Carbohydrate nutrition associated with health of overwintering honey bees.

In temperate climates, honey bees rely on stored carbohydrates to sustain them throughout the winter. In nature, honey serves as the bees' source of carbohydrates, but when managed, beekeepers often harvest honey and replace it with cheaper, artificial feed. The effects of alternative carbohydrate sources on colony survival, strength, and individual bee metabolic health are poorly understood. We assessed the impacts of carbohydrate diets (honey, sucrose syrup, high-fructose corn syrup, and invert syrup) on colony winter survival, population size, and worker bee nutritional state (i.e., fat content and gene expression of overwintered bees and emerging callow bees). We observed a nonsignificant trend for greater survival and larger adult population size among colonies overwintered on honey compared to the artificial feeds, with colonies fed high-fructose corn syrup performing particularly poorly. These trends were mirrored in individual bee physiology, with bees from colonies fed honey having significantly larger fat bodies than those from colonies fed high-fructose corn syrup. For bees fed honey or sucrose, we also observed gene expression profiles consistent with a higher nutritional state, associated with physiologically younger individuals. That is, there was significantly higher expression of vitellogenin and insulin-like peptide 2 and lower expression of insulin-like peptide 1 and juvenile hormone acid methyltransferase in the brains of bees that consumed honey or sucrose syrup relative to those that consumed invert syrup or high-fructose corn syrup. These findings further our understanding of the physiological implications of carbohydrate nutrition in honey bees and have applied implications for colony management.

Metagenomic analysis of the honey bee queen microbiome reveals low bacterial diversity and Caudoviricetes phages.

In eusocial insects, the health of the queens-the colony founders and sole reproductive females-is a primary determinant for colony success. Queen failure in the honey bee Apis mellifera, for example, is a major concern of beekeepers who annually suffer colony losses, necessitating a greater knowledge of queen health. Several studies on the microbiome of honey bees have characterized its diversity and shown its importance for the health of worker bees, the female non-reproductive caste. However, the microbiome of workers differs from that of queens, which, in comparison, is still poorly studied. Thus, direct investigations of the queen microbiome are required to understand colony-level microbiome assembly, functional roles, and evolution. Here, we used metagenomics to comprehensively characterize the honey bee queen microbiome. Comparing samples from different geographic locations and breeder sources, we show that the microbiome of queens is mostly shaped by the environment experienced since early life and is predicted to play roles in the breakdown of the diet and protection from pathogens and xenobiotics. We also reveal that the microbiome of queens comprises only four candidate core bacterial species, Apilactobacillus kunkeei, Lactobacillus apis, Bombella apis, and Commensalibacter sp. Interestingly, in addition to bacteria, we show that bacteriophages infect the queen microbiome, for which Lactobacillaceae are predicted to be the main reservoirs. Together, our results provide the basis to understand the honey bee colony microbiome assemblage, can guide improvements in queen-rearing processes, and highlight the importance of considering bacteriophages for queen microbiome health and microbiome homeostasis in eusocial insects.IMPORTANCEThe queen caste plays a central role in colony success in eusocial insects, as queens lay eggs and regulate colony behavior and development. Queen failure can cause colonies to collapse, which is one of the major concerns of beekeepers. Thus, understanding the biology behind the queen's health is a pressing issue. Previous studies have shown that the bee microbiome plays an important role in worker bee health, but little is known about the queen microbiome and its function in vivo. Here, we characterized the queen microbiome, identifying for the first time the present species and their putative functions. We show that the queen microbiome has predicted nutritional and protective roles in queen association and comprises only four consistently present bacterial species. Additionally, we bring to attention the spread of phages in the queen microbiome, which increased in abundance in failing queens and may impact the fate of the colony.

A longitudinal experiment demonstrates that honey bee colonies managed organically are as healthy and productive as those managed conventionally.

Honey bee colony management is critical to mitigating the negative effects of biotic and abiotic stressors. However, there is significant variation in the practices implemented by beekeepers, which results in varying management systems. This longitudinal study incorporated a systems approach to experimentally test the role of three representative beekeeping management systems (conventional, organic, and chemical-free) on the health and productivity of stationary honey-producing colonies over 3 years. We found that the survival rates for colonies in the conventional and organic management systems were equivalent, but around 2.8 times greater than the survival under chemical-free management. Honey production was also similar, with 102% and 119% more honey produced in conventional and organic management systems, respectively, than in the chemical-free management system. We also report significant differences in biomarkers of health including pathogen levels (DWV, IAPV, Vairimorpha apis, Vairimorpha ceranae) and gene expression (def-1, hym, nkd, vg). Our results experimentally demonstrate that beekeeping management practices are key drivers of survival and productivity of managed honey bee colonies. More importantly, we found that the organic management system-which uses organic-approved chemicals for mite control-supports healthy and productive colonies, and can be incorporated as a sustainable approach for stationary honey-producing beekeeping operations.

Indoor winter fumigation with formic acid for control of Acarapis woodi (Acari: Tarsonemidae) and nosema disease, Nosema sp.

Indoor fumigation of honey bees, Apis mellifera L., with formic acid to control varroa mites, Varroa destructor Anderson & Trueman, allows simultaneous fumigation of multiple colonies with little labor input and good efficacy. Several experiments were designed to test the efficacy of formic acid as a treatment for honey bee mites, Acarapis woodi (Rennie) (Acari: Tarsonemidae), and nosema disease, Nosema sp., indoors in winter. The objectives of this study were (1) to determine the efficacy of formic acid fumigation for honey bee mite control by using both the thoracic slice and live dissection methods and (2) to determine whether indoor fumigation can reliably prevent the buildup of nosema disease in overwintering honey bee colonies. Indoor winter fumigation of honey bee colonies with formic acid was effective in killing a high percentage of honey bee mites but did not significantly reduce the proportion of bees with infested tracheae over the duration of the experiments. Thus, the method used to determine the efficacy of the treatment affected the results. Under conditions of relatively low or decreasing levels of nosema, fumigation tended to suppress the mean abundance of nosema spores relative to the controls. In three separate fumigation experiments using a range of formic acid concentrations, there was no statistical difference between the buildup or maintenance of nosema spore mean abundance over the winter in bees from formic acid fumigated colonies compared with untreated controls. However, fumigation with formic acid during winter at a low concentration for extended periods significantly suppressed spore buildup of mixed populations of nosema (Nosema apis and Nosema ceranae) in 1 yr.

Beekeeping Management Practices Are Associated with Operation Size and Beekeepers' Philosophy towards in-Hive Chemicals.

Management by beekeepers is of utmost importance for the health and survival of honey bee colonies. Beekeeping management practices vary from low to high intervention regarding the use of chemicals, hive manipulations, and supplemental feeding of colonies. In this study, we use quantitative data from the Bee Informed Partnership's national survey to investigate drivers of management practices among beekeepers in the United States. This is the first study to quantitatively examine these variables to objectively describe the management practices among different groups of beekeepers in the United States. We hypothesized that management practices and goals among beekeepers are different based on the beekeeper's philosophy (as determined by their willingness to use chemicals to control pests and pathogens) and the size of the beekeeping operation. Using a multiple factor analysis, we determined that beekeepers use a continuum of management practices. However, we found that beekeepers' willingness to use in-hive chemicals and the number of colonies in their operation are non-randomly associated with other aspects of beekeeping management practices. Specifically, the size of the beekeeping operation was associated with beekeepers' choices of in-hive chemicals, while beekeepers' philosophy was most strongly associated with choices of in-hive chemicals and beekeeping goals. Our results will facilitate the development of decision-making tools for beekeepers to choose management practices that are appropriate for the size of their operations and their beekeeping philosophy.

Are Non-Target Honey Bees (Hymenoptera: Apidae) Exposed to Dinotefuran From Spotted Lanternfly (Hemiptera: Fulgoridae) Trap Trees?

The spotted lanternfly, Lycorma delicatula, is an introduced plant hopper that causes significant damage to host plants in the United States. Because of its affinity for tree of heaven, Ailanthus altissima, control efforts have focused on the use of the systemic insecticide, dinotefuran, in designated trap trees. There is concern about exposure to this pesticide by non-target species, especially honey bees, Apis mellifera, via lanternfly honeydew. Therefore, honey bee colonies were established in areas of high densities of trap trees and samples of honey, bees, and beeswax were collected in May, July, and October of 2017 for analysis. Samples were extracted by the QuEChERS method and analyzed using high-performance liquid chromatography with tandem mass spectrometry to determine the presence and quantity of dinotefuran. Additionally, honeydew from lanternflies was analyzed for dinotefuran and informal observations of trap tree visitors were made. None of the worker bee, wax, or honey samples indicated detectable levels of dinotefuran; however, honeydew samples collected did contain dinotefuran above the detection limit with amounts ranging from 3 to 100 ng per sample. The lack of dinotefuran in honey bee products matches the general absence of honey bees at trap trees in informal observations.

Short-term fumigation of honey bee (Hymenoptera: Apidae) colonies with formic and acetic acids for the control of Varroa destructor (Acari: Varroidae).

Controlling populations of varroa mites is crucial for the survival of the beekeeping industry. Many treatments exist, and all are designed to kill mites on adult bees. Because the majority of mites are found under capped brood, most treatments are designed to deliver active ingredients over an extended period to control mites on adult bees, as developing bees and mites emerge. In this study, a 17-h application of 50% formic acid effectively killed mites in capped worker brood and on adult bees without harming queens or uncapped brood. Neither acetic acid nor a combined treatment of formic and acetic acids applied to the West Virginia formic acid fumigator was as effective as formic acid alone in controlling varroa mites. In addition, none of the treatments tested in late summer had an effect on the late-season prevalence of deformed wing virus. The short-term formic acid treatment killed > 60% of varroa mites in capped worker brood; thus, it is a promising tool for beekeepers, especially when such treatments are necessary during the nectar flow.

Effect of concentration and exposure time on treatment efficacy against Varroa mites (Acari: Varroidae) during indoor winter fumigation of honey bees (Hymenoptera: Apidae) with formic acid.

The combination of the concentration of formic acid and the duration of fumigation (CT product) during indoor treatments of honey bee, Apis mellifera L., colonies to control the varroa mite, Varroa destructor Anderson & Trueman, determines the efficacy of the treatment. Because high concentrations can cause queen mortality, we hypothesized that a high CT product given as a low concentration over a long exposure time rather than as a high concentration over a short exposure time would allow effective control of varroa mites without the detrimental effects on queens. The objective of this study was to assess different combinations of formic acid concentration and exposure time with similar CT products in controlling varroa mites while minimizing the effect on worker and queen honey bees. Treated colonies were exposed to a low, medium, or high concentration of formic acid until a mean CT product of 471 ppm*d in room air was realized. The treatments consisted of a long-term low concentration of 19 ppm for 27 d, a medium-term medium concentration of 42 ppm for 10 d, a short-term high concentration of 53 ppm for 9 d, and an untreated control. Both short-term high-concentration and medium-term medium-concentration fumigation with formic acid killed varroa mites, with averages of 93 and 83% mortality, respectively, but both treatments also were associated with an increase in mortality of worker bees, queen bees, or both. Long-term low-concentration fumigation had lower efficacy (60% varroa mite mortality), but it did not increase worker or queen bee mortality. This trend differed slightly in colonies from two different beekeepers. Varroa mite mean abundance was significantly decreased in all three acid treatments relative to the control. Daily worker mortality was significantly increased by the short-term high concentration treatment, which was reflected by a decrease in the size of the worker population, but not an increase in colony mortality. Queen mortality was significantly greater under the medium-term medium concentration and the short-term high concentration treatments than in controls.

Indoor winter fumigation of Apis mellifera (Hymenoptera: Apidae) colonies infested with Varroa destructor (Acari: Varroidae) with formic acid is a potential control alternative in northern climates.

Formic acid treatment for the control of the ectoparasitic varroa mite, Varroa destructor Anderson & Trueman, infesting honey bee, Apis mellifera L., colonies is usually carried out as an in-hive outdoor treatment. This study examined the use of formic acid on wintered colonies kept indoors at 5 degrees C from 24 November 1999 to 24 March 2000. Colonies were placed in small treatment rooms that were not treated (control) or fumigated at three different concentrations of formic acid: low (mean 11.9 +/- 1.2 ppm), medium (mean 25.8 +/- 1.4 ppm), or high (mean 41.2 +/- 3.3 ppm), for 48 h on 22-24 January 2000. Queen bee, worker bee, and varroa mite mortality were monitored throughout the winter, and tracheal mite, Acarapis woodi (Rennie), prevalence and mean abundance of nosema, Nosema apis Zander, spores were assessed. This study revealed that formic acid fumigation of indoor-wintered honey bees is feasible and effective. The highest concentration significantly reduced the mean abundance of varroa mites and nosema spores without increasing bee mortality. Tracheal mite prevalence did not change significantly at any concentration, although we did not measure mortality directly. The highest concentration treatment killed 33.3% of queens compared with 4.8% loss in the control. Repeated fumigation periods at high concentrations or extended fumigation at low concentrations may increase the efficacy of this treatment method and should be tested in future studies. An understanding of the cause of queen loss and methods to prevent it must be developed for this method to be generally accepted.

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.

Colony collapse disorder: a descriptive study.

BACKGROUND: Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L.) colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD) because the main trait was a rapid loss of adult worker bees. We initiated a descriptive epizootiological study in order to better characterize CCD and compare risk factor exposure between populations afflicted by and not afflicted by CCD. METHODS AND PRINCIPAL FINDINGS: Of 61 quantified variables (including adult bee physiology, pathogen loads, and pesticide levels), no single measure emerged as a most-likely cause of CCD. Bees in CCD colonies had higher pathogen loads and were co-infected with a greater number of pathogens than control populations, suggesting either an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Levels of the synthetic acaricide coumaphos (used by beekeepers to control the parasitic mite Varroa destructor) were higher in control colonies than CCD-affected colonies. CONCLUSIONS/SIGNIFICANCE: This is the first comprehensive survey of CCD-affected bee populations that suggests CCD involves an interaction between pathogens and other stress factors. We present evidence that this condition is contagious or the result of exposure to a common risk factor. Potentially important areas for future hypothesis-driven research, including the possible legacy effect of mite parasitism and the role of honey bee resistance to pesticides, are highlighted.

A survey of honey bee colony losses in the U.S., fall 2007 to spring 2008.

BACKGROUND: Honey bees are an essential component of modern agriculture. A recently recognized ailment, Colony Collapse Disorder (CCD), devastates colonies, leaving hives with a complete lack of bees, dead or alive. Up to now, estimates of honey bee population decline have not included losses occurring during the wintering period, thus underestimating actual colony mortality. Our survey quantifies the extent of colony losses in the United States over the winter of 2007-2008. METHODOLOGY/PRINCIPAL FINDINGS: Surveys were conducted to quantify and identify management factors (e.g. operation size, hive migration) that contribute to high colony losses in general and CCD symptoms in particular. Over 19% of the country's estimated 2.44 million colonies were surveyed. A total loss of 35.8% of colonies was recorded; an increase of 11.4% compared to last year. Operations that pollinated almonds lost, on average, the same number of colonies as those that did not. The 37.9% of operations that reported having at least some of their colonies die with a complete lack of bees had a total loss of 40.8% of colonies compared to the 17.1% loss reported by beekeepers without this symptom. Large operations were more likely to have this symptom suggesting that a contagious condition may be a causal factor. Sixty percent of all colonies that were reported dead in this survey died without dead bees, and thus possibly suffered from CCD. In PA, losses varied with region, indicating that ambient temperature over winter may be an important factor. CONCLUSIONS/SIGNIFICANCE: Of utmost importance to understanding the recent losses and CCD is keeping track of losses over time and on a large geographic scale. Given that our surveys are representative of the losses across all beekeeping operations, between 0.75 and 1.00 million honey bee colonies are estimated to have died in the United States over the winter of 2007-2008. This article is an extensive survey of U.S. beekeepers across the continent, serving as a reference for comparison with future losses as well as providing guidance to future hypothesis-driven research on the causes of colony mortality.

The effects of temperature and dose of formic acid on treatment efficacy against Varroa destructor (Acari: Varroidae), a parasite of Apis mellifera (Hymenoptera: Apidae).

In order to decrease the variability of formic acid treatments against the honey bee parasite the varroa mite, Varroa destructor (Anderson and Trueman 2000), it is necessary to determine the dose-time combination that best controls mites without harming bees. The concentration x time (CT) product is a valuable tool for studying fumigants and how they might perform under various environmental conditions. This laboratory study is an assessment of the efficacy of formic acid against the varroa mite under a range of formic acid concentrations and temperatures. The objectives are 1) to determine the effect of temperature and dose of formic acid on worker honey bee and varroa mite survival, 2) to determine the CT50 products for both honey bees and varroa mites and 3) to determine the best temperature and dose to optimize selectivity of formic acid treatment for control of varroa mites. Worker honey bees and varroa mites were fumigated at 0, 0.01, 0.02, 0.04, 0.08, and 0.16 mg/L at 5, 15, 25, and 35 degrees C for 12 d. Mite and bee mortality were assessed at regular intervals. Both mite and bee survival were affected by formic acid dose. Doses of 0.08 and 0.16 mg/L were effective at killing mites at all temperatures tested above 5 degrees C. There was a significant interaction between temperature, dose, and species for the CT50 product. The difference between the CT50 product of bees and mites was significant at only a few temperature-dose combinations. CT product values showed that at most temperatures the greatest fumigation efficiency occurred at lower doses of formic acid. However, the best fumigation efficiency and selectivity combination for treatments occurred at a dose of 0.16 mg/L when the temperature was 35 degrees C.