Tue, Apr 03, 2012 - Page 9 News List

Toxic pollen and the mad bee disease disaster

By Alison Benjamin  /  The Guardian, LONDON

In July 19, French beekeepers reported that their honeybee population had displayed strange, agitated behavior and had “melted away.” “Mad bee disease,” as it quickly became known, was thought to have caused the death of as many as 40 percent of bee colonies, and beekeepers looking for an explanation for the catastrophe began pointing the finger at a new type of pesticide.

Systemic pesticides are those that are transported in the sap of a plant from the seed up through the stem into the leaves and flowers. Here they contaminate nectar and pollen and, hence, any insect that picks them up.

Since then, imidacloprid and other neonicotinoid systemic pesticides, such as thiamethoxam, have been implicated in the worldwide collapse of honeybee colonies.

Laboratory and semi-field studies in France and Italy have shown that imidacloprid can disorientate foraging bees and impair their memory and communication so that they do not return home with food, and the colonies in the hive dwindle and die. However, the pesticide’s manufacturer, Bayer, has always maintained that bees are given much higher doses in trials than they would come into contact with in the field.

In contrast, its own research concluded that Gaucho (an imidacloprid seed treatment) “caused neither a reduced visitation of flowers nor an increased loss of foraging honeybees” and found “no records of behaviorally impaired honeybees.” It also argues that so many factors affect bee health, including parasites, viruses and malnutrition, that there is no one single assailant.

Most scientists and governments around the world seem to share this view. They were quick to dismiss pesticides as the likely cause when colony collapse disorder hit the headlines in 2007.

Yet it is only now, with the results of these two new trials that expose honeybees and bumblebees for the first time to field-realistic sub-lethal levels of neonics that we can say with confidence what many beekeepers have instinctively known for years, that these pesticides do contribute to the death of bee colonies. It is a step nearer to revealing the truth of what is killing our pollinators and to what we can do to prevent their deaths.

Alison Benjamin is the author of A World Without Bees.

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