Oral exposure to thiacloprid-based pesticide (Calypso SC480) causes physical poisoning symptoms and impairs the cognitive abilities of bumble bees

Abstract Background: Pesticides are identified as one of the major reasons for the global pollinator decline. However, the sublethal effects of pesticide residue levels found in pollen and nectar on pollinators have been studied little. The aim of our research was to study whether oral exposure to the thiacloprid levels found in pollen and nectar affect the learning and long-term memory of bumble bees. We tested the effects of two exposure levels of thiacloprid-based pesticide (Calypso SC480) on buff-tailed bumble bee (Bombus terrestris) in laboratory utilizing a learning performance and memory tasks designed to be difficult enough to reveal large variations across the individuals. Results: The lower exposure level of the thiacloprid-based pesticide impaired the bees’ learning performance but not long-term memory compared to the untreated controls. The higher exposure level caused severe acute symptoms, due to which we were not able to test the learning and memory. Conclusions: Our results show that oral exposure to a thiacloprid-based pesticide, calculated based on residue levels found in pollen and nectar, not only causes sublethal effects but also acute lethal effects on bumble bees. Our study underlines an urgent demand for better understanding of pesticide residues in the environment, and of the effects of those residue levels on pollinators. These findings fill the gap in the existing knowledge and help the scientific community and policymakers to enhance the sustainable use of pesticides

Chronic oral exposure to Amistar fungicide does not significantly affect colour discrimination but may impact memory retention in bumblebees

Abstract Background: Intensive agriculture, including pesticides, is one of the many reasons for pollinator decline. The EU legislation on plant protection products (hereon pesticides) demands that the risks of active substances and their use in pesticide products are assessed for bees. However, the risk assessment is not always sufficient as shown, for example, in the case of the fungicide Amistar. The fungicide has been shown to cause lethal and sublethal effects on bumblebees at levels that, according to the EU risk assessment, do not require risk mitigation measures to protect bees. In order to understand the effects of chronic Amistar exposure on bumblebees, we studied whether 5 days of oral exposure to 0.015 µl Amistar (3.75 µg azoxystrobin/day) impairs bumblebees’ learning and memory performance in the 10-colour discrimination task. Results: Chronic Amistar treatment did not impair the learning of the bees, but a statistically non-significant negative trend was observed in memory retention between the final learning bout and the subsequent memory test. Conclusions: The results of our study suggest that chronic sublethal exposure to Amistar fungicide did not significantly impair the learning ability of bumblebees. However, there was a trend towards impaired memory retention, although this was not statistically significant. These findings provide further support for the hypothesis that Amistar may have a negative effect on bee cognitive performance. It is important to continue studying the effects of widely used pesticides on pollinators, as their decline is a complex issue with multiple contributing factors. Understanding the effects of different pesticide residue levels on bumblebees can inform policymakers in making more sustainable pesticide legislation and help protect pollinators