Sublethal neonicotinoid insecticide exposure reduces solitary bee reproductive success

1. Pollinating insects provide crucial and economically important ecosystem services to crops and wild plants, but pollinators, particularly bees, are globally declining as a result of various driving factors, including the prevalent use of pesticides for crop protection. Sublethal pesticide exposure negatively impacts numerous pollinator lifehistory traits, but its influence on reproductive success remains largely unknown. Such information is pivotal, however, to our understanding of the long-term effects on population dynamics. 2 We investigated the influence of field-realistic trace residues of the routinely used neonicotinoid insecticides thiamethoxam and clothianidin in nectar substitutes on the entire life-time fitness performance of the red mason bee Osmia bicornis. 3 We show that chronic, dietary neonicotinoid exposure has severe detrimental effects on solitary bee reproductive output. Neonicotinoids did not affect adult bee mortality; however, monitoring of fully controlled experimental populations revealed that sublethal exposure resulted in almost 50% reduced total offspring production and a significantly male-biased offspring sex ratio. 4 Our data add to the accumulating evidence indicating that sublethal neonicotinoid effects on non-Apis pollinators are expressed most strongly in a rather complex, fitness-related context. Consequently, to fully mitigate long-term impacts on pollinator population dynamics, present pesticide risk assessments need to be expanded to include whole life-cycle fitness estimates, as demonstrated in the present study using O. bicornis as a model.

L’éternel retour du "travail des enfants" dans les politiques publiques au Burkina Faso : perspective historique

Dans une perspective historique, ce chapitre cherche à comprendre comment le travail des enfants a été construit comme « problème » dans les politiques publiques au Burkina Faso. En remontant aux politiques coloniales françaises dans le pays, il se propose de répondre à la question suivante : face à l’émergence et au renforcement des politiques publiques de lutte contre le travail des enfants, assiste-t-on à une disparition du modèle de l’enfant du lignage qui percevait l’enfant comme une « richesse » et une force de travail complémentaire? Le chapitre présente d’abord la construction progressive du travail des enfants en « problème » de politiques publiques pendant la colonisation. Il analyse ensuite l’évolution et la portée de l’intervention des gouvernements successifs après l’indépendance pour imposer une nouvelle vision de l’enfant (l’enfant de la Nation). Enfin, il révèle que malgré l’engouement récent pour la prise en compte du point de vue l’enfant, le statut de l’enfant travailleur comme sujet peine à être reconnu. L’analyse globale montre une tension permanente, à des degrés différents, entre les modèles de l’enfant de la nation, de l’enfant du lignage et de l’enfant sujet : ce qui traduit aussi la complexité du travail des enfants et de sa lutte au Burkina Faso contemporain. Le texte est issu d’un travail de terrain mené au Burkina Faso en 2008 et 2009 dans le cadre de notre thèse.

Impact of chronic neonicotinoid exposure on honeybee colony performance and queen supersedure

BACKGROUND: Honeybees provide economically and ecologically vital pollination services to crops and wild plants. During the last decade elevated colony losses have been documented in Europe and North America. Despite growing consensus on the involvement of multiple causal factors, the underlying interactions impacting on honeybee health and colony failure are not fully resolved. Parasites and pathogens are among the main candidates, but sublethal exposure to widespread agricultural pesticides may also affect bees. METHODOLOGY/PRINCIPAL FINDINGS: To investigate effects of sublethal dietary neonicotinoid exposure on honeybee colony performance, a fully crossed experimental design was implemented using 24 colonies, including sister-queens from two different strains, and experimental in-hive pollen feeding with or without environmentally relevant concentrations of thiamethoxam and clothianidin. Honeybee colonies chronically exposed to both neonicotinoids over two brood cycles exhibited decreased performance in the short-term resulting in declining numbers of adult bees (-28%) and brood (-13%), as well as a reduction in honey production (-29%) and pollen collections (-19%), but colonies recovered in the medium-term and overwintered successfully. However, significantly decelerated growth of neonicotinoid-exposed colonies during the following spring was associated with queen failure, revealing previously undocumented long-term impacts of neonicotinoids: queen supersedure was observed for 60% of the neonicotinoid-exposed colonies within a one year period, but not for control colonies. Linked to this, neonicotinoid exposure was significantly associated with a reduced propensity to swarm during the next spring. Both short-term and long-term effects of neonicotinoids on colony performance were significantly influenced by the honeybees' genetic background. CONCLUSIONS/SIGNIFICANCE: Sublethal neonicotinoid exposure did not provoke increased winter losses. Yet, significant detrimental short and long-term impacts on colony performance and queen fate suggest that neonicotinoids may contribute to colony weakening in a complex manner. Further, we highlight the importance of the genetic basis of neonicotinoid susceptibility in honeybees which can vary substantially.