Sensitivity of bees to pesticides: a comparative approach

Bees, including managed and wild bees, provide important ecological functions, sustaining basic ecosystem services and human food production. In Europe, many crops depend directly on insect pollination and the honey bee, Apis mellifera, is considered one of the most important pollinators. However, there are thousands of other bee species and their contribution in the pollination service has been recently identified. Following the recent honey bee and wild bee populations declining worldwide, concern has been growing about the risks posed by pesticides and, on the appropriateness of the current risk assessment scheme for the approval and authorisation of pesticides. The current risk assessment for pesticides focuses on A. melliferaand suggests to extrapolate data from honey bees to other bee species based on the assumption that they are the most sensitive species, although a quantitative approach for comparing the difference in sensitivity among bees has not yet been reported. In this study, a systematic review of the relevant literature on the topic followed by a metaanalysis has been performed. Both the contact and oral acute LD50 and the chronic LC50 reported in laboratory studies for as many substances as possible have been extracted from the papers in order to compare the sensitivity to pesticides of honey bees and other bee species (Apiformes). The sensitivity ratio between the endpoint for the species A. melliferaand the other species of bees was calculated considering 150 different combinations of bee species and pesticide, including 19 bee species and 53 pesticides in total. The results of the meta-analysis showed a high variability of sensitivity among bee species and 9 of the 19 species were more sensitive than honey bees to pesticides. In about 5% of cases, the sensitivity of other species was more than 10 times higher than honey bees. In conclusion, according to the results of this study, it needs to cover a greater range of bee species in the risk assessment of Plant Protection Products, in order to protect wild bees as well as honey bees. At the same time, exposure levels must also be considered because the effect of pesticides can vary among bees depending on the specific life cycle, nesting activity and foraging behaviour.