Parasite and Pesticide Impacts on the Bumblebee (Bombus terrestris) Haemolymph Proteome.

Pesticides pose a potential threat to bee health, especially in combination with other stressors, such as parasites. However, pesticide risk assessment tests pesticides in isolation from other stresses, i.e., on otherwise healthy bees. Through molecular analysis, the specific impacts of a pesticide or its interaction with another stressor can be elucidated. Molecular mass profiling by MALDI BeeTyping® was used on bee haemolymph to explore the signature of pesticidal and parasitic stressor impacts. This approach was complemented by bottom-up proteomics to investigate the modulation of the haemoproteome. We tested acute oral doses of three pesticides-glyphosate, Amistar and sulfoxaflor-on the bumblebee Bombus terrestris, alongside the gut parasite Crithidia bombi. We found no impact of any pesticide on parasite intensity and no impact of sulfoxaflor or glyphosate on survival or weight change. Amistar caused weight loss and 19-41% mortality. Haemoproteome analysis showed various protein dysregulations. The major pathways dysregulated were those involved in insect defences and immune responses, with Amistar having the strongest impact on these dysregulated pathways. Our results show that even when no response can be seen at a whole organism level, MALDI BeeTyping® can detect effects. Mass spectrometry analysis of bee haemolymph provides a pertinent tool to evaluate stressor impacts on bee health, even at the level of individuals.

Sulfoxaflor insecticide and azoxystrobin fungicide have no major impact on honeybees in a realistic-exposure semi-field experiment.

Exposure to pesticides is considered a major threat to bees and several neonicotinoid insecticides were recently banned in cropland within the European Union in light of evidence of their potential detrimental effects. Nonetheless, bees remain exposed to many pesticides whose effects are poorly understood. Recent evidence suggests that one of the most prominent replacements of the banned neonicotinoids - the insecticide sulfoxaflor - harms bees and that fungicides may have been overlooked as a driver of bee declines. Realistic-exposure studies are, however, lacking. Here, we assess the impact of the insecticide Closer (active ingredient: sulfoxaflor) and the widely used fungicide Amistar (a.i.: azoxystrobin) on honeybees in a semi-field study (10 flight cages containing a honeybee colony, for each of three treatments: Closer, Amistar, control). The products were applied according to label instructions either before (Closer) or during (Amistar) the bloom of purple tansy. We found no significant effects of Closer or Amistar on honeybee colony development or foraging activity. Our study suggests that these pesticides pose no notable risk to honeybees when applied in isolation, following stringent label instructions. The findings on Closer indicate that a safety-period of 5-6 days between application and bloom, which is only prescribed in a few EU member states, may prevent its impacts on honeybees. However, to conclude whether Closer and Amistar can safely be applied, further realistic-exposure studies should examine their effects in combination with other chemical or biological stressors on various pollinator species.

Toxicity of fungicides to terrestrial non-target fauna - Formulated products versus active ingredients (azoxystrobin, cyproconazole, prothioconazole, tebuconazole) - A case study with Enchytraeus crypticus (Oligochaeta).

Despite the high usage of pesticides in current agricultural practices, its effects to humans and to the environment (non-target species) are a continuous concern. Soil dwelling organisms are among the first in line of exposure to pesticides, however their risks are often based on the pure active ingredient (a.i.) and not on the commercial formulated products (FPs) actually applied in the fields. In the present study, we investigated the effects of two fungicide FPs versus its a.i. (s): Amistar® XTRA and the respective a.i. (s) azoxystrobin and cyproconazole, and Prosaro® 250 EC and the respective a.i. (s) prothioconazole and tebuconazole, to the non-target soil oligochaete Enchytraeus crypticus. The standard Enchytraeid Reproduction Test was used to assess effects on survival and reproduction. Results showed that Amistar was more toxic than Prosaro, particularly for reproduction (EC50 = 161 mg Amistar/kg soil, EC50 = 350 mg Prosaro/kg soil). For both FPs, reproductive effects were mainly related to one of its a.i. (s) (azoxystrobin [EC50 = 37 mg azosxystrobin/kg soil] for Amistar, and tebuconazole [EC50 = 41 mg tebuconazole/kg soil] for Prosaro), while lethal effects were not predicted by the toxicity of its a.i. (s) (particularly in the case of Prosaro, which was more toxic than its a.i. (s)). These findings highlight the need to further explore the toxicity data of the FPs compared to the a.i. (s), aiming to predict a more realistic environmental hazard of pesticides.