Neonicotinoid Clothianidin reduces honey bee immune response and contributes to Varroa mite proliferation

The neonicotinoid Clothianidin has a negative impact on NF-\u3baB signaling and on immune responses controlled by this transcription factor, which can boost the proliferation of honey bee parasites and pathogens. This effect has been well documented for the replication of deformed wing virus (DWV) induced by Clothianidin in honey bees bearing an asymptomatic infection. Here, we conduct infestation experiments of treated bees to show that the immune-suppression exerted by Clothianidin is associated with an enhanced fertility of the parasitic mite Varroa destructor, as a possible consequence of a higher feeding efficiency. A conceptual model is proposed to describe the synergistic interactions among different stress agents acting on honey bees

Neonicotinoid Clothianidin reduces honey bee immune response and contributes to Varroa mite proliferation

The neonicotinoid Clothianidin has a negative impact on NF-κB signaling and on immune responses controlled by this transcription factor, which can boost the proliferation of honey bee parasites and pathogens. This effect has been well documented for the replication of deformed wing virus (DWV) induced by Clothianidin in honey bees bearing an asymptomatic infection. Here, we conduct infestation experiments of treated bees to show that the immune-suppression exerted by Clothianidin is associated with an enhanced fertility of the parasitic mite Varroa destructor, as a possible consequence of a higher feeding efficiency. A conceptual model is proposed to describe the synergistic interactions among different stress agents acting on honey bees

Intra-specific variation in sensitivity of <i>Bombus terrestris</i> and <i>Osmia bicornis</i> to three pesticides

There is growing evidence that pesticides may be among the causes of worldwide bee declines, which has resulted in repeated calls for their increased scrutiny in regulatory assessments. One recurring concern is that the current frameworks may be biased towards assessing risks to the honey bee. This paradigm requires extrapolating toxicity information across bee species. Most research effort has therefore focused on quantifying differences in sensitivity across species. However, our understanding of how responses to pesticides may vary within a species is still very poor. Here we take the first steps towards filling this knowledge gap by comparing acute, lethal hazards in sexes and castes of the eusocial bee Bombus terrestris and in sexes of the solitary bee Osmia bicornis after oral and contact exposure to the pesticides sulfoxaflor, Amistar (azoxystrobin) and glyphosate. We show that sensitivity towards pesticides varies significantly both within and across species. Bee weight was a meaningful predictor of pesticide susceptibility. However, weight could not fully explain the observed differences, which suggests the existence of unexplored mechanisms regulating pesticide sensitivity across bee sexes and castes. Our data show that intra-specific responses are an overlooked yet important aspect of the risk assessment of pesticides in bees

Pan-european assessment, monitoring, and mitigation of stressors on the health of bees

Within the PoshBee Project, we have worked out precise protocols for testing the toxicological endpoints and metabolisation rate of agrochemicals on and in bees. Three agrochemical classes (insecticides, fungicides and herbicides) were tested on three bee groups (honey bees, bumble bees and solitary mason bees). The specific protocols, different for each combination of the pesticide class and bee group, were designed based on the existing toxicity testing methods and modified according to the specificities of the different bee groups, their castes and the different exotoxicological features of the compounds. Sulfoxaflor, Azoxystrobin, and Glyphosate were used respectively as examples of the three pesticide classes. Apis mellifera, Bombus terrestris and Osmia bicornis were chosen as the examples of the three bee groups. The protocols for honey bees and bumble bees were designed based on the official existing guidelines edited by OECD. Nevertheless, given that the OECD guidelines provide recommendations to fit with most agrochemicals, many of the parameters are defined with low precision in order to be flexible and adapt to different categories of molecules. While OECD has no guidelines for testing solitary bees, we used information from the unpublished ring test protocols for Osmia bicornis by the ICPPR non- Apis working group.Prepared under contract from the European Commission; Grant agreement No. 773921; EU Horizon 2020 Research and Innovation action.Prepared under contract from the European Commission; Grant agreement No. 773921; EU Horizon 2020 Research and Innovation action

Pan-european assessment, monitoring, and mitigation of stressors on the health of bees

Inter-individual differences in pesticide sensitivity may trigger variability in the risk posed by pesticides. Therefore, to better inform pesticide risk assessment for bees, we studied the variability of responses to several pesticides based on endogenous (developmental stage, genetic background, caste) and exogenous factors (pesticide co-exposure). We mainly investigated the toxicity of the insecticide sulfoxaflor, the fungicide azoxystrobin and the herbicide glyphosate. We first used LD50 tests to determine the acute oral and contact toxicity of these pesticides across the different bee species, developmental stages (larva vs adult in honey bees), castes (honey bee and bumble bee workers, queens and drones), and genetic backgrounds (honey bee subspecies). We then considered the risks posed by chronic and sublethal exposures to pesticides by implementing behavioural and reproductive endpoints in the screening of pesticide toxicity. Data showed that azoxystrobin and glyphosate under the test conditions were mildly toxic to bees. However, a large variability in bee sensitivity to sulfoxaflor was found, especially across species and individuals of different castes or sex. This variability is therefore important to consider for increasing the safety margin of the risk posed by insecticides in bees. Several effects induced by sublethal concentrations or doses of pesticides are also described, such as the occurrence of a Non-Monotonic Dose-Response (NMDR) and delayed effects in honey bees, impairment of reproductive performances in bumble bees, and a decreased longevity of Osmia adult females (although no effects were found on larval development). Finally, an interaction between pesticides was found when exposure was by contact, but not under oral exposure. In conclusion, the range of effects described here provides very useful insights for better understanding the toxicity of pesticides and therefore the risks they might pose to bees.Prepared under contract from the European Commission; Grant agreement No. 773921; EU Horizon 2020 Research and Innovation action.Prepared under contract from the European Commission; Grant agreement No. 773921; EU Horizon 2020 Research and Innovation action

Pan-european assessment, monitoring, and mitigation of stressors on the health of bees

Within the PoshBee Project we have tested three bee species – honey bees Apis mellifera, bumble bees Bombus terrestris and solitary bees Osmia bicornis – for their sensitivity to pesticides and analysed the clearance of pesticides from bees. For each species, all castes and sexes were studied. We synthesised the mortality data (LD50 or results of limit tests) with the toxicokinetic patterns and analysed this against the background of inter- and intraspecific variation in life-histories of the tested bees. The clearance of sulfoxaflor is relatively similar across all bee species tested and in females after contact treatment it tends to be retained. The toxicity increases over time independently of the clearance from the body. The clearance of azoxystrobin was rapid in Osmia and bumble bees, as well as in honey bee queens, but in honey bee workers there was very little clearance. Similar to sulfoxaflor the toxicity increased over time, although the residues were detected at very low levels. Glyphosate tended to be retained in bumble bees after contact treatment but cleared rapidly after oral treatment. For Osmia bees only in males after contact treatment was the glyphosate almost lost. The toxicity of a pesticide is dependent on the exact dosage, but also the exposure route and time, as well as the speed of detoxification and clearance from a body. The assessment for the hazard that a less toxic pesticide might pose, can be largely dependent on the exposure route. The effects of pesticide toxicity can increase even after the molecules have been cleared out of the body.Prepared under contract from the European Commission; Grant agreement No. 773921; EU Horizon 2020 Research and Innovation action.Prepared under contract from the European Commission; Grant agreement No. 773921; EU Horizon 2020 Research and Innovation action

No effect of dual exposure to sulfoxaflor and a trypanosome parasite on bumblebee olfactory learning

Bees are important pollinators in wild and agricultural ecosystems, and understanding the factors driving their global declines is key to maintaining these pollination services. Learning, which has been a focus of previous ecotoxicological studies in bees, may play a key role in driving colony fitness. Here we move beyond the standard single-stressor approach to ask how multiple stressors, an agrochemical (sulfoxaflor, a relatively new insecticide) and a parasite (Crithidia bombi, a prevalent gut parasite of bumblebees), impact learning in the bumblebee Bombus terrestris. We developed a modified version of the classic proboscis extension reflex assay to assess the combined effects of acute oral sulfoxaflor exposure and infection by C. bombi on olfactory learning of bumblebee workers. We found no evidence that either sulfoxaflor, C. bombi, or their combination had any significant effect on bumblebee olfactory learning, despite their known negative impacts on other aspects of bumblebee health. This suggests that losses in cognitive ability, as measured here, are unlikely to explain the impacts of sulfoxaflor and its interactions with other stressors on bumblebees. Our novel methodology provides a model system within which to test interactive effects of other key stressors on bee health

Influence of Microwave Exposure on the Developmnent of Phaseolus vulgaris L. Plants,

Seeds and sprouts of Phaseolus vulgaris L. were exposed to 2.45 GHz electromagnetic field (EMF) corresponding to a SAR of 40 mW/g. A The effects were assessed on the above-ground growth of mature plants. Seeds exposed to EMF showed a significant higher germination time in soil compared to control. No significant differences were observed in some growth parameters (total height, number of leaves and leaf expansion) between plants developed from seeds exposed to EMF and plant controls. On the contrary, when bean sprouts were exposed to EMF a significant decrease of the growth parameters was evident in plants developed from sprouts exposed to EMF compared to those obtained from sprouts not expose