A deadly new type of neuro-pesticide is decimating bee colonies, by damaging the queens

New and sophisticated pesticides are jeopardising the survival of honeybee colonies across the world by seriously damaging the health of their queens, a groundbreaking new study confirms.

Honeybees have been in decline for decades; the Nature Conservancy estimates that their populations have fallen from four million worldwide in the 1970s to just 2.5 million today.

No one knows for sure what is destroying these vital pollinators, but the evidence is stacking up against neonicotinoids—a relatively new class of neuro-active insecticides, which are used to control agricultural pests such as aphids.

Up until now, all the research has focused on the ill effects of neonics on worker bees. The compounds have been shown to disrupt foraging behaviour, homing ability, communication and larval development in workers, as well as making them more prone to parasites and diseases.

However, a recent study led by bee experts in Switzerland and Canada has discovered that two neonics—thiamethoxam and clothianidin—also pose a threat to queen bees. Queens that had been exposed to the toxins were found to have enlarged ovaries, to collect less sperm during mating with drones, and to lay fewer eggs.

A marked honey bee queen on a waxcomb. Photo by Geoffrey Williams University of Bern
A marked honey bee queen on a waxcomb.
Photo by Geoffrey Williams University of Bern

The findings are particularly troubling because honeybee hives contain only one queen, whose good health is essential to the survival of the colony. Not only do queen bees have a monopoly on female reproduction, but they also secrete pheromones which promote social cohesion amongst workers and drones.

‘This is the first study on the impact of neonicotinoids on the physiology, anatomy and reproductive success of queen bees,’ said lead researcher, Dr Geoffrey Williams from the Institute for Bee Health at the University of Bern. ‘The results show that these chemicals harm queens and therefore may be responsible for the loss of bee colonies.’

The use of neonics has been heavily restricted in the European Union since 2013 due to their potential impact on bees and other pollinating insects. Nevertheless, the UK government temporarily lifted the ban this summer in parts of the country despite widespread condemnation from scientists, environmental organisations and the public.

An inter-governmental review of neonics is due to take place in the coming months and the researchers hope that their findings will lead to further restrictions on the hazardous pesticides.

Honeybees pollinate 40% of the world’s leading food crops, including apples, citrus fruits, tomatoes, sunflowers, rapeseed and soya, helping to produce over 80 million tonnes of food in the EU each year.