Ralitsa Balkanska

Honeybee colonies are affected by bacterial, fungal, viral, microsporidian, and parasitic diseases that impair brood viability, adult survival, productivity, and beekeeping sustainability. Conventional control relies on sanitary measures, antibiotics where permitted, and synthetic acaricides, but these approaches are constrained by residues, resistance, regulation, and variable field performance. This narrative review critically evaluates essential oils as alternative or complementary tools against American foulbrood, European foulbrood, varroosis, nosemosis, chalkbrood, and mite-associated viral pressure. Evidence indicates that thymol, carvacrol, eugenol, cinnamaldehyde, and related constituents can show marked antibacterial, antifungal, acaricidal, antioxidant, and host-supportive activity under controlled conditions. However, most bacterial, fungal, and nosemosis data remain laboratory-based, and direct antiviral applications against honeybee viruses are not field validated. The strongest practical evidence concerns thymol-based control of Varroa destructor, where efficacy depends on formulation, release rate, temperature, colony status, and safety margins. Essential oils should therefore be considered components of integrated honeybee health management, not substitutes for established measures. Future studies should prioritize chemical standardization, dose–response testing, colony-level trials, brood and queen safety, sublethal behavior and physiology, gut microbiota, residues, and reproducible delivery systems.

The aim of the study was to determine the effect of pollen supplementation on lactating ewes and their lambs. An experiment was carried out for a period of 4 weeks with 22 lactating ewes and their offspring of the breed Ile de France (28 lambs), matched for lambing date and live weight of the lambs. The sheep were divided into two groups: control and experimental. Feeding was the same for both groups. The experimental group was supplemented with bee pollen at a dose of 6 g/twice per week at regular intervals of 3 days. The live weight of the lambs was determined at the beginning and at the end of the experiment, and the average daily gain was calculated. Blood samples were taken from the ewes, and some biochemical parameters were examined. The live weights and growth of lambs at the beginning and end of the experiment showed a slight trend towards higher values in the experimental group, which were not significant. In the biochemical profile, the values of the parameters studied during both periods were within the reference range for the animals, with the exception of glucose, which was lower. Significant differences (P

Honeybees are the most valuable pollinators for ecosystems. This study aimed to determine the effects of inverted sugar syrup on the sealed worker brood and colony strength in Roger-Delon hives. The study was conducted in 2024, involving 14 Roger-Delon hives. The experiment was conducted at an altitude of 860 meters in the area of the town of Tran, Pernik region. Bee colonies were assigned to two treatment groups: inverted sugar syrup supplementation (experimental group with 7 bee colonies) and supplementation with sugar solution (control group with 7 bee colonies), at a rate of 250 ml per colony twice a week. In the present experiment with Roger-Delon hives, the bee colonies supplemented with inverted sugar syrup had significantly higher average values of sealed worker brood and colony strength, than those in the control group (p<0.001), following spring and autumn feedings. These results confirm that inverted sugar syrup is more effective supplemental feed for improving brood production in honeybee colonies, probably due to its higher digestibility. Further studies are needed over longer periods of time, as they could provide a deeper insight into the long-term effects of inverted sugar syrup on bee colony growth and productivity in Roger-Delon hives.

Royal jelly has a rich nutrient content and valued natural bee product which has been mainly used in traditional medicines to protects and strengthens the health. It is a yellowish-white and acidic secretion of hypopharyngeal and mandibular glands of nurse bees used to feed young worker larvae during the first three days and the entire life of queen bees. Because of its functional properties, royal jelly is very effective in accelerating the protection of health and healing process in many diseases. The high quality and scientific standardization of royal jelly is very important for using it in prevention of health and medical use in treatment disease in complimentary medicine. This review explains the effects of royal jelly on medical use for human health.

The aim of the present study is to evaluate the egg-laying dynamics of queen bees in Roger-Delon and Warre hives located in an apiary at an altitude of less than 1000 m. The study was conducted during the active season of 2023, in an apiary located at an altitude of 860 m in south-western Bulgaria, Pernik district. The bee colonies were balanced before the beginning of the experiment. Two groups of 6 colonies were formed from each Roger-Delon and Warre system. Sealed worker brood was measured until the appearance of constant nectar flow (April – June), and after the appearance of constant nectar flow (September – November). There is currently a need to examine and quantify the egg-laying dynamics of queens in new hive systems. Queen egg-laying activity is affected by a variety of seasonal, nutritional and social factors. According to the results obtained, the average sealed worker brood in Warre hives and Roger-Delon hives are 10484±1031 cm2 and 9564±1057 cm2 (mean±SD) respectively, for the whole period until appearance of constant nectar flow.

In the last few years, the isolation and amplification of DNA or RNA from the environment (eDNA/eRNA) has proven to be an alternative and non-invasive approach for molecular identification of pathogens and pests in beekeeping. We have recently demonstrated that bee pollen and bee bread represent suitable biological material for the molecular identification of viral RNA. In the present study, we extracted total RNA from different bee products (pollen, n = 25; bee bread, n = 17; and royal jelly, n = 15). All the samples were tested for the presence of six of the most common honey bee-associated viruses—Deformed wing virus (DWV), Acute bee paralysis virus (ABPV), Chronic bee paralysis virus (CBPV), Sacbrood virus (SBV), Kashmir bee virus (KBV), and Black queen cell virus (BQCV)—using a reverse transcription polymerase chain reaction (RT-PCR). We successfully detected six records of DWV (10.5%, 6/57), four of ABPV (7.0%, 4/57), three of Israeli acute paralysis virus (IAPV) (5.3%, 3/57), and two of BQCV (3.5%, 2/57). Using ABPV primers, we also successfully detected the presence of IAPV. The obtained viral sequences were analyzed for phylogenetic relationships with the highly similar sequences (megablast) available in the GenBank database. The Bulgarian DWV isolates revealed a high homology level with strains from Syria and Turkey. Moreover, we successfully detected a DWV strain B for the first time in Bulgaria. In contrast to DWV, the ABPV isolates formed a separate clade in the phylogenetic tree. BQCV was closely grouped with Russian isolates, while Bulgarian IAPV formed its own clade and included a strain from China. In conclusion, the present study demonstrated that eRNA can be successfully used for molecular detection of honey bee-associated viruses in bee products. The method can assist the monitoring of the health status of honey bee colonies at the local, regional, and even national levels.

Honeybee products are highly valued food products in the nutrition and medicine.This work aims to determine physicochemical parameters of polyfloral and sunflower honey, which are produced in Bulgaria. Twelve sunflower and 17 polyfloral honey samples were used in this study. The parameters color, water content, electrical conductivity, specific optical rotation, pH, proline, invertase, diastase, hydroxymethylfurfural (HMF) were analyzed. Bulgarian sunflower and polyfloral honeys were characterized by main physicochemical parameters and compared to products from other countries. The color correlates with the electrical conductivity and diastase correlates with invertase in the sunflower honey. The results of the present study indicated that Bulgarian sunflower and polyfloral honey are known for its good quality since the criteria that were closely correlated with the honey’s quality were measured.

Among many pathogens and pests, honey bee viruses are known as one of the most common cause of diseases in honey bee colonies. In this study, we demonstrate that pollen grains and bee bread are potential sources of viral DNA. We extracted DNA from 3 types of pollen samples: directly provided by beekeepers (n = 12), purchased from trade markets (n = 5), and obtained from honeycombs (bee bread, n = 10). The extracted DNA was used for molecular detection (RT-PCR analysis) of six of the most widely distributed honey bee viruses: deformed wing virus, sacbrood virus, acute bee paralysis virus, black queen cell virus, Kashmir bee virus, Israeli acute paralysis virus, and chronic bee paralysis virus. We successfully managed to establish only the deformed wing virus (DWV) and the sacbrood virus (SBV), with different distribution frequencies depending on the territory of the country. The phylogenetic analyses of Bulgarian isolates were performed with the most similar sequences available in molecular databases from other countries. Phylogenies of Bulgarian viral strains demonstrated genetically heterogeneous populations of DWV and relatively homogenous populations of SBV. In conclusion, the results obtained from the current study have shown that pollen is a valuable source for molecular detection of honey bee pathogens. This allows epidemiological monitoring of honey bee diseases at a regional and a national level.

Polyfloral honey samples from Bulgaria were subject to parallel analyses of their botanical origin and composition using traditional melissopalynology, DNA barcoding based on the plastid rbcL gene and NMR analysis. The obtained datasets were compared with each other to evaluate the information capacity of the applied experimental methods. The results from the melissopalynological and DNA-barcoding studies demonstrated a significantly higher resolution of the latter, revealing the presence of pollen from a total of 17 plant families, 21 plant genera and 5 plant species in comparison to pollen from only 7 plant families, 3 plant genera and 4 plant species identified by melissopalynology. The higher resolution of DNA barcoding allows a more detailed characterisation of the diet and foraging preferences of honey bees, including foraging on plant species growing in lower abundance in the area. The comparison of the quantitative data on floral honey composition for several plant genera and species reveals significant differences between the relative abundance of the pollen grains estimated by melissopalynological analysis and the relative abundance of rbcL clones in rbcL libraries determined after DNA barcoding. All three applied methods confirm the polyfloral botanical origin of the analysed samples and support routine NMR use for the assessment of the floral origin of honey.