Insecticides

Clouds of emerging mayflies were once a regular sight on English summer evenings and they are a key part of the food chain that supports fish, birds and mammals. But modest levels of pollution found in many English rivers are having a devastating impact on mayflies, new research suggests, killing about 80% of all eggs. In October, a study found that the abundance of flying insects has plunged by 75% in 25 years, prompting warnings that the world is “on course for ecological Armageddon”, with profound impacts on human society.

Experimental studies have revealed that neonicotinoids pose potential risks for the nervous systems of non-target species, but the brain regions responsible for their behavioral effects remain incompletely understood. This study aimed to assess the neurobehavioral effects of clothianidin (CTD), a later neonicotinoid developed in 2001 and widely used worldwide, and to explore the target regions of neonicotinoids in the mammalian brain.

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.

Though unnoticed by the world at large, a whole giant ecosystem is collapsing. It has taken us a lot of time to understand this catastrophe for two reasons: one cultural, one scientific. Firstly, we generally do not care for insects (bees and butterflies excepted). In the population as a whole there is little sympathy for the fate of the chitin-skeletoned little things that creep and crawl; our default reaction is a shudder. Fewer bugs in the world? Many would cheer.

Across host–parasite systems, there is evidence that pesticide exposure increases parasite loads and mortality following infection. However, whether these effects are driven by reductions in host resistance to infection or slower rates of parasite clearance is often unclear. Using controlled laboratory experiments, we examined the ability of larval northern leopard frogs (Lithobates pipiens) and American toads (Anaxyrus americanus) to resist and clear trematode (Echinoparyphium sp.) infections following exposure to the insecticide carbaryl.

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.

Die Zulassungsbehörden in Deutschland müssen die indirekten Folgen von Pflanzenschutzmitteln für die Artenvielfalt stärker berücksichtigen. Zu diesem Urteil kommen die Autoren eines am vergangenen Freitag vorgestellten Rechtsgutachtens, das vom Umweltbundesamt (UBA) in Auftrag gegeben wurde. Nach Angaben des Umweltbundesamtes entstehen solche Effekte beispielsweise, wenn Vögel keine Nahrung mehr auf Äckern finden, da Pflanzenschutzmittel unbeabsichtigt Insekten und andere Nahrung der Vögel töten.