Infestation level and ecological association of Nosema spp. (Microsporida: Nosematidae) and Varroa destructor (Mesostigmata: Varroidae) in honeybee colonies in south-west Nigeria

Varroa mites are ecto-parasites of honeybees and are a threat to the beekeeping industry. We identified the haplotype of Varroa mites and evaluated potential factors that influence their prevalence and infestation levels in the eastern and western highland agro-ecological zones of Uganda. This was done by collecting samples of adult worker bees between December 2014 and September 2015 in two sampling moments. Samples of bees were screened for Varroa using the ethanol wash method and the mites were identified by molecular techniques. All DNA sequences obtained from sampled mite populations in the two zones were 100 % identical to the Korean Haplotype (AF106899). Mean mite prevalence in the apiaries was 40 and 53 % for the western and eastern zones, respectively, during the first sampling. Over the second sampling, mean mite prevalence increased considerably in the western (59 %) but not in the eastern (51 %) zone. Factors that were associated with Varroa mite infestation levels include altitude, nature of apiary slope and apiary management practices during the first sampling. Our results further showed that Varroa mites were spreading from lower to higher elevations. Feral colonies were also infested with Varroa mites at infestation levels not significantly different from those in managed colonies. Colony productivity and strength were not correlated to mite infestation levels. We recommend a long-term Varroa mite monitoring strategy in areas of varying landscape and land use factors for a clear understanding of possible changes in mite infestation levels among African honeybees for informed decision making.

The mite Varroa destructor (Anderson & Treuman 2000) is one of the world’s most important plagues of apiculture. In Brazil this mite does not encounter good conditions for parasitism because weather conditions are not ideal for its maintenance, and some strains of Africanized honey bees are resistant to the parasite. This status is reflected in the low number of dead colonies caused by varroatosis and also the stability of infestation levels. The aim of this study was to evaluate the damage caused by mite infestations in hives with higher levels of infestation than the ones considered normal for Brazilian apiaries. The level of infestation in each colony was determined and the mortality rates of parasitized bees during development were periodically recorded. The G Test of Independence and a Test of Proportions were used to compare the data. The rates of mortality of pupae and larvae were mostly proportional to the level of infestation in each colony. All colonies showed mortality rates significantly higher than the control one. In Africanized honeybee colonies with high rates of infestation by Varroa destructor mortality rates varied from 19.27% to 23.28% in pupae ( X = 21.27%) and from 15.71% to 16.15% in larvae ( X = 15.93%), against 3.85% and 3.74% in the control colony, respectively. In the parasitized colonies the average rates of mortality caused by the hurtful effects of the mite were, respectively, 5.52 and 4.26 times greater in those two developmental stages. Thus it can be concluded that even in tropical regions, like Brazil, it is necessary to give special attention to the levels of mite infestation (IR), particularly where the IR tends to be higher.

Varroa destructor is a parasitic mite responsible for the loss of honey bee (Apis mellifera) colonies. This study aimed to find a promising marker in honey for the bee colony infestation level using fluorescence spectroscopy and biochemical analyses. We examined whether the parameters of the honey samples’ fluorescence spectra and biochemical parameters, both related to proteins and phenolics, may be connected with the level of honey bee colonies’ infestation. The infestation level was highly positively correlated with the catalase activity in honey (r = 0.936). Additionally, the infestation level was positively correlated with the phenolic spectral component (r = 0.656), which was tentatively related to the phenolics in honey. No correlation was found between the diastase activity in honey and the colonies’ infestation level. The results indicate that the catalase activity in honey and the PFC1 spectral component may be reliable markers for the V. destructor infestation level of the colonies. The obtained data may be related to the honey yield obtained from the apiaries.

This study was carried out to determine the eff ects of the Varroa (Varroa destructor) infestation level (in fall) on the wintering ability and survival rates of honeybee (A. mellifera) colonies. Four diff erent infestation levels of Varroa in honeybee colonies were tested in this study. Ten honeybee colonies, in which infestation levels were similar, were used for each group. The average wintering abilities in low, medium, high and extreme groups were found to be 94.28%, 91.42%, 63.92% and 23.28% respectively. An average survival rate for the low, medium, high and extreme groups were found to be 100%, 100%, 80% and 40% respectively. Diff erences among the groups for wintering ability (P<0.01) were significant.

Summary This study was carried out to determine the eff ects of the Varroa (Varroa destructor) infestation level (in fall) on the wintering ability and survival rates of honeybee (A. mellifera) colonies. Four diff erent infestation levels of Varroa in honeybee colonies were tested in this study. Ten honeybee colonies, in which infestation levels were similar, were used for each group. The average wintering abilities in low, medium, high and extreme groups were found to be 94.28%, 91.42%, 63.92% and 23.28% respectively. An average survival rate for the low, medium, high and extreme groups were found to be 100%, 100%, 80% and 40% respectively. Diff erences among the groups for wintering ability (P<0.01) were significant.

Environment or beekeeping management: What explains better the prevalence of honey bee colonies with high levels of Varroa destructor?

Plant extracts are considered as a suitable alternative to chemical acaricides for the Varroa mite control. Therefore, the present study aimed to investigate the acaricidal and insecticidal activity of extract of Prangos ferulacea plant against Varroa mite and its host in the honey bee colonies in the climatic conditions of Kurdistan province from 2022 to 2024. The P. ferulacea plant was collected in June 2022 from different regions of Kurdistan province in the flowering stage, extracted and then its chemical compounds were identified using GC-MS. The present study was conducted in the form of a factorial experiment based on a completely random basic design with four treatments and seven replications. Before conducting the bioassay experiments, the experimental colonies were homogenized in terms of queen age, population (adults and brood), and honey storage. Also, the initial infestation rate of colonies with Varroa mites was evaluated for adult and brood. The results showed that the extract of 50% of P. ferulacea was relatively favorable acaricidal properties. So that, there was no significant difference with oxalic acid and Apistan treatments in terms of mite mortality percentage in the first time of spraying. Also, the result showed that the bee’s mortality percentage was not more than 7% in any of the times of spraying with the 50% extract of the P. ferulacea, and there was observed a significant difference compared to the oxalic acid and Apistan treatments in terms of bee’s mortality percentage (P<0.01).The queen superseding was not observed in any of the experimental treatments. According to the findings of the present research, the concentration of 50% of the extract P. ferulaceous can be suggested as a suitable alternative to synthetic acaricides and organic acids to control the Varroa mite in honey bee colonies.

The varroa mite (Varroa destructor) is the most economically important parasitic pest of honey bees (Apis mellifera) that causes global colony decline and loss. Since its first detection in Ethiopia in 2010, little is known about the current infestation levels and contributing factors to the mite's distribution across the country. In this study, we conducted a large‐scale assessment of varroa prevalence and infestation levels in managed colonies across three potential beekeeping regions of Ethiopia; Oromia, Amhara and Southern Nations, Nationalities and Peoples Region (SNNPR). A total of 360 samples from 39 apiaries were collected following standard protocols and the mite prevalence and infestation levels were determined using the established method of varroa research. Overall, 89% of sampled colonies were infested by the mite, with varying prevalence rates across the regions: 95.8% in Oromia, 85.2% in Amhara and 71.9% in SNNPR, indicating the widespread nature of the parasite throughout the country. The varroa infestation levels were lower in local hives (2.6 ± 5.9) than in frame hives (5.0 ± 0.9), and significantly higher in brood bees (5.6 ± 0.8) than in adult bees (1.93 ± 0.17) (p &lt; 0.001). Possible factors contributing to the varied mite prevalence and infestation levels in the country include differences in agro‐ecology, beekeeping practices, host age preference and the nature of bee hives. Therefore, our study provides insights into the current status of varroa prevalence and associated factors across regions in Ethiopia. Further investigation is required to explore the probable impact of the parasite on the health and productivity of local honey bees, in order to design future monitoring strategies.

Determining varroa mite infestation levels in honey bee colonies and the proper method and time to perform a diagnosis are important for efficient mite control. Performing a powdered sugar shake or counting mites that drop from combs and bees onto a hive bottom board are two reliable methods for sampling varroa mite to evaluate the efficacy of an acaricide treatment. This overview summarizes studies that examine the efficacy of organic acids and essential oils, mite monitoring, and brood interruption for integrated varroa mite control in organic beekeeping.

Assessment of colony infestation by Varroa destructor is a crucial part of the Integrated Pest Management (IPM) applied to beekeeping. Natural mite fall, quantified by counting the mites on sticky sheets, is considered a reference method to estimate varroa infestation level in honey bee colonies. However, in recent years, alternative methods that can be used in field conditions have been investigated. In this paper, we report the results of the evaluation of two different methods to estimate the levels of varroa infestation. The experiment involved 151 honey bee colonies in nine apiaries of four countries (Algeria, Croatia, Italy, Poland). After the main honey flow, we compared the 10-day natural mite fall and the powdered sugar roll methods with the varroa population in each colony. According to our results, the powdered sugar roll method could be suggested to beekeepers as a suitable IPM tool for varroa control, while natural mite fall represents a more accurate method that could be adopted for selection/research purposes.

A computer vision system to monitor the infestation level of Varroa destructor in a honeybee colony

&lt;p dir="ltr"&gt;&lt;b&gt;Varroa destructor mites (varroa hereafter) are devastating ectoparasites of the European honey bee (Apis mellifera) and can vector several viral pathogens to bees while feeding. Varroa is most closely associated with the honey bee pathogen Deformed wing virus (DWV). Together, varroa and DWV have detrimental and multifaceted effects on honey bee health and are considered one of the leading causes of colony losses around the world. Currently, beekeepers rely on a few chemical-based pesticides for controlling varroa infestations in their beehives and mitigating the negative effects of DWV. However, some varroa pesticides can have negative effects on bees and reports of resistance to some available pesticides have been increasing among varroa populations. Therefore, development of effective, specific and sustainable treatments for controlling varroa and DWV is important for improving honey bee health as well as providing beekeepers with alternative management strategies.&lt;/b&gt;&lt;/p&gt;&lt;p dir="ltr"&gt;RNA interference is a highly conserved intracellular mechanism of gene regulation and antiviral defence in eukaryotes, which has widely been proposed as a promising strategy to control pests and pathogens through administration of specific double stranded RNA (dsRNA) sequences. This thesis focuses on investigating the effectiveness of RNAi as a novel control method for varroa and DWV using pest and pathogen-specific dsRNA sequences.&lt;/p&gt;&lt;p dir="ltr"&gt;To test effects of DWV-specific dsRNA on DWV loads and symptoms in parasitised and non-parasitised honey bees reared from larvae I conducted laboratory experiments with mini-hives consisting of adult bees, larvae and varroa mites. Bees parasitised during their development had significantly higher DWV loads compared to non-parasitised bees (PERMANOVA, p &lt; 0.010). However, DWV-dsRNA did not reduce DWV loads (PERMANOVA, p = 0.66) or symptoms of mini-hive reared bees (ANOVA, 0.49). RNA-sequencing (RNA-seq) was used to assess the impact of DWV-dsRNA on viral loads and gene expression in brood-parasitising varroa mites. Varroa mites from DWV-dsRNA treated mini-hives did not show an elevated RNAi response or reduced DWV loads. Next, I tested effects of the same DWV-dsRNA sequences at a higher concentration on DWV loads in adult bees reared in either varroa-free or varroa-infested cages. Similarly, bees from varroa-free (PERMANOVA, p = 0.473) and varroa-infested (PERMANOVA, p = 0.151) cages fed DWV-dsRNA did not show significantly reduced DWV loads. Analysis of DWV loads in actively parasitising mites from varroa-infested cages found no significant effects of dsRNA on DWV loads in mites (PERMANOVA, p = 0.200). Interestingly, varroa-infested bees fed GFP-dsRNA (as a non-specific dsRNA control) showed significantly higher DWV loads compared to bees fed sugar water (PERMANOVA, p = 0.036). For varroa-infested cages, bee survival was also negatively affected by GFP-dsRNA and DWV-dsRNA (Cox proportional-hazards model, p &lt; 0.001). These results suggest that effects of dsRNA on honey bees may be influenced by varroa parasitism.&lt;/p&gt;&lt;p dir="ltr"&gt;GreenLight Bioscience Inc. (Medford, MA, USA) has recently developed a dsRNA product specific in sequence to a V. destructor mRNA encoding the calcium signalling protein calmodulin (VdCaM-dsRNA) as a potential biopesticide for varroa. Testing this product in field trials conducted in the U.S reduced varroa mite infestation in honey bee colonies. Here, I used laboratory mini-hives of bees and varroa mites to test the effects of two concentrations of VdCaM-dsRNA on varroa reproduction, survival and gene expression. Varroa were sampled from brood cells of developing pupae either 5 days after cell capping or just prior to bees emerging from brood cells, as a measure for time since mite exposure to VdCaM-dsRNA. While VdCaM-dsRNA did not have a significant effect on survival of adult female varroa mites, varroa reproduction was significantly and substantially reduced in high and low dose VdCaM-dsRNA treated mini-hives (PERMANOVA, p &lt; 0.001). Calmodulin expression was only significantly reduced in VdCaM-dsRNA treated mites from brood cells 5 days post capping (Kruskal-Wallis, p &lt; 0.001), while effects of VdCaM-dsRNA on calmodulin expression appeared to have waned in mites from emerging bees (PERMANOVA, p = 0.543). Differential gene expression analysis and gene ontology results suggest that VdCaM-dsRNA induced reduction in calmodulin-mediated calcium signalling dysregulates non-canonical Wnt and notch signalling pathways that are critical for embryogenesis. Finally, given that current varroa pesticides are used to mitigate negative effects of DWV in honey bee colonies I investigated short-term effects of VdCaM-dsRNA on DWV loads and symptoms in mini-hive reared bees. Varroa RNA-sequencing data was also used to assess viral community abundance in mites, with a focus on DWV loads. For mites sampled from brood cells of emerging bees, DWV loads were significantly lower in VdCaM-dsRNA high dose treated mites compared to non-specific dsRNA treated mites (ANOVA, p = 0.040). Mites sampled from brood cells 5 days after cell capping showed no effect of dsRNA treatment on DWV loads. While DWV loads in bees was not significantly affected by VdCaM-dsRNA, DWV loads followed a strong bimodal distribution in dsRNA treated bees, possibly indicating some interacting factors that influence effects of dsRNA on DWV loads in bees.&lt;/p&gt;&lt;p dir="ltr"&gt;Results from this thesis show that VdCaM-dsRNA is a highly promising biopesticide for controlling varroa mite infestation levels by significantly reducing mite reproduction in honey bee hives. Moreover, using RNA-seq to investigate the underlying molecular mechanism of VdCaM-dsRNA provided a deeper understanding to molecular pathways important for varroa reproduction and suggests that calmodulin-mediated calcium signalling plays an important role in regulating embryo developmental processes. On the other hand, using DWV-dsRNA to control DWV loads in bees and varroa mites was less successful possibly due to sequence divergence between the DWV-dsRNA sequences used and the DWV variants circulating in New Zealand honey bees and varroa. Possible DWV-dsRNA targets specific to New Zealand DWV variants are suggested, which will be useful for testing this hypothesis and better understanding the role of RNAi as a potential DWV control strategy.&lt;/p&gt;

The aim of this study was to assess infestation levels of Varroa destructor in some honey bee colonies from the National breeding program in the central part of Iran, and the relationship between mite infestation levels and postcapping period (PCP) of worker brood cells. Shortening the PCP is an important parameter limiting the success of varroa mite reproduction in honey bee colonies. In the present study, four pure-bred line colonies from isolated areas were selected to investigate the brood capping durations and mite infestation levels. Cages were used to synchronize egg laying of the queens and the time of capping and emerging of the brood cells was recorded at two-hour intervals. The results did not show any significant differences on the average of PCP of brood cells and mite infestation levels among test colonies. In addition, non-significant correlations were found between mite infestation and the capping period during the experiment. A relatively shorter capping period of brood cells was observed in one of the provinces compared to others, corresponding with slightly lower mite levels in the same colonies, which might suggest that reducing capping duration may be one of the factors which can potentially affect mite populations in honey bee colonies and therefore should be considered in breeding programs.

Gregorc A.: Efficacy of Oxalic Acid and Apiguard Against Varroa Mites in Honeybee (Apis mellifera) Colonies. Acta Vet. Brno 2005, 74: 441-447. This trial assessed the comparative efficacy of oxalic acid solution (OA), which consists of 2.9% oxalic acid and 31.9% sugar in water, and Apiguard, a thymol gel, in controlling the honeybee mite Varroa destructor. In comparison with untreated control colonies, mite mortality, which was evaluated throughout the pre- and post-treatment periods, increased significantly (p < 0.001) in both Apiguard and OA treated colonies. The mite mortality after two Apiguard applications, on August 7 and 21, was 41.98% (± 21.59) and was 42.63% (± 25.22) after three OA applications, on August 7, 14 and 21. All applications were given to colonies with brood. Further three OA treatments conducted during October, on previously untreated control colonies, resulted in mite mortality of 87.92 % (± 12.66). However, these levels of mite reduction were insufficient for all colonies to survive the winter. The results indicate that OA and Apiguard are of limited use during periods with brood. The possible use of OA and Apiguard against the varroa mite in honeybee colonies is discussed in this study.

Over the past fifty years, annual honeybee (Apis mellifera) colony losses have been steadily increasing worldwide. These losses have occurred in parallel with the global spread of the honeybee parasite Varroa destructor. Indeed, Varroa mite infestations are considered to be a key explanatory factor for the widespread increase in annual honeybee colony mortality. The host-parasite relationship between honeybees and Varroa is complicated by the mite's close association with a range of honeybee viral pathogens. The 10-year history of the expanding front of Varroa infestation in New Zealand offered a rare opportunity to assess the dynamic quantitative and qualitative changes in honeybee viral landscapes in response to the arrival, spread and level of Varroa infestation. We studied the impact of de novo infestation of bee colonies by Varroa on the prevalence and titres of seven well-characterised honeybee viruses in both bees and mites, using a large-scale molecular ecology approach. We also examined the effect of the number of years since Varroa arrival on honeybee and mite viral titres. The dynamic shifts in the viral titres of black queen cell virus and Kashmir bee virus mirrored the patterns of change in Varroa infestation rates along the Varroa expansion front. The deformed wing virus (DWV) titres in bees continued to increase with Varroa infestation history, despite dropping infestation rates, which could be linked to increasing DWV titres in the mites. This suggests that the DWV titres in mites, perhaps boosted by virus replication, may be a major factor in maintaining the DWV epidemic after initial establishment. Both positive and negative associations were identified for several pairs of viruses, in response to the arrival of Varroa. These findings provide important new insights into the role of the parasitic mite Varroa destructor in influencing the viral landscape that affects honeybee colonies.