but there was no significant difference in food consumption. The imidacloprid 50 μg/L diet significantly decreased syrup consumption of A. mellifera compared with the control diet. The combination of T. mercedesae infestation and imidacloprid 50 μg/L exposure reduced survival and increased pollen consumption of A. mellifera. T. mercedesae infestation or a combination of T. mercedesae infestation and exposure to 25 μg/L imidacloprid affected the midgut bacterial composition of honey bees. T. mercedesae infestation and imidacloprid exposure may reduce the survival and affect honey bee health.

Evaluation and comparison of the effects of three insect growth regulators on honey bee queen oviposition and egg eclosion

Honey bees (Apis mellifera) are highly valued pollinators that help to ensure national food security in the United States, but reports of heavy annual losses to managed colonies have caused concerns and prompted investigations into the causes of colony losses. One factor that can negatively affect honey bee health and survival is agrochemical exposure. Investigations into the sublethal effects of agrochemicals on important metrics of colony health such as reproduction and queen fecundity has been limited by the availability of targeted methods to study honey bee queens. This work investigates the effects of three insect growth regulators (IGR), a class of agrochemicals known to target pathways involved in insect reproduction, on honey bee queen oviposition, egg hatching, and worker hypopharyngeal development in order to quantify their effects on the fecundity of mated queens. The reported results demonstrate that none of the IGRs affected oviposition, but all three affected egg eclosion. Worker bees consuming methoxyfenozide had significantly larger hypopharyngeal glands at two weeks of age than bees not fed this compound. The results suggest that although IGRs may not exhibit direct toxic effects on adult honey bees, they can affect larval eclosion from eggs and the physiology of workers, which may contribute to colony population declines over time.

Assessment of lethal and sublethal effects of imidacloprid, ethion, and glyphosate on aversive conditioning, motility, and lifespan in honey bees (Apis mellifera L.)

Honeybees (Apis mellifera) play an important role in agriculture worldwide. Several factors including agrochemicals can affect honey bee health including habitat fragmentation, pesticide application, and pests. The growing human population and subsequent increasing crop production have led to widespread use of agrochemicals and there is growing concern that pollinators are being negatively impacted by these pesticides. The present study compares acute exposure to imidacloprid (0.2 and 0.4 mgL−1), ethion (80 and 106.7 mgL−1) or glyphosate (0.12 and 0.24 mgL−1) on aversive learning and movement, to chronic exposure at these and higher concentrations on movement, circadian rhythms, and survival in honey bee foragers. For acute learning studies, a blue/yellow shuttle box experiment was conducted; we observed honey bee choice following aversive and neutral stimuli. In learning studies, control bees spent >50% of the time on yellow which is not consistent with previous color bias literature in the subspecies or region of the study. The learning apparatus was also used to estimate mobility effects within 20 min of exposure. Chronic exposure (up to 2 weeks) with the above metrics was recorded by an automated monitoring system. In chronic exposure experiments, RoundUp®, was also tested to compare to its active ingredient, glyphosate. We found that imidacloprid and ethion have negative impacts on aversive learning and movement following a single-dose and that chronic exposure effects were dose-dependent for these two insecticides. In contrast, glyphosate had no effect on learning and less of an effect on movement; RoundUp® showed dose-dependent results on circadian rhythmicity. Overall, the results suggest that short-term exposure to imidacloprid and ethion adversely affect honey bee foragers and chronic exposure to glyphosate may affect pollination success.

Pesticide-Virus Interactions in Honey Bees: Challenges and Opportunities for Understanding Drivers of Bee Declines.

Honey bees are key agricultural pollinators, but beekeepers continually suffer high annual colony losses owing to a number of environmental stressors, including inadequate nutrition, pressures from parasites and pathogens, and exposure to a wide variety of pesticides. In this review, we examine how two such stressors, pesticides and viruses, may interact in additive or synergistic ways to affect honey bee health. Despite what appears to be a straightforward comparison, there is a dearth of studies examining this issue likely owing to the complexity of such interactions. Such complexities include the wide array of pesticide chemical classes with different modes of actions, the coupling of many bee viruses with ectoparasitic Varroa mites, and the intricate social structure of honey bee colonies. Together, these issues pose a challenge to researchers examining the effects pesticide-virus interactions at both the individual and colony level.

Meta-analysis of honey bee neurogenomic response links Deformed wing virus type A to precocious behavioral maturation

Crop pollination by the western honey bee Apis mellifera is vital to agriculture but threatened by alarmingly high levels of colony mortality, especially in Europe and North America. Colony loss is due, in part, to the high viral loads of Deformed wing virus (DWV), transmitted by the ectoparasitic mite Varroa destructor, especially throughout the overwintering period of a honey bee colony. Covert DWV infection is commonplace and has been causally linked to precocious foraging, which itself has been linked to colony loss. Taking advantage of four brain transcriptome studies that unexpectedly revealed evidence of covert DWV-A infection, we set out to explore whether this effect is due to DWV-A mimicking naturally occurring changes in brain gene expression that are associated with behavioral maturation. Consistent with this hypothesis, we found that brain gene expression profiles of DWV-A infected bees resembled those of foragers, even in individuals that were much younger than typical foragers. In addition, brain transcriptional regulatory network analysis revealed a positive association between DWV-A infection and transcription factors previously associated with honey bee foraging behavior. Surprisingly, single-cell RNA-Sequencing implicated glia, not neurons, in this effect; there are relatively few glial cells in the insect brain and they are rarely associated with behavioral plasticity. Covert DWV-A infection also has been linked to impaired learning, which together with precocious foraging can lead to increased occurrence of infected bees from one colony mistakenly entering another colony, especially under crowded modern apiary conditions. These findings provide new insights into the mechanisms by which DWV-A affects honey bee health and colony survival.

The development of an attract-and-kill bait for controlling the small hive beetle (Coleoptera: Nitidulidae)

This research investigates the development of an attract-and-kill bait for in-hive control of the small hive beetle, Aethina tumida. The control method employs attracting the beetles to an in-hive trap with a feeding attractant/stimulant where a toxicant is delivered by consuming an edible bait. Investigations into mild insecticides led to the use of boric acid. At low doses, boric acid is non-toxic to humans but lethal to insects. This research was designed to identify key compounds that would attract small hive beetles, develop an edible bait using those compounds and if the diet would be consumed by the beetle, determine the lethal dose with the lowest amount of toxicant, and the effects the toxicant would have on the honey bee. Attractive compounds were identified from honey bee pollen patties inoculated Kodamaea ohmeri yeast and resulted in the identification of three key components: ethyl propionate, isobutyl propionate, and ethyl butyrate. A diet comprised of corn gluten meal, barley flour, soy flour, Brewer’s yeast, and glycerin containing the attractant/feeding stimulant was highly attractive and readily consumed. In laboratory trials, the treatments containing the attract-and-kill with 2% boric acid reduced the beetle population to zero within a few days. There was no significant difference between the sex of the beetle for survival on any of the treatments. Honey bee survival was reduced by ingesting the boric acid. The development of an inexpensive small hive beetle trapping system is essential for in-hive control of this devastating pest. This system has the potential to provide beekeepers a tool for control of this pest species that affects honey bee health and survival worldwide.

Epidemiological study of honeybee pathogens in Europe: The results of Castilla-La Mancha (Spain)

As a part of a Pilot Monitoring Program of honey bee health coordinated by the EURL (European Union Reference Laboratory) and according to the criteria established for Spain, 14 apiaries in Castilla-La Mancha were selected at random and sampled during the autumns of 2012-2014 to identify the most prevalent nosogenic agents, potentially those related to the honey bee colony collapse phenomenon. In all the apiaries studied, Nosema ceranae was the most prevalent pathogen detected over the three years, confirming the worldwide spread of this microsporidian, a pathogen that negatively affects honey bee health at an individual and colony level. Trypanosomatids were also very prevalent in honey bee colonies, although the majority of Trypanosomatids detected were not Crithidia mellificae but rather the genetically distinct Lotmaria passim lineage. We also detected Varroa destructor mites, and the particularly high prevalence in 2014 suggests a possible problem regarding mite control in field conditions that requires attention. In agreement with data from other regions, the BQCV and DWV were the most prevalent viruses in honey bee colonies and thus, the Varroa-DVW interaction may be an important cause of bee colony mortality. While there was little evidence of a relationship between the BQCV virus and N. ceranae under field conditions during 2012, this was not the case in 2013 and 2014. Finally, the AKI-complex or LSV-complex was not detected. The information obtained in this study should help orientate future plans for honey bee disease control.

Comparative Flight Activities and Pathogen Load of Two Stocks of Honey Bees Reared in Gamma-Irradiated Combs.

Gamma irradiation is known to inactivate various pathogens that negatively affect honey bee health. Bee pathogens, such as Deformed wing virus (DWV) and Nosema spp., have a deleterious impact on foraging activities and bee survival, and have been detected in combs. In this study, we assessed the effects of gamma irradiation on the flight activities, pathogen load, and survival of two honey bee stocks that were reared in irradiated and non-irradiated combs. Overall, bee genotype influenced the average number of daily flights, the total number of foraging flights, and total flight duration, in which the Russian honey bees outperformed the Italian honey bees. Exposing combs to gamma irradiation only affected the age at first flight, with worker bees that were reared in non-irradiated combs foraging prematurely compared to those reared in irradiated combs. Precocious foraging may be associated with the higher levels of DWV in bees reared in non-irradiated combs and also with the lower amount of pollen stores in colonies that used non-irradiated combs. These data suggest that gamma irradiation of combs can help minimize the negative impact of DWV in honey bees. Since colonies with irradiated combs stored more pollen than those with non-irradiated combs, crop pollination efficiency may be further improved when mite-resistant stocks are used, since they performed more flights and had longer flight durations.

Lethal effects of Cr(III) alone and in combination with propiconazole and clothianidin in honey bees

Several anthropogenic contaminants, including pesticides and heavy metals, can affect honey bee health. The effects of mixtures of heavy metals and pesticides are rarely studied in bees, even though bees are likely to be exposed to these contaminants in both agricultural and urban environments. In this study, the lethal toxicity of Cr alone and in combination with the neonicotinoid insecticide clothianidin and the ergosterol-biosynthesis-inhibiting fungicide propiconazole was assessed in Apis mellifera adults. The LD50 and lowest benchmark dose of Cr as Cr(NO3)3, revealed a low acute oral toxicity on honey bee foragers (2049 and 379 mg L−1, respectively) and the Cr retention (i.e. bee ability to retain the heavy metal in the body) was generally low compared to other metals. A modified method based on the binomial proportion test was developed to analyse synergistic and antagonistic interactions between the three tested contaminants. The combination of an ecologically-relevant field concentration of chromium with clothianidin and propiconazole did not increase bee mortality. On the contrary, the presence of Cr in mixture with propiconazole elicited a slight antagonistic effect.

Variations in the Availability of Pollen Resources Affect Honey Bee Health.

Intensive agricultural systems often expose honey bees (Apis mellifera L.) to large temporal variations in the availability (quantity, quality and diversity) of nutritional resources. Such nutritional irregularity is expected to affect honey bee health. We therefore tested under laboratory conditions the effect of such variation in pollen availability on honey bee health (survival and nursing physiology—hypopharyngeal gland development and vitellogenin expression). We fed honey bees with different diets composed of pollen pellets collected by honey bees in an agricultural landscape of western France. Slight drops (5–10%) in the availability of oilseed rape (Brassica napus L.) pollen resulted in significant reductions of all tested variables. Despite some variations in taxonomic diversity and nutritional quality, the pollen mixes harvested over the season had a similar positive influence on honey bee health, except for the one collected in late July that induced poor survival and nursing physiology. This period coincided with the mass-flowering of maize (Zea mays L.), an anemophilous crop which produces poor-quality pollen. Therefore, changes in bee health were not connected to variations in pollen diversity but rather to variations in pollen depletion and quality, such as can be encountered in an intensive agricultural system of western France. Finally, even though pollen can be available ad libitum during the mass-flowering of some crops (e.g. maize), it can fail to provide bees with diet adequate for their development.

Effect of Bodily Fluids from Honey Bee (Apis mellifera) Larvae on Growth and Genome-Wide Transcriptional Response of the Causal Agent of American Foulbrood Disease (Paenibacillus larvae)

Paenibacillus larvae, the causal agent of American Foulbrood disease (AFB), affects honey bee health worldwide. The present study investigates the effect of bodily fluids from honey bee larvae on growth velocity and transcription for this Gram-positive, endospore-forming bacterium. It was observed that larval fluids accelerate the growth and lead to higher bacterial densities during stationary phase. The genome-wide transcriptional response of in vitro cultures of P. larvae to larval fluids was studied by microarray technology. Early responses of P. larvae to larval fluids are characterized by a general down-regulation of oligopeptide and sugar transporter genes, as well as by amino acid and carbohydrate metabolic genes, among others. Late responses are dominated by general down-regulation of sporulation genes and up-regulation of phage-related genes. A theoretical mechanism of carbon catabolite repression is discussed.

Direct effect of acaricides on pathogen loads and gene expression levels in honey bees Apis mellifera

The effect of using acaricides to control varroa mites has long been a concern to the beekeeping industry due to unintended negative impacts on honey bee health. Irregular ontogenesis, suppression of immune defenses, and impairment of normal behavior have been linked to pesticide use. External stressors, including parasites and the pathogens they vector, can confound studies on the effects of pesticides on the metabolism of honey bees. This is the case of Varroa destructor, a mite that negatively affects honey bee health on many levels, from direct parasitism, which diminishes honey bee productivity, to vectoring and/or activating other pathogens, including many viruses. Here we present a gene expression profile comprising genes acting on diverse metabolic levels (detoxification, immunity, and development) in a honey bee population that lacks the influence of varroa mites. We present data for hives treated with five different acaricides; Apiguard (thymol), Apistan (tau-fluvalinate), Checkmite (coumaphos), Miteaway (formic acid) and ApiVar (amitraz). The results indicate that thymol, coumaphos and formic acid are able to alter some metabolic responses. These include detoxification gene expression pathways, components of the immune system responsible for cellular response and the c-Jun amino-terminal kinase (JNK) pathway, and developmental genes. These could potentially interfere with the health of individual honey bees and entire colonies.

Acaricide Treatment Affects Viral Dynamics in Varroa destructor-Infested Honey Bee Colonies via both Host Physiology and Mite Control

Honey bee (Apis mellifera) colonies are declining, and a number of stressors have been identified that affect, alone or in combination, the health of honey bees. The ectoparasitic mite Varroa destructor, honey bee viruses that are often closely associated with the mite, and pesticides used to control the mite population form a complex system of stressors that may affect honey bee health in different ways. During an acaricide treatment using Apistan (plastic strips coated with tau-fluvalinate), we analyzed the infection dynamics of deformed wing virus (DWV), sacbrood virus (SBV), and black queen cell virus (BQCV) in adult bees, mite-infested pupae, their associated Varroa mites, and uninfested pupae, comparing these to similar samples from untreated control colonies. Titers of DWV increased initially with the onset of the acaricide application and then slightly decreased progressively coinciding with the removal of the Varroa mite infestation. This initial increase in DWV titers suggests a physiological effect of tau-fluvalinate on the host's susceptibility to viral infection. DWV titers in adult bees and uninfested pupae remained higher in treated colonies than in untreated colonies. The titers of SBV and BQCV did not show any direct relationship with mite infestation and showed a variety of possible effects of the acaricide treatment. The results indicate that other factors besides Varroa mite infestation may be important to the development and maintenance of damaging DWV titers in colonies. Possible biochemical explanations for the observed synergistic effects between tau-fluvalinate and virus infections are discussed.

Individual forager profits in Apis mellifera unaffected by a range of colony Varroa destructor densities

The parasitic mite Varroa destructor Anderson and Trueman negatively affects honey bee health, flight activity, and foraging behavior, all of which can be expected to affect foraging energetics. We tested this hypothesis in a 3-year field study. In each year, four-frame nucleus colonies with varying loads of varroa were placed under cages with mature rabbiteye blueberry plants, Vaccinium ashei. Individual bee weights consistently decreased as colony varroa populations increased, affirming that the design produced a range of colony mite effects. However, average forager flower handling times and nectar ingestion rates were unaffected by changes in colony varroa levels. Moreover, there were no significant effects of colony varroa levels on individual net foraging energy gain determined per flower, per second handling time, or per second total foraging time. We conclude that individual forager profits in Apis mellifera are unaffected by the range of colony V. destructor densities used in this study. These results are relevant to the question of the extent to which foraging of individuals relates to colony state in social Hymenoptera.