Bee mortality: ANSES recommends reinforcing European plant protection product regulation and emphasises the need for a multifactorial approach to risks

Cruiser OSR is a seed-dressing insecticide authorised for oilseed rape cultivation. It contains three active ingredients, including thiamethoxam, a neonicotinoid-class insecticide. The results of a study published recently in the journal Science highlights the harmful effect of sub-lethal doses of thiamethoxam on the ability of forager bees to return to the hive. In this context, ANSES, in conjunction with its European counterpart EFSA, stresses the need to pursue research work in this area. It also calls for changes in the European regulations which would incorporate experiments enabling a better understanding of the sub-lethal effects of exposure to neonicotinoids into the process of plant protection product assessment. It also emphasises the need for a multifactorial approach to the risks in order to effectively counter the bee mortality phenomenon.

ANSES was formally requested by the Ministry of Agriculture on 23 March 2012 to provide scientific and technical support on the possible repercussions of a study published in the journal Science (Henry et al, 2012). This experimental study reports the effects on bees of neonicotinoid seed treatment of nectar-producing crops (i.e. oilseed rape). The study suggests that exposure of bees to sub-lethal doses of thiamethoxam causes a certain number of behavioural impairments, and by altering the bees' ability to return to the hive may contribute to mechanisms which weaken bee colonies.

To effectively carry out its expert assessment, ANSES held a hearing of the study's authors. The Agency also obtained anaylsis results regarding thiamethoxam, clothianidin and nectar sugar concentrations in samples taken at the request of the public authorities from different varieties of oilseed rape treated this spring with Cruiser OSR, so as to compare the levels of exposure used in the experimental study with actual field data. Lastly, the Agency compared the results from the study with all available data, and in particular the data from the Cruiser OSR marketing authorisation application dossier.

Below are the conclusions of this expert assessment, validated by the Agency's Expert Committee on plant protection products:

  • the experiment conducted by the authors of the study is based on the monitoring of the return to the hive of individual bees using an RFID microchip technique, an innovative method for studying the behaviour of forager bees exposed to a plant protection product substance. It highlights the harmful effect of a sub-lethal dose of thiamethoxam on forager bees' ability to return to the hive ;
  • the field data indicate that, under current farming practice conditions, exposure of bees to thiamethoxam via oilseed rape nectar residues (from 0.1 to 0.33 ng/bee according to the analysis results obtained) is lower than the dose used in the experiment (1.34 ng/bee). However, exposure to this dose cannot be totally excluded in certain circumstances ;
  • the outcome of the observed effects on the future of bee colonies, which applies a mathematical model that has not been validated for this specific use, has not been clearly established. The results presented in the study do not necessarily call into question the conclusions of the risk assessment conducted according to the current regulatory criteria in the context of the marketing authorisation application dossier for the Cruiser OSR seed treatment product. However, they do emphasise the limitations of the models used in this context for evaluating the foragers' return to the hive.

The European Food Safety Authority (EFSA), whose opinion was formally requested by the European Commission, participated along with ANSES in the hearing procedure and came to similar conclusions.

Lastly, in addition to the publication analysed by ANSES, other recent studies conducted using different protocols have also demonstrated certain harmful effects of exposure to sub-lethal doses of neonicotinoids on the health of bee and bumblebee colonies.
Based on this, ANSES recommends:

  • pursuing experiments based on RFID technology, while varying the levels of exposure to more closely match the doses to which bees are commonly exposed, and delving more deeply into the consequences of the harmful effects observed in individual bees on the dynamics of the bee colony as a whole. This work would make it possible to validate a research protocol to more effectively describe the sub-lethal effects of exposure to neonicotinoids, and could be used as a basis for changes in the European regulations ;
  • instigating a reassessment on the European level of neonicotinoid active substances (thiamethoxam, clothianidin, etc.) based on new scientific data from recent studies.

ANSES wishes to emphasise that bee mortality is multifactorial in origin and immediate action should therefore be taken to deal with all the factors which may be implicated in this phenomenon. In this context, and in its role as a European Union Reference Laboratory, ANSES is in charge of coordinating a vast Europe-wide epidemiological surveillance programme which aims to improve characterisation of the bee mortality phenomenon by taking pathogens into account among the hive-weakening factors.

By the end of 2012 ANSES will set up a specific expert group dedicated to furthering comprehension of the effects on the fate of bee colonies of co-exposure to pesticides and pathogens, in preparation for possible recommendations by 2014 and their integration into the regulations as a complement to the work conducted by EFSA.