Honey Bee Pests Research Articles

Invasion pathway of the honeybee pest, small hive beetle, Aethina tumida (Coleoptera: Nitidulidae) in the Republic of Korea inferred by mitochondrial DNA sequence analysis

Abstract The small hive beetle (SHB), Aethina tumida, is native to the Sub-Saharan region of Africa, but it became invasive in many countries after its first introduction to the USA in 1996. The SHB is a destructive pest of the honey industry and can cause damage in apiaries due to feeding on the honey, pollen, honey bee brood and honey fermentation. SHB was recently found infesting honeybee colonies in the South-Eastern part of Korea, Miryang city in 2016. No inference of the origin or the pathway of the invasion into Korea has been made, so far. We analyzed partial cytochrome oxidase I gene of mitochondrial DNA to unveil the possible source of the invasive populations of SHB in South Korea. A Bayesian inference tree and median joining haplotype network revealed a strong relationship between South Korean and North American populations suggesting that the SHB in South Korea came from the USA. Low genetic variation among Korean populations suggests that the invasion might have occurred in a single event with small number of founders. In addition, a new global distributional map of SHB is provided.

Toxicity of oxalic acid and impact on some antioxidant enzymes on in vitro-reared honeybee larvae.

Nowadays, Varroa destructor is considered as a serious pest of honeybees (Apis mellifera) and its resistance to acaricides has been reported in Europe since the early 1990s. That is why new methods of treatment for Varroa mites are still in focus of many scientists. In our study, we determined the lethal concentration LC50 (72 h) of 2.425% oxalic acid solution following single spray exposure of honeybee larvae under laboratory conditions (Guideline OECD 237 2013). Potential sublethal effects of oxalic acid were monitored through the determination of the activity of antioxidant enzymes. Activation of primary antioxidant enzymes was observed at 1.75% of oxalic acid; 3.5% of oxalic acid brought on a statistically significant increase of glutathione S-transferase activity. This change was accompanied by an increase in thiobarbituric acid reactive substances, products of lipid peroxidation. Our results indicate that oxalic acid may be harmful to bee brood when present during application.

Honey Bee Parasitic Mite Contains the Sensilla-Rich Sensory Organ on the Foreleg Tarsus Expressing Ionotropic Receptors With Conserved Functions.

Honey bee parasitic mites (Tropilaelaps mercedesae and Varroa destructor) detect temperature, humidity, and odor but the underlying sensory mechanisms are poorly understood. To uncover how T. mercedesae responds to environmental stimuli inside a hive, we first identified the sensilla-rich sensory organ on the foreleg tarsus. The organ appeared to correspond to Haller’s organ in ticks and contained four types of sensilla, which may respond to different stimuli based on their morphology. We searched for differentially expressed genes between the forelegs and hindlegs to identify mRNAs potentially associated with the sensory organ. The forelegs were enriched with mRNAs encoding sensory proteins such as ionotropic receptors (IRs) and gustatory receptors, as well as proteins involved in ciliary transport. We also found that T. mercedesae IR25a and IR93a were capable of rescuing temperature and humidity preference defects in Drosophila melanogaster IR25a and IR93a mutants. These results demonstrate that the structures and physiological functions of ancient IRs have been conserved during arthropod evolution. Our study provides insight into the sensory mechanisms of honey bee parasitic mites, as well as potential targets for methods to control the most serious honey bee pest.

Gene expression, sperm viability, and queen (Apis mellifera) loss following pesticide exposure under laboratory and field conditions

Honey bee (Apis mellifera) queens are failing, and this may be due in part to widespread miticide use by beekeepers. The ectoparasitic mite, Varroa destructor, is a major pest of honeybees and synthetic insecticides are often used to control Varroa. Amitraz is widely used by beekeepers worldwide. Amitraz is thought to be of low toxicity to bees, but applying high doses can cause negative effects. Here, we demonstrate a sublethal dose of amitraz can affect the detoxification, cyclic adenosine monophosphate (cAMP)-dependent protein kinase, immunity, antioxidant capacity, and development of honeybee queens when queens were exposed to amitraz (2.5 ppm) under laboratory conditions. Downregulation of genes related to detoxification enzymes, cAMP-dependent protein kinase, immunity, antioxidant enzymes, and development was observed. Sublethal doses of amitraz had no effects on the viability of spermatozoa stored in spermathecae of queen when treated topically in the laboratory. Lastly, we treated colonies with three formulations of amitraz and followed queens in these colonies for 3 months to explore queen loss and/or other adverse effects of miticide treatment. Queen loss averaged about 30% over all treatment groups including untreated control colonies and no reduction in sperm viability was seen with amitraz treatments when queens remaining after 3 months were dissected. This research demonstrates that chemical exposure can affect some aspects of the queen immune system but sperm viability and queen longevity over 3 months were unaffected by colony level amitraz treatments under real-world conditions in honey bee colonies.

Large Hive Beetles: An Emerging Serious Honey Bee Pest in the Coastal Highlands of Kenya

Surveys in Kenya have established the main arthropod pests associated with honey bees (Apis mellifera) to be small hive beetles, Aethina tumida (Coleoptera: Nitidulidae); Oplostomus haroldi and Opl...

Losing the Arms Race: Greater Wax Moths Sense but Ignore Bee Alarm Pheromones.

The greater wax moth, Galleria mellonella L., is one of main pests of honeybees. The larvae burrow into the wax, damaging the bee comb and degenerating bee products, but also causes severe effects like driving the whole colony to abscond. In the present study, we used electroantennograms, a Y maze, and an oviposition site choice bioassay to test whether the greater wax moth can eavesdrop on bee alarm pheromones (isopentyl acetate, benzyl acetate, octyl acetate, and 2-heptanone), to target the bee colony, or if the bee alarm pheromones would affect their preference of an oviposition site. The results revealed that the greater wax moth showed a strong electroantennogram response to these four compounds of bee alarm pheromones even in a low concentration (100 ng/μL), while they showed the highest response to octyl acetate compared to the other three main bee alarm components (isopentyl acetate, benzyl acetate, and 2-heptanone). However, the greater wax moth behavioral results showed no significant preference or avoidance to these four bee alarm pheromones. These results indicate that bees are currently losing the arms race since the greater wax moth can sense bee alarm pheromones, however, these alarm pheromones are ignored by the greater wax moth.

Behavioral response of the small hive beetle, Aethina tumida (Coleoptera: Nitidulidae) to volatiles of Apicure®, a plant-based extract

Background: The small hive beetle (SHB), Aethina tumida is an invasive pest of the honey bee. Although no previous methods have led to its successful management, yeast inoculated pollen baited-traps have showed promise as quick monitoring tools. In this study, we evaluated the role of olfaction in SHB response to Apicure®, an essential oil-based biopesticide that has shown potential for the management of honey bee pests and diseases. Methods: Volatiles from Apicure® were collected using super Q adsorbent traps. Subsequent analysis was done using Gas chromatography- mass spectrophotometry (GC-MS) to ascertain the components of Apicure®. The selectivity and sensitivity of antennal receptors of A. tumida adults to the volatile compounds were determined using behavioral assays and Gas Chromatography-Electroantennodetection (GC-EAD). Results: GC-MS analysis showed that Apicure® consists of 40 compounds. GC-EAD analysis isolated 11 compounds that elicited antennal response with the SHB. Of these, linalool, camphor, geraniol and α-terpineol were confirmed to be strongly repellant, while limonene was attractive to SHB in dual-choice olfactometer assays. Conclusion: Our results demonstrate that the major components in Apicure® are mainly repellants thus prospective in disrupting the host recognition by the SHB. The product therefore can be up-scaled for the management of SHB.

Survival of Ectoparasitic Mites Tropilaelaps mercedesae in Association with Honeybee Hive Products.

The global trade of honeybee hive products imposes the risk of the introduction of exotic pests. However, data on the potential of specific products enabling pest survival are often lacking. This holds especially true for ectoparasitic mites Tropilaelaps spp., which are mandatory pests of honeybees in many countries. Here, we evaluated the longevity of Tropilaelaps mercedesae mites associated with empty honeycomb and dry pollen as two possible global import routes. Mites were able to survive up to three days in dry pollen and up to six days in empty honeycomb, thereby suggesting a sufficient time window for the potential introduction of T. mercedesae into mite-free countries via import of these hive products.

Complete mitochondrial DNA sequence of the small hive beetle Aethina tumida (Insecta: Coleoptera) from Hawaii

We analyzed the complete mitochondrial genome of the small hive beetle Aethina tumida, a major honeybee pest that was accidentally transported to the Hawaii Islands, USA. The mitochondrial genome of A. tumida was identified as a 15,198 bp circular molecule containing 13 protein-coding genes, 22 tRNA genes, and two rRNA genes, along with one A + T-rich control region. The average AT content was found to be 76.2%. The heavy strand was predicted to have nine protein-coding and 14 tRNA genes; while the light strand was predicted to contain four protein-coding, eight tRNA, and two rRNA genes. Among the 13 PCGs, the initiation codon ATT was found in five, ATA in three, ATG in four, and TTG in one gene. Six PCGs used TAA as the stop codon, whereas three PCGs used TAG as the stop codon. Incomplete stop codon TA (COIII, ND5, and ND4) and T (COII) were identified. We found that the genetic distance between A. tumida from Hawaii and the beetles’ natural home South Africa, was small, indicating that the Hawaii population may have originated for the South Africa region.

Evaluating Plant Extracts Effects against Aethinatumuda Pests of Honeybees (Apismellifera)

Evaluating Plant Extracts Effects against Aethinatumuda Pests of Honeybees (Apismellifera)

Small Hive Beetle (Coleoptera: Nitidulidae) and the Yeast, Kodamaea ohmeri: A Facultative Relationship Under Laboratory Conditions.

The small hive beetle, Aethina tumida Murray, is a pest of honeybees, Apis mellifera L. (Hymenoptera: Apidae). We investigated the significance of its association with the yeast, Kodamaea ohmeri (Etchells & Bell) (Ascomycota: Saccharomycotina), in laboratory experiments. The mean (± SEM) viability of A. tumida eggs was 84 (± 3)%; the viability was not affected if eggs were separated from clutches or if mucilage containing K. ohmeri was removed from the egg surface. Life tables of conventional (= K. ohmeri contaminated) A. tumida and K. ohmeri-free A. tumida revealed no differences in stage-specific mortality between the treatments; in both cases, the highest mortality occurred in the first larval instar. There was no significant difference in the initial egg production of conventionally reared and K. ohmeri-free A. tumida under laboratory conditions. The volatile profiles of pollen dough (Bee Build) fed on by conventional and K. ohmeri-free A. tumida larvae were qualitatively and quantitatively different; the volatiles produced by pollen dough fed on by conventional A. tumida were more attractive to adult beetles. There was a clear difference between growth of K. ohmeri on pollen dough substrate in the presence and absence of A. tumida. Results suggest that this association is facultative for A. tumida under laboratory conditions but has benefit for the yeast associate, K. ohmeri. A clearer understanding of the nature of this fungus-insect association is essential for the development of management strategies for this pest, especially in the development of fermentate-based attractants in trapping systems.

Uncovering the spatial pattern of invasion of the honeybee pest small hive beetle, Aethina tumida, in Italy

The fast tracking of invasion spatial patterns of alien species is crucial for the implementation of preventive and management strategies of those species. Recently, a honeybee pest, the small hive beetle Aethina tumida (hereafter SHB), has been reported in Italy, where it colonized more than 50 apiaries in an area of about 300km2. SHB is a nest parasite and scavenger of honeybee colonies native of Sub-Saharian Africa. Likely being helped by the globalization of apiculture, SHB underwent several invasions in the last twenty years, causing locally relevant economic impact. While many features of its biology have been addressed, an important knowledge gap concerns the spatial invasion dynamics in invaded areas. In this paper we coupled two spatial analysis techniques (geographic profiling and a density-based spatial clustering algorithm) to uncover the possible invasion pattern of SHB in Italy. We identified the port town of Gioia Tauro as the most likely point from which SHB may have spread and suggested the possible successive axes of diffusion. These putative diffusion paths suggest that the SHB spread in south Italy might have been due to a mix of natural dispersal between close apiaries and longer distance movement through faster, likely human-mediated, communication routes.

Hygienic behaviour selection via freeze-killed honey bee brood not associated with chalkbrood resistance in eastern Australia.

Hygienic behaviour is a social immune response in honey bees shown to help provide resistance to honey bee pests and diseases. A survey of hygienic behaviour and brood diseases was conducted on 649 colonies in eastern Australia to initiate a selective breeding program targeting disease resistance and provide a level of resistance to Varroa (Varroa destructor Anderson and Trueman and V. jacobsoni Oudemans) mites should they become established in Australia. The test population showed a remarkably high baseline level of hygienic behaviour with 17% of colonies meeting or exceeding breeding selection thresholds. Colonies belonging to a breeding program were 5.8 times more likely to be highly hygienic and colonies headed by queens raised from hygienic queen mothers were 2.2 times more likely. Nectar availability (nectar yielding flowering plants within honey bee forage range) influenced hygienic behaviour expression but was not a significant predictor of level of hygienic behaviour. Surprisingly, hygienic behaviour was not a significant predictor of the presence of infection of the honey bee brood disease chalkbrood (Ascosphaera apis) and was not influential in predicting severity of chalkbrood infection in surveyed honey bee colonies. This study, along with reports from commercial beekeepers that chalkbrood infection is on the rise, warrants a deeper exploration of the host-pathogen relationship between Apis mellifera and Ascosphaera apis in Australia.

Home sick: impacts of migratory beekeeping on honey bee (Apis mellifera) pests, pathogens, and colony size

Honey bees are important pollinators of agricultural crops and the dramatic losses of honey bee colonies have risen to a level of international concern. Potential contributors to such losses include pesticide exposure, lack of floral resources and parasites and pathogens. The damaging effects of all of these may be exacerbated by apicultural practices. To meet the pollination demand of US crops, bees are transported to areas of high pollination demand throughout the year. Compared to stationary colonies, risk of parasitism and infectious disease may be greater for migratory bees than those that remain in a single location, although this has not been experimentally established. Here, we conducted a manipulative experiment to test whether viral pathogen and parasite loads increase as a result of colonies being transported for pollination of a major US crop, California almonds. We also tested if they subsequently transmit those diseases to stationary colonies upon return to their home apiaries. Colonies started with equivalent numbers of bees, however migratory colonies returned with fewer bees compared to stationary colonies and this difference remained one month later. Migratory colonies returned with higher black queen cell virus loads than stationary colonies, but loads were similar between groups one month later. Colonies exposed to migratory bees experienced a greater increase of deformed wing virus prevalence and load compared to the isolated group. The three groups had similar infestations of Varroa mites upon return of the migratory colonies. However, one month later, mite loads in migratory colonies were significantly lower compared to the other groups, possibly because of lower number of host bees. Our study demonstrates that migratory pollination practices has varying health effects for honey bee colonies. Further research is necessary to clarify how migratory pollination practices influence the disease dynamics of honey bee diseases we describe here.

Semiochemical Exploitation of Host-Associated Cues by Seven Melittobia Parasitoid Species: Behavioral and Phylogenetic Implications

Chemical compounds (infochemicals or semiochemicals) play an important role both in intra-specific and inter-specific communication. For example, chemical cues appear to play a key role in the host selection process adopted by insect parasitoids. In recent years significant advances have been made in order to understand the chemical ecology of insect parasitoids. However, little information is available about the evolution of semiochemical use in the host location process of insect parasitoids. Here we investigated the strategy adopted by seven closely related parasitoid species in the genus Melittobia when foraging for four different suitable hosts. By using an integrated approach that combined olfactometer bioassays and phylogenetic investigations, we found that: 1) exploitation of host-derived semiochemicals is widespread in the Melittobia genus; 2) there is specificity of attraction towards the different host species tested; in particular, the early-branching species in the Melittobia genus are attracted to odors associated with leaf cutting bees (Megachile rotundata) whereas the most-diverged species are attracted to odors associated with solitary mud dauber wasps (Trypoxyilon politum). Regardless of the phylogenetic relationships, no Melittobia species exhibited attraction towards odors of factitious laboratory hosts (i.e. the flesh fly Sarcophaga bullata). Interestingly, five Melittobia species are also attracted by odors associated with honeybees hosts which indicate that these parasitoids could be potential pests of honeybees. Our study shed light on the host location within the Melittobia genus and represents a first attempt to understand semiochemical use in an evolutionary perspective in the context of parasitoids’ foraging behavior.

A Varroa destructor protein atlas reveals molecular underpinnings of developmental transitions and sexual differentiation

Varroa destructor is the most economically damaging honey bee pest, weakening colonies by simultaneously parasitizing bees and transmitting harmful viruses. Despite these impacts on honey bee health, surprisingly little is known about its fundamental molecular biology. Here, we present a Varroa protein atlas crossing all major developmental stages (egg, protonymph, deutonymph, and adult) for both male and female mites as a web-based interactive tool (http://foster.nce.ubc.ca/varroa/index.html). We used intensity-based label-free quantitation to find 1,433 differentially expressed proteins across developmental stages. Enzymes for processing carbohydrates and amino acids were among many of these differences as well as proteins involved in cuticle formation. Lipid transport involving vitellogenin was the most significantly enriched biological process in the foundress (reproductive female) and young mites. In addition, we found that 101 proteins were sexually regulated and functional enrichment analysis suggests that chromatin remodeling may be a key feature of sex determination. In a proteogenomic effort, we identified 519 protein-coding regions, 301 of which were supported by two or more peptides and 169 of which were differentially expressed. Overall, this work provides a first-of-its-kind interrogation of the patterns of protein expression that govern the Varroa life cycle and the tools we have developed will support further research on this threatening honey bee pest.

First Detection of Nosema Ceranae and Nosema Apis in Greater Wax Moth Galleria Mellonella

Abstract The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae), one of the pests of honey bee (Apis mellifera L.) colonies, has spread almost all over the world. Although the G. mellonella is often reported to infest weak honey bee colonies that are exposed to pesticides and diseases, it is also a threat for healthy colonies. Therefore, there is a fairly high probability of transmission of both microflora-specific bacteria and pathogen microorganisms, especially Nosema species, between these organisms (Moth and bees). The aim of this study was to investigate the presence of Nosema species in greater wax moth G. mellonella collected from apiaries as well as grown in laboratory conditions. Adults and late instar larva of wax moth were used for detecting Nosema apis and Nosema ceranae. Real-time PCR amplification studies were performed and specific ITS regions were targeted to distinguish Nosema species. Real-time PCR results showed that N. apis and N. ceranae were found in both phases of G. mellonella. This is the first study to confirm that N. apis and N. ceranae are present in greater wax moth collected from apiaries and grown at laboratories in Turkey.

The effect of thyme (Thymus caucasicus) ethanol extract on Varroa mite (Varroa destructor), an ectoparasite mite of Apis mellifera meda (Hym: Apidae)

Chemical control of the Varroa mite (Varroa destructor), which is one of the most important pests of honey bees, is practiced on a worldwide scale. However, because of abundant use of different acaricides, the mites have become resistant to many of them. We chose to apply non-synthetic chemicals for control of Varroa mites by using thyme (Thymus caucasicus) ethanol extract on honey bees. In September-October 2013, we collected wild thyme growing in Kurdistan mountains, ground it, and its ethanol extract was made by using 95% ethylic alcohol. We used a randomized complete design with ten treatments of different concentrations of ethanol extract of thyme as a statistical model and one control with pure 95% ethanol with four replications. The interior temperature of the brood chamber was measured to be 30 ± 1°C, and the ambient temperature surrounding them was 33 ± 2°C. We sprayed the extracted thyme solution on honey bees and counted the number of dead mites by picking them out from the bottom board of each hive at every 12 h, 24 h, and 48 h intervals after spraying. The results showed that the use of the thyme extract influenced significantly the percentage of mortality of dead mites in the extract-sprayed treatment and the control treatment. The percentage of mortality of the honey bees in control hives and the honey bees treated by thyme ethanol extract did not have a significant difference. Results of our experiment using ethanol extract of thyme showed that its use in hives was safe without a high risk of mortality for honey bees.

Hygienic and grooming behaviors in African and European honeybees-New damage categories in Varroa destructor.

Varroa destructor is an ectoparasitic pest of honeybees, and a threat to the survival of the apiculture industry. Several studies have shown that unlike European honeybees, African honeybee populations appear to be minimally affected when attacked by this mite. However, little is known about the underlying drivers contributing to survival of African honeybee populations against the mite. We hypothesized that resistant behavioral defenses are responsible for the survival of African honeybees against the ectoparasite. We tested this hypothesis by comparing grooming and hygienic behaviors in the African savannah honeybee Apis mellifera scutellata in Kenya and A. mellifera hybrids of European origin in Florida, USA against the mite. Grooming behavior was assessed by determining adult mite infestation levels, daily mite fall per colony and percentage mite damage (as an indicator of adult grooming rate), while hygienic behavior was assessed by determining the brood removal rate after freeze killing a section of the brood. Our results identified two additional undescribed damaged mite categories along with the six previously known damage categories associated with the grooming behavior of both honeybee subspecies. Adult mite infestation level was approximately three-fold higher in A. mellifera hybrids of European origin than in A. m. scutellata, however, brood removal rate, adult grooming rate and daily natural mite fall were similar in both honeybee subspecies. Unlike A. mellifera hybrids of European origin, adult grooming rate and brood removal rate did not correlate with mite infestation levels on adult worker honeybee of A. m. scutellata though they were more aggressive towards the mites than their European counterparts. Our results provide valuable insights into the tolerance mechanisms that contribute to the survival of A. m. scutellata against the mite.

Are Dispersal Mechanisms Changing the Host-Parasite Relationship and Increasing the Virulence of Varroa destructor (Mesostigmata: Varroidae) in Managed Honey Bee (Hymenoptera: Apidae) Colonies?

Varroa (Varroa destructor Anderson and Trueman) are a serious pest of European honey bees (Apis mellifera L.), and difficult to control in managed colonies. In our 11-mo longitudinal study, we applied multiple miticide treatments, yet mite numbers remained high and colony losses exceeded 55%. High mortality from varroa in managed apiaries is a departure from the effects of the mite in feral colonies where bees and varroa can coexist. Differences in mite survival strategies and dispersal mechanisms may be contributing factors. In feral colonies, mites can disperse through swarming. In managed apiaries, where swarming is reduced, mites disperse on foragers robbing or drifting from infested hives. Using a honey bee-varroa population model, we show that yearly swarming curtails varroa population growth, enabling colony survival for >5 yr. Without swarming, colonies collapsed by the third year. To disperse, varroa must attach to foragers that then enter other hives. We hypothesize that stress from parasitism and virus infection combined with effects that viruses have on cognitive function may contribute to forager drift and mite and virus dispersal. We also hypothesize that drifting foragers with mites can measurably increase mite populations. Simulations initialized with field data indicate that low levels of drifting foragers with mites can create sharp increases in mite populations in the fall and heavily infested colonies in the spring. We suggest new research directions to investigate factors leading to mite dispersal on foragers, and mite management strategies with consideration of varroa as a migratory pest.