Bijen

Honey bees are exposed to a wealth of synergistically interacting stress factors, which may induce colony losses often associated with high infection levels of pathogens. Neonicotinoid insecticides have been reported to enhance the impact of pathogens, but the underlying immune alteration is still obscure. In this study we describe the molecular mechanism through which clothianidin adversely affects the insect immune response and promotes replication of a viral pathogen in honey bees bearing covert infections. Our results shed light on a further level of regulation of the immune response in insects and have implications for bee conservation.

A study published in the journal Science, reveals that the number of slugs, spiders, worms and other invertebrates has fallen by 45 per cent over the past 35 years. Experts fear this will harm the planet as creepy crawlies play an important role in pollinating crops, pest control, decomposition and ensuring soil remains packed with nutrients, as well as water filtration. In the UK the number of beetles, butterflies, bees and wasps has fallen by up to 60 per cent. Experts warn that fewer insects would have a huge effect on crop production as up to 75 percent are pollinated by insects, amounting to around 10 per cent of the world's food supply. Scientists fear a drop in the insect population could also spark a decline in birds, which prey on pests that damage crops, and amphibians, which help keep water supplies free from algae.

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 (228%) and brood (213%), as well as a reduction in honey production (229%) and pollen collections (219%), 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. 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.

Pour François Ramade, professeur émérite d'écologie à l'université de Paris-Sud, les insecticides modernes, notamment les néonicotinoïdes, sont responsables d'une véritable "catastrophe écologique". Et, selon lui, "la réponse des pouvoirs publics des pays développés et des institutions multilatérales est absente ou dérisoire". Les personnes de plus de 40 ans se souviennent des pare-brise, phares et calandres de voiture constellés de cadavres d'insectes. La propreté des voitures actuelles est le signe d'une disparition massive d'insectes qui doit nous alarmer. L'agriculture moderne a permis, par l'usage massif d'« intrants », une augmentation considérable de la productivité des cultures. Elle atteint depuis quelques décennies des limites dues à l'impact environnemental de ses pratiques. En effet, l'accroissement de productivité qu'elle a permis n'est pas dû à une révolution biologique dans le contrôle de la photosynthèse, mais à un recours sans cesse accru aux engrais chimiques et aux pesticides, dont les conséquences écologiques néfastes sont connues.

Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. The compounds are highly persistent in soils, tend to accumulate in soils and sediments, have a high runoff and leaching potential to surface and groundwater and have been detected frequently in the global environment. For imidacloprid, including its neurotoxic metabolites, lethal toxicity can increase up to 100,000 times compared to acute toxicity when the exposure is extended in time (Suchail et al. 2001). Recent studies have shown that chronic toxicity of neonicotinoids can more adequately be expressed by time to 50 % mortality instead of by the 10 day LD50 (Sánchez-Bayo 2009; Maus and Nauen 2010; Tennekes 2010; Tennekes 2011; Tennekes and Sánchez-Bayo 2012; Mason et al. 2013; Rondeau et al. 2014). There is a linear relation between the logarithm of the daily dose and the logarithm of the time to 50 % mortality (Tennekes 2010, 2011; Tennekes and Sánchez-Bayo 2012; Tennekes and Sánchez-Bayo 2013; Rondeau et al. 2014).

Neuere Forschungsergebnisse zur Gefährdung von Bestäuberinsekten, Vögeln und weiterer Organismen durch systemische Pestizidwirkstoffe (insbesondere Neonicotinoide) und der sich daraus ergebende Handlungsbedarf für Regulierung und Forschung.