Seasonal Variability in the Prevalence of DWV Strains in Individual Colonies of European Honeybees in Hawaii.

The most prevalent viral pathogen of honeybees is Deformed Wing Virus (DWV) and its two most widely studied and common master-variants are DWV-A and DWV-B. The prevalence of DWV variants in the UK and in the US is changing, with the prevalence of the DWV-A strain declining and DWV-B increasing over time. In 2012, only DWV-A was detected on the Hawaiian Islands of Oahu. In this study we focused on a colony-level survey of DWV strains in a single apiary and examined the prevalence of DWV variants over the course of two years. In 2018 and 2019, a total of 16 colonies underwent viral testing in January, May, and September. Of those 16 colonies, four were monitored in both 2018 and 2019. Individual colonies showed variability of DWV master variants throughout the sampling period. DWV-A was consistently detected; however, the detection of DWV-B was variable across time in individual colonies. Ultimately, this study demonstrated a seasonal variation in both viral prevalence and load for DWV-B, providing a perspective on the dynamic nature of DWV master variants emerging in Hawaii.

Management practice for small hive beetle as a source of microplastic contamination in honey and honeybee colonies.

Microplastics (MP) have emerged as a widespread environmental contaminant affecting bee health. In this study we report on the impact of one of the cultural practices used to control the small hive beetle (SBH, Aethina tumida). Management of the beetle often includes the use of in-hive traps of different kinds, such as non-woven microfiber wipes. When placed inside the hive, bees chew on these wipes, which then become fuzzy and fray to the point where beetles become entangled in their fibers. The current study aimed to examine the composition of these microfiber sheets and to evaluate whether their use resulted in unintended MP contamination of bees and honey. We treated hives with one blue microfiber sheet placed on top of the frames for at least three months. After that time, we collected adult bees and honey samples from treated hives, control hives in the same apiary (control near), and control hives in an apiary 7.5 km away (control far). Honey from treated hives had a significantly greater number of blue MF than honey from the control hives (mean ± SD, treatment 11.83 ± 3.76, control near 2.25 ± 0.92 and control far 0.25 ± 0.5 MF/20 gr honey). Also, hives treated with the microfiber sheets had a significantly greater number of blue microfibers in the gut and cuticle of bees, than the control hives located in a different apiary. However, the control and treated bees located in the same apiary had a similar number of blue microfibers (mean ± SD, treatment 4.7 ± 2.28, control near 3 ± 1.63 and control far 0.5 ± 0.58 MF in 20 bees). Thus, the current study raises concerns of the use of microfibers sheets to trap the SBH as it results in the incorporation of microfibers into the ecosystem and the food chain.

Ten Years of Deformed Wing Virus (DWV) in Hawaiian Honey Bees (Apis mellifera), the Dominant DWV-A Variant Is Potentially Being Replaced by Variants with a DWV-B Coding Sequence.

The combination of Deformed wing virus (DWV) and Varroa destructor is arguably one of the greatest threats currently facing western honey bees, Apis mellifera. Varroa's association with DWV has decreased viral diversity and increased loads of DWV within honey bee populations. Nowhere has this been better studied than in Hawaii, where the arrival of Varroa progressively led to the dominance of the single master variant (DWV-A) on both mite-infested Hawaiian Islands of Oahu and Big Island. Now, exactly 10 years following the original study, we find that the DWV population has changed once again, with variants containing the RdRp coding sequence pertaining to the master variant B beginning to co-dominate alongside variants with the DWV-A RdRp sequence on the mite-infested islands of Oahu and Big Island. In speculation, based on other studies, it appears this could represent a stage in the journey towards the complete dominance of DWV-B, a variant that appears better adapted to be transmitted within honey bee colonies.

Bees increase crop yield in an alleged pollinator-independent almond variety.

Wild pollinators are declining and the number of managed honey bee colonies is growing slower than agricultural demands for pollination. Because of these contrasting trends in pollinator demand and availability, breeding programs for many pollinator-dependent crops have focused on reducing the need for pollinators. Although numerous crop varieties are now available in the market with the label of pollinator-independent, the real dependence of these varieties on pollinators is mostly unknown. We evaluated the hypothesis of pollinator independence in the Independence almond variety, the fastest growing variety in California that is the main almond production region in the world. In this presumed pollinator-independent variety, we measured the effect of honey bees on fruit set, yield, and kernel nutritional quality at tree level. Fruit set was 60% higher in bee-pollinated than bee-isolated trees, which translated into a 20% increase in kernel yield. Despite its effect on almond production, there was no evidence that bee visitation affected almond nutritional quality. Based on these results, we recommend the use of bees, whether they are wild or managed, to maximize yield even in self-fertile almond varieties.

Towards Precision Nutrition: A Novel Concept Linking Phytochemicals, Immune Response and Honey Bee Health.

The high annual losses of managed honey bees (Apis mellifera) has attracted intensive attention, and scientists have dedicated much effort trying to identify the stresses affecting bees. There are, however, no simple answers; rather, research suggests multifactorial effects. Several works have been reported highlighting the relationship between bees' immunosuppression and the effects of malnutrition, parasites, pathogens, agrochemical and beekeeping pesticides exposure, forage dearth and cold stress. Here we analyze a possible connection between immunity-related signaling pathways that could be involved in the response to the stress resulted from Varroa-virus association and cold stress during winter. The analysis was made understanding the honey bee as a superorganism, where individuals are integrated and interacting within the colony, going from social to individual immune responses. We propose the term "Precision Nutrition" as a way to think and study bees' nutrition in the search for key molecules which would be able to strengthen colonies' responses to any or all of those stresses combined.

Evidence of Varroa-mediated deformed wing virus spillover in Hawaii.

Varroa destructor, a parasitic mite of honey bees, is also a vector for viral diseases. The mite displays high host specificity and requires access to colonies of Apis spp. to complete its lifecycle. In contrast, the Deformed Wing Virus (DWV), one of the many viruses transmitted by V. destructor, appears to have a much broader host range. Previous studies have detected DWV in a variety of insect groups that are not directly parasitized by the mite. In this study, we take advantage of the discrete distribution of the Varroa mite in the Hawaiian archipelago to compare DWV prevalence on non-Apis flower visitors, and test whether Varroa presence is linked to a "viral spillover". We selected two islands with different viral landscapes: Oahu, where V. destructor has been present since 2007, and Maui, where the mite is absent. We sampled individuals of Apis mellifera, Ceratina smaragdula, Polistes aurifer, and Polistes exclamens, to assess and compare the DWV prevalence in the Hymenoptera community of the two islands. The results indicated that, as expected, honey bee colonies on Oahu have much higher incidence of DWV compared to Maui. Correspondingly, DWV was detected on the Non-Apis Hymenoptera collected from Oahu, but was absent in the species examined on Maui. The study sites selected shared a similar geography, climate, and insect fauna, but differed in the presence of the Varroa mite, suggesting an indirect, but significant, increase on DWV prevalence in the Hymenoptera community on mite-infected islands.

Moku virus; a new Iflavirus found in wasps, honey bees and Varroa.

There is an increasing global trend of emerging infectious diseases (EIDs) affecting a wide range of species, including honey bees. The global epidemic of the single stranded RNA Deformed wing virus (DWV), driven by the spread of Varroa destructor has been well documented. However, DWV is just one of many insect RNA viruses which infect a wide range of hosts. Here we report the full genome sequence of a novel Iflavirus named Moku virus (MV), discovered in the social wasp Vespula pensylvanica collected in Hawaii. The novel genome is 10,056 nucleotides long and encodes a polyprotein of 3050 amino acids. Phylogenetic analysis showed that MV is most closely related to Slow bee paralysis virus (SBPV), which is highly virulent in honey bees but rarely detected. Worryingly, MV sequences were also detected in honey bees and Varroa from the same location, suggesting that MV can also infect other hymenopteran and Acari hosts.

Do the honeybee pathogens Nosema ceranae and deformed wing virus act synergistically?

The honeybee pathogens Nosema ceranae and deformed wing virus (DWV) cause the collapse of honeybee colonies. Therefore, it is plausible that these two pathogens act synergistically to increase colony losses, since N.ceranae causes damage to the mid-gut epithelial ventricular cells and actively suppresses the honeybees' immune response, either of which could increase the virulence of viral pathogens within the bee. To test this hypothesis we exploited 322 Hawaiian honeybee colonies for which DWV prevalence and load is known. We determined via PCR that N.ceranae was present in 89-95% of these colonies, with no Nosema apis being detected. We found no significant difference in spore counts in colonies infected with DWV and those in which DWV was not detected, either on any of the four islands or across the entire honeybee population. Furthermore, no significant correlation between DWV loads (ΔCT levels) and N.ceranae spore counts was found, so these two pathogens are not acting synergistically. Although the Hawaiian honeybees have the highest known prevalence of N.ceranae in the world, with average number of spores been 2.7 million per bee, no acute Nosema related problems i.e. large-scale colony deaths, have been reported by Hawaiian beekeepers.

Global honey bee viral landscape altered by a parasitic mite.

Emerging diseases are among the greatest threats to honey bees. Unfortunately, where and when an emerging disease will appear are almost impossible to predict. The arrival of the parasitic Varroa mite into the Hawaiian honey bee population allowed us to investigate changes in the prevalence, load, and strain diversity of honey bee viruses. The mite increased the prevalence of a single viral species, deformed wing virus (DWV), from ~10 to 100% within honey bee populations, which was accompanied by a millionfold increase in viral titer and a massive reduction in DWV diversity, leading to the predominance of a single DWV strain. Therefore, the global spread of Varroa has selected DWV variants that have emerged to allow it to become one of the most widely distributed and contagious insect viruses on the planet.

Effects of diet, ginger root oil, and elevation on the mating competitiveness of male Mediterranean fruit flies (Diptera: Tephritidae) from a mass-reared, genetic sexing strain in Guatemala.

The release of sterile males is a key component of an areawide program to eradicate the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), from Guatemala and southern Mexico. The objective of our study was to assess the effects of adult diet, exposure to ginger root oil (Zingiber officinale Roscoe), and elevation on the mating competitiveness of the sterile males used in an areawide program. Sterile males were maintained on a protein-sugar (protein-fed) or a sugar-only (protein-deprived) diet and were exposed (for 4 h 1 d before testing) or not exposed to ginger root oil. In field-cage trials conducted at a high (1,500 m) and low (700 m) site, we monitored the influence of these treatments on the mating success of sterile males in competition with wild males (reared exclusively on the protein-sugar diet and without ginger root oil exposure) for wild females. Elevation and ginger root oil exposure had significant effects, with sterile males having higher mating success at the low-elevation site and ginger root oil-exposed males having greater success than ginger root oil-deprived males at both sites. Diet did not have a significant overall effect, and its influence varied with elevation (dietary protein seemed to provide an advantage at the high-elevation site but not at the low-elevation site). Possible implications of these findings for eradication programs against the Mediterranean fruit fly are discussed.