Varroa Destructor Research Articles

An amitraz-based miticide does not appear to affect the bacterial microbiota of Apis mellifera (Apidae: Hymenoptera, Linnaeus, 1758) or Varroa destructor (Acari: Varroidae, Anderson & Trueman, 2000)

ABSTRACT The use of pesticides in beehives constitutes an important health issue for honey bees (Apis mellifera). Miticide treatments are not lethal to bees but could still impose significant sublethal costs. This study examined the impacts of amitraz, a commonly used miticide, on the bacterial communities of the honey bee gut and Varroa destructor mites. We sequenced and compared gut 16S rDNA composition pre – and post-amitraz treatment. Amitraz did not significantly influence bacterial gut communities in either honey bees or mites during the first six weeks following treatment. The gut bacterial community of bees was mainly dominated by the commonly observed microbiota in bees, which included species in the genera Gilliamella, Snodgrassella, and Frischella. Deformed wing virus (DWV) loads were analysed but were also unaffected by amitraz treatment over the six-week period studied. The bacterial community of Varroa destructor mites was heavily dominated by Bartonella spp., in contrast to results observed elsewhere. Our results indicating that amitraz does not appear to affect honey bee microbiota should be helpful for beekeepers who rely on this pesticide for mite control.

Results of the nationale survery on algerian beekeebing (breeding practices, health situation)

The honey bee plays a crucial role in maintaining plant biodiversity and environmental equilibrium, making beekeeping a vital activity in Algeria. However, the proliferation of Varroa ectoparasitic mites, causing varroasis, poses a significant threat to beekeeping in the region. This study, conducted between March and July 2022, aimed to comprehensively characterize the state of beekeeping in Algeria and identify its primary challenges. The survey was disseminated via email to beekeeping associations and individual beekeepers, with responses from 100 participants subjected to analysis, most of the respondents 97%, are men. 66% of the respondents practice sedentary and 34% transhumance. The findings shed light on the impediments to beekeeping development in recent years, including factors such as drought, elevated mortality rates, and the prevalence of bee pathologies. Notably, a significant portion of beekeepers refrains from conducting mortality analyses. The survey also revealed a substantial decline in honey production compared to previous years. However, positive aspects emerged, such as the presence of beekeepers employing sound beekeeping practices, including frame renewal, colony protection against adverse weather conditions, and the practice of transhumance. Furthermore, periodic varroasis screening in bee colonies was observed as a promising practice. Most beekeepers 98% use annual treatments for varroa mites in light of these findings, it is imperative for beekeeping associations to actively engage and take measures to organize and enhance the beekeeping sector, thereby addressing the current challenges.

Lactic acid treatment on infested honey bees works through a local way of action against Varroa destructor

Lactic acid is an alternative treatment to hard chemicals against Varroa destructor, the parasitic mite of the Western honey bee Apis mellifera. This soft acaricide is used only for small apiaries due to its laborious administration. However, the mode of action of this honey bee medication remains unknown. Previous studies showed that a direct contact between the arolia of V. destructor and lactic acid altered their morphology and led to an impairment of grip. Yet, there is no evidence for the way of action of lactic acid in a realistic in-hive scenario, i.e. after an indirect exposure of the mite through honey bees. We investigated the nature of lactic acid activity in the hive treatment context. The local and/or systemic way of action of this honey bee treatment against V. destructor was studied through a behavioural and toxicological approach at the individual level. On one hand, we confirmed the altered morphology for the arolia of mites and studied the evolution of the process over time. On the other hand, we found that haemolymph contaminated with lactic acid did not kill the feeding parasitic mite. These findings support a local mode of action. In order to unravel the sequence of events leading to the local contact between the acid and the mite on bees, we also documented the olfactory valence of lactic acid for A. mellifera and V. destructor. This work provides a new comprehension of lactic acid activity against the parasitic mite through honey bee exposure and gives new opportunities for control strategies against V. destructor.

Molecular survey and phylogenetic analysis of bee pathogens; with a note first detection of Apis mellifera Filamentous Virus, Varroa destructor virus-1, Apis rhabdovirus-1, and Apis rhabdovirus-2 in Türkiye

Turkey is one of the most important bee centers in the world, but there is limited information about honey bee pathogens in the country. This study aimed to investigate bee pathogens using microscopic and molecular techniques (PCR, RT-PCR, nested-PCR, and sequencing) in Sivas province, the second-biggest beekeeping center in Turkey. For this purpose, bee samples were obtained from 149 bee colonies belonging to 74 local beekeepers in eight districts of the Sivas province. The bee samples were examined for pathogens, and at least one pathogen was detected in 148 bee colonies. In this study, a single infection was determined in 26.17% (39/149) of the bee samples, while the prevalence of co-infection was 73.15% (109/149). Nosema ceranae, Varroa destructor haplotype-K, Apis mellifera Filamentous Virus, Deformed wing virus, Varroa destructor virus-1, Lake Sinai virus-2, Apis rhabdovirus-1, and Apis rhabdovirus-2 were detected. Apis mellifera Filamentous Virus, Varroa destructor virus-1, Apis rhabdovirus-1, and Apis rhabdovirus-2 were found for the first time in Turkey with the current study. Furthermore, nucleotide sequence analysis and phylogeny relationships of bee pathogens obtained from samples were done, and sequences were deposited to GenBank. This study provides molecular data on the presence and prevalence of important bee pathogens in the region. As the prevalence of many pathogens has been determined, especially the existence of viral new species has been revealed, the effects of the species on beekeeping should be studied, and beekeepers should take effective control measures to reduce the effects of these pathogens.

A novel antibody treatment reduces deformed wing virus loads in the western honey bee (Apis mellifera).

Deformed wing virus (DWV) is considered to be a key component of declining honey bee health which threatens global food production. The virus can result in significantly shortened lifespan, deformities in developing bees, and impaired cognition. There is currently no method to directly control the virus. The virus can be indirectly controlled with acaricidal treatments that target a key vector, the parasitic varroa mite (Varroa destructor). But acaricide resistance and a lack of effective alternatives for the control of both Varroa and DWV are major threats to beekeeping and the wider agricultural industry. Our research presents a significant development in the ability to reduce DWV burden in honey bees using IgY antibodies. Moreover, immunoglobulin Y has the potential to be more broadly established as a new treatment modality to combat other pathogens and parasites in A. mellifera.

Characterisation of proteomic alterations in worker bees in response to amitraz treatment during summer to winter transition in Apis mellifera colonies

The application of treatments to reduce/control the number of Varroa destructor mites within Apis mellifera colonies is a common apicultural practice. The effectiveness of the treatments in reducing Varroa mites from colonies has been extensively studied, however, the effects of these treatments on the bees within the colonies are poorly characterised. This work utilised label-free quantitative proteomic analysis to investigate how the presence of the anti-Varroa treatment amitraz, affected worker bees. Samples of A. mellifera were isolated from colonies one week before amitraz treatment (T0) and 1, 3, 6 and 8 weeks post-treatment application. The trial was conducted during the transition period from short-lived summer workers to long-lived winter workers. The results highlight two large proteomic shifts; a decrease in the abundance of cuticular proteins and an increase in ribosomal protein abundance in Weeks 3, 6, and 8. The changes in the protein abundance in Week 8 may not be a response to amitraz exposure alone but may also be attributed to a potential change in the population of short-lived to long-lived winter bees. The work provides insight into the effect of amitraz on the honey bee proteome during the transition period from summer to winter colony and how it may contribute to inducing a stress response in individual bees.

Evidence of circulating recombinants between deformed wing virus and Varroa destructor virus-1 in honey bee colonies in Türkiye.

Deformed wing virus (DWV), which is an important honey bee virus transmitted by Varroa destructor (V. destructor), causes colony losses in honey bee colonies. This study aimed to investigate the prevalence and genetic diversity of DWV in honey bees in Türkiye and to determine the role of V. destructor in the transmission of the genetic variants of DWV. Honey bee samples were collected from 62 apiaries, by simple random sampling, during March 2022 and April 2023. The presence of V. destructor in collected bee samples was examined using a stereo microscope. Real-time RT-PCR was used for the detection of DWV-A and DWV-B (Varroa destructor virus-1 (VDV-1)) viruses. Genetic characterisation of the positive samples was conducted by sequencing polyprotein genomic region. Considering the V. destructor infestation rate of 3% as relevant, out of the 62 apiaries examined, 17 (27.4%) were positive. However, DWV-A and VDV-1 specific RNA was not detected in V. destructor samples. VDV-1 specific RNA was detected in 6.5% (4/62) of the apiaries, whereas DWV-A was not detected in the sampled apiaries. Phylogenetic analysis showed that isolates detected in this study were located in a separate cluster from previously characterised DWV-A and VDV-1 isolates. According to RDP4 and GARD analyses, DWV-VDV-1 recombination breakpoints were detected in field isolates. To the best our knowledge, this is the first report of the presence of VDV-1-DWV recombinants in Türkiye. Further studies are needed to determine the impact of VDV-1-DWV recombinants and their virological and antigenic properties.

Managing the parasitic honey bee mite Tropilaelaps mercedesae through combined cultural and chemical control methods

The western honey bee (Apis mellifera) is severely impacted by the parasitic Tropilaelaps mercedesae mite, which has the capacity to outcompete Varroa destructor mites (the current leading cause of colony losses) and more rapidly overwhelm colonies. While T. mercedesae is native to Asia, it has recently expanded its geographic range and has the potential to devastate beekeeping worldwide if introduced to new regions. Our research exploited the dependence of T. mercedesae on developing honey bees (brood) by combining a cultural technique (brood break) with U.S. registered chemical products (oxalic acid or formic acid) to manage T. mercedesae infestation. To evaluate this approach, we compared four treatment groups: (1) Brood Break; (2) Brood Break + Formic Acid (FormicPro®); (3) Brood Break + Oxalic Acid dribble (Api-Bioxal®); and (4) untreated Control. We found that the mite infestation rate of worker brood in Control colonies rose from 0.4 to 15.25% over 60 days, whereas all other treatment groups had infestation rates under 0.11% on Day 60. Mite fall assessments showed similar results, whereby Control colonies had 15.48 mites fall per 24 h on day 60 compared to less than 0.2 mites for any other treatment group. Evaluation of colony strength revealed that Brood Break + Formic Acid colonies had slightly reduced adult honey bee populations. No treatment eliminated all mites, so additional measures may be needed to eradicate T. mercedesae if detected in countries that do not currently have T. mercedesae.

Unique brood ester profile in a Varroa destructor resistant population of European honey bee (Apis mellifera)

Varroa destructor is one of the greatest threats to Apis mellifera worldwide and if left untreated will kill a colony in less than three years. A Varroa-resistant population from Gotland, Sweden, has managed to survive for 25 years with little to no Varroa treatment by reducing the mite’s reproductive success. The underlying mechanisms of this trait is currently not known, though previous research indicates that it is the honey bee brood, and not adult bee influence, that contributes to this phenotype. As the mite’s own reproduction is synchronized with the brood’s development though the interception of brood pheromones, it is possible that a change in pheromone profile would disrupt the mite’s reproductive timing. To investigate this, we characterized the brood ester pheromone (BEP) profile of our resistant Gotland population compared to a non-resistant control. This was done by extracting and analyzing key cuticular compounds of the BEP using gas chromatography. A significant difference was found immediately after brood capping, indicating a divergence in their pheromonal production at this time point. This is an important step to understanding the mechanisms of the Gotland population’s Varroa-resistance and contributes to our global understanding of Varroa destructor infestation and survival.

Chemosensory function of Varroa gnathosoma: transcriptomic and proteomic analyses

In this study, we evaluated the role of the gnathosoma (mouthparts) in chemosensing of the most devastating honey bee parasite, Varroa destructor mite. Through transcriptomic analysis, we compared the expression of putative chemosensory genes between the body parts containing the main chemosensory organs (the forelegs), gnathosoma and the rest of the body devoid of these two body parts. Furthermore, we checked the presence of chemosensory-related transcripts in the proteome of the gnathosoma. Our comparative transcriptomic analysis revealed the presence of 83 transcripts with known characteristic conserved domains belonging to eight chemosensory gene families in the three Varroa transcriptomes. Among these transcripts, 11 were significantly upregulated in the mite’s forelegs, compared to 8 and 10 in the gnathosoma and body devoid of both organs, respectively. Whilst the gnathosoma and the forelegs share similar expression of some putative lipid carrier proteins, membrane-bound receptors, and associated proteins, they also differ in the expression profiles of some transcripts belonging to these protein families. This suggests two functional chemosensory organs that may differ in their chemosensory function according to specific characteristics of compounds they detect. Moreover, the higher expression of some chemosensory transcripts in the body devoid of forelegs and gnathosoma compared to the gnathosoma alone, may suggest the presence of additional function of these transcripts or alternatively presence of additional external or internal chemosensory organs. Insights into the functional annotation of a highly expressed gustatory receptor present in both organs using RNA interference (RNAi) are also revealed.

Differential impact of Paenibacillus infection on the microbiota of Varroa destructor and Apis mellifera

The Western honey bee (Apis mellifera) is a vital agricultural pollinator whose populations are threatened by the parasitic mite Varroa destructor and associated pathogens. While the impact of Paenibacillus species on honey bees, particularly Paenibacillus larvae causing American foulbrood, is documented, their effect on the microbiota of Varroa mites remains unclear. This study aimed to investigate the influence of Paenibacillus sp. on the bacterial communities of Varroa mites and adult honey bees. We hypothesized that Paenibacillus sp. would significantly alter the microbiota of Varroa mites but have minimal effect on that of adult honey bees. Utilizing 16S rRNA sequencing data from a previous study, we reanalyzed samples categorized into four groups based on Paenibacillus sp. infection load: highly infected and lowly infected honey bees (A. mellifera) and mites (V. destructor). Infection status was determined by Paenibacillus sp. read counts, with more than three reads indicating high infection. Microbial diversity was assessed using alpha and beta diversity metrics. Co-occurrence networks were constructed to visualize bacterial community assemblies, and network robustness was evaluated through node addition and removal tests. Keystone taxa were identified based on eigenvector centrality and relative abundance. Highly infected Varroa mites exhibited a significant reduction in alpha diversity and a markedly different bacterial community composition compared to lowly infected mites (p < 0.05). Their bacterial co-occurrence networks showed decreased connectivity and robustness, indicating a disruptive effect of Paenibacillus sp. In contrast, adult honey bees displayed no significant differences in alpha diversity or network structure between highly and lowly infected groups (p > 0.05), suggesting a resilient microbiota. Keystone taxa analysis revealed fewer central species in highly infected Varroa mites, potentially impacting network stability. High Paenibacillus sp. infection is associated with significant alterations in the microbiota of Varroa mites, disrupting bacterial communities and potentially affecting mite physiology. The microbiota of adult honey bees appears more robust against Paenibacillus sp. influence. These findings enhance our understanding of the complex interactions within the "honey bee–mite–microorganism" system and may inform future strategies for managing Varroa mite infestations and associated pathogens.

Molecular detection and phylogenetic analysis of six bee viruses from Varroa destructor in Korea

In the beekeeping industry, the control of Varroa destructor and viruses is a crucial factor in maintaining the health of the western honey bee Apis mellifera L. Recently, in Korea, beekeepers suffered for high colony losses during the overwintering, and the presence of V. destructor and viruses has been considered an important factor for honey bee health. In this study, we investigated the presence of six honey bee viruses [deformed wing virus (DWV), sacbrood virus (SBV), Kashmir bee virus (KBV), Israeli acute paralysis virus (IAPV), chronic bee paralysis virus (CBPV), and black queen cell virus (BQCV)] in V. destructor in Korea. V. destructor was collected from 46 apiaries in nine provinces in Korea, and viruses were detected using reverse transcription–polymerase chain reaction. DWV was most predominantly detected at 87% of apiaries, followed by IAPV, SBV, KBV, BQCV, and CBPV that were detected in 65.2%, 17.4%, 13%, 8.7%, and 6.5% of apiaries in Korea. Phylogenetic analysis revealed that five viruses (IAPV, SBV, BQCV, and CBPV) were grouped into clades of viruses originating from China, Russia, and Australia, but KBV showed no distinct clades of countries. This study confirmed the presence of various types of bee viruses in V. destructor in Korea, indicating that domestic honey bees are exposed to multiple viruses via V. destructor.

Transcriptional responses of detoxification genes to coumaphos in a nontarget species, Galleria mellonella (greater wax moth) (Lepidoptera: Pyralidae), in the beehive environment

The greater wax moth Galleria mellonella is a cosmopolitan pest of hives of the western honey bee Apis mellifera, where it remains exposed to varroicides applied by beekeepers in past decades as pest management chemicals for control of Varroa destructor, a devastating ectoparasite of bees. The prolonged presence of coumaphos residues, an organophosphate varroicide, in beeswax may be responsible for current levels of tolerance exhibited by G. mellonella, a non-target species that infests beehives. In this study, a field-collected strain of waxworms exhibited a higher LC50 value for coumaphos than that of a laboratory strain that had not been continuously exposed to coumaphos residues at field concentrations. Despite its higher tolerance for coumaphos, the field strain experienced growth inhibition at ecologically relevant concentration of coumaphos. Moreover, at low environmental concentrations that did not alter growth, detoxification gene expression levels were substantially altered. RNA-Seq analysis revealed 1181 and 658 differentially expressed genes in fat body and midgut, respectively, with 378 and 186 of those genes upregulated. This large-scale upregulation encompassed 21 genes encoding cytochrome P450 monooxygenases (CYPs), 13 encoding UDP-glycosyltransferases (UGTs), 5 encoding glutathione-S-transferases (GSTs), 2 encoding carboxylesterases (COEs), and 2 encoding ABC transporters (ABCs) in either tissue. Expression analysis of 13 selected candidate detoxification genes by RT-qPCR was consistent with their expression from RNA-Seq data. In sum, our results indicate that long-lasting pesticide residues in beeswax from past Varroa mite management may continue to act as selective agents on detoxification systems of hive residents other than the initial target species and that multiple resistance mechanisms to these chemicals may coexist within the beehive fauna.

The selection traits of mite non-reproduction (MNR) and Varroa sensitive hygiene (VSH) show high variance in subsequent generations and require intensive time investment to evaluate

The honey bee ectoparasite Varroa destructor is the main cause of honey bee colony losses worldwide. Over the last decades, several projects have focused on improving the robustness of Apis mellifera against this parasitic mite. Selection traits, such as mite non-reproduction (MNR) and Varroa sensitive hygiene (VSH), are favored selection factors in Varroa resistance projects. VSH is a trait where adult honey bees remove the Varroa-infested brood. During this process, the female mites are arrested in their reproductive cycle leading to a reduction of the Varroa population within the bee colony. From 2019 to 2022, 1402 queens were instrumentally inseminated with single or multiple drones in a breeding program. Colonies headed by these queens were established annually, and the MNR and VSH levels were analyzed. VSH was evaluated in response to cells artificially infested with Varroa, and colonies with high VSH values were used to generate our selected VSH stock. Despite crossing high VSH drones and queens, we measured a remarkable heterogeneity of MNR and VSH in the next generation(s), most likely due to the well-described, high recombination rate in the honey bee genome. When assessed multiple times in the same colony, great variance between measurements was observed. Detailed evaluations of daughter colonies are thus required if selection programs want to breed colonies with reliable VSH traits. This constant need to evaluate all offspring to ensure the desirable resistance traits are present results in high workloads and great expenses in selection programs. Furthermore, such large-scale breeding programs are inefficient due to high fluctuations between measurements and generations, indicating we need to develop new approaches and improved methods for assessing Varroa resistance.

Nested object detection using mask R-CNN: application to bee and varroa detection

AbstractIn this paper, we address an essential problem related to object detection and image processing: detecting objects potentially nested in other ones. This problem exists particularly in the beekeeping sector: detecting varroa parasites on bees. Indeed, beekeepers must ensure the level of infestation of their apiaries by the varroa parasite which settles on the backs of bees. As far as we know, there is no yet a published approach to deal with nested object detection using only one neural network trained on two different datasets. We propose an approach that fills this gap. Therefore, we improve the accuracy and the efficiency of bee and varroa detection task. Our work is based on deep learning, more precisely Mask R-CNN neural network. Instead of segmenting detected objects (bees), we segment internal objects (varroas). We add a branch to Faster R-CNN to segment internal objects. We extract relevant features for internal object segmentation and suggest efficient method for training the neural network on two different datasets. Our experiments are based on a set of images of bee frames, containing annotated bees and varroa mites. Due to differences in occurrence rates, two different sets were created. After carrying out experiments, we ended up with a single neural network capable of detecting two nested objects without decreasing accuracy compared to two separate neural networks. Our approach, compared to traditional separate neural networks, improves varroa detection accuracy by 1.9%, reduces infestation level prediction error by 0.22%, and reduces execution time by 28% and model memory by 23%. In our approach, we extract Res4 (a layer of the ResNet neural network) features for varroa segmentation, which improves detection accuracy by 11% compared to standard FPN extraction. Thus, we suggest a new approach that detects nested objects more accurately than two separate network approaches.

Detection of mutations in the voltage-gated sodium channel gene of Varroa destructor (Acari: Varroidae) populations

The honeybee (Apis mellifera) ectoparasite, Varroa destructor, is one of the most important honeybee pests worldwide. Acaricides, including the pyrethroids (tau-fluvalinate, flumethrin), and organophosphate (coumaphos) have been applied to control this mite within apiaries, still the long-term, constant, and excessive use of these products has led to the development of resistance in many populations. Three different mutations (L925V, L925I, L925M) at position 925 and one mutation (M918L) at 918 position of the V. destructor voltage-gated sodium channel (VGSC) have been associated with the resistance to these compounds. In the present study, we examined the presence of resistance mutations in the VGSC gene, encoding the target of pyrethroids, in the V. destructor population collected from the Kayseri and Sivas provinces of Central Anatolia Region of Türkiye. A total of 200 V. destructor samples were collected from 20 apiaries in two provinces throughout 2023. To investigate the mutations in Varroa samples, the domain II region of the VGSC gene was amplified using PCR and sequenced. The nucleotide sequencing of the IIS4-IIS5 linker region of the VGSC gene revealed one amino acid change at position 925: a leucine to isoleucine substitution (L925I). No mutations at other positions were identified. Homozygous resistant alleles were detected in 20 (40 %) of the sequenced 50 samples in the study areas. However, we detected the homozygous sensitive allele (wild-type allele, L925) in the remaining samples (50/30, 60 %). The result shows that this status may indicate a problem for Varroa control in the future. Thus, alternative acaricide with a mode of action of different pyrethroids should be considered in the control of V. destructor populations in these provinces.

Infectious diseases of bees and their impact on the vital activity and honey productivity of honey bee colonies in Ukraine

The article presents the results of the study of the mass mortality of honey bee colonies in different apiaries from different regions of Ukraine. The epizootic status of 102 honey bee colonies was studied and 607 samples of pathological material were analyzed in 2021–2023. According to the results of the monitoring of the epizootic situation in Ukrainian beekeeping it was found that the share of parasitic diseases (54.4%, 74.0%, 69.3%) constantly prevails over infectious diseases. It was noted that the incidence of varroosis in honey bees (34.4%, 71.4%, 41.47%) remains the highest among other diseases. Against the background of severe damage to honey bee colonies by the Varroa mite, infectious diseases began to appear in an atypical form, which significantly complicates their differential diagnosis. A probable increase in the incidence of nosemosis in adult bees and the detection of Nosema cysts in the intestines of bees, both in spring and summer, and the detection of cysts in honey indicate the spread of another pathogen, Nosema cerana, which causes nosemosis in the summer season. The reason for the periodic mass death of bees in Ukraine is the combination of a high number of parasitic Varroa mites in the honey bee colony with the presence of bee infection with microsporidia Nosema spp. These pathogens negatively affect the immunity of the honey bee colony, and cause exacerbation of latent infections in bees, which leads to a decrease in the number of honey bee colonies, weakening their viability and reducing the quality of honey products

A new mutation in the octopamine receptor associated with amitraz resistance in Varroa destructor

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Causal network linking honey bee (Apis mellifera) winter mortality to temperature variations and Varroa mite density

Winter season is a critical time for honey bees (Apis mellifera) colonies when individual mortalities may lead to total colony losses or diminish productivity in subsequent seasons. A deeper understanding of the causes and consequences of winter mortality is required. In this study, we analyzed winter (November–March) individual bee mortality in an apiary in Central Europe from 1991 to 2023. We observed consistency in mortality times among years, but also some systematic departures from the shared trend. We distinguished four clusters of year-specific mortality trajectories. However, we found no statistically significant differences in means of spring (March–May), autumn (October), winter (November–March) temperatures, or autumn Varroa destructor density among clusters. Nevertheless, our insights into the dynamics of individual bee mortality may be important for determining critical moments during wintering when implementing additional protective measures could prove beneficial. Hypothesis-driven path analysis indicated causal links in our study system, including both direct and indirect influences. The density of V. destructor in autumn was positively related to temperature, especially in the preceding spring, but to a lesser extent also in autumn. Increased winter mortality was related to lower winter temperatures and a higher mite infestation in autumn. We found no significant effects of individual winter mortality on honey harvests in subsequent seasons. Honey harvest was determined by bee abundance in spring, and the latter, unexpectedly, was not related to winter mortality. Our study adds to accumulating evidence of the major role of weather and climatic conditions in the resilience of honey bee colonies and improves our understanding of mortality processes. We highlighted the importance of causative factors, especially seasonal temperatures and V. destructor density, and their potential as predictive indicators of individual winter mortality, bee colony fate, and honey productivity.

Population Dynamics of the Mite Varroa destructor in Honey Bee (Apis mellifera) Colonies in a Temperate Semi-Arid Climate.

This study aimed to analyze the population dynamics of the mite Varroa destructor in honey bee (Apis mellifera) colonies in a temperate semi-arid climate in Mexico. Ten colonies homogeneous in population, food stores, and levels of mite infestation were used. The mite infestation rate in brood and adult bees, total number of mites, daily mite fall, brood and adult bee population, and food stores were determined periodically for 10 months. There was a significant effect (p < 0.05) of sampling period on the population of V. destructor in adult bees, brood, total mite population, and daily fallen mites. The total mite population increased by 26% on average per colony. The increase in brood amount reduced the mite infestation rate in adult bees, and the opposite occurred when the brood decreased. Monitoring V. destructor populations by recording fallen mites is more reliable than determining mite infestation rates in bees, as mite fall has a dynamic pattern similar to that of the total mite population. The best period to apply an acaricide treatment in the region of study is between November and December because most mites were in the phoretic phase, since there was less brood in the colonies compared to other times.