Social Apoptosis in Varroa Mite Resistant Western Honey Bees (Apis mellifera)

Honey bees are eusocial animals that exhibit both individual and social immune responses, which influence colony health. This is especially well-studied regarding the mite Varroa destructor Anderson and Trueman (Parasitiformes: Varroidae), a parasite of honey bee brood and disease vector. Varroa was introduced relatively recently to Apis mellifera L. (Hymenoptera: Apidae) and is a major driver of the catastrophic die-off of honey bee colonies in the last decade. In contrast, the original host species, Apis cerana Fabricius (Hymenoptera: Apidae) is able to survive mite infestations with little effect on colony health and survival. This resilience is due in part to a newly identified social immune response expressed by developing worker brood. Varroa infested female A. cerana brood experience delayed development and eventually die in a process called ‘social apoptosis’. Here, an individual’s susceptibility to Varroa results in colony level resistance. We tested for the presence of the social apoptosis trait in two Varroa resistant stocks of A. mellifera (Pol-line and Russian) with different selection histories and compared them to a known Varroa-susceptible stock (Italian). We assessed the survival and development of worker brood reared in either highly or lightly infested host colonies, then receiving one of three treatments: uninfested, experimentally inoculated with a Varroa mite, or wounded to simulate Varroa damage. We found that response to treatment was only differentiated in brood reared in lightly infested host colonies, where experimentally infested Russian honey bees had decreased survival relative to the mite-susceptible Italian stock. This is the first evidence that social apoptosis can exist in Western honey bee populations.     

Within-Year Effects of Prescribed Fire on Bumble Bees (Hymenoptera: Apidae) and Floral Resources

Despite the importance of bumble bees (genus Bombus Latreille) for their services to natural and agricultural environments, we know little about the relationship between grassland management practices and bumble bee conservation. Prescribed fire is a common grassland maintenance tool, including in areas where endangered and threatened bumble bees are present. Thus, knowledge of the effects of prescribed fire on bumble bees is essential for designing management schemes that protect and bolster their populations. Using nonlethal surveys to record bumble bee species richness, abundance, and community composition, we evaluated the effects of spring controlled burns on summer bumble bee gynes and workers across five sites in southern Wisconsin. In addition, we explored the effects of fire on floral resources by measuring floral genus richness, abundance, ground cover, and proportion of transects containing blooming flowers in adjacent burned and unburned parcels. Prescribed fire had no measurable effects on bumble bee gyne or worker community composition, species richness, or abundance. However, consistent with previous studies prescribed fire increased floral genus richness and ground cover. The disconnect between bumble bee and floral responses to fire highlights some opportunities for improving our understanding of fire’s effects on bumble bee diapause, nest site choice, and foraging.     

Understanding the Enemy: A Review of the Genetics,Behavior and Chemical Ecology of Varroa destructor,the Parasitic Mite of Apis mellifera

Varroa destructor (Mesostigmata: Varroidae) is arguably the most damaging parasitic mite that attacks honey bees worldwide. Since its initial host switch from the Asian honey bee (Apis cerana) (Hymenoptera: Apidae) to the Western honey bee (Apis mellifera) (Hymenoptera: Apidae), Varroa has become a widely successful invasive species, attacking honey bees on almost every continent where apiculture is practiced. Two haplotypes of V. destructor (Japanese and Korean) parasitize A. mellifera, both of which vector various honey bee-associated viruses. As the population of Varroa grows within a colony in the spring and summer, so do the levels of viral infections. Not surprisingly, high Varroa parasitization impacts bees at the individual level, causing bees to exhibit lower weight, decreased learning capacity, and shorter lifespan. High levels of Varroa infestation can lead to colony-wide varroosis and eventually colony death, especially when no control measures are taken against the mites. Varroa has become a successful parasite of A. mellifera because of its ability to reproduce within both drone cells and worker cells, which allows populations to expand rapidly. Varroa uses several chemical cues to complete its life cycle, many of which remain understudied and should be further explored. Given the growing reports of pesticide resistance by Varroa in several countries, a better understanding of the mite’s basic biology is needed to find alternative pest management strategies. This review focuses on the genetics, behavior, and chemical ecology of V. destructor within A. mellifera colonies, and points to areas of research that should be exploited to better control this pervasive honey bee enemy.     

The Complete Mitochondrial Genome of Lepidotrigona flavibasis (Hymenoptera: Meliponini) and High Gene Rearrangement in Lepidotrigona Mitogenomes

We reported the sequence and characteristics of the complete mitochondrial genome of an ecologically important stingless bee, Lepidotrigona flavibasis (Hymenoptera: Meliponini), that has suffered serious population declines in recent years. A phylogenetic analysis based on complete mitogenomes indicated that L. flavibasis was first clustered with another Lepidotrigona species (L. terminata) and then joined with the other two Melipona (Hymenoptera: Meliponini) stingless bees (M. scutellaris and M. bicolor), forming a single clade of stingless bees. The stingless bee clade has a closer relationship with bumblebees (Bombus) (Hymenoptera: Apidae) than with honeybees (Apis) (Hymenoptera: Apidae). Extremely high gene rearrangements involving tRNAs, rRNAs, D-loop regions, and protein-coding genes were observed in the Lepidotrigona mitogenomes, suggesting an overactive evolutionary status in Lepidotrigona species. These mitogenomic organization variations could provide a good system with which to understand the evolutionary history of Meliponini.     

Hygiene-Eliciting Brood Semiochemicals as a Tool for Assaying Honey Bee (Hymenoptera: Apidae) Colony Resistance to Varroa (Mesostigmata: Varroidae)

Despite numerous interventions, the ectoparasitic mite Varroa (Varroa destructor Anderson and Trueman [Mesostigmata: Varroidae]) and the pathogens it vectors remain a primary threat to honey bee (Apis mellifera Linnaeus [Hymenoptera: Apidae]) health. Hygienic behavior, the ability to detect, uncap, and remove unhealthy brood from the colony, has been bred for selectively for over two decades and continues to be a promising avenue for improved Varroa management. Although hygienic behavior is expressed more in Varroa-resistant colonies, hygiene does not always confer resistance to Varroa. Additionally, existing Varroa resistance selection methods trade efficacy for efficiency, because those achieving the highest levels of Varroa resistance can be time-consuming, and thus expensive and impractical for apicultural use. Here, we tested the hypothesis that hygienic response to a mixture of semiochemicals associated with Varroa-infested honey bee brood can serve as an improved tool for predicting colony-level Varroa resistance. In support of our hypothesis, we demonstrated that a mixture of the compounds (Z)-10-tritriacontene, (Z)-8-hentriacontene, (Z)-8-heptadecene, and (Z)-6-pentadecene triggers hygienic behavior in a two-hour assay, and that high-performing colonies (hygienic response to ≥60% of treated cells) have significantly lower Varroa infestations, remove significantly more introduced Varroa, and are significantly more likely to survive the winter compared to low-performing colonies (hygienic response to <60% of treated cells). We discuss the relative efficacy and efficiency of this assay for facilitating apiary management decisions and selection of Varroa-resistant honey bees, as well as the relevance of these findings to honey bee health, pollination services, and social insect communication.     

Assessing Repeated Oxalic Acid Vaporization in Honey Bee (Hymenoptera: Apidae) Colonies for Control of the Ectoparasitic Mite Varroa destructor

The American beekeeping industry continually experiences colony mortality with annual losses as high as 43%. A leading cause of this is the exotic, ectoparasitic mite, Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae). Integrated Pest Management (IPM) options are used to keep mite populations from reaching lethal levels, however, due to resistance and/or the lack of suitable treatment options, novel controls for reducing mites are warranted. Oxalic acid for controlling V. destructor has become a popular treatment regimen among commercial and backyard beekeepers. Applying vaporized oxalic acid inside a honey bee hive is a legal application method in the U.S., and results in the death of exposed mites. However, if mites are in the reproductive stage and therefore under the protective wax capping, oxalic acid is ineffective. One popular method of applying oxalic is vaporizing multiple times over several weeks to try and circumvent the problem of mites hiding in brood cells. By comparing against control colonies, we tested oxalic acid vaporization in colonies treated with seven applications separated by 5 d (35 d total). We tested in apiaries in Georgia and Alabama during 2019 and 2020, totaling 99 colonies. We found that adult honey bees Linnaeus (Hymenoptera: Apidae), and developing brood experienced no adverse impacts from the oxalic vaporization regime. However, we did not find evidence that frequent periodic application of oxalic during brood-rearing periods is capable of bringing V. destructor populations below treatment thresholds.     

Validation of Diagnostic Methods for European Foulbrood on Commercial Honey Bee Colonies in the United States

One of the most serious bacterial pathogens of Western honey bees (Apis mellifera Linnaeus [Hymenoptera: Apidae]) is Melissococcus plutonius, the cause of the disease European foulbrood. Because European foulbrood is highly variable, with diverse outcomes at both the individual and colony levels, it is difficult to diagnose through visual inspection alone. Common lab diagnostic techniques include microscopic examination and molecular detection through PCR. In 2009, a lateral flow device was developed and validated for field diagnosis of European foulbrood. At the time, M. plutonius was thought to be genetically homogenous, but we have subsequently learned that this bacterium exists as multiple strains, including some strains that are classified as ‘atypical’ for which the lateral flow device is potentially less effective. These devices are increasingly used in the United States, though they have never been validated using strains from North America. It is essential to validate this device in multiple locations as different strains of M. plutonius circulate in different geographical regions. In this study, we validate the field use of the lateral flow device compared to microscopic examination and qPCR on larval samples from 78 commercial honey bee colonies in the United States with visual signs of infection. In this study, microscopic diagnosis was more sensitive than the lateral flow device (sensitivity = 97.40% and 89.47%, respectively), and we found no false positive results with the lateral flow device. We find high concurrence between the three diagnostic techniques, and all three methods are highly sensitive for diagnosing European foulbrood.     

The Life Span and Levels of Oxidative Stress in Foragers Between Feral and Managed Honey Bee Colonies

Molecular damage caused by oxidative stress may lead to organismal aging and result in acute mortality to organisms. Thus, oxidative stress resistance and longevity are closely linked. Honey bees (Apis mellifera) are the most important managed pollinator in agriculture, but the long-term survival of honey bees is seriously threatened. Feral honey bee colonies can be used as natural resources to improve honey bee health. One question we ask here is whether feral honey bees are stress resistant or survive longer than managed bee populations. More work is needed to determine the impact of oxidative stress on honey bee health and survival. In this study, we used paired colony designs to compare the life span of worker bees (foragers) between feral and managed colonies and their levels of oxidative stress. Each pair of colonies shared similar foraging resources. The results indicated that foragers in feral colonies had longer survival times and life spans than those in managed colonies. The levels of oxidative stress from lipid damage content in feral colonies were higher than those in managed colonies, indicating that they used a tolerance mechanism rather than a repair mechanism to survive. Our study provides new insights into a colony difference in the physiology and oxidative stress resistance of feral honey bees compared with managed colony stocks.     

Context-Dependent Viral Transgenerational Immune Priming in Honey Bees (Hymenoptera: Apidae)

Transgenerational immune priming is the process of increased resistance to infection in offspring due to parental pathogen exposure. Honey bees (Apis mellifera L. (Hymenoptera: Apidae)) are hosts to multiple pathogens, and this complex immune function could help protect against overwhelming infection. Honey bees have demonstrated transgenerational immune priming for the bacterial pathogen Paenibacillus larvae; however, evidence for viral transgenerational immune priming is lacking across insects in general. Here we test for the presence of transgenerational immune priming in honey bees with Deformed wing virus (DWV) by injecting pupae from DWV-exposed queens and measuring virus titer and immune gene expression. Our data suggest that there is evidence for viral transgenerational immune priming in honey bees, but it is highly context-dependent based on route of maternal exposure and potentially host genetics or epigenetic factors.     

Surfing the Sweet Wave: Migrating Giant Honey Bees (Hymenoptera: Apidae: Apis dorsata) Display Spatial and Temporal Fidelity to Annual Stopover Site in Thailand

Apis dorsata F. (Hymenoptera: Apidae), the giant honey bee of southern Asia, is an important pollinator of crops and non-cultivated angiosperms, and a producer of honey and beeswax. Its populations are in decline in many areas. Colonies migrate seasonally between highland and lowland nesting sites, taking advantage of available food sources. In 2009, a stopover site was discovered in Thailand where numerous migrating colonies bivouacked near one another. Bivouacs used the site again in 2010. I went to the site in 2016 to test the hypothesis that bees use the site regularly as part of an annual migration. I witnessed many bivouacs, spanning almost precisely the same time period and occupying the same area as in 2010. Here I describe their migratory dances in preparation for departure and their subsequent flights as well as periodic mass flight and defensive behavior. Analysis of photographs indicated that the bivouacking bees aged slowly and may thus live long enough to be capable of intergenerational transmission of migratory route knowledge. I describe attributes of the stopover site, e.g., abundant food and water availability, its location along a major river, and other possible navigational cues. Although the site is the only one of its kind so far known to researchers, such stopover sites probably exist wherever giant honey bees undertake long seasonal migrations. I recommend searching for bivouacking sites, particularly along rivers, wherever giant honey bees migrate. Stopover sites are undoubtedly essential to the life history and health of migratory bee populations, and thus warrant conservation policies.     

Differential Expression of Three Dopamine Receptors in Varroa-Resistant Honey Bees

Various stocks of honey bees (Apis mellifera L. (Hymenoptera: Apidae)) employ multiple mechanisms to control varroa mite (Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae)) infestations. Identification of trait-associated genes and markers can improve efficiency of selective breeding. Dopamine receptors show promise in this regard in their association with numerous traits in honey bees, high plasticity, and indicated association with varroa resistance through QTL analysis. We assessed the relationship between exposure to mite-infested brood and gene expression of the honey bee dopamine receptors, Amdop1, Amdop2, and Amdop3, in bees and stocks with known levels of varroa resistance, in Spring 2016 (VSH vs Italian) and Summer 2019 (Pol-line vs Italian). Relative mRNA expression levels varied both by honey bee stock and before/after exposure to varroa-infested brood, in 7-, 10-, and 14-day-old bees. However, the trials revealed contrasting patterns in expression of the three dopamine receptors. In 2016, downregulation was evident in VSH bees, but varied by days post-emergence and by gene. The 2019 trial showed upregulation post-exposure in both stocks, and at all ages, for Amdop1, Amdop2, and Amdop3, with the exception of 14 d Italian bees for Amdop2 and Amdop3. Stock comparison in 2019 showed upregulation of all three dopamine-like receptors in post-exposure bees of all ages. Season and associated differences in mite loads may have contributed to the differences observed across trials. Differential expression of all three dopamine receptors suggests a role for the dopaminergic system in varroa resistance and suggests that further characterization of these receptors for breeding potential is warranted.     

Reproductive and Morphological Quality of Commercial Honey Bee (Hymenoptera: Apidae) Drones in the United States

Exploration into reproductive quality in honey bees (Apis mellifera Linneaus (Hymenoptera: Apidae) largely focuses on factors that affect queens, with drones primarily being considered insofar as they pass on effects of environmental stressors to the queen and subsequent offspring. In those studies that consider drone quality explicitly, a primary focus has been on the dimorphic nature of drones laid in worker cells (either through rare queen error or worker reproduction) as compared to drones laid by the queen in the slightly larger drone cells. The implication from these studies is that that there exists a bimodality of drone morphological quality that is related to reproductive quality and competitive ability during mating. Our study quantifies the presence of such small drones in commercial populations, finding that rates of ‘low-quality’ drones are far higher than theoretically predicted under optimum conditions. Observations from commercial colonies also show significant inter-colony variation among the size and fecundity of drones produced, prompting speculation as to the mechanisms inducing such variation and the potential use of drone-quality variation for the colony- or apiary-level exposure to nutrition, agrichemical, or parasitic stressors.     

A Visual Tracking System for Honey Bee (Hymenoptera: Apidae) 3D Flight Trajectory Reconstruction and Analysis

We describe the development, field testing, and results from an automated 3D insect flight detection and tracking system for honey bees (Apis mellifera L.) (Hymenoptera: Apidae) that is capable of providing remarkable insights into airborne behavior. It comprises two orthogonally mounted video cameras with an observing volume of over 200 m³ and an offline analysis software system that outputs 3D space trajectories and inflight statistics of the target honey bees. The imaging devices require no human intervention once set up and are waterproof, providing high resolution and framerate videos. The software module uses several forms of modern image processing techniques with GPU-enabled acceleration to remove both stationary and moving artifact while preserving flight track information. The analysis system has thus far provided information not only on flight statistics (such as speeds and accelerations), but also on subtleties associated with flight behavior by generating heat maps of density and classifying flight patterns according to patrol and foraging behavior. Although the results presented here focus on behavior in the locale of a beehive, the system could be adapted to study a wide range of airborne insect activity.     

Characterization and Developmental Expression Patterns of Four Hexamerin Genes in the Bumble Bee,Bombus terrestris (Hymenoptera: Apidae)

Hexamerins are members of the hemocyanin superfamily and play essential roles in providing amino acids and energy for the nonfeeding stages of insects. In this study, we cloned and analyzed the expression patterns of four hexamerin genes (hex 70a, hex 70b, hex 70c, and hex 110) at different worker development stages and queen diapause statuses in the bumble bee, Bombus terrestris. The results of this study showed that hex 110 has the longest open reading frame (ORF; 3,297 bp) compared to the ORFs of hex 70a (2,034 bp), hex 70b (2,067 bp), and hex 70c (2,055 bp). The putative translation product of Hex 70a, Hex 70b, Hex70c, and Hex 110 has 677, 688, 684, and 1,098aa with predicted molecular mass of 81.13, 79.69, 81.58, and 119 kDa. In the development stages of workers, the expression levels of hex 70a, hex 70b, and hex 70c increased gradually from the larval stage and exhibited high expression levels at the pink eyed and brown eyed pupae stage, whereas hex 110 exhibited the highest expression level at the larval period. Four hexamerin genes were highly expressed at the prediapause status of queen (P < 0.05), and compared to the eclosion queen, the lowest upregulation was 3.7-fold, and the highest upregulation was 1,742-fold. The expression levels of hex 70b, hex 70c, and hex 110 at diapause were significantly higher than those at postdiapause (P < 0.05). In conclusion, hexamerins may play important roles in queen diapause and metamorphosis of larval and pupal stages.     

Impact of Honey Bee Migratory Management on Pathogen Loads and Immune Gene Expression is Affected by Complex Interactions With Environment,Worker Life History,and Season

The effects of honey bee management, such as intensive migratory beekeeping, are part of the ongoing debate concerning causes of colony health problems. Even though comparisons of disease and pathogen loads among differently managed colonies indicate some effects, the direct impact of migratory practices on honey bee pathogens is poorly understood. To test long- and short-term impacts of managed migration on pathogen loads and immunity, experimental honey bee colonies were maintained with or without migratory movement. Individuals that experienced migration as juveniles (e.g., larval and pupal development), as adults, or both were compared to control colonies that remained stationary and therefore did not experience migratory relocation. Samples at different ages and life-history stages (hive bees or foragers), taken at the beginning and end of the active season, were analyzed for pathogen loads and physiological markers of health. Bees exposed to migratory management during adulthood had increased levels of the AKI virus complex (Acute bee paralysis, Kashmir bee, and Israeli acute bee paralysis viruses) and decreased levels of antiviral gene expression (dicer-like). However, those in stationary management as adults had elevated gut parasites (i.e. trypanosomes). Effects of environment during juvenile development were more complex and interacted with life-history stage and season. Age at collection, life-history stage, and season all influenced numerous factors from viral load to immune gene expression. Although the factors that we examined are not independent, the results illuminate potential factors in both migratory and nonmigratory beekeeping that are likely to contribute to colony stress, and also indicate potential mitigation measures.     

Evaluating and Comparing the Natural Cell Structure and Dimensions of Honey Bee Comb Cells of Chinese Bee,Apis cerana cerana (Hymenoptera: Apidae) and Italian Bee,Apis mellifera ligustica (Hymenoptera: Apidae)

The hexagonal structure of the honey bee comb cell has been the source of many studies attempting to understand its structure and function. In the storage area of the comb, only honey is stored and no brood is reared. We predicted that honey bees may construct different hexagonal cells for brood rearing and honey storage. We used quantitative analyses to evaluate the structure and function of the natural comb cell in the Chinese bee, Apis cerana cerana and the Italian bee, A. mellifera ligustica. We made cell molds using a crystal glue solution and measured the structure and inclination of cells. We found that the comb cells of A. c. cerana had both upward-sloping and downward-sloping cells; while the A. m. ligustica cells all tilted upwards. Interestingly, the cells did not conform to the regular hexagonal prism structure and showed irregular diameter sizes. In both species, comb cells also were differentiated into worker, drone and honey cells, differing in their diameter and depth. This study revealed unique differences in the structure and function of comb cells and showed that honey bees design their cells with precise engineering to increase storage capacity, and to create adequate growing room for their brood.     

Evidence for Bombus occidentalis (Hymenoptera: Apidae) Populations in the Olympic Peninsula,the Palouse Prairie,and Forests of Northern Idaho

Since the mid-1990s, Bombus occidentalis (Green) has declined from being one of the most common to one of the rarest bumble bee species in the Pacific Northwest of the United States. Although its conservation status is unresolved, a petition to list this species as endangered or threatened was recently submitted to the U.S. Fish and Wildlife Service. To shed light on the conservation situation and inform the U.S. Fish and Wildlife Service decision, we report on the detection and abundance of B. occidentalis following bumble bee collection between 2012 and 2014 across the Pacific Northwest. Collection occurred from the San Juan Islands and Olympic peninsula east to northern Idaho and northeastern Oregon, excluding the arid region in central Washington. B. occidentalis was observed at 23 collection sites out of a total of 234. With the exception of three sites on the Olympic peninsula, all of these were in the southeastern portion of the collection range.     

Identification and Physicochemical Properties of the Novel Hemolysin(s) From Oral Secretions of Helicoverpa armigera (Lepidoptera: Noctuidae)

Hemolysins cause the lysis of invading organisms, representing major humoral immunity used by invertebrates. Hemolysins have been discovered in hemolymph of Helicoverpa armigera larvae as immune factors. As oral immunity is great important to clear general pathogens, we presumed that hemolysins may be present in oral secretions (OS). To confirm this hypothesis, we conducted four testing methods to identify hemolysin(s) in larval OS of H. armigera, and analyzed physicochemical properties of the hemolysin in comparison with hemolytic melittin of Apis mellifera (L.) (Hymenoptera: Apidae) venom. We found hemolysin(s) from OS of H. armigera for the first time, and further identified in other lepidopteran herbivores. It could be precipitated by ammonium sulfate, which demonstrates that the hemolytic factor is proteinaceous. Labial gland showed significantly higher hemolytic activity than gut tissues, suggesting that hemolysin of OS is mainly derived from saliva secreted by labial glands. Physicochemical properties of hemolysin in caterpillar’s OS were different from bee venom. It was noteworthy that hemolytic activity of OS was only partially inhibited even at 100°C. Hemolytic activity of OS was not inhibited by nine tested carbohydrates contrary to bee venom melittin. Moreover, effects of metal ions on hemolytic activity were different between OS and bee venom. We conclude that there is at least a novel hemolysin in OS of herbivorous insects with proposed antibacterial function, and its hemolytic mechanism may be different from melittin. Our study enriches understanding of the potential role of hemolysins in insect immunity and provides useful data to the field of herbivorous insect-pathogen research.     

Physicochemical Parameters and Antioxidant Activity of Bee Honey Enriched With Herbs

Three groups of products enriched with herbs were studied: (1) commercial herb honeys (n?=?5) produced by bees fed a syrup with an herbal extract, (2) natural herbal honey (n?=?3) produced by bees from the nectar of herbs, and (3) creamed multifloral honey with added dried herbs (n?=?5). As a control, multifloral honey (n?=?5) was used. The physicochemical parameters (i.e., sugar extract, water content, specific rotation, conductivity, hydroxymethylfurfural content, pH and acidity), sugar profiles (HPLC analysis), antioxidant activity and total phenolic compounds content of the studied samples were compared. Although great diversity in the basic properties of the studied products was observed, they were comparable to multifloral honey and complied with honey regulations. Significant differences in sugar composition were observed, and adversely positive rotation (excluding nettle herb honey) was detected in group 1, likely resulting from the change in bee feeding. The best antioxidant activity for creamed honeys with dried herbs (group 2) was investigated, whereas herb honeys (group 1) exhibited similar antioxidant properties as multifloral honey. The use of controlled feeding of bees appears to be an effective method of enriching honey with desirable plant bioactive components to create innovative bee products.     

Pollen Treated with a Combination of Agrochemicals Commonly Applied During Almond Bloom Reduces the Emergence Rate and Longevity of Honey Bee (Hymenoptera: Apidae) Queens

Honey bee (Apis mellifera L.) colonies that pollinate California’s almond orchards are often exposed to mixtures of agrochemicals. Although agrochemicals applied during almond bloom are typically considered bee-safe when applied alone, their combined effects to honey bees are largely untested. In recent years, beekeepers providing pollination services to California’s almond orchards have reported reductions in queen quality during and immediately after bloom, raising concerns that pesticide exposure may be involved. Previous research identified a synergistic effect between the insecticide active ingredient chlorantraniliprole and the fungicide active ingredient propiconazole to lab-reared worker brood, but their effects to developing queens are unknown. To test the individual and combined effects of these pesticides on the survival and emergence of developing queens, we fed worker honey bees in closed queen rearing boxes with pollen artificially contaminated with formulated pesticides containing these active ingredients as well as the spray adjuvant Dyne-Amic, which contains both organosilicone and alkyphenol ethoxylate. The translocation of pesticides from pesticide-treated pollen into the royal jelly secretions of nurse bees was also measured. Despite consistently low levels of all pesticide active ingredients in royal jelly, the survival of queens from pupation to 7 d post-emergence were reduced in queens reared by worker bees fed pollen containing a combination of formulated chlorantraniliprole (Altacor), propiconazole (Tilt), and Dyne-Amic, as well as the toxic standard, diflubenzuron (Dimilin 2L), applied in isolation. These results support recommendations to protect honey bee health by avoiding application of pesticide tank-mixes containing insecticides and adjuvants during almond bloom.