Dust abraded from thiamethoxam-treated seed during sowing: Refining the risk assessment for native bees in Brazil.

During sowing using pneumatic machinery, dust may be abraded from pesticide-treated seed and contaminate adjacent bee-attractive off-crop areas. This study quantified the risk to native bees of dust released during sowing of Brazilian crop seeds treated with a thiamethoxam formulation (Cruiser 350FS). To address toxicity to native bees, adult acute contact LD50 data for thiamethoxam were collated from the literature, a species sensitivity distribution generated, and the HD5 calculated. The LD50 HD5 was used to refine the default safety factor applied to the honeybee acute contact LD50 from 10 to 5.45 for thiamethoxam. Crop-specific abraded dust data (Heubach dust and Heubach AI) were generated for seeds treated with Cruiser 350FS sourced from on-farm and industrial facilities. The mean Heubach dust levels was ranked as cotton = maize > sunflower = soybean > drybean. There was no correlation between the measured residues of thiamethoxam (Heubach AI) and those estimated in dust based on the thiamethoxam content of Cruiser 350FS. A hazard quotient (HQ) for each crop (based on application rate, the default dust deposition factor, and the honeybee contact LD50/10) identified risks during sowing for all crops. Refinement of the application rate with the measured 90th percentile Heubach dust (assuming 100% thiamethoxam) resulted in sowing of industrially treated soybean and on-farm treated cotton being identified as risks. Further refinement using either the measured 90th percentile Heubach AI or the acute contact LD50 (HD5 ) resulted in sowing of all crops treated with Cruiser 350FS as being identified as low risk. Similar high quality seed treatment should be demonstrated for other formulations containing insecticides with high toxicity to bees. Data on dust drift from machinery and crops more representative of those in Brazil may allow further refinement of the default dust deposition value of 17% used in this study. Integr Environ Assess Manag 2023;19:1361-1373. © 2023 SETAC.

Are honeybees suitable surrogates for use in pesticide risk assessment for non-Apis bees?

Historically, bee regulatory risk assessment for pesticides has centred on the European honeybee (Apis mellifera), primarily due to its availability and adaptability to laboratory conditions. Recently, there have been efforts to develop a battery of laboratory toxicity tests for a range of non-Apis bee species to directly assess the risk to them. However, it is not clear whether the substantial investment associated with the development and implementation of such routine screening will actually improve the level of protection of non-Apis bees. We argue, using published acute toxicity data from a range of bee species and standard regulatory exposure scenarios, that current first-tier honeybee acute risk assessment schemes utilised by regulatory authorities are protective of other bee species and further tests should be conducted only in cases of concern. We propose similar analysis of alternative exposure scenarios (chronic and developmental) once reliable data for non-Apis bees are available to expand our approach to these scenarios. In addition, we propose that in silico (simulation) approaches can then be used to address population-level effects in more field-realistic scenarios. Such an approach could lead to a protective, but also workable, risk assessment for non-Apis species while contributing to pollination security in agricultural landscapes around the globe. © 2019 Society of Chemical Industry.

Workshop on Pesticide Exposure Assessment Paradigm for Non-Apis Bees: Foundation and Summaries.

Current pesticide risk assessment practices use the honey bee, Apis mellifera L., as a surrogate to characterize the likelihood of chemical exposure of a candidate pesticide for all bee species. Bees make up a diverse insect group that provides critical pollination services to both managed and wild ecosystems. Accordingly, they display a diversity of behaviors and vary greatly in their lifestyles and phenologies, such as their timing of emergence, degree of sociality, and foraging and nesting behaviors. Some of these factors may lead to disparate or variable routes of exposure when compared to honey bees. For those that possess life histories that are distinct from A. mellifera, further risk assessments may be warranted. In January 2017, 40 bee researchers, representative of regulatory agencies, academia, and agrochemical industries, gathered to discuss the current state of science on pesticide exposure to non-Apis bees and to determine how well honey bee exposure estimates, implemented by different regulatory agencies, may be protective for non-Apis bees. Workshop participants determined that although current risk assessment procedures for honey bees are largely conservative, several routes of exposure are unique to non-Apis bees and warranted further investigation. In this forum article, we discuss these key routes of exposure relevant to non-Apis bees and identify important research gaps that can help inform future bee risk assessment decisions.

Risk assessment for honey bees and pesticides--recent developments and 'new issues'.

In 2008, major areas of discussion at the ICPBR Bee Protection Group meeting were the development of a honey bee risk assessment scheme for systemic pesticides and revision of the test guidelines for semi-field and field studies. The risk assessment scheme for systemic pesticides is based on analysis of conditions for exposure of bees to residues. These are based on a stepwise approach, starting with simple calculations based on existing data in dossiers and progressing to higher-tier semi-field and field studies (the guidelines for these have been modified in line with this). The proposed scheme has been tested with data packages of high- and low-risk PPPs. A future area of interest for the group may be the risks posed by guttation fluid containing systemic pesticides. A recent paper on 'Translocation of neonicotinoid insecticides from coated seeds to seedling guttation drops: a novel way of intoxication for bees' has focused significant interest on the possible risks posed by the presence of residues of systemic pesticides in guttation fluid to water-collecting honey bees. The occurrence of guttation and the presence of pesticide residues in the fluid are discussed, together with remaining questions that will need to be addressed in answering whether such a route of exposure may pose a risk to honey bees.

The relevance of sublethal effects in honey bee testing for pesticide risk assessment.

The option of an evaluation and assessment of possible sublethal effects of pesticides on bees has been a subject of discussion by scientists and regulatory authorities. Effects considered included learning behaviour and orientation capacity. This discussion was enhanced by the French bee issue and allegations against systemic insecticides that were linked to the hypothesis that sublethal intoxication might even have led to reported colony losses. This paper considers whether and, if so, how sublethal effects should be incorporated into risk assessment, by addressing a number of questions: What is meant by a sublethal effect? Which sublethal effects should be measured, when and how? How are sublethal effects to be included in risk assessments? The authors conclude that sublethal studies may be helpful as an optional test to address particular, compound-specific concerns, as a lower-tier alternative to semi-field or field testing, if the effects are shown to be ecologically relevant. However, available higher-tier data (semi-field, field tests) should make any additional sublethal testing unnecessary, and higher-tier data should always override data of lower-tier trials on sublethal effects.

Behavioural effects of pesticides in bees--their potential for use in risk assessment.

This paper reviews a wide variety of behavioural effects that have been reported in bees following exposure to pesticides, primarily insecticides. These range from effects on odour discrimination in the individual to the loss of foraging bees due to disruption of their homing behaviour. Some of these effects have the potential to have a significant impact on the development and survival of colonies. However, there is currently little guidance available on the types of behavioural data which should be collected during laboratory, semi-field or field regulatory studies or how they should be included and interpreted in risk assessment. Further work is required to allow risk assessment to include significant behavioural effects and their longer term consequences on colony survival and development. Such an approach will require a larger base set of data to predict the longer-term consequences on colonies of short-term effects on individuals, e.g. through population modelling.