July 10, 2014
Pesticide Use Is Impairing Bees’ Abilities To Forage
April Flowers for redOrbit.com - Your Universe Online
Bees with long-term exposure to neonicotinoid pesticides exhibit a decreased ability to forage for pollen, according to a new study led by the University of Guelph. The study, which involved fitting bees with tiny radio frequency transmitters, was published in a recent issue of Functional Ecology.
The researchers — Nigel Raine, a professor in Guelph’s School of Environmental Sciences, and Richard Gill of Imperial College London — reveal how long term pesticide exposure affects the day-to-day behavior of individual bees. Such behaviors include pollen collection and which specific flowers worker bees choose to visit.
“Bees have to learn many things about their environment, including how to collect pollen from flowers,” said Raine, who holds the Rebanks Family Chair in Pollinator Conservation. “Exposure to this neonicotinoid pesticide seems to prevent bees from being able to learn these essential skills.”
By using radio frequency identification (RFID) tags similar to those used by courier firms to track packages, the researchers monitored individual bee activity — including when they left and returned to the hive, how much pollen they collected, and from which flowers.
They found that bees from untreated colonies were more successful at collecting pollen as they learned to forage. Bees with exposure to neonicotinoid insecticides lost their ability to collect pollen successfully over time. To combat this loss, treated colonies even sent out more foragers.
Raine said that "the flower preferences of neonicotinoid-exposed bees were different to those of foraging bees from untreated colonies.”
The team investigated the effects of two particular neonicotinoid insecticides: imidacloprid (currently banned by the European Commission for use on crops attractive to bees), and pyrethroid (lambda cyhalothrin). Over the course of four weeks, the researchers assessed the behavior of individual bumblebees from over 40 colonies when exposed to one or both of these insecticides.
“Although pesticide exposure has been implicated as a possible cause for bee decline, until now we had limited understanding of the risk these chemicals pose, especially how it affects natural foraging behavior,” Raine said.
Approximately 30 percent of the global pesticide market is comprised of neonicotinoid insecticides. Neonicotinoid-treated seeds produce plants with the pesticide in all their tissues, including the nectar and pollen.
“If pesticides are affecting the normal behavior of individual bees, this could have serious knock-on consequences for the growth and survival of colonies,” explained Raine.
“Bumblebees may be much more sensitive to pesticide impacts as their colonies contain a few hundred workers at most, compared to tens of thousands in a honeybee colony,” Raine said.
Image 2 (below): Bumblebee (Bombus terrestris) workers with Radio Frequency Identification (RFID) tags. Credit: Richard Gill