A gel formulation of formic acid for control of Varroa destructor

The mite Varroa destructor is widely acknowledged as the most destructive threat to honey bee (Apis mellifera) colonies on a global scale. Varroa mite infestations in bee colonies are intricately linked with viral infections, collaboratively leading to diminished bee populations and accelerated colony losses. Extensive research has firmly established the correlation between varroa mites and viruses, underscoring the mite's efficiency in spreading viruses among bees and colonies. The effective control of varroa mites is expected to result in a decrease in viral infections within bee colonies. Research suggests that thermal treatments (hyperthermia) present a viable approach to combat varroa mites, with studies demonstrating the role of heat stress in reducing viral infections in affected bees. This article examines the extant literature surrounding the utilization of hyperthermia as a potential method to ameliorate the adverse impacts of varroa mites and their associated viral infections on honey bee colonies. It also outlines the thermal characteristics of these stressors. Diverse devices can be used for subjecting colonies to hyperthermia treatment, targeting mites both within and outside of brood cells. The application of thermal treatments, typically ranging between 40 and 42 °C for 1.5-3 h, as a method to reduce varroa mites and viral infections, has shown promise. Notably, the precise effectiveness of hyperthermia treatment in comparison with alternative varroa mite control measures remains uncertain within the available literature. The potential deleterious repercussions of this control mechanism on immature and mature honey bees are evaluated. Concurrently, the detrimental implications of prolonged treatment durations on colonies are discussed. Regarding viral infections, hyperthermia treatment can impact them negatively by either reducing varroa mite infestations or by inducing the production of heat shock proteins that possess potential antiviral properties. Various factors are identified as influential on hyperthermia treatment efficacy within bee colonies, including the device type and treatment duration, necessitating further empirical investigations. Additionally, this article highlights the existing gaps in the knowledge and provides insights into the prospective directions of research concerning this control method.

Simple SummaryHoney bee colonies deployed for pollination must be healthy to meet industry demand. Monitoring the activity of bees can indicate hive status but it is a complex task because bee colonies are inherently variable and require a holistic approach. In this study, we endeavored to monitor honey bee hives in the field using a combination of remote surveillance to quantify flights and by assessing the risk of pesticide exposure to bees from the pollen they collect. In Australia, vast almond orchards are grown as monoculture and in a semi-arid region, and so a lack of floral diversity may also impact bee health during pollination. Almonds are not produced without honey bees, and so it is essential to protect bee colonies, to ensure that there will be sufficient hives available in the following years. We showed that honey bee activity can be measured in the field to test for differences between hives. No insecticides were detected in pollen but combinations of fungicide residues were, although the individual concentrations were likely not hazardous. Floral diversity was perhaps less important for promoting bee activity compared to pollen availability, however, flowering weeds and trees in hedgerows may be important to help support hives.Certain crops depend upon pollination services for fruit set, and, of these, almonds are of high value for Australia. Stressors, such as diseases, parasites, pesticides, and nutrition, can contribute to honey bee Apis mellifera L. colony decline, thereby reducing bee activity and pollination efficiency. In Australia, field studies are required to monitor honey bee health and to ascertain whether factors associated with colony decline are impacting hives. We monitored honey bee colonies during and after pollination services of almond. Video surveillance technology was used to quantify bee activity, and bee-collected pollen was periodically tested for pesticide residues. Plant species diversity was also assessed using DNA metabarcoding of the pollen. Results showed that bee activity increased in almond but not in bushland. Residues detected included four fungicides, although the quantities were of low risk of oral toxicity to bees. Floral diversity was lower in the pollen collected by bees from almonds compared to bushland. However, diversity was higher at the onset and conclusion of the almond bloom, suggesting that bees foraged more widely when availability was low. Our findings suggest that commercial almond orchards may sustain healthier bee colonies compared to bushland in early spring, although the magnitude of the benefit is likely landscape-dependent.

Effective control of the parasitic mite Varroa destructor in honey bee (Apis mellifera) colonies relies on integrated pest management (IPM) strategies to prevent mite populations from reaching economic injury levels. Formulations of oxalic acid combined with glycerin may provide a viable summer treatment option in continental Northern climates. This study evaluated the efficacy of oxalic acid and glycerin strips compared to oxalic acid dribble and 65% formic acid when applied in mid-August. Mite levels and colony health parameters were assessed, and honey samples from oxalic acid-treated colonies were analyzed for residue levels. Results showed that the oxalic acid and glycerin strips had a moderate acaricidal efficacy (55.8 ± 3.2%), which was significantly higher than those of 65% formic acid (42.6 ± 3.2%) and oxalic acid dribble (39.5 ± 4.3%), which did not differ between them, suggesting potential for summer mite control. No significant adverse effects on cluster size, worker mortality, queen status, or colony survival were observed. Oxalic acid and glycerin increased the proportion of spotty brood patterns at early timepoints after treatment, but recovery was noted after 45 days of starting the treatment. Similar effects on brood were observed with 65% formic acid 14 days after starting the treatment, with recovery by 28 and 45 days after starting the treatment. No significant differences in oxalic acid residues in honey from the control and treatment colonies were found. Oxalic acid and glycerin strips might help control varroa mite populations, delaying their exponential growth and helping reduce economic losses for beekeepers, but this treatment should be considered as part of an IPM strategy and not a stand-alone method for V. destructor control.

Simple SummaryThe Varroa destructor mite is a severe problem for the development of beekeeping in many parts of the world. The presented study concerns the control of this harmful nuisance mite via a disease management protocol for the first time. Poor field conditions made it possible to evaluate the protocol’s effectiveness against mites in a natural and uncontrolled way. “Personalised” (tailored) applications consist of adjusting the number of control agents with different doses of amitraz to the number of detected parasite females in a given colony, taking into account a specific brood of queen bees (sisters) with a specific brood area. We showed that the number of treatments did not affect egg laying (brood surface) by mother sisters. We confirmed that amitraz should be increased by more than the number of mites found. The best results were obtained by repeating the procedure four times. We confirmed that effectiveness depends on the degree of Varroa infestation in a given family and the treatment of mites before the procedure. This procedure enables the protocol (personalisation) to effectively control of the impact of parasites on the bee colony. In such a procedure, one of the reasons for efficacy is the genetic conditions related to the reproductive potential of queens resulting from the bee breed. Based on new research, the presented study may change the overall effects of Varroa treatment in bee colonies.The requirement for the protection of bee colonies against Varroa destructor invasions has been noted by many breeders and is included as an aspect of the development of beekeeping. This research aimed to check the effect of the development of a colony exposed to laying eggs (brood surface) by queen bees with similar chemical potential (sisters) on the effect of a preparation combating V. destructor depending on the number of mites found in a given colony. We chose this as a standard model of conduct that treats each bee colony as one organism subjected to individual parasite control. For this purpose, we created a bee colony with a mother-of-one breeding line and fertilised drones from one colony. Infection with V. destructor occurred naturally and uncontrollably. Without interfering with the colony’s development, the frame insulator helped each colony’s brood (mothers’ reproductive potential) and the initial and final individuals from the mites themselves. The study was carried out in four species (two control species and two species with up to 20 and over 21 mites, respectively). Treatments with amitraz to combat damage were divided into four treatment subgroups: two treatments every four days or four treatments every two days. We observed the number of individuals that were protected in all subgroups in the average brood area. The reproductive potential of the sisters’ mothers did not change after the treatments with amitraz, which indicated that amitraz did not affect the delegation of egg laying. The invasion rate was also tracked relative to the control group, which allowed us to conclude that a two-time treatment with amitraz reduced the frequency of mites and a four-time treatment checked the effectiveness. Tailoring the control of V. destructor in bee colonies may be an effective measure in the fight against this parasite.

The objective of this study was to measure the efficacy of two organic acid treatments, formic acid (FA) and oxalic acid (OA) for the spring control of Varroa destructor (Anderson and Trueman) in honey bee (Apis mellifera L.) colonies. Forty-eight varroa-infested colonies were randomly distributed amongst six experimental groups (n = 8 colonies per group): one control group (G1); two groups tested applications of different dosages of a 40 g OA/l sugar solution 1:1 trickled on bees (G2 and G3); three groups tested different applications of FA: 35 ml of 65% FA in an absorbent Dri-Loc(®) pad (G4); 35 ml of 65% FA poured directly on the hive bottom board (G5) and MiteAwayII™ (G6). The efficacy of treatments (varroa drop), colony development, honey yield and hive survival were monitored from May until September. Five honey bee queens died during this research, all of which were in the FA treated colonies (G4, G5 and G6). G6 colonies had significantly lower brood build-up during the beekeeping season. Brood populations at the end of summer were significantly higher in G2 colonies. Spring honey yield per colony was significantly lower in G6 and higher in G1. Summer honey flow was significantly lower in G6 and higher in G3 and G5. During the treatment period, there was an increase of mite drop in all the treated colonies. Varroa daily drop at the end of the beekeeping season (September) was significantly higher in G1 and significantly lower in G6. The average number of dead bees found in front of hives during treatment was significantly lower in G1, G2 and G3 versus G4, G5 and G6. Results suggest that varroa control is obtained from all spring treatment options. However, all groups treated with FA showed slower summer hive population build-up resulting in reduced honey flow and weaker hives at the end of summer. FA had an immediate toxic effect on bees that resulted in queen death in five colonies. The OA treatments that were tested have minimal toxic impacts on the honey bee colonies.

In East Africa, honey bees (Apis mellifera) provide critical pollination services and income for small-holder farmers and rural families. While honey bee populations in North America and Europe are in decline, little is known about the status of honey bee populations in Africa. We initiated a nationwide survey encompassing 24 locations across Kenya in 2010 to evaluate the numbers and sizes of honey bee colonies, assess the presence of parasites (Varroa mites and Nosema microsporidia) and viruses, identify and quantify pesticide contaminants in hives, and assay for levels of hygienic behavior. Varroa mites were present throughout Kenya, except in the remote north. Levels of Varroa were positively correlated with elevation, suggesting that environmental factors may play a role in honey bee host-parasite interactions. Levels of Varroa were negatively correlated with levels of hygienic behavior: however, while Varroa infestation dramatically reduces honey bee colony survival in the US and Europe, in Kenya Varroa presence alone does not appear to impact colony size. Nosema apis was found at three sites along the coast and one interior site. Only a small number of pesticides at low concentrations were found. Of the seven common US/European honey bee viruses, only three were identified but, like Varroa, were absent from northern Kenya. The number of viruses present was positively correlated with Varroa levels, but was not correlated with colony size or hygienic behavior. Our results suggest that Varroa, the three viruses, and Nosema have been relatively recently introduced into Kenya, but these factors do not yet appear to be impacting Kenyan bee populations. Thus chemical control for Varroa and Nosema are not necessary for Kenyan bees at this time. This study provides baseline data for future analyses of the possible mechanisms underlying resistance to and the long-term impacts of these factors on African bee populations.

This study characterized the mitochondrial DNA (mtDNA) genetic variation in Arkansas honey bee, Apis mellifera L., by sequencing a portion of the mitochondrial cytochrome oxidase (COI-COII) intergenic region). The samples were primarily of hobbyist-managed origin (n = 180), as well as 32 feral colonies and two swarms. Of the 214 honey bee colonies and swarms sampled, 23 haplotypes were observed. The haplotypes were from the: A (African) (1.87%); C (South eastern European) (92.52%); M (Northern and Western European) (3.27%); and O (Near East and Middle East) lineages (2.34%). Six C lineage haplotypes were predominantly detected (n = 189, 88.31%), all of which are common in U.S. commercial queen breeder colonies. The remaining 27 honey bee samples represented 19 haplotypes, all of which are absent from commercial queen breeder colonies but have been observed in feral honey bee populations collected in other States. These haplotypes, particularly those from the M and O lineages, are likely hundred-year-old remnants of historical importations, surviving for generations despite the arrival of threats, such as Varroa mites. Understanding honey bee genetics and population structure are valuable for maintaining genetic diversity. Results from this study provide evidence that Arkansas honey bee populations differ from U.S. commercial queen breeder colonies. The 15 haplotypes detected in our Arkansas study absent from commercial queen breeder colonies could be important sources of genetic diversity in future honey bee breeding programs, highlighting the importance of State-level genetic surveys.

Pollinator refuges such as wildflower strips are planted on farms with the goals of mitigating wild pollinator declines and promoting crop pollination services. It is unclear, however, whether or how these goals are impacted by managed honey bee (Apis mellifera L.) hives on farms. We examined how wildflower strips and honey bee hives and/or their interaction influence wild bee communities and the fruit count of two pollinator-dependent crops across 21 farms in the Mid-Atlantic U.S. Although wild bee species richness increased with bloom density within wildflower strips, populations did not differ significantly between farms with and without them whereas fruit counts in both crops increased on farms with wildflower strips during one of 2 years. By contrast, wild bee abundance decreased by 48%, species richness by 20%, and strawberry fruit count by 18% across all farm with honey bee hives regardless of wildflower strip presence, and winter squash fruit count was consistently lower on farms with wildflower strips with hives as well. This work demonstrates that honey bee hives could detrimentally affect fruit count and wild bee populations on farms, and that benefits conferred by wildflower strips might not offset these negative impacts. Keeping honey bee hives on farms with wildflower strips could reduce conservation and pollination services.

ABSTRACTHoney bees are globally important pollinators threatened by many different pathogens, including viruses. We investigated the virome of honey bees collected at the end of the beekeeping season (August/September) in Czechia, a Central European country. Samples were examined in biological replicates to assess the homogeneity, stability, and composition of the virome inside a single hive. By choice of healthy workers from colonies, where Varroa destructor was under control, we could identify ubiquitous bee viruses. Deformed wing virus (DWV) was highly prevalent, even though the bees were healthy, without any noticeable disease signs. The overall virome composition (consisting of honey bee-, plant-, and bacterium-infecting viruses) was driven primarily by the hive and its location. However, honey bee-specific viruses showed an uneven distribution within the same hive. In addition, our results point to an unusual cooccurrence between two rhabdoviruses and reveal the presence of five distinct lineages of Lake Sinai viruses (LSVs) clustering with other LSV strains described globally. Comparison of our results with the virome of Australian honey bees, the last truly Varroa- and DWV-free population, showed a strong difference with respect to DWV and a set of diverse members of the Picornavirales, of which the latter were absent in our samples. We hypothesize that the occurrence of DWV introduced by Varroa strongly affects the virome structure despite the mite being under control.IMPORTANCE The Western honey bee, Apis mellifera, is a vital part of our ecosystem as well as cultural heritage. Annual colony losses endanger beekeeping. In this study, we examined healthy bees from the heart of Central Europe, where honey bee colonies have been commonly affected by varroosis over 5 decades. Our virome analysis showed the presence of ubiquitous viruses in colonies where the mite Varroa destructor was under control and no honey bee disease signs were observed. Compared to previous studies, an important part of our study was the analysis of multiple replicates from individual hives. Our overall results indicate that the virome structure (including bee-infecting viruses, plant-infecting viruses, and bacteriophages) is stable within hives; however, the bee-infecting viruses varied largely within interhive replicates, suggesting variation of honey bee viruses within individual bees. Of interest was the striking difference between the viromes of our 39 pools and 9 pools of honey bee viromes previously analyzed in Australia. It could be suggested that Varroa not only affects DWV spread in bee colonies but also affects diverse members of the Picornavirales, which were strongly decreased in Czech bees compared to the Varroa- and DWV-naive Australian bees.

Honey bees are pollinators, accounting for around 90% of commercial pollination of animal-pollinated plants and approximately 35% of global food production. Global populations of honey bees have declined significantly recently with heavy losses attributed to Colony Collapse Disorder, pesticides, parasites and pathogens. One of the factors that may be contributing to an increase in susceptibility to these stresses is the quality of food available in a hive. This thesis focuses on the interactions between honey bee nutrition, microbial communities and fitness. In Chapter 2 the nutritional composition of bee bread (pollen stored inside hives) was studied. The composition in terms of protein and reducing sugar was found to vary both spatially and temporally; lipid and starch content was found to vary temporally through the season. The spatial trends in protein content were found to be associated with changes in landscape composition, as estimated by the Countryside Survey database. The implications for these findings are that certain landscape types may produce higher quality diets for honey bees. In Chapter 3, the link between nutritional composition of bee bread and the species of plant that comprise it was investigated. Previous research indicates that pollens vary in their nutritional content and using molecular tools, we investigated the impact of complex plant communities in this system. The number of plant species in bee bread was positively correlated with increasing protein levels, and specifically certain individual plant species were found to be driving this pattern. These results indicate that a more diverse diet of plants will benefit honey bees by increasing their dietary protein intake. The conversion of pollen to bee bread requires the activity of certain microorganisms. In chapter 4, we again used molecular tools to study the microbial community found associated with bee bread. We found a community that was not significantly different between hives located in different areas, but which varied significantly in is composition through the beekeeping season. This suggests that the environment does not determine the bacterial communities in honey bee hives; rather it is being determined by seasonal changes. Finally, in chapter 5 the relationship between the nutritional composition of bee bread and the immunocompetence of larval and adult honey bees was examined. The results showed that dietary protein and carbohydrate is significantly correlated with the overall fitness of a hive in terms of expression a constituent immune response. The link between landscape composition and nutrition established in chapter 2 was used to predict honey bee nutrition across the UK, and then was used to predict immune response for all UK bees. These predictions were comparable to honey bee disease records maintained by UK government. This thesis provides a detailed examination of the effects of landscape composition on honey bee nutrition and immunity. The results presented here have implications for understanding spatial patterns in bee fitness and bee disease epidemiology.

Recent years have seen a worsening in the decline of honey bees (Apis mellifera L.) colonies. This phenomenon has sparked a great amount of attention regarding the need for intense bee hive monitoring, in order to identify possible causes, and design corresponding countermeasures. Honey bees have a key role in pollination services of both cultivated and spontaneous flora, and the increase in bee mortality could lead to an ecological and economical damage. Despite many smart monitoring systems for honey bees and bee hives, relying on different sensors and measured quantities, have been proposed over the years, the most promising ones are based on sound analysis. Sounds are used by the bees to communicate within the hive, and their analysis can reveal useful information to understand the colony health status and to detect sudden variations, just by using a simple microphone and an acquisition system. The work here presented aims to provide a review of the most interesting approaches proposed over the years for honey bees sound analysis and the type of knowledge about bees that can be extracted from sounds.

The aim of this study was to assess the potential harmful effects of neonicotinoids inside honey bee colonies and especially on the honey bee pest, Varroa destructor. This paper shortly summarized previous studies which investigated the toxicity of neonicotinoids to honey bees. The possible exposure routes of these insecticides to Varroa mites inside and outside bee colonies were studied. And finally, the link between the adverse effects of neonicotinoids and Varroa mite life cycle in the brood cells and the influence of these chemicals on the mites inside bee colonies were investigated. It was concluded that the application of neonicotinoid insecticides on a variety of agricultural crops may result in the exposure of honey bees to these chemicals and as a consequence, Varroa mites (parasites living inside bee colonies) also got exposed to these insecticides indirectly. The present study re-emphasized on ecotoxicological attempts assessing the risk of these insecticides to honey bees as well as on ecological and behavioral aspects of their application inside bee colonies.

Voltage-gated chloride channel blocker DIDS as an acaricide for Varroa mites

Studies were conducted in two apiaries in order to assess the comparative efficacy of oxalic acid (OA), formic acid (FA) and Thymovar® against varroa mites in honey bee colonies. Treatments were performed using 85% FA, and OA consisted of 2.9% OA dihydrate and 31.9% sugar in water. Consecutive short term FA treatments proceeding Thymovar® application, resulted in an average varroa mortality of 11 and 18% respectively. These varroa mortalities were higher than that in the pre-treatment period (p < 0.05). Mortality rates in FA and OA treated colonies were 42 and 34% of the total mite counts. OA treatment in broodless colonies, after caging the queens for 25 days, reduced the varroa population by 11%. Also consecutive OA sublimations reduced varroa populations by 11, 24, and 16% respectively and the final autumn reduction was 77%. In the second experiment using broodless colonies by caging and isolating the queens, initial OA treatments caused 24% varroa mortality, but three additional autumn OA treatments resulted in 97% varroa efficacy. These studies found that consecutive Thymovar® or OA treatments in colonies with brood have a limited effect on reducing varroa mites. Caging queens to obtain broodless conditions was also not sufficient alone for effectively reducing the varroa mites in colonies during summer months. We conclude, however, that a combination of different treatment protocols, using organic means, can ensure an effective varroa control in colonies.

In this study, the effectiveness of combining various biotechnical methods with thymol was investigated against the mite, Varroa destructor during late summer. Experimental colonies were randomly selected and six study groups were formed with nine colonies in each group. Experimental colonies were created as follows: colonies of renewed queen bees (RQ); colonies in which the queen is trapped on one comb, but worker bees can come and go to carry out their duties (CT); colonies in which ten grams of powdered thymol was added to 90 g of the bee cake, and 100 g of the bee cake with thymol was applied to the colonies (TY); colonies in which the requeen method plus the thymol method were used (RQ+TY); colonies in which the comb trapping method plus the thymol method were used (CT+TY); and untreated control colonies (CC). During the late summer period, the mite infestation level, sealed brood areas, bee population, and effectiveness of applications were determined in the groups. There was no significant difference in the infestation rate, sealed brood areas, and bee populations in the treatment groups before brood interruption. The efficacy of the requeen method, the comb trapping method, the thymol method, the requeen plus thymol method, and comb trapping plus other groups against V. destructor infestation were 40.23, 39.76, 80.45, 98.28 and 97.93%, respectively. These results showed that combining biotechnical methods with thymol is a safe, easy and effective alternative to late summer therapy against V. destructor. Key words: Comb trapping, honey bee, requeening, thymol, Varroa destructor. &nbsp