Entomopathogenic nematode performance in three honey bee pests: small hive beetle, greater and lesser wax moths

The small hive beetle (SHB), Aethina tumida, is a pest of honeybee (Apis mellifera) colonies. Endemic to sub-Saharan Africa, this pest has been reported in Africanized honeybee (AHB) colonies in North, Central, and South America. Specifically in Central America, it was first found in El Salvador in 2013, in Nicaragua in March 2014, and in Guatemala in August 2020. In Nicaragua, SHB was confirmed in AHB colonies in San Juan del Sur, Department of Rivas, approximately eight kilometers north of the Costa Rican border, which increased the risk of entry to this country. After SHB was confirmed in Nicaragua, a sentinel apiary with four beehives was established close to the border in Santa Cecilia, La Cruz, province of Guanacaste, Costa Rica. In addition, epidemiological surveillance was conducted in the main beekeeping areas in the country (2015-2022) to determine SHB’s possible distribution. Hives were monitored visually by examining all individual honeycombs, hive covers, and bottom boards. Furthermore, training was offered to beekeepers such as workshops and fieldwork, and training materials were distributed such as brochures focused on SHB recognition and identification and methods for colony inspection. SHB was detected and confirmed in the sentinel apiary in August 2015 in La Cruz, Guanacaste, Costa Rica, where only adult beetles were detected inside AHB colonies. To date, in collaboration with trained beekeepers, SHB has been found in different commercial apiaries, mainly in the province of Guanacaste. In conclusion, implementing strategies to detect and monitor SHB, as it spreads to new countries or beekeeping areas, requires implementing sentinel apiaries, developing epidemiological surveillance, and providing training activities for beekeepers, as demonstrated in the case in Costa Rica.

Simple SummaryEstablishment and distribution of invasive insects depends on their cold tolerance especially in temperate regions. The small hive beetle (SHB) is native to Sub-Saharan African countries, from where it has now invaded all over the world, including South Korea as a destructive pest of honey bees. Therefore, the present study first time provided information about the survival and adaptation capacity of immature stages of SHBs to tolerate the cold environment. All tested immature stages: feeding larvae, wandering larvae and pupae of SHB were sensitive to chilling injuries. However, wandering larvae and pupae showed substantially enhanced survival in cold lethal temperatures after acclimation, but not the feeding larval stage. This plasticity of cold tolerance in wandering larvae and pupae could contribute to the winter survival of the SHB population for better establishment and range expansion in temperate regions such as in Korea.The small hive beetle (SHB) Aethina tumida Murray, (Coleoptera: Nitidulidae) is now a global invasive pest of honey bees, but its cold tolerance potential has not been yet explored. Therefore, we measured the supercooling point (SCP) of different stages of SHBs and also the impact of acclimation on their SCPs and survival as a measure for cold tolerance. Combinations of different temperatures (0, 3, 5, 7, and 10 °C) for different hours (1, 3, 5, 7, 12, 24, 35, and 48 h) were used to assess SHB survival. The supercooling points occurred at lower temperatures (−19.4 °C) in wandering larvae than in the other stages (pupae: −12.5 °C, and feeding larvae: −10.7 °C). A lethal temperature (LT50) of feeding larvae was achieved earlier at 4.9 °C after 7 h exposure than the wandering larvae (3.7 °C at 48 h) and pupae (5.6 °C at 48 h). The sum of injurious temperature (SIT) is the most suitable estimation to describe cold resistance of the SHB immatures. The wandering larvae were the most cold tolerant, followed by pupae and feeding larvae based on SIT values of −286.8, −153.7 and −28.7 DD, respectively, and also showed more phenotypic plasticity after acclimation than feeding larvae and slightly more than pupae. Our results show that all stages, i.e., feeding larvae, wandering larvae and pupae, are chill susceptible. However, these stages, especially wandering larvae and pupae, showed the capacity to acclimate to cold temperatures, which may help them to survive in winter for the continuity of the SHB population, especially in a scenario of climate change.

Representative honey bee viruses do not replicate in the small hive beetle, Aethina tumida Murray

Simple SummaryMexico is an important honey producer, but not much information exists about the health of honey bees in the country. This study analyzed the sanitary status of adult honey bees in five different beekeeping regions of Mexico. Samples from hives were analyzed to identify pests, parasites, and viruses. The mite Varroa destructor was found in 83.5% of the samples, with the Pacific Coast having the highest frequency (>95%) and levels (4.5% ± 0.6). Another mite, Acarapis woodi, was found in only one sample from the Pacific Coast, whereas the fungi Nosema spp. were present in 48.5% of the samples, with the highest frequency in the Yucatan Peninsula (64.6%). For viruses, deformed wing virus (DWV) was more frequently found in the Pacific Coast region (44.7%), and Israeli acute paralysis virus (IAPV) was detected in only 3.2% of the samples. Sacbrood bee virus (SBV) was frequently found in the High Plateau region (36.4%), and the small hive beetle (SHB) was common in the Yucatan Peninsula (39.2%). This information could be useful to design disease control strategies for honey bee colonies in different regions of Mexico.Mexico is a major honey producer, but not much information exists about the health status of honey bees (Apis mellifera L.) in the country. This study was conducted to determine the sanitary status of adult honey bees in Mexico’s five beekeeping regions. Samples from 369 apiaries were diagnosed to identify pathogens such as Varroa destructor, which was quantified, Acarapis woodi, Nosema spp., and five viruses. Colonies were also inspected for the presence of the small hive beetle (SHB), Aethina tumida. Varroa destructor was found in 83.5% of the apiaries, with the Pacific Coast region having the highest prevalence (>95%) and rates (4.5% ± 0.6). Acarapis woodi was detected in only one apiary from the Pacific Coast, whereas Nosema spp. were prevalent in 48.5% of the apiaries, with the highest and lowest frequencies in the Yucatan Peninsula and North regions (64.6% and 10.2%, respectively). For viruses, deformed wing virus (DWV) was detected in 26.1% of the apiaries, with the highest frequency in the Pacific Coast region (44.7%). Israeli acute paralysis virus (IAPV) was diagnosed in 3.2% of the samples and sacbrood bee virus (SBV) in 23.3% of them, with the highest frequency in the High Plateau region (36.4%). Chronic bee paralysis and Kashmir bee viruses were not detected. SHB prevalence was 25.2% nationwide, with the highest frequency in the Yucatan Peninsula (39.2%). This study shows that the most common parasites of adult honey bees in Mexico are V. destructor and Nosema spp., and that the most prevalent virus is DWV, whereas SHB is highly prevalent in the Yucatan Peninsula. This information could be useful to design disease control strategies for honey bee colonies in different regions of Mexico.

Simple SummarySocial insects use cuticular hydrocarbons for chemical recognition and communication. Cuticular hydrocarbons can also be exploited by parasites to their advantage for undermining host recognition systems. The small hive beetle (SHB) is a parasite of honey bee colonies but can also infest nests of other bee species. However, its chemical profile is still not known. For the first time, the present study investigated the SHB chemical profile and compared it with that of its honey bee host. The results show that the SHB has a low chemical profile that is similar to its honey bee host’s. However, while honey bees had a clear colony-specific chemical profile, SHBs did not. The generic chemical profile of the SHB is most likely linked to its free-flying behaviour in the field as these parasites are known to switch between host colonies, possibly limiting the acquisition of a colony specific chemical profile. Our findings also suggest that SHBs do not exploit any finely tuned chemical strategy to conceal their presence inside host colonies and probably rely on behavioural adaptations.Cuticular hydrocarbons (CHCs) cover insects’ bodies and play important roles in chemical communication, including nestmate recognition, for social insects. To enter colonies of a social host species, parasites may acquire host-specific CHCs or covertly maintain their own CHC profile by lowering its quantity. However, the chemical profile of small hive beetles (SHBs), Aethina tumida, which are parasites of honey bee, Apis mellifera, colonies, and other bee nests, is currently unknown. Here, adults of SHB and honey bee host workers were collected from the same field colonies and their CHC profiles were analysed using GC-MS. The chemical profiles of field-sampled SHBs were also compared with those of host-naive beetles reared in the laboratory. Laboratory-reared SHBs differed in their CHC profiles from field-sampled ones, which showed a more similar, but ten-fold lower, generic host CHC profile compared to host workers. While the data confirm colony-specific CHCs of honey bee workers, the profile of field-collected SHBs was not colony-specific. Adult SHBs often commute between different host colonies, thereby possibly preventing the acquisition of a colony-specific CHC profiles. An ester was exclusive to both groups of SHBs and might constitute an intraspecific recognition cue. Our data suggest that SHBs do not use any finely tuned chemical strategy to conceal their presence inside host colonies and instead probably rely on their hard exoskeleton and defence behaviours.

To explore alternative strategies to synthetic insecticides for control of Aethina tumida, the small hive beetle (SHB), treatments already established against two other honeybee pests, Varroa destructor and Galleria mellonella, were investigated. In the laboratory, eggs, larvae, and adults of SHB were treated with thymol (10, 20, and 50 mg) or with organic acids: 85% formic acid (0.125, 0.25, 0.5, 0.75, 1.0, and 2.0 mL), 15% lactic acid (0.5, 1.0, 1.5, and 2.0 mL), oxalic acid (dihydrate crystals 35 g/L; 0.25, 0.5, 0.75, 1.0, and 2.0 mL), and 65% acetic acid (0.5, 1.0, 1.5, and 2.0 mL). Some of the chosen concentrations of formic and oxalic acid resulted in high mortalities of all SHB life stages. Therefore, they were further evaluated in the field utilising standard methods for control of V. destructor in Europe. After exposure to evaporating formic acid (85%, Nassenheider®) and oxalic acid (2 g dehydrate crystals, Varrox®), mortality in all SHB tested stages did not increase significantly. The same was true for trials with 85% (adults) or 60% (eggs and larvae) formic acid, evaporating from sponge tissues in diagnostic trays. In fact, some SHBs used the diagnostic trays to hide or oviposit. Despite treating extracted honey combs with 65% acetic acid, SHBs still reproduced on the combs’ pollen cells. In conclusion, none of the tested methods can be recommended to control SHBs.

Honey bee, Apis mellifera L., is considered as an essential organism to the agricultural sector due to its role in pollination and alleviation of poverty in rural areas. Many pests attack honey bee colonies causing severe damages and economic losses. These pests include Varroa mites, Vespa hornets, wax moths, small hive beetles, and parasitic flies. Using chemical methods to control these pests causes some negative effects on honey bees and contaminates their products, while using biological control agents is promising and has no serious hazards. This article aimed to review available studies on the role of biological control agents mainly predators, parasitoids, and pathogens in controlling bee’s pests and to present new perspectives. Also, obstacles of using biocontrol agents inside and outside the hives were presented. This article is essential for planning integrated management programs for honey bee pests.

BackgroundThe small hive beetle, Aethina tumida, is a rapidly emerging global pest of honey bee colonies. Small hive beetle infestation can be extremely destructive, which may cause honey bees to abscond and render colony infrastructure unusable. Due to the impacts small hive beetles have on honey bees, a wide variety of physical, cultural, and chemical control measures have been implemented to manage small hive beetle infestations. The use of insecticides to control small hive beetle populations is an emerging management tactic. Currently, very little genomic information exists on insecticide target sites in the small hive beetle. Therefore, the objective of this study is to utilize focused in silico comparative genomics approaches to identify and assess the potential insecticide sensitivity of the major insecticide target sites in the small hive beetle genome.ResultsNo previously described resistance mutations were identified in any orthologs of insecticide target sites. Alternative exon use and A-to-I RNA editing were absent in AtumSC1. The ryanodine receptor in small hive beetle (Atum_Ryr) was highly conserved and no previously described resistance mutations were identified. A total of 12 nAChR subunits were identified with similar alternative exon use in other insects. Alternative exon use and critical structural features of the GABA-gated chloride channel subunits (Atum_RDL, Atum_GRD, and Atum_LCCH3) were conserved. Five splice variants were found for the glutamate-gated chloride channel subunit. Exon 3c of Atum_GluCl may be a beetle-specific alternative exon. The co-occurrence of exons 9a and 9b in the pH-sensitive chloride channel (Atum_pHCl) is a unique combination that introduces sites of post-translational modification. The repertoire and alternative exon use for histamine-gated chloride channels (Atum-HisCl), octopamine (Atum_OctR) and tyramine receptors (Atum_TAR) were conserved.ConclusionsThe recently published small hive beetle genome likely serves as a reference for insecticide-susceptible versions of insecticide target sites. These comparative in silico studies are the first step in discovering targets that can be exploited for small hive beetle-specific control as well as tracking changes in the frequency of resistance alleles as part of a resistance monitoring program. Comparative toxicity alongside honey bees is required to verify these in silico predictions.

Invasive pests may disturb and destructively reformat the local ecosystem. The small hive beetle (SHB), Aethina tumida, originated in Africa and has expanded to America, Australia, Europe, and Asia. A key factor facilitating its fast global expansion is its ability to subsist on diverse food inside and outside honey bee colonies. SHBs feed on various plant fruits and exudates in the environment while searching for bee hives. After sneaking into a bee hive, they switch their diet to honey, pollen, and bee larvae. How SHBs survive on such a broad range of food remains unclear. In this study, we simulated the outside and within hive stages by providing banana and hive resources and quantified the SHB associated microbes adjusted by the diet. We found that SHBs fed on bananas were colonized by microbes coding more carbohydrate-active enzymes and a higher alpha diversity than communities from SHBs feeding on hive products or those collected directly from bee hives. SHBs fed on bananas and those collected from the hive showed high symbiont variance, indicated by the beta diversity. Surprisingly, we found the honey bee core symbiont Snodgrassella alvi in the guts of SHBs collected in bee hives. To determine the role of S. alvi in SHB biology, we inoculated SHBs with a genetically tagged culture of S. alvi, showing that this symbiont is a likely transient of SHBs. In contrast, the fungus Kodamaea ohmeri is the primary commensal of SHBs. Diet-based microbiome shifts are likely to play a key role in the spread and success of SHBs.

Beekeepers need new registered products to control the small hive beetle (SHB), Aethina tumida, a significant pest of western honey bee (Apis mellifera) colonies. Few approved chemical controls exist, and there is no standardized system for screening compounds against SHBs. We outline a detailed method for an acute toxicity bioassay that delivers compounds via pollen. We provide a detailed method for a field trial that delivers treated pollen in traps made from modified compact disc cases. We applied both methods in proof-of-concept experiments to assess acetamiprid as a SHB control agent. Using the laboratory bioassay, we found acetamiprid (LC50 = 20.5 µg/g) to be more toxic to SHBs than coumaphos was (LC50 = 1250 µg/g), yet less toxic to SHBs than fipronil was (LC50 = 1.78 µg/g). In our field trial, colonies treated with acetamiprid and fipronil significantly reduced (p < 0.001) live SHB populations over those of control colonies. Traps containing acetamiprid retained significantly higher (p < 0.001) numbers of dead SHBs than did traps containing fipronil. We outline the first detailed methods to assess the toxicity of compounds delivered in pollen for adult SHB control. Our proof-of-concept experiments showed acetamiprid to be a promising control agent for SHBs.

The small hive beetle (SHB) is still present in Calabria one year after its first detection in September
\n2014. Detailed epidemiological studies would improve our knowledge of the survival, spread and
\nestablishment of the pest. Movement of an infested hive could spread SHB rapidly over large distances. Modelling of SHB spread in absence of movement of hives, suggests that natural spread of the beetle alone will take more than hundred years to reach Abruzzo from Calabria (around 250 km). A model considering the ownership of multiple apiaries per beekeeper indicates that spread would be 10 times faster. Opportunity maps indicate that, once introduced, the SHB could complete its life cycle in all EU Member States between May and September. It is recommended that restrictions on the movement of honey bees, bumblebees and commodities from infested to non-infested areas be maintained until SHB is eradicated, to prevent spread of the pest. Strengthening visual inspection, preventing infestation using a fine mesh and issuing a health certificate for intra-EU trade of queen bees, within 24 hours before dispatch, could reduce the risk of SHB transmission via consignments. In general, visual inspection of the beehive, as described in this document, is the preferred method of detecting SHB. Traps could help to detect and reduce SHB infestation levels. Maintaining good honey house hygiene and good beekeeping practices are the most important measures to control SHB where eradication is no longer the objective, given that no approved veterinary medicine is available in the EU. A field experiment found natural infestation of commercial bumblebee (Bombus impatiens) colonies placed next to SHB-infested honey bee hives. However, there are no data published on SHB infestation in natural bumblebee colonies. Studies are needed of the capacity of B. terrestris, occurring in Europe, to act as a SHB host.

To compare resistance to small hive beetles (Coleoptera: Nitidulidae) between Russian and commercial Italian honey bees (Hymenoptera: Apidae), the numbers of invading beetles, their population levels through time and small hive beetle reproduction inside the colonies were monitored. We found that the genotype of queens introduced into nucleus colonies had no immediate effect on small hive beetle invasion. However, the influence of honey bee stock on small hive beetle invasion was pronounced once test bees populated the hives. In colonies deliberately freed from small hive beetle during each observation period, the average number of invading beetles was higher in the Italian colonies (29 +/- 5 beetles) than in the Russian honey bee colonies (16 +/- 3 beetles). A similar trend was observed in colonies that were allowed to be freely colonized by beetles throughout the experimental period (Italian, 11.46 +/- 1.35; Russian, 5.21 +/- 0.66 beetles). A linear regression analysis showed no relationships between the number of beetles in the colonies and adult bee population (r2 = 0.1034, P = 0.297), brood produced (r2 = 0.1488, P = 0.132), or amount of pollen (P = 0.1036, P = 0.295). There were more Italian colonies that supported small hive beetle reproduction than Russian colonies. Regardless of stock, the use of entrance reducers had a significant effect on the average number of small hive beetle (with reducer, 16 +/- 3; without reducer, 27 +/- 5 beetles). However, there was no effect on bee population (with reducer, 13.20 +/- 0.71; without reducer, 14.60 +/- 0.70 frames) or brood production (with reducer, 6.12 +/- 0.30; without reducer, 6.44 +/- 0.34 frames). Overall, Russian honey bees were more resistant to small hive beetle than Italian honey bees as indicated by fewer invading beetles, lower small hive beetle population through time, and lesser reproduction.

Small hive beetle (Aethina tumida Murray) control has become an issue of increasing importance for North American apiculturists throughout the past two decades. Aethina tumida was discovered in Florida in 1989, presumably transported from its native habitat of sub-Saharan Africa through the shipment of European honey bee (Apis mellifera L) queens. Estimates of damage from A. tumida were as high as $3 million annually in the United States by the year 2004, and A. tumida was found in nearly every state by 2008. When adult beetles emerge from pupation in soil surrounding the hive, they are attracted to A. mellifera hives through a variety of pheromones and volatile organic compounds from bees and hive products. Aethina tumida larvae and adults consume hive products and bee brood, generating fermenting waste (or slime), which can eventually lead to hive abandonment in cases of severe infestation. Pest management efforts for A. tumida have focused on trapping adults, applying lime, diatomaceous earth, pyrethroid soil drenches, and entomopathogenic nematodes to the soil surrounding A. mellifera hives. Understanding the biology and life history of A. tumida, along with current control methods, can aid apiculturists in making informed integrated pest management decisions. Additionally, understanding critical knowledge gaps in the current research is an important step in identifying promising future management tactics in the ongoing efforts to manage this invasive pest.

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.

Currently, there is no integrated pest management approach for controlling small hive beetles (Aethina tumida), a widespread honey bee (Apis mellifera) pest. To date, only hive trapping has shown any effectiveness in controlling the pest. In this study, we tested several possible active ingredients that have been shown previously to demonstrate low toxicity towards honey bees. To test their toxicities, we treated both SHBs and honey bees topically and exposed SHBs to these compounds orally via pollen. Coumaphos (industry standard), a solvent control (acetone), and a positive control (dimethoate) were used for comparisons. Thiacloprid (LD50 = 1.3 ng/SHB; LC50 = 12 µg/g pollen) was the most toxic active ingredient tested against SHBs both topically and through pollen. Topically, thiacloprid was 340× more toxic to SHBs than coumaphos (LD50 = 431 ng/SHB). However, acetamiprid (selectivity ratio = 152) was much more toxic to SHBs than to honey bees compared to thiacloprid (selectivity ratio = 3). These findings demonstrate the need to find other active ingredients other than coumaphos and that acetamiprid has the greatest potential to reduce SHB populations safely in a honey bee hive. Field research using acetamiprid should be conducted to explore possible sub-lethal effects on honey bees.