Search Results (93)

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. Full article

Varroa destructor, an ectoparasitic mite of honey bees, is a major contributor to global colony declines. To manage infestations, beekeepers frequently apply both synthetic and organic miticides—sometimes in combination. While much attention has been given to foragers’ pesticide exposure, nurse bees are also at risk due to direct miticide contact and prolonged exposure to residuals in hive matrices. Despite this, little is known about the effects of sequential miticide applications on nurse bees. In this study, we evaluated the toxicities of single and pairwise consecutive applications of three synthetic miticides (fluvalinate, coumaphos, and amitraz) and two organic miticides (formic acid and oxalic acid) at field-realistic concentrations. Miticides were topically applied to nurse bees with 24 h between consecutive treatments. Synthetic miticides caused minimal mortality, while both organic miticides—especially formic acid—significantly reduced survivorship. Consecutive treatments generally produced mortality rates comparable to that of the corresponding organic miticide alone, indicating that observed toxicities were primarily driven by the organic agents. Notably, the fluvalinate–formic acid combination induced no significant adverse effects. These findings highlight the need for caution when using miticides in combination and support the development of safer application strategies to protect vulnerable in-hive bee populations.. Full article

Honey bees and other pollinators are key to functioning natural and managed ecosystems. However, their health is threatened by many factors, including pesticides. Spraying fungicides during flowering of fruit trees is widespread even though it directly exposes pollinators to these fungicides. Here, we report a series of experiments designed to understand how the combination of propiconazole and carbendazim, marketed in China as Chunmanchun^®, affects honey bee health. With an acute oral toxicity of 23.8 μg a.i./bee over 24 h in the laboratory, we considered the acute mortality risk from normal Chunmanchun^® applications as relatively low. However, our comprehensive studies revealed other diverse effects: Chunmanchun^® reduced memory after classic conditioning by approximately 25% and altered the activity of protective enzymes and the composition of the honey bees’ gut microbiota. Specifically, the genus Lactobacillus was decreased by ~13%, and Bartonella and Snodgrassella were increased by ~10% and ~7.5%, respectively. The gut metabolome was also disrupted in diverse ways, possibly as a functional consequence of the microbiome changes. Thus, we demonstrated numerous sublethal effects of the combination of propiconazole and carbendazim, which adds to the growing evidence that agrochemicals and fungicides in particular can harm pollinator health in subtle ways that are not captured in simple mortality assays. Full article

Honey bees are one of the most significant pollinators and contribute to the pollination of various crops. The honey bee, Apis mellifera (Linnaeus, 1758), has unique characteristics that could be successfully used to improve biomonitoring approaches in assessing environmental interactions. Three apiaries with different rates of honey bee colony losses were included in the study—Dimovtsi, Plovdiv, and Krasnovo, Bulgaria. Male individuals (immature and mature) were collected from five colonies for each of the three apiaries and studied for histopathological changes in the gonads. The results concerning the rate of honey bee colony losses in the studied apiaries from 2022 and 2023 showed honey bee losses in the tested colonies due to queen problems, which were reported for Plovdiv, as well as the death of honey bees or a reduction in their number to a few hundred bees in the colony. The chemical analysis showed the presence of different organic substances, such as Coumaphos, DEET (N, N-diethyl-M-toluamide), Fluvalinate, and Piperonyl-butoxide, in the alive and dead honey bee samples and those of food stocks (wax, pollen, and honey) within the hives. Among the sample types, those of the dead honey bees contained the greatest variety of pesticide residues, particularly in Plovdiv and Dimovtsi, reinforcing the link between pesticide exposure and honey bee mortality. The histopathological alterations were mainly associated with the thinning of the covering epithelium of the seminiferous tubules and the detachment of the basement membrane of the seminiferous tubules. The more severe histopathological lesion, necrosis, was observed in a higher degree of expression in the drones from Plovdiv, indicating a higher pollution level in this region. Full article

In Argentina, various studies have reported the detection of multiple viruses in honey-producing and queen-rearing apiaries, with Aparavirus apisacutum, the causal agent of acute bee paralysis (ABP), demonstrating a particularly high prevalence. The potential of RNA interference (RNAi) as a strategy to control honey bee viruses has been explored, with initial findings indicating that RNAi could aid in mitigating the economic losses associated with viral infections. This study aimed to evaluate the effect of RNAi technology mediated by double-stranded RNA (dsRNA) on the dynamics of ABPV infection in adult honey bees. Fragments of the ABPV replicase and VP1 genes were used as templates for dsRNA synthesis via in vitro transcription. A gene silencing experiment was conducted through oral administration using five treatments: control, specific dsRNA + Virus, Virus alone, specific dsRNA alone, and non-specific dsRNA + virus. Bee survival was recorded over 10 days for all treatments, and samples were subsequently processed for viral quantification using quantitative real-time PCR. The oral administration of specific dsRNA reduced the viral replication curve, decreased the average viral loads and increased bee survival. This is the first report demonstrating the reduction in ABPV infection in adult honey bees through post-transcriptional gene silencing achieved via oral administration of dsRNA. Full article

Fungal diseases of agricultural crops cause severe economic losses to the growers. For the control of these diseases, azoxystrobin is one of the recommended fungicides. This fungicide is systemic in action and is expected to reach the floral part of the treated crop and its residue in the pollen and nectar, the natural food sources of honey bees, which could be collected and fed on by honey bees, thus affecting their health. The purpose of this study was to determine the physiological and chemical changes caused by this fungicide in honey bee workers (Apis mellifera L). Workers of this honey bee at 1, 8, and 21 days old were treated with 125, 167, and 250 mg/L concentrations of azoxystrobin for seven days; their survival rates, activities of carboxylesterase (CarE), glutathione S-transferases (GSTs), cytochrome P450 enzyme (CYP450), catalase (CAT), and superoxide dismutase (SOD) enzymes, and the expression levels of immune (Aba, Api, Def1, and Hym) and nutrition genes (Ilp1, Ilp2, and Vg) were detected. Our findings revealed that azoxystrobin affected the survival of workers, particularly 1- and 21-day-old workers, who responded to azoxystrobin stress with increased activities of detoxification and protective enzymes, which might have physiological costs. Additionally, azoxystrobin affected the expression of immune and nutrition genes, with a decreased expression trend in 21-day-old workers compared to the 1- and 8-day-old workers, leading to reduced resistance to external stressors and increased mortality rates. These findings provide important insights into the adverse effects of azoxystrobin on workers of different ages and emphasize the potential risks of this chemical to colony stability and individual health. This study recommends an urgent ban on such a harmful fungicide being used for fungi control in agriculture, especially during plant flowering. Full article

In recent decades, bee poisoning due to pesticides and agrochemicals has increased, posing significant challenges to honey bee health and contributing to the so-called “Colony Collapse Disorder” (CCD). Poor knowledge about the level of exposure of bee colonies to pesticides and agrochemicals, whether from the environment or beekeeping management practices, is a major limiting factor in preventing these diseases. Collaboration among different stakeholders, such as beekeeping associations, local veterinary authorities, and researchers, is essential to create monitoring programs that can collect these data and enable the prompt implementation of surveillance and preventive actions to address potential bee colony poisoning incidents caused by these contaminants. The present study describes the results obtained through a collaborative initiative that was implemented for monitoring and preventing pesticide-induced bee poisonings in a territory of northern Italy where the exposure of honey bee colonies to different types of pesticides and agrochemicals may occur. Four sentinel apiaries were selected based on possible sources of pollution throughout the territory. Pollen samples were collected at different times during the years 2021–2022 and analyzed for pesticides using gas and liquid chromatography tandem quadrupole mass spectrometry (GC-MS/MS and LC-MS/MS) techniques. The findings showed the presence of a number of pesticides, such as pyrethroids, permethrin, cypermethrin, amitraz, and pendimethalin, at varying concentrations. Acute bee mortality was observed in a field case related to pyrethroid exposure in 2022, in an urban area. These results confirm the need for timely interventions, improved sampling methods, and continuous monitoring to safeguard bee populations. Collaboration with local beekeepers and public authorities is thus essential in addressing pesticide use and bee health challenges, fostering efficient communication and training efforts to support sustainable beekeeping. Full article

The impact of agrochemicals on pollinators, especially honey bees, has drawn significant attention due to its critical implications for worldwide food stability and ecosystems. Given the potential threat of insecticides to honey bees, bees may encounter multiple insecticides simultaneously during foraging. This study investigated the toxic effect of an insecticide mixture (IM) containing acetamiprid (neonicotinoid) and deltamethrin (pyrethroid) on the survival and cognitive appetitive performance of Apis mellifera jemenitica, a vital native pollinator in arid regions of Saudi Arabia. The lethal concentration (LC₅₀) was determined by assessing bees’ mortality rates following exposure to IM through topical and oral routes. Significant bee mortality occurred at 4–48 h post treatment with IM through both exposure routes, showing a trend of increased mortality with higher IM concentrations compared to the control bees. Throughout all tested times, topical exposure proved relatively more effective, resulting in significantly greater bee mortality compared to oral exposure to IM. Food intake declined progressively with rising IM concentrations during oral exposure. The LC₅₀ values of IM at 24 h after treatment were 12.24 ppm for topical and 10.45 ppm for oral exposure. The corresponding LC₁₀, LC₂₀, and LC₃₀ values were 3.75 ppm, 5.63 ppm, and 7.54 ppm for topical exposure and 2.45 ppm, 4.04 ppm, and 5.78 ppm for oral exposure, respectively. The combination index (CI) revealed a synergistic effect (0.43) for topical exposure and antagonistic effects (1.43) for oral exposure, highlighting differential toxicity dynamics. IM exposure significantly impaired cognitive acquisition and memory reinforcement in honey bees, as demonstrated through behavioral assays, indicating potential neurotoxic effects. Learning and memory formation significantly declined at 2, 12, and 24 h after exposure to sublethal concentrations of IM through both topical and oral routes. Thus, evaluating the interactive impact of multiple pesticides on bees’ health and cognitive function is essential, particularly in regions where diverse agrochemicals are routinely utilized. Full article

The honey bee (Apis mellifera) is the most widely managed pollinator and is vital for crop fertilization. Recently, bee colonies have been suffering high mortality rates, exacerbated by factors such as land-use changes and the use of pesticides. Our work aimed to explore the residues of pesticides in honey-bee-collected pollen and how this contamination was affected by seasonality and the landscape composition. We selected six apiaries from different landscapes in Latvia, and pollen samples were collected during the flowering season (2023). We analyzed 39 samples and found 21 pesticide residues (mainly fungicides) with a frequency of 93 occurrences where the values were above the limit of quantification. The most frequently encountered substances were acetamiprid, boscalid, fluopyram, and prothioconazole. However, the highest concentrations were for dimoxystrobin (44 µg kg⁻¹), acetamiprid (37 µg kg⁻¹), azoxystrobin (27 µg kg⁻¹), prothioconazole (25 µg kg⁻¹), and boscalid (15 µg kg⁻¹). We then calculated the Pollen Hazard Quotient (PHQ) for each pollen sample. No sample had a PHQ value above the critical value of 50. The highest contamination level was observed in the first half of the vegetation season (the end of May and the beginning of June), but later, it significantly decreased. We did not find any significant influence of landscape composition on pesticide pollution. Full article

Global climate change, environmental pollution, and frequent pesticide use severely reduce bee populations, greatly challenging beekeeping. Pesticides such as deltamethrin, a pyrethroid insecticide commonly used to control mosquitoes, can kill individual bees and entire colonies, depending on the exposure. Due to mosquito resistance to pyrethroid insecticides, components that enhance their effect are commonly used. This study explores the potential of Agaricus bisporus mushroom extract in mitigating oxidative stress in bees triggered by pesticides and Nosema ceranae infection. Our findings indicate that A. bisporus extract significantly reduced mortality rates of bees and spore counts of N. ceranae. Furthermore, the extract demonstrated antioxidant properties that lower enzyme activity related to oxidative stress (CAT, SOD, and GST) and MDA concentration, which is linked to lipid peroxidation. These results indicate that natural extracts like A. bisporus can aid bee health by mitigating the effects of pesticides and pathogens on honey bees, thus improving biodiversity. Full article

Humans and bees share millennia of history that have resulted in ever-increasing connection and interdependence. Thus, today, it is impossible to ignore the influence of humans on bees, particularly regarding the decrease in their numbers due to environmental contamination. Although they do not cause immediate mortality, heavy and toxic metals, along with dangers such as bee diseases, pesticides, habitat destruction, and climate change, threaten the number of bees and should not be ignored. Honeybees, their colonies, and their products are recognized as accumulators of metals and biological indicators of the presence of these metals in all environmental components. This study is an overview of prominent research from the past three decades on heavy and toxic metal levels in honeybees (Apis mellifera L.), honey, wax, and pollen. This research compares metals such as Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn in natural environments and in an environment where anthropogenic pressure manifests. The presented studies represent a range of research using analytical methods to determine the presence of heavy and toxic metals in different segments of bees and their products, linking these findings with the state of the environment. It has been repeatedly established that if heavy and toxic metals are present in higher concentrations in components of the environment that are under anthropogenic pressure, then their concentrations in bees, honey, and wax will also be higher. By summarizing this research in one place, this study can provide guidelines for future scientific work on this subject, promoting sustainable development through safe beekeeping and healthy bees. Full article

Environment, forage quality, management practices, pathogens, and pesticides influence honeybee responses to stressors. This study proposes an innovative approach to assess colony health and performance using molecular diagnostic tools by correlating hemolymph proteins with common measures of colony strength, prevalent honeybee pathogens (Varroa destructor and Nosema spp.), and essential trace elements (iron, zinc and copper). Colonies were selected from four apiaries located in different environmental and foraging conditions in the province of Bologna (Italy). Hemolymph samples were taken from June to October 2019. The Varroa infestation of the colonies was estimated by assessing the natural mortality of the mites, while the bees were tested for Nosema spp. spores using a microscopic method. Hemolymph proteins were quantified and separated using SDS-PAGE, and colony performance was assessed by determining adult bees, total brood, honey, and pollen reserves. The biomarkers measured proved to be useful for monitoring changes in performance and trophic conditions during summer and early autumn. Significant correlations were found between hemolymph proteins and colony performance measures. A positive correlation between pollen reserves, vitellogenin, and hexamerin 70a highlights the importance of these proteins for successful overwintering. In October, Varroa infestation was negatively correlated with total proteins, vitellogenin, apolipophorin II, transferrin, and hexamerin 70a, with negative implications for overwintering; furthermore, Varroa infestation was also negatively correlated with iron content, potentially affecting iron homeostasis. Full article

The honey bee, a significant crop pollinator, encounters pesticides through various routes of exposure during foraging and flower visitation. Considering the potential threat of pesticide poisoning, the indigenous Saudi bee Apis mellifera jemenitica is susceptible to the risks associated with acetamiprid, a neonicotinoid insecticide. This study investigates the acetamiprid-induced effects on the survival, olfactory learning, and memory formation of A. m. jemenitica through two exposure routes: topical application and oral ingestion. Field-realistic and serially diluted concentrations (100, 50, 25, and 10 ppm) of acetamiprid led to notable mortality at 4, 12, 24, and 48 h after treatment, with peak mortality observed at 24 h and 48 h for both exposure routes. Bee mortality was concentration-dependent, increasing with the rising concentration of acetamiprid at the tested time intervals. Food consumption following oral exposure exhibited a concentration-dependent pattern, steadily decreasing with increasing concentrations of acetamiprid. Oral exposure resulted in a substantially higher cumulative mortality (55%) compared to topical exposure (15%), indicating a significant disparity in bee mortality between the two exposure routes. The 24 h post-treatment LC₅₀ values for acetamiprid were 160.33 and 12.76 ppm for topical application and oral ingestion, respectively. The sublethal concentrations (LC₁₀, LC₂₀, and LC₃₀) of acetamiprid were 15.23, 34.18, and 61.20 ppm, respectively, following topical exposure, and 2.85, 4.77, and 6.91 ppm, respectively, following oral exposure. The sublethal concentrations of acetamiprid significantly decreased learning during the 2nd–3rd conditioning trials and impaired memory formation at 2, 12, and 24 h following both topical and oral exposure routes, compared to the control bees. Notably, the sublethal concentrations were equally effective in impairing bee learning and memory. Taken together, acetamiprid exposure adversely affected bee survival, hindered learning, and impaired the memory retention of learned tasks. Full article

Honey bees (Apis mellifera) play a crucial role in agriculture through their pollination activities. However, they have faced significant health challenges over the past decades that can limit colony performance and even lead to collapse. A primary culprit is the parasitic mite Varroa destructor, known for transmitting harmful bee viruses. Among these viruses is deformed wing virus (DWV), which impacts bee pupae during their development, resulting in either pupal demise or in the emergence of crippled adult bees. In this study, we focused on DWV master variant B. DWV-B prevalence has risen sharply in recent decades and appears to be outcompeting variant A of DWV. We generated a molecular clone of a typical DWV-B strain to compare it with our established DWV-A clone, examining RNA replication, protein expression, and virulence. Initially, we analyzed the genome using RACE-PCR and RT-PCR techniques. Subsequently, we conducted full-genome RT-PCR and inserted the complete viral cDNA into a bacterial plasmid backbone. Phylogenetic comparisons with available full-length sequences were performed, followed by functional analyses using a live bee pupae model. Upon the transfection of in vitro-transcribed RNA, bee pupae exhibited symptoms of DWV infection, with detectable viral protein expression and stable RNA replication observed in subsequent virus passages. The DWV-B clone displayed a lower virulence compared to the DWV-A clone after the transfection of synthetic RNA, as evidenced by a reduced pupal mortality rate of only 20% compared to 80% in the case of DWV-A and a lack of malformations in 50% of the emerging bees. Comparable results were observed in experiments with low infection doses of the passaged virus clones. In these tests, 90% of bees infected with DWV-B showed no clinical symptoms, while 100% of pupae infected with DWV-A died. However, at high infection doses, both DWV-A and DWV-B caused mortality rates exceeding 90%. Taken together, we have generated an authentic virus clone of DWV-B and characterized it in animal experiments. Full article

Microsporidiosis, which is caused by the pathogen Vairimorpha ceranae, is a prevalent disease in the honey bee (Apis mellifera) and might lead to significant adult honey bee mortality. In this study, we conducted an annual survey of the mature spore load of V. ceranae in the guts of nurse bees and forager bees in the apiary of National Chung Hsing University (NCHU) in Taiwan. The results indicated that, on average, honey bees hosted approximately 2.13 × 10⁶ mature spore counts (MSCs)/bee in their guts throughout the entire year. The highest number of MSCs was 6.28 × 10⁶ MSCs/bee, which occurred in April 2020, and the lowest number of MSCs was 5.08 × 10⁵ MSCs/bee, which occurred in November 2020. Furthermore, the guts of forager bees had significantly higher (>58%) MSCs than those of nurse bees. To evaluate the potential of the probiotic to treat microsporidiosis, the lactic acid bacterium Leuconostoc mesenteroides TBE-8 was applied to honey bee colonies. A significant reduction (>53%) in MSCs following probiotic treatment was observed, indicating the potential of probiotic treatment for managing microsporidiosis. This research provided information on V. ceranae MSCs in the honey bee gut at NCHU in Taiwan and the MSCs’ correlation with the annual season. Furthermore, a potential probiotic treatment for microsporidiosis was assessed for future management. Full article