Common pesticide causes bumblebees to shrink, study says

Experts fear smaller bees will be less effective at foraging for nectar and carrying out their vital task of distributing pollen.

Scientists in the UK conducted laboratory tests which showed how a pyrethroid pesticide stunted the growth of worker bumblebee larvae, causing them to hatch out reduced in size.

Gemma Baron, one of the researchers from the School of Biological Sciences at Royal Holloway, University of London, said: “We already know that larger bumblebees are more effective at foraging.

“Our result, revealing that this pesticide causes bees to hatch out at a smaller size, is of concern as the size of workers produced in the field is likely to be a key component of colony success, with smaller bees being less efficient at collecting nectar and pollen from flowers.”

Pyrethroid pesticides are commonly used on flowering crops to prevent insect damage.

The study, the first to examine the pesticides’ impact across the entire lifecycle of bumblebees, tracked the growth of bee colonies over a four-month period. Researchers exposed half the bees to a pyrethroid while monitoring the size of the colonies as well as weighing individual insects on micro-scales. They found that worker bees from colonies affected by the pesticides over a prolonged period grew less.

Findings from the study, funded by the Natural Environment Research Council (Nerc), appear in the Journal of Applied Ecology.

Currently, a Europe-wide moratorium on the use of three neonicotinoid pesticides is in force because of their alleged harmful effect on bees.