Researchers in the U.K. have found a link between pesticide use and a decline in both the lifespan and natural foraging behavior of bumblebees.
40 early-stage bumblebee colonies were exposed over a four-week period to pesticides neonicotinoid and pyrethroid, two globally used products.
The study, led by University of London researcher Richard Gill, found that neonicotinoid led bees to collect less pollen at a slower rate while pyrethroid exposure increased their death rate significantly.
The pesticides together resulted in a combined effect, Gill said.
Published this week in the journal Nature, the research stated, "Widespread agricultural intensification means that bees are exposed to numerous pesticides when foraging, yet the possible combinatorial effects of pesticide exposure have rarely been investigated.
"Here we show that chronic exposure of bumblebees to two pesticides (neonicotinoid and pyrethroid) at concentrations that could approximate field-level exposure impairs natural foraging behaviour and increases worker mortality leading to significant reductions in brood development and colony success."
Gill said the global decline in bee populations justifies more research to better understand the impact of pesticide use.
"I think the problem is we’re not that sure which [pesticides] are the most harmful," Gill told www.freshfruitportal.com.
"The decline of bees is like a jigsaw. A major part of that jigsaw will be these pesticides."
Bees are considered a crucial pollinator, contributing to 80% of insect pollination, the study said, and can be exposed to neonicotinoid pesticides when foraging on flowering crops. Topical exposure to pyrethroid, on the other hand, may result during pesticide spraying.
Gill said that previous studies have only exposed bees to pesticides for a short period of time, up to 96 hours, and have not considered multiple pesticides. He encouraged longer tests that examine multiple pesticides. He also encouraged further research to determine what bee population decline could mean and how the effect on individual bees might impact colony behavior.