Bijen

Neonicotinoïden veroorzaken bijensterfte op de lange termijn

Voor het eerst is de afname van Engelse wilde bijen gekoppeld aan het gebruik van controversiële neonicotinoïden. Dat zijn pesticiden waarmee boeren hun koolzaadolieplantages beschermen tegen ongedierte. Aan het zaadje van een koolzaadplant voegt de boer neonicotinoïden toe. Als de plant is opgegroeid en opgebloeid, zijn deze stoffen over de volledige koolzaad verspreid, dus ook in de bloemen. Hierdoor krijgen de beestjes die van de nectar snoepen de pesticiden binnen.

Systemic pesticide concerns extend beyond the bees

In the summer of 2010, Henk Tennekes from Experimental Toxicology Services Nederland at Zutphen warned that the accumulation of neonicotinoids in the environment would not only decimate useful insects but also have a knock-on effect on other species, including birds (Curr. Biol. (2011) 21, R137–R139). At the time, Tennekes did not find much support for his views and went on to publish his warnings as a book — The Systemic Insecticides: A Disaster in the Making.

Die Zahl der weltweit bedrohten Tier- und Pflanzenarten hat dieses Jahr einen neuen Rekordstand erreicht

Mit rund 25'800 bedrohten Tier- und Pflanzenarten sei im zu Ende gehenden Jahr ein neuer dramatischer Höchststand erreicht worden. Ein Jahr zuvor waren es noch 24'000 bedrohte Arten. "Wir Menschen verursachen das grösste Artensterben seit Ende der Dinosaurier", resümierte Eberhard Brandes, Vorstand des WWF Deutschland. Auch in der Schweiz gingen die Bestände einiger Arten merklich zurück. Mehr als 40 Prozent der Insektenarten in der Schweiz gälten als bedroht, darunter Bienen und Schmetterlinge, sagte WWF-Sprecherin Perrette Rey in Lausanne auf Anfrage.

Immunosuppression in Honeybee Queens by Thiacloprid and Clothianidin

Queen health is crucial to colony survival of honeybees, since reproduction and colony growth rely solely on the queen. Queen failure is considered a relevant cause of colony losses, yet few data exist concerning effects of environmental stressors on queens. Here we demonstrate for the first time that exposure to field-realistic concentrations of neonicotinoid pesticides can severely affect the immunocompetence of queens of western honeybees (Apis mellifera L.).

Combined neonicotinoid pesticide and parasite stress alter honeybee queens’ physiology and survival

Honeybee colony survival strongly relies on the queen to overcome worker losses exposed to combined stressors like pesticides and parasites. Queen’s capacity to withstand these stressors is however very little known. The effects of the common neonicotinoid pesticide imidacloprid in a chronic and sublethal exposure together with the wide distributed parasite Nosema ceranae have therefore been investigated on queen’s physiology and survivorship in laboratory and field conditions.

The neonicotinoids thiacloprid, imidacloprid, and clothianidin affect the immunocompetence of honey bees

A strong immune defense is vital for honey bee health and colony survival. This defense can be weakened by environmental factors that may render honey bees more vulnerable to parasites and pathogens. Honey bees are frequently exposed to neonicotinoid pesticides, which are being discussed as one of the stress factors that may lead to colony failure.

Low nutrient diets resulting from intensive agriculture make bees more vulnerable to neonicotinoids

Intensive agriculture is known to decrease the quality of nutrients, in the form of sugars, available in the nectar and pollen that bees eat. Now scientists have found that when bees eat a low sugar diet, they are 50 per cent more likely to die as a result of neonicotinoid exposure. "These findings should cause us to rethink our current pesticide risk assessment procedures, which, based upon our findings, may underestimate the toxic effects of pesticides on bees," said Dr Simone Tosi, a University of California San Diego researcher who co-authored the study.

Chronic exposure to neonicotinoids reduces honey bee health near corn crops

Experiments linking neonicotinoids and declining bee health have been criticized for not simulating realistic exposure. Here we quantified the duration and magnitude of neonicotinoid exposure in Canada’s corn-growing regions and used these data to design realistic experiments to investigate the effect of such insecticides on honey bees. Colonies near corn were naturally exposed to neonicotinoids for up to 4 months—the majority of the honey bee’s active season.

Immunosuppression in Honeybee Queens by the Neonicotinoids Thiacloprid and Clothianidin

Queen health is crucial to colony survival of honeybees, since reproduction and colony growth rely solely on the queen. Queen failure is considered a relevant cause of colony losses, yet few data exist concerning effects of environmental stressors on queens. Here we demonstrate for the first time that exposure to field-realistic concentrations of neonicotinoid pesticides can severely affect the immunocompetence of queens of western honeybees (Apis mellifera L.).

Synergistic mortality between clothianidin and propiconazole in three bee species

We explore synergistic mortality between a neonicotinoid (clothianidin) and an ergosterol-biosynthesis-inhibitor fungicide (propiconazole) in three bee species (A. mellifera, Bombus terrestris, Osmia bicornis) following oral exposure in the laboratory. We developed a new approach based on the binomial proportion test to analyze synergistic interactions. We estimated uptake of clothianidin per foraging bout in honey bees foraging on seed-coated rapeseed fields.