Bee Mortality Research Articles

Trap-Nesting Hymenoptera and Their Network with Parasites in Recovered Riparian Forests Brazil.

Different aspects of human activities can cause environmental change that endanger species persistence, alter species distributions, and lead to changes in antagonistic and mutualistic interactions, whereas deforestation and flooding of riparian forest results in landscapes consisting of patchily distributed riparian forest fragments in a matrix of pastures, plantations, and urban areas. Therefore, we assessed the richness, abundance, and trophic interactions of trap-nesting Hymenoptera and their parasites at four patches of restored riparian forest and at one reference natural fragment, of different sizes and ages, located at the Volta Grande Reservoir, in Minas Gerais and São Paulo states to answer the following questions: (1) Does the richness and abundance of cavity-nesting bees and wasps differ in riparian forest fragments according to the seasonal periods? (2) Does the composition of cavity-nesting bees and wasps vary among restoration and reference sites and between climate seasons (wet and dry)? (3) How do the degrees of specialization of the parasites vary among the patches of forest? We recorded 12 species of wasps, eight of bees, and nine species of parasites. Areas with longer time since restoration (reference site) showed higher species richness. However, the abundance was higher in most recent areas. The composition of bee and wasp assembly has not significantly changed between the climate seasons, although it is different between sampling areas. The richness and abundance were higher in warmer and rainy periods. The rate of bee and wasp mortality was high. The degree of specialization of parasites varies among sampling units, and the network of host-parasite interaction has a modular configuration with generalists and specialists. We concluded that the restored areas with more complex habitat could provide better conditions for the reestablishment of ecological interactions among these insects, the local flora, and other invertebrates, which together contribute to the success of the restored environments.

Limited impacts of truck-based ultra-low-volume applications of mosquito adulticides on mortality in honey bees (Apis mellifera).

Adulticides applied against mosquitoes can reduce vector populations during times of high arbovirus transmission. However, impacts of these insecticides on pollinators and other non-target organisms are of concern to mosquito control professionals, beekeepers and others. We evaluated mortality of Culex quinquefasciatus and Apis mellifera when caged insects were exposed to low and high label rates of four common adulticides (Aqua-Pursuit™ [permethrin], Duet® [prallethrin + sumithrin], Fyfanon® [malathion] and Scourge® [resmethrin]) at six distances up to 91.4 m from a truck-mounted ultra-low-volume sprayer. Honey bee mortality was both absolutely low (61 m had limited impacts on honey bee mortality while providing effective mosquito control.

Spring mortality in honey bees in northeastern Italy: detection of pesticides and viruses in dead honey bees and other matrices

In spring there is often a rise in honey bee mortality incidents. The aim of this study was to investigate the potential correlation, in the reported incidents, between exposure to pesticide treatments and virus infections. Here we summarize the situation in northeastern Italy during spring 2014, evaluated by monitoring 150 active ingredients and three honey bee viruses in dead honey bees and other matrices. At least one active ingredient was found in 72.2% of the 79 dead honey bee samples, with the most abundant (59.4%) being insecticides, mainly belonging to the class of neonicotinoids (41.8%), followed by fungicides (40.6%). Imidacloprid, chlorpyrifos, tau-fluvalinate, and cyprodinil were the most frequently detected active ingredients. Multiple virus infections were monitored, revealing a high prevalence of chronic bee paralysis virus (CBPV) and deformed wing virus (DWV), detected in all samples except one. 71 and 37% of the CBPV- and DWV positive samples, respectively, showed a high number of viral copies per bee (>107). This work emphasizes the possible relationship between spring mortality in honey bees and pesticide treatments. Honey bee viruses could synergistically exacerbate the negative impact of pesticides on honey bee health, endangering the survival of colonies.

Performance of honey bee colonies under a long-lasting dietary exposure to sublethal concentrations of the neonicotinoid insecticide thiacloprid.

BACKGROUNDSubstantial honey bee colony losses have occurred periodically in the last decades. The drivers for these losses are not fully understood. The influence of pests and pathogens are beyond dispute, but in addition, chronic exposure to sublethal concentrations of pesticides has been suggested to affect the performance of honey bee colonies. This study aims to elucidate the potential effects of a chronic exposure to sublethal concentrations (one realistic worst‐case concentration) of the neonicotinoid thiacloprid to honey bee colonies in a three year replicated colony feeding study.RESULTSThiacloprid did not significantly affect the colony strength. No differences between treatment and control were observed for the mortality of bees, the infestation with the parasitic mite Varroa destructor and the infection levels of viruses. No colony losses occurred during the overwintering seasons. Furthermore, thiacloprid did not influence the constitutive expression of the immunity‐related hymenoptaecin gene. However, upregulation of hymenoptaecin expression as a response to bacterial challenge was less pronounced in exposed bees than in control bees.CONCLUSIONUnder field conditions, bee colonies are not adversely affected by a long‐lasting exposure to sublethal concentrations of thiacloprid. No indications were found that field‐realistic and higher doses exerted a biologically significant effect on colony performance. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Toksisitas beberapa jenis fungisida komersial pada serangga penyerbuk, Trigona (Tetragonula) laeviceps Smith

Fungicide is one of the common pesticide applies in agriculture. Even though fungicide is specifically designed to prevent growth of fungi, some studies reported neurotoxic effects of fungicide to some tested animals. Therefore there are concerns about the possible determintal effects of fungicide to beneficial non target organisms, like pollinating insects. This study was conducted to determine the toxicity of commercial fungicide to pollinator, Trigona ( Tetrgonula ) laeviceps Smith, by determining the LD 50 and hazard quotient (HQ). The fungicides tested were triazole (tridimefon and difenoconazole), propamorcab (propamocarb HCl), and dithiocarbamate (mancozeb and propineb). Forager bees were collected and anasthesized by exposing the bees to low temperature (-10 o C) for 1 min. About 1 µl of tiadimefon (6,25; 12,5; 25; 37,25; 50 µg/bee), difenoconazole (1,25; 2,5; 5; 6,25; 12,5; 25 µg/bee), propamocarb HCl (72.,25; 144,5; 216,6; 361,25; 433,5 µg/bee), mancozeb (1,6; 3,2; 4,8; 6,4; 8 µg/bee), and propineb (0.9; 1.8; 2.7; 6; 8.4; 16.8; 25.2 µg/bee) were applied using topical application on dorsal area of bees. Ten bees were used for each concentration and replicated 3 times. Mortality of bees was recorded for 48 hours. Results showed that LD 50 and HQ for each tested fungicide were as follow: triadimefon LD 50 13.43 ±1.78 µg/bee, HQ = 18.62; difenoconazole LD 50 9.25 ± 1.21 µg/bee, HQ = 27.03; propamocarb HCl LD 50 270.45 ± 19.48 µg/bee, HQ = 14.34; mancozeb LD 50 3.75±0.47 µg/bee, HQ = 512; and propineb LD 50 9.71 ±2.20 µg/bee, HQ = 144.18. Among all 5 tested fungicide, two fungicide, mancozeb and propineb, has intermediate level of toxicity to foragers of T. laeviceps and could produce determintal effect to colony.

Distribution of RNA-containing bee viruses in honey bee (Apis mellifera) in several regions of Russia

In several regions of Russia, broad distribution of RNA-containing bee viruses was found at apiaries of honey bee Apis mellifera using RT-PCR. Detected RNA-containing bee viruses are transferred simultaneously with invasion of mite Varroa destructor and lead to mass bee mortality that results in economic losses in bee breeding. In samples of Varroa destructor, bee viruses DWV and ABPV were found. High degree of RNA-containing virus (BQCV, DWV SBV, ABPV, CBPV and KBV) infection was revealed: in the average, at least 50% for bee families with mite infection. In the bee families studied in this work, mixed infection with 2-6 viruses simultaneously was detected. Amplified fragments of viruses BQCV, DWV and SBV obtained using RT-PCR were sequenced and registered in Genbank.

Os apicultores da Beira Alta: percepções e comportamentos face ao risco do uso de pesticidas

The collapsing of bee colonies at global level, is a concern for beekeepers and for the scientific and technical communities. Several studies suggest that the use of pesticides is one of the causes for the bee mortality that is occurring in the United States and in several European countries, including Portugal. In Portugal, the assessment of the risks posed by pesticides to the beekeeping practice and the beekeepers, to the bee populations and the quality and safety of the honey and of other products of the hive is difficult because of its extensive character. Thus, the aim of this work was to characterize beekeepers from the Beira Alta region and their practices as well as the risk associated with agricultural practices implemented in the area of ​​influence of their apiaries. A geographic information system of the beekeepers (members of the Beira Alta Beekeepers Association) and their apiaries in Viseu region was designed and used to establish a risk scale based on the ecosystems mosaic on a 500m radius around each apiary. In addition, a data survey was applied to a sample of 15 representative beekeepers, to collect information on the beekeeper, apiary and beekeeping practices, and to assess the potential risks due to pesticide use associated with farming in the surroundings of the apiaries. It was estimated that in 70% of the beehives the risks to bees due to the use of pesticides are reduced, since they are in predominantly forest areas. However, about 20% of beehives fall into high risk areas, since the surroundings are dominated by annual crops, vineyards and orchards in which the risk of pesticide use is high.

New evidence of pseudo scorpion Ellingsenius indicus Chamberlin as predator of Indian honey bee Apis cerana F.

Traditional wall hives in the two villages of Kullu district, Himachal Pradesh namely Bhindi and Daula, recorded a heavy mortality of Indian honey bees (Apis cerana) due to the attack of an arachnid predator identified as a pseudo scorpion Ellingsenius indicus. It was observed that the pseudo scorpions did not venture the comb full of bees but attacked only those bees which were either moving in isolation or in groups of 1-3 or those coming and going to the hive entrance for foraging. There was a complete loss of bees in three colonies whereas in other two colonies more than 70% of worker mortality was noticed. The observations recorded from the wall hives as well as from the laboratory experiments, revealed that generally 1-3 pseudo scorpions (E. indicus) caught hold of the single bee preferably from its legs and sometimes from its wings and did not leave the bee from their grip so long it was not dead.

Laboratory cage studies on the efficacy of some medicinal plant essential oils for controlling varroosis in Apis mellifera (Hym.: Apidae)

Varroosis is a disease of Apis mellifera L. caused by the mite Varroa destructor Anderson and Trueman. Essential oils and their chemical constituents offer a safe alternative to synthetic acaricides for the control of this mite in bee hives. The present study was conducted to evaluate anti-parasitic activity of essential oils from Thymus kotschyanus Bioss & Hohen., Mentha longifolia L., Eucalyptus camaldulensis Dehnh., and Ferula gummosa L. at concentrations of 1, 2.5, 4, and 5.5 µl/l air for 5 and 10 h. Findings indicated that mite mortality increased as oils concentration and exposure time increased. T. kotschyanus oil at 5.5 µl/l air caused a mite mortality rate of 54.4% and 84.43% after 5 and 10 h fumigation, respectively. At the same concentration and exposure time, the honey bee mortality was 0% and 7.2%, respectively. Application of M. longifolia and E. camaldulensis oils at 5.5 µl/l air resulted in 65.53% and 71.06% mortality in Varroa mites and 10.13% and 12% mortality in honey bees after 10 h exposure. Despite moderate acaricidal activity of F. gummosa oil against Varroa mite (49.69%), it was highly toxic to honey bee (30%). Also, GC/MS analysis of the oils showed that carvacrol (47.99%) and thymol (30.61%) in T. kotschyanus oil, piperitenone (36.86%), piperitenone oxide (27.53%),Cispiperitone epoxide (22.21%), and pulegone (8.38%) in M. longifoliaoil, 1,8-cineol (74.7%) and α-pinene (8.35%) in E. camaldulensis oil, and β-pinene (87.29%) in F. gummosa oil were the main chemical constituents. Collectively, our results led to a conclusion that T. kotschyanus, M. longifolia, and E. camaldulensis oils have enough potential to play an important role in integrated control programs of varroosis in apiaries.

Effect of dengue mosquito control insecticide thermal fogging on non-target insects

AbstractDengue vector control programmes are mainly focused on insecticide fogging/space spraying to control adultAedesmosquito vector populations. Due to the diurnal habit of the vectors, spraying is routinely conducted during the day when many other insect species are also active. This study reports the simultaneous effect of fogging on non-target insects by direct counting of knockdown in the insect population. Eight fogging treatments were conducted in two sites in Kurunegala District of Sri Lanka. Pesguard insecticide was sprayed in each treatment for 8 minutes according to the standard methodology and the ‘knockdown insects’ were collected on randomly spread polyethythene sheets (10 m2). A total of 3884 insects (24.3 insects per treatment per m2) belonging to 12 orders were collected and 12.44% of them recovered during a 24-hr recovery period. Diptera was the most affected insect order (36%) followed by Collembola (30%) and Thysanoptera (17%). Out of the 31 mosquitoes (<1%) collected, only two (<0.1%) belonged to the genusAedes. Body length of 93% of the affected insects ranged from 0.35 mm to 1.8 mm. Positive controls using the WHO standard cage bioassays with the mosquitoAe. albopictus(n = 417) and the stingless beeTrigona iridipennis(n = 122) showed 100% initial knockdown, and 83.5% mosquito and 93.5% bee mortalities after the recovery period. The study shows that insecticide fogging does have a severe effect on non-target insects such as pollinators; therefore, fogging operations should be done in a controlled manner and indiscriminate fogging should be avoided.

Suitability of Starch Syrups for Winter Feeding of Honeybee Colonies

Abstract Three different starch syrups available on the Polish market for winter feeding of bees were evaluated for two consecutive beekeeping seasons (2012/2013 and 2013/2014). Sugar syrup and inverted sucrose syrup were used as the control. Winter feeding was conducted at two times: earlier and later in the season. After supplementation of winter feeding was stopped, we measured colony strength (number of combs covered by bees) and brood area. After overwintering (spring 2013 and 2014), we estimated the influence of these foods on: bee mortality during overwintering (number of dead bees in winter debris), food consumption, colony strength and brood area in spring (two measurements in three-week intervals), development dynamics and honey yield from spring flow. An analysis of the results for the parameters assessed before overwintering, after its end and during spring development did not show significant differences between bee colonies fed with different types of food. No relevant difficulties concerning food crystallisation were encountered. The analysed syrups turned out to be as suitable for winter feeding of bees as sugar and inverted sucrose syrups.

Azadirachtin-induced antifeeding in Neotropical stingless bees

The ongoing debate regarding the role of pesticides in the global decline of bee populations is increasing the demand for use of biopesticides, compounds generally believed to be less harmful to pollinators. However, there is lack of evidence justifying such perceptions, particularly regarding native pollinator species like Neotropical stingless bees. Here, we investigated whether azadirachtin, a neem-based biopesticide, causes significant lethal and sublethal effects on adult workers of the Neotropical stingless bee species Melipona quadrifasciata and Partamona helleri. Susceptibility to azadirachtin varied with several factors, including the route of exposure, the concentration of the biopesticide, and the bee species. We found that although azadirachtin did not affect worker bee mortality, flight, or respiration rate, it did, however, induce a significant antifeeding effect on the stingless bee species.

Israeli acute paralysis virus associated paralysis symptoms, viral tissue distribution and Dicer-2 induction in bumblebee workers (Bombus terrestris).

Although it is known that Israeli acute paralysis virus (IAPV) can cause bee mortality, the symptoms of paralysis and the distribution of the virus in different body tissues and their potential to respond with an increase of the siRNA antiviral immune system have not been studied. In this project we worked with Bombus terrestris, which is one of the most numerous bumblebee species in Europe and an important pollinator for wild flowers and many crops in agriculture. Besides the classic symptoms of paralysis and trembling prior to death, we report a new IAPV-related symptom, crippled/immobilized forelegs. Reverse-transcriptase quantitative PCR showed that IAPV accumulates in different body tissues (midgut, fat body, brain and ovary). The highest levels of IAPV were observed in the fat body. With fluorescence in situ hybridization (FISH) we detected IAPV in the Kenyon cells of mushroom bodies and neuropils from both antennal and optic lobes of the brain in IAPV-infected workers. Finally, we observed an induction of Dicer-2, a core gene of the RNAi antiviral immune response, in the IAPV-infected tissues of B. terrestris workers. According to our results, tissue tropism and the induction strength of Dicer-2 could not be correlated with virus-related paralysis symptoms.

Wintering of honey bee colonies in cylindrical nest cavities versus oblong box-hives in a North European climate

We compared the efficacy of wintering honey bee colonies in wooden cylinders and wooden oblong box hives. Five colonies in “cylinders” and three colonies in “box-hives” were compared over two winters. The cylinders were 450 mm high with an internal diameter of 280 mm. The oblong box hives were Estonian standard one-box long hives with a frame size of 414 × 277 mm. Eight vertical rows of thermistors were fixed along the inner walls of both cylinders and hives and temperatures were measured at about weekly intervals. Food consumption and bee mortality of colonies were also assessed. In the cylinders, the winter clusters remained close to their front walls and away from the back wall, especially in cold weather. It was considerably warmer by the inner walls of the cylinders than in the hives, especially in the lower part. The surface of warm area decreased with cold weather and increased at around 0 °C indicating contraction and expansion of the cluster, respectively. In the second half of winter, there was a larger warm area in the cylinders than in the hives indicating that the clusters touched the walls of the cylinder more, thereby reducing heat losses further. Considerably, less food (13.5%) was consumed in the cylinders than in the hives. The numbers of dead bees on the floor was significantly lower in the cylinders than in the hives, but total bee mortality (dead bees on the floor + bees flown out in winter) differed little between cylinders and hives.

Honey Bee Inhibitory Signaling Is Tuned to Threat Severity and Can Act as a Colony Alarm Signal.

Alarm communication is a key adaptation that helps social groups resist predation and rally defenses. In Asia, the world’s largest hornet, Vespa mandarinia, and the smaller hornet, Vespa velutina, prey upon foragers and nests of the Asian honey bee, Apis cerana. We attacked foragers and colony nest entrances with these predators and provide the first evidence, in social insects, of an alarm signal that encodes graded danger and attack context. We show that, like Apis mellifera, A. cerana possesses a vibrational “stop signal,” which can be triggered by predator attacks upon foragers and inhibits waggle dancing. Large hornet attacks were more dangerous and resulted in higher bee mortality. Per attack at the colony level, large hornets elicited more stop signals than small hornets. Unexpectedly, stop signals elicited by large hornets (SS large hornet) had a significantly higher vibrational fundamental frequency than those elicited by small hornets (SS small hornet) and were more effective at inhibiting waggle dancing. Stop signals resulting from attacks upon the nest entrance (SS nest) were produced by foragers and guards and were significantly longer in pulse duration than stop signals elicited by attacks upon foragers (SS forager). Unlike SS forager, SS nest were targeted at dancing and non-dancing foragers and had the common effect, tuned to hornet threat level, of inhibiting bee departures from the safe interior of the nest. Meanwhile, nest defenders were triggered by the bee alarm pheromone and live hornet presence to heat-ball the hornet. In A. cerana, sophisticated recruitment communication that encodes food location, the waggle dance, is therefore matched with an inhibitory/alarm signal that encodes information about the context of danger and its threat level.

Evaluation of the Effectiveness of Selected Treatments of Nosema Spp. Infection by the Hemocytometric Method and Duplex Pcr

Abstract Recent years have witnessed an increase in the mortality of honey bees in many regions of the world. The observed decrease in the bee population results from a combination of factors, and microsporidian parasites Nosema apis and N. ceranae are among the main contributors. Those parasites cause a microsporidian infection that shortens the lifespan of bees and reduces the productivity of bee colonies. The aim of this study was to evaluate the effectiveness of Nozevit, Api Herb and ApiX (acetylsalicylic acid + Artemisia absinthium L. extract) in the control of infections caused by Nosema spp. in a field experiment. Two groups of worker bees were evaluated - hive bees and forager bees returning to the hive. The effect of the analyzed therapies on the number of spores and the microsporidia species were analyzed by the hemocytometric method and duplex PCR. A statistical analysis revealed that the applied treatments had reduced the number of spores by 31.15% on average. In hive bees, Nosema spp. infection was most effectively reduced by Nozevit (67.85%) and ApiX (63.36%). Coinfections (N. ceranae and N. apis) were affirmed in all bee samples before treatments. However, after the treatments, single infection of N. apis and N. ceranae were detected. The tested treatments were more effective in the control of N. apis than N. ceranae.

How Hives Collapse: Allee Effects, Ecological Resilience, and the Honey Bee.

We construct a mathematical model to quantify the loss of resilience in collapsing honey bee colonies due to the presence of a strong Allee effect. In the model, recruitment and mortality of adult bees have substantial social components, with recruitment enhanced and mortality reduced by additional adult bee numbers. The result is an Allee effect, a net per-individual rate of hive increase that increases as a function of adult bee numbers. The Allee effect creates a critical minimum size in adult bee numbers, below which mortality is greater than recruitment, with ensuing loss of viability of the hive. Under ordinary and favorable environmental circumstances, the critical size is low, and hives remain large, sending off viably-sized swarms (naturally or through beekeeping management) when hive numbers approach an upper stable equilibrium size (carrying capacity). However, both the lower critical size and the upper stable size depend on many parameters related to demographic rates and their enhancement by bee sociality. Any environmental factors that increase mortality, decrease recruitment, or interfere with the social moderation of these rates has the effect of exacerbating the Allee effect by increasing the lower critical size and substantially decreasing the upper stable size. As well, the basin of attraction to the upper stable size, defined by the model potential function, becomes narrower and shallower, indicating the loss of resilience as the hive becomes subjected to increased risk of falling below the critical size. Environmental effects of greater severity can cause the two equilibria to merge and the basin of attraction to the upper stable size to disappear, resulting in collapse of the hive from any initial size. The model suggests that multiple proximate causes, among them pesticides, mites, pathogens, and climate change, working singly or in combinations, could trigger hive collapse.

Multi-Drug Resistance Transporters and a Mechanism-Based Strategy for Assessing Risks of Pesticide Combinations to Honey Bees.

Annual losses of honey bee colonies remain high and pesticide exposure is one possible cause. Dangerous combinations of pesticides, plant-produced compounds and antibiotics added to hives may cause or contribute to losses, but it is very difficult to test the many combinations of those compounds that bees encounter. We propose a mechanism-based strategy for simplifying the assessment of combinations of compounds, focusing here on compounds that interact with xenobiotic handling ABC transporters. We evaluate the use of ivermectin as a model substrate for these transporters. Compounds that increase sensitivity of bees to ivermectin may be inhibiting key transporters. We show that several compounds commonly encountered by honey bees (fumagillin, Pristine, quercetin) significantly increased honey bee mortality due to ivermectin and significantly reduced the LC50 of ivermectin suggesting that they may interfere with transporter function. These inhibitors also significantly increased honey bees sensitivity to the neonicotinoid insecticide acetamiprid. This mechanism-based strategy may dramatically reduce the number of tests needed to assess the possibility of adverse combinations among pesticides. We also demonstrate an in vivo transporter assay that provides physical evidence of transporter inhibition by tracking the dynamics of a fluorescent substrate of these transporters (Rhodamine B) in bee tissues. Significantly more Rhodamine B remains in the head and hemolymph of bees pretreated with higher concentrations of the transporter inhibitor verapamil. Mechanism-based strategies for simplifying the assessment of adverse chemical interactions such as described here could improve our ability to identify those combinations that pose significantly greater risk to bees and perhaps improve the risk assessment protocols for honey bees and similar sensitive species.

The efficacy and tolerability of Api-Bioxal® as a winter varroacide in a cool temperate climate

This two-year study aimed to assess the efficacy and tolerability of the oxalic acid product Api-Bioxal® as a winter treatment administered using the trickling and vaporizer methods at the dosage rate recommended by the manufacturers (Trial 1) and at the lower dosage recommended by The European Group for Integrated Varroa Control for cool temperate climates such as Ireland (Trial 2). Trial 1: In August 2011, 45 colonies were standardized based on brood area and blocked into 2 treatment groups (n = 15) and a control group using natural mite-fall pre-treatment. Three weeks post-treatment a control treatment (CheckMite+) was administered to the test colonies and the percent efficacy of Api-Bioxal® was calculated. Invasion pressure was monitored by treating the control colonies continuously with CheckMite+. Tolerability was assessed by monitoring adult bee mortality post-treatment and spring build-up was assessed on brood area. The mean (± s.e.) percent efficacy for the trickling method (81.5 ± 3.5%) was significantly lower than for the vaporizer (95.2 ± 1.6%) and control (97.7 ± 1.0%) groups. Bee mortality post-treatment was significantly higher in the trickling group but Api-Bioxal® treatment had no negative impact on spring build-up irrespective of the application method. This high bee mortality and relatively low efficacy led to Trial 2. Trial 2: In August 2012, 72 colonies were standardized using brood area and divided into 5 treatment groups (n = 12) plus a control group. The application methods and dosage rates recommended by the manufacturers (6.0% trickling method in a 1:1 sugar/water syrup and 2.3-g vaporizer method) were again assessed in addition to a lower dosage of 4.5% in 1:1 sugar/water using the trickling method and 1.3 g for vaporizer method. The control colonies were untreated. The mean percent efficacy calculated for the five treatment groups exceeded 90% and were all significantly higher than the 8.57% efficacy estimated for the control group. Bee mortality was again significantly higher in the colonies treated using the trickling method at the 6.0% concentration and significantly decreased when the dosage concentration was reduced to 4.5%. Api-Bioxal® applied using the vaporizer method, irrespective of the quantity administered, was well tolerated by the colonies and bee mortality was similar to the natural mortality observed in the control group. We conclude that in a cool temperate climate, Api-Bioxal® is an effective varroacide when administered as a single winter treatment under broodless conditions using both the trickling and vaporizer methods. Colonies tolerated the product better at the reduced dosage rate of 4.5% using trickling method or 1.3 g using the vaporizer method without compromising the efficacy of the treatment.

Influence of the presence of Cacoxenus indagator Loew. parasite larvae in brood chambers on the emergence rate and size of red mason bees

Cacoxenus indagator is one of cleptoparasites most frequently found in the nests of Osmia bicornis L. The goal of this experiment was to examine the influence of the presence of 2-3 C. indagator larvae in the brood chamber on the cocoon mass, on the mass and size of bee imagines, and on their emergence rate. During the analysis of red mason bee nest material, 200 cocoons were taken from brood chambers, each of them also containing 2-3 larvae of C. indagator (CC). The control group consisted of 200 randomly chosen cocoons from brood chambers with no parasites inside (CFFC). The cocoons and the emerged bees were weighed, and then the size of the bees was determined by the microscope image analysis software Axio Vision Rel. 4.0 coupled with a Stereo Lumar V12 stereoscopic microscope (Carl Zeiss, Germany). This involved measuring the sum of the widths of tergites 3 and 4, the distance between the wings and the forewing length and width. It was found that the presence of 2-3 C. indagator larvae in the brood chamber had no impact on the mortality of bees in cocoons. The research demonstrates that CC cocoons do not have to be removed when collecting cocoons from artificial nests in managed O. bicornis populations, as bees emerging from such cocoons are fully developed.