Fred Heimbach (tier3 solutions) and Richard Schmuck (Bayer CropScience)
An important point of any regulatory environmental risk assessment concerns the question whether adverse effects observed for individuals under controlled experimental conditions in the laboratory translate into significant (unacceptable) risks for populations in field environments. In field environments, individuals are not homogeneously exposed to contaminants, since the level of contamination often varies from one compartment to another (dilution of exposure), and population structures provide a resilient buffer against losses of individuals (resilience by loss compensation). Some systemic insecticides like nitro-substituted neonicotinoids reveal a very high acute toxicity to bee species, and even minute doses have been shown to cause significant adverse effects to individuals under controlled laboratory or field conditions. The purpose of this session was to capture the risks posed by systemic insecticides to bee species in their natural social and environmental context.
Twelve platform presentations were delivered in the session with eight presenting findings from differently designed field and field-monitoring studies where domestic honeybees, bumblebees and mason bees were exposed to residues of systemic neonicotinoid insecticides in artificial syrup, in natural pollen or nectar, or in drifted seed dust particles. One presentation examined the influence of these systemic insecticides on the immune system of honeybees, and one introduced a new class of systemic insecticides (diamides), which were shown to not pose an unacceptable risk to bee species. Two presentations introduced modeling approaches to examine our mechanistic understanding of field exposure patterns based on the foraging behavior of honeybees and the dissipation behavior of systemic compounds within the beehive. Another presentation followed up on the importance to adequately consider the ecological consequences of both, using and not using systemic compounds, in regulatory decision-making.
Presentations concerning exposure of bee species in field environments included studies with confined (dust particle exposure) and unconfined (exposure to residues in food) bee populations. These presentations demonstrated that exposure to low residues of systemic insecticides either in nectar, pollen, sucrose solution or drifted seed dust particles do not result in observable adverse effects to honeybees, bumblebees or solitary bees (mason bees). The effects of residues in natural nectar and pollen to managed honeybee colonies, bumblebee colonies and solitary bees were examined in one pair of similar landscapes of 65 km² in size, with controlled treatments in nearly 1,000 ha winter oilseed rape. It was discussed, with considerable disagreement, whether the six test locations within each landscape can be regarded as true replicates. Also, the treatment of the majority of oilseed rape fields in both landscapes with pyrethroids was further challenged, although it was acknowledged that these compounds were classified as non-hazardous to bees and were necessary to ensure the health of the oilseed rape plants, which otherwise would have differed in their attractiveness and nutritional value for the examined bees. Finally, the potential ecological consequences of a suspension of systemic neonicotinoid insecticides and their substitution by less effective products was summarized from a food production and trade-flow perspective, and it was emphasized that the environmental risks of substitutes need to be carefully examined not to risk an even poorer environmental record in the end.
The session on field evidence-based risk assessment of systemic insecticides was very well attended with over one hundred attendees for several presentations. The key points for the 12 presentations included:
- Field and field-monitoring studies provide the most valuable input data for a solid evaluation of risks
- Field and field-monitoring studies need to compromise between statistical power (replication) and standardization of environmental conditions (level of control of other impact factors)
- Data modeling and weight of evidence approaches are considered as highly supportive tools to reduce uncertainties in interpretation of field data and to make these highly relevant data usable for regulatory decisions
- An effective and environmentally protective regulation requires an appropriate integration of field data and a comprehensive consideration of the ecological impacts of both, the use and non-use of (specific) agrochemicals
Authors’ contact information: firstname.lastname@example.org and email@example.com