Bern study helps explain duds in bee sperm

A newly emerged male honey bee, known as a drone, on a wax bee frame Geoffrey Williams, University of Bern / Agroscope

Insecticide seems to be harming the health of male honey bees and their sperm, say scientists from the University of Bern.

The two insecticides in question are partially banned in Europe. Researchers from Bern, together with partners from Thailand and Germany, are now calling for more thorough environmental risk assessments of these neonicotinoids – as well as other crop protection products.

The international research team – led by the University of BernExternal link and AgroscopeExternal link – has found that two neonicotinoids might reduce drone lifespan and sperm counts. As the study released on Wednesday points out, any drop in the number of living sperm will have an adverse effect on the queen’s ability to breed and the resulting health of the colony.

“We know multiple stressors can affect honey bee health, including parasites and poor nutrition. It is possible that agricultural chemicals may also play an important role,” says senior author Geoff Williams of the University of Bern and Agroscope.

Beekeepers throughout the northern hemisphere have been struggling to maintain healthy honey bee colonies in recent years.

Fluorescence microscopy revealing living (stained bluish-green) and dead (stained red) male honey bee sperm Lars Straub, University of Bern

This was the first study to investigate the effects of neonicotinoids on drones, and one of the first to study the effects of these agricultural chemicals on males in general. Previous research has identified risks to honey bee females from exposure.

“Most neonicotinoid studies that employ honey bees have focused on workers, which are typically the non-reproductive females of the colony. Male honey bees have really been neglected by honey bee health scientists,” says lead author and doctoral student Lars Straub from the University of Bern.

In 2013, the European Union and Switzerland took a precautionary approach by partially restricting the application of the widely used neonicotinoid insecticides thiamethoxam, clothianidin, and imidacloprid – with the mandate to perform further environmental risk assessments. A new inter-governmental review is currently taking place.