Search Results (28)

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 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

Beekeepers use a variety of methods to control Varroa destructor (varroa). Chemical control relies heavily on flumethrin, amitraz, coumaphos, and tau-fluvalinate products. However, increasing colony losses in recent years have been linked to the development of resistance in varroa mites to these insecticides. Varroa mites develop mutations in the voltage-gated sodium channel (VGSC) that confer resistance to pyrethroids such as flumethrin. Specifically, researchers have identified substitutions of the leucine amino acid at VGSC L925 with isoleucine, methionine, or valine. This study investigated phenotypic and genotypic resistance to flumethrin in varroa populations in Muğla, Türkiye. LD₅₀ values (lethal dose for 50% mortality) were quantified, and PCR and sequencing were used to analyze the VGSC L925 gene region. The PCR results confirmed mutations in the target gene region in all samples. Sequencing revealed that 95% of the population carried homozygous resistant alleles, while 5% were heterozygous. At the VGSC L925 locus, leucine was replaced by isoleucine (91%), methionine (6%), and valine (3%). Phenotypic assays showed an average LD₅₀ value of 49.1 µg (range: 31–61.8 µg). Comparison of LD₅₀ between resistant and susceptible populations was not possible because no susceptible individuals were identified. Despite the resistance, mortality increased with escalating doses, suggesting that current protocols may be temporarily mitigating infestations. However, urgent dose adjustments and alternative control strategies are critical to prevent imminent colony collapse. Full article

Sixty commercial honey bee colonies were monitored over the course of one year with the goal of assessing potential correlations between measured colony strength and environmental stressors, including exposures to pesticides and pathogens. We developed a new method for assessing colony health by determining the fractional change in population of the four colonies on each pallet between peak population on 1 June and the last population assessment prior to winter on 1 October. This fractional change in population was evaluated as a function of pesticide load per pallet for each of the 37 pesticide chemicals detected, grouping pallets by beekeeper. The analysis of individual chemicals showed that both imidacloprid and cyprodinil were negatively correlated with colony health, while tau-fluvalinate and dinotefuran (at very low concentrations) were positively correlated, possibly because of effects on Varroa control. Exposure to groups of chemicals was also evaluated. Normalization of each chemical concentration to the maximum observed for that chemical provided an equal weighting for each chemical, even though their relative occurrence in the environment and their effective toxicities might differ. A total of 24 chemical groups whose members share a structural commonality, a functional commonality, or suspected synergistic actions were considered, demonstrating negative correlations between colony health and exposures to neonicotinoids as a group and neonicotinoids in combination with (1) methoxyfenozide (2) organophosphates, and (3) diflubenzuron. Analysis of several groups of fungicides applied to almonds during pollination also showed negative correlations with colony health. Full article

Aquatic products are good sources of essential nutrients, but the presence of pyrethroids (PYRs) as contaminants may pose risks to consumer health as the intricate matrices of PYRs usually obstruct chemical hazard detection. In this study, a gas chromatographic method was established and validated for simultaneously detecting residues of seven PYRs (cyhalothrin, permethrin, cyfluthrin, cypermethrin, tau-fluvalinate, fenvalerate, deltamethrin) in aquatic products. The aim of this method was to assess better the potential risks of pesticide residues in aquatic products. The PYRs in aquatic products were extracted with acetonitrile, purified with n-hexane saturated with acetonitrile, and cleaned up on a Cleanert^® Alumina N column. Statistical analysis and orthogonal array experimental design were used to optimize the key parameters. To validate the proposed method, commonly consumed aquatic products (such as carp, crucian carp, whiteleg shrimp, river crab, sea cucumber, and scallop) were obtained from local supermarkets in Shanghai. Satisfied linearity of the calibration curves was achieved in a matrix-matched standard solution, with a correlation coefficient (R²) larger than 0.995. The average recoveries at five fortification levels varied from 77.0% to 117.2%, with relative standard deviations (RSDs) below 11.1%. Concerning electron capture detection, the limits of detection (LOD) and limits of quantification (LOQ) were 2.0–5.0 µg/kg and 5.0–10.0 µg/kg, respectively. These results demonstrate the high stability and sensitivity of this method for simultaneously detecting PYRs in aquatic products, having great practicability and which can be popularized easily. Full article

In greenhouse production, grey mould caused by Botrytis cinerea Pers. is one of the most widespread and damaging diseases affecting medicinal cannabis (MC). Fungicide options to control this disease are extremely limited due to the regulations surrounding fungicides and chemical residues as the product end users are medical patients, often with compromised immune systems. Screening for alternative disease control options, such as biological and organic products, can be time-consuming and costly. Here, we optimise and validate a detached leaf assay as a quick and non-destructive method to evaluate interactions between plants and pathogens, allowing the assessment of potential pathogens’ infectivity and product efficacy. We tested eight industrial hemp varieties for susceptibility to B. cinerea infection. Using detached leaves from a susceptible variety, we screened a variety of chemical or organic products for efficacy in controlling the lesion development caused by B. cinerea. A consistent reduction in lesion growth was observed using treatments containing Tau-fluvalinate and Myclobutanil, as well as the softer chemical alternatives containing potassium salts. The performance of treatments was pH-dependent, emphasizing the importance of applying them at optimal pH levels to maximise their effectiveness. The detached leaf assay differentiated varietal susceptibility and was an effective method for screening treatment options for diseases caused by Botrytis. The results from the detached leaf assays gave comparable results to responses tested on whole plants. Full article

The invasive apricot aphid (Myzus mumecola Matsumura) is an important pest of apricot trees (Prunus armeniaca L.). In the presented study, laboratory bioassays using treated leaf disks of apricot were conducted to test the efficacy of twelve insecticides according to the maximum field dose. Additionally, dose-response curves were established for selected insecticides, and the effects on colony development were evaluated. Furthermore, a field trial was conducted to investigate the effectiveness of commonly used insecticides in apricot cultivation. The dose-response curves showed LC₅₀ values ranging from 0.08 mg/L for flupyradifurone, 0.15 mg/L for acetamiprid, 0.70 mg/L for etofenprox, 1.89 mg/L for sulfoxaflor, 2.64 mg/L for pirimicarb, 3.97 mg/L for deltamethrin, up to 6.79 mg/L for tau-fluvalinate. These aforementioned insecticides resulted in mortality rates ranging from 95 to 100% at the field dose. Azadirachtin, flonicamid, and pyrethrins showed mortality rates of 27 to 45%. Spirotetramat reduced the colony development and decreased the number of infested shoots by 86%. Spinosad, which is not recommended against aphids, showed minimal impact; reducing the number of exuviae in nymphs in the colony development bioassay. It can be concluded that the majority of the tested insecticides are effective against M. mumecola. Full article

The honey bee (Apis mellifera) faces a significant threat from Varroa destructor, causing the losses of millions of colonies worldwide. While synthetic acaricides are widely used to control Varroa infestations, excessive application has led to resistant strains and poses side effects on the host. Consequently, there is an urgent need for a new acaricide that is both effective and affordable, yet safe to use on bees. One potential source of these acaricides is essential oils (EOs) and their constituents. This study evaluated the acaricidal properties of four essential oils (Eucalyptus globulus, Rosemary officinalis, Trachyspermum ammi (Ethiopian and Indian varieties), their constituents and mixture of constituents against V. destructor through the complete exposure method. Our finding showed that a 1:1 mixture of thymol and carvacrol (4 h-LC₅₀ = 42 μg/mL), thymol (4 h-LC₅₀ = 71 μg/mL), and T. ammi oil (4 h-LC₅₀ = 81–98 μg/mL) were the most toxic test samples against V. destructor. Honey bee behavior and selectivity were also assessed with one additional EO Thymus schimperi, indicating that T. schimperi, T. ammi, and their components were selective and did not affect the learning and memory of bees. In conclusion, the thymol and carvacrol (1:1) mixture was shown to be a promising replacement for synthetic acaricides, being three times more toxic than a commercial acaricide, fluvalinate (4 h-LC₅₀ = 143 μg/mL). Full article

There is high demand for honey in Saudi Arabia, honey bees make a valuable contribution to agriculture and the economy, and therefore it is important to know levels of colony loss and potential reasons for losses. While there is much research into honey bee colony losses worldwide, little is known about colony losses in Saudi Arabia, management practices or beekeeping experience there. The aims of this work were to address this knowledge gap. Results of a survey of beekeepers in southwest Saudi Arabia conducted in summer 2018 are presented, including colony losses in five different seasons. Data collection involved face-to-face interviews, supplemented by an online survey, using a purpose-designed questionnaire. Responses were obtained from 109 beekeepers, all male, managing 135 to 1700 colonies, with 2 to 45 years of beekeeping experience. Most (73.1%) respondents mainly kept local hybrid bees, while 25.9% mainly kept Apis mellifera jemenitica. Honey yields per colony varied much more between beekeepers than between bee races. A high proportion (83.5%) of beekeepers reported losing colonies over the period studied. The reported colony loss rate was significantly higher in summer than in other seasons, but still low. The overall proportion of colonies lost was 11.4% in summer 2017 and was lowest in spring 2018 (6.6%). The main reported causes of loss were Varroa destructor and disease. Most beekeepers (88.0%) treated against the Varroa mite, although only one method was reported, tau-fluvalinate as Apistan strips, and only 41.7% used a screened bottom board. The results establish a benchmark for future beekeeper surveys in Saudi Arabia and other environmentally similar countries where colony losses are of interest in all seasons of the year. Informing and supporting Saudi beekeepers concerning Varroa monitoring and treatment and optimal hive management could result in fewer losses, higher honey yields, potential to market organic honey and a greater share of the domestic honey market. Full article

Pesticides can be found in beehives for several reasons, including contamination from surrounding crops or for their use by beekeepers, which poses a risk to bee ecosystems and consumers. Therefore, efficient and sensitive methods are needed for determining pesticide residues in bee products. In this study, a new analytical method has been developed and validated to determine seven acaricides (atrazine, chlorpyrifos, chlorfenvinphos, α-endosulfan, bromopropylate, coumaphos, and τ-fluvalinate) in bee pollen using gas chromatography coupled to mass spectrometry. After an optimization study, the best sample treatment was obtained when using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method employing an ethyl acetate and cyclohexane as the extractant mixture, and a mixture of salts for the clean-up step. A chromatographic analysis (<21 min) was performed in an Agilent DB-5MS column, and it was operated under programmed temperature conditions. The method was fully validated in terms of selectivity, limits of detection (0.2–3.1 µg kg⁻¹) and quantification (0.6–9.7 µg kg⁻¹), linearity, matrix effect (<20% in all cases), trueness (recoveries between 80% and 108%), and precision. Finally, the proposed method was applied to analyze commercial bee pollen samples, and some of the target pesticides (chlorfenvinphos, α-endosulfan, coumaphos, and τ-fluvalinate) were detected. Full article

Background: Bees encounter a plethora of environmental contaminants during nectar and pollen collection from plants. Consequently, after their entrance into the beehives, the transfer of numerous pollutants to apicultural products is inevitable. Methods: In this context, during the period of 2015–2020, 109 samples of honey, pollen, and beebread were sampled and analyzed for the determination of pesticides and their metabolites. More than 130 analytes were investigated in each sample by applying two validated multiresidue methods (HPLC-ESI-MS/MS and GC-MS/MS). Results: Until the end of 2020, 40 determinations were reported in honey, resulting in a 26% positive to at least one active substance. The concentrations of pesticides ranged from 1.3 ng/g to 785 ng/g honey. For seven active substances in honey and pollen, maximum residue limits (MRLs) exceedances were observed. Coumaphos, imidacloprid, acetamiprid, amitraz metabolites (DMF and DMPF), and tau-fluvalinate were the predominant compounds detected in honey, while several pyrethroids such as λ-cyhalothrin, cypermethrin, and cyfluthrin were also found. Pollen and beebread, as expected, accumulated a higher number of active substances and metabolites (32 in total), exhibiting almost double the number of detections. Conclusions: Although the above findings verify the occurrence of numerous pesticide and metabolite residues in both honey and pollen, the human risk assessment in the majority of the cases does not raise any concerns, and the same applies to bee risk assessment. Full article

Fluvalinate is a widely used insecticide for varroa mite control in apiculture. While most beekeepers have ignored the effects of low levels of fluvalinate on bees, this study aims to demonstrate its effects at very low concentrations. We first used fluvalinate doses ranging from 0.4 to 400 ng/larva to monitor the capping, pupation, and emergence rates of larval bees. Second, we used the honey bees’ proboscis extension reflex reaction to test the learning ability of adult bees that were exposed to fluvalinate doses from 0.004 to 4 ng/larva in the larval stage. The brood-capped rate of larvae decreased dramatically when the dose was increased to 40 ng/larva. Although no significant effect was observed on brood-capping, pupation, and eclosion rates with a dose of 4 ng/larva, we found that the olfactory associative behavior of adult bees was impaired when they were treated with sublethal doses from 0.004 to 4 ng/larva in the larval stage. These findings suggest that a sublethal dose of fluvalinate given to larvae affects the subsequent associative ability of adult honey bee workers. Thus, a very low dose may affect the survival conditions of the entire colony. Full article

Varroa destructor is considered one of the most devastating parasites of the honey bee, Apis mellifera, and a major problem for the beekeeping industry. Currently, the main method to control Varroa mites is the application of drugs that contain different acaricides as active ingredients. The pyrethroid tau-fluvalinate is one of the acaricides most widely used in beekeeping due to its efficacy and low toxicity to bees. However, the intensive and repetitive application of this compound produces a selective pressure that, when maintained over time, contributes to the emergence of resistant mites in the honey bee colonies, compromising the acaricidal treatments efficacy. Here we studied the presence of tau-fluvalinate residues in hives and the evolution of genetic resistance to this acaricide in Varroa mites from honey bee colonies that received no pyrethroid treatment in the previous four years. Our data revealed the widespread and persistent tau-fluvalinate contamination of beeswax and beebread in hives, an overall increase of the pyrethroid resistance allele frequency and a generalized excess of resistant mites relative to Hardy–Weinberg equilibrium expectations. These results suggest that tau-fluvalinate contamination in the hives may seriously compromise the efficacy of pyrethroid-based mite control methods. Full article

In this case report, we analyze the possible causes of the poor health status of a professional Apis mellifera iberiensis apiary located in Gajanejos (Guadalajara, Spain). Several factors that potentially favor colony collapse were identified, including Nosema ceranae infection, alone or in combination with other factors (e.g., BQCV and DWV infection), and the accumulation of acaricides commonly used to control Varroa destructor in the beebread (coumaphos and tau-fluvalinate). Based on the levels of residues, the average toxic unit estimated for the apiary suggests a possible increase in vulnerability to infection by N. ceranae due to the presence of high levels of acaricides and the unusual climatic conditions of the year of the collapse event. These data highlight the importance of evaluating these factors in future monitoring programs, as well as the need to adopt adequate preventive measures as part of national and international welfare programs aimed at guaranteeing the health and fitness of bees. Full article

Member states of the European Union are required to ensure the initiation of monitoring programs to verify honey bee exposure to pesticides, where and as appropriate. Based on 620 samples of dead honey bees—42 of pollen, 183 of honey and 32 of vegetables—we highlighted the presence, as analyzed by liquid and gas chromatography coupled with tandem mass spectrometric detection, of many active substances, mainly tau-fluvalinate, piperonyl butoxide, chlorpyrifos and chlorpyrifos-methyl, permethrin and imidacloprid. Among the active substances found in analyzed matrices linked to honey bee killing incidents, 38 belong to hazard classes I and II, as methiocarb, methomyl, chlorpyrifos, cypermethrin and permethrin, thus representing a potential risk for human health. We have shown that, at different times between 2015 and 2020, during implementation of the Italian national guidelines for managing reports of bee colony mortality or depopulation associated with pesticide use, pesticide pollution events occurred that could raise concern for human health. Competent authorities could, as part of a One Health approach, exploit the information provided by existing reporting programs on honey bees and their products, in view of the close correlation to human health, animal health and ecosystem health. Full article