Studies Link Bee Decline to Insecticide

Could explain rapid decline of colonies across US, Europe

The pollination efforts of honeybees are worth an estimated $18 billion per year in the United States.
The pollination efforts of honeybees are worth an estimated $18 billion per year in the United States.



A commonly used insecticide disorients bees, making it difficult for them to find their way back to the hive, according to new research.

That may help explain an alarming decline in the numbers of these vital insects seen across the United States and Europe, and the puzzling phenomenon called colony collapse disorder.

A new study, published in Science, shows honeybees exposed to low levels of an insecticide known as a neonicotinoid - which is used by farmers worldwide - left the hive and never returned at about twice the rate of their untreated hivemates.

A second study published in Science saw similar effects on wild bumblebees. Their hives grew more slowly and produced far fewer queens when exposed to a neonicotinoid.

Billion-dollar bees

Bees pollinate the flowers that become fruits, nuts and vegetables. The work these insects do is worth about $18 billion a year to U.S. farmers.

Researchers tagged honeybees with microchips to keep track of them after exposure to insecticide.
Researchers tagged honeybees with microchips to keep track of them after exposure to insecticide.

But honeybee colonies in the United States have been shrinking by about a third each year for the past several years.

Colorado beekeeper Tom Theobald says the worst of the die-offs usually happen in the winter.

“If you were a rancher, you’d go out there and you’d have a dead cow. In the case of the bees, there may or may not be a carcass,” he says. “They may have mostly disappeared with just a small remnant [of the hive] left.”

Mysterious disappearance

This mysterious disappearance has been termed colony collapse disorder. Colony collapses account for about a third of the overall loss of honeybees each year, according to the U.S. Department of Agriculture.

No one knows exactly why it happens. A parasite called the varroa mite started attacking honeybee hives in the 1980s.

But Theobald says even as beekeepers started getting the mite problem under control, “The losses not only continued but they escalated. And as we look back, it appears that the reason for that is that the influence of the systemic pesticides was beginning to become more and more dominant.”

Systemic pesticides called neonicotinoids first introduced in the 1990s are now commonly used to coat the seeds of many major crops. The seedlings absorb the chemical as they grow. So, rather than needing to indiscriminately spray a whole field, there is a little bit of insecticide inside each plant.

Bumblebees pollinate tomatoes, raspberries, strawberries and other fruits and vegetables.
Bumblebees pollinate tomatoes, raspberries, strawberries and other fruits and vegetables.

But that includes the plant's pollen and nectar that the bees are after. It is not enough to kill them. Some studies have show it may be harming them nonetheless. But not all researchers have been convinced.

Intoxicated bees

In one of the new studies, researchers glued tiny microchips to the backs of honeybees. The chips tracked the insects as they came and went from their hive.

The researchers fed the bees sugar water spiked with a low dose of a neonicotinoid and sent them out to forage.

They found these bees were about twice as likely to fail to return as bees not exposed to the insecticide.

Lead author Mickaël Henry from the French national agriculture research institute, INRA, says the bees basically get drunk.

“Intoxicated honeybees with those small doses may just get lost and are unable to find their way back home,” he says.

Wild bees also affected

And it’s not just honeybees that are affected.

Some research has shown bumblebees have a harder time gathering nectar in the laboratory when exposed to neonicotinoids. Bumblebee researcher Dave Goulson at Britain’s University of Sterling and colleagues studied colonies in real-world conditions.

The second study in Science, they found colonies of bees treated with a low dose of a neonicotinoid were smaller than untreated colonies.

Most significantly, Goulson says, “There were 85 percent fewer queens produced when they’d been exposed to realistic field levels of neonicotinoids, which clearly could have very significant implications for bumblebee populations in the wild.”

Only bumblebee queens survive the winter to start new colonies each spring.

That could help explain why bumblebee populations are declining along with the honeybees. And around the world, wild pollinators like bumblebees are more important than honeybees for certain crops.


Bayer CropScience, which makes neonicotinoid pesticides, disputes the findings.

“Instead of dosing the animals at field-relevant concentrations as the authors intended," says Bayer spokesman Jack Boyne, "they instead dosed them at levels that are far greater than what would commonly be experienced in the field." Sixty times greater, Boyne says. At that level, he says, it is not surprising that the bees were disoriented.

And he notes that researchers are studying many other factors affecting bee populations, including parasites, diseases, and the stress of transporting commercial beehives.

Purdue University insect scientist Christian Krupke agrees there are a lot of factors threatening bees. But he says the new studies give regulators something to think about.

“Our regulatory system is based on a lethal dose. Is the bee dead, or is it alive? And these studies show that these bees may be alive, but there’s a sublethal dose that’s causing harm to the colony.”

Some European regulators have banned neonicotinoids, and calls for bans in the United States are growing as well.

This forum has been closed.
Comment Sorting
by: lizt
April 02, 2012 10:17 AM
farmer should reduced their use of this pesticide which MURDERED our tiny
fruits -makers????

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam Wari
Katherine Gypson
May 25, 2015 1:32 AM
For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.

Video Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam War

For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.

Video Female American Soldiers: Healing Through Filmmaking

According to the United States Defense Department, there are more than 200-thousand women serving in the U.S. Armed Forces.  Like their male counterparts, females have experiences that can be very traumatic.  VOA's Bernard Shusman tells us about a program that is helping some American women in the military heal through filmmaking.

Video Iowa Family's Sacrifice Shaped US Military Service for Generations

Few places in America have experienced war like Waterloo. This small town in the Midwest state of Iowa became famous during World War II not for what it accomplished, but what it lost. As VOA’s Kane Farabaugh reports, the legacy of one family’s sacrifice is still a reminder today of the real cost of war for all families on the homefront.

Video On Film: How Dance Defies Iran's Political Oppression

'Desert Dancer' by filmmaker Richard Raymond is based on the true story of a group of young Iranians, who form an underground dance troupe in the Islamic Republic of Iran. This is the latest in a genre of films that focus on dance as a form of freedom of expression against political oppression and social injustice. VOA’s Penelope Poulou has more.

Video Turkey's Ruling Party Trying to Lure Voters in Opposition Stronghold

Turkey’s AK (Justice and Development) Party is seeking a fourth successive general election victory, with the goal of securing two-thirds of the seats in Parliament to rewrite the constitution and change the country's parliamentary system into a presidential one. To achieve that, the party will need to win seats in opposition strongholds like the western city of Izmir. Dorian Jones reports.

Video Millions Flock to Ethiopia Polls

Millions of Ethiopians cast their votes Sunday in the first national election since the 2012 death of longtime leader Meles Zenawi. Mr. Meles' party, the Ethiopian People's Revolutionary Democratic Front, is almost certain of victory again. VOA's Anita Powell reports from Addis Ababa.

Video Scientists Testing Space Propulsion by Light

Can the sun - the heart of our solar system - power a spacecraft to the edge of our solar system? The answer may come from a just-launched small satellite designed to test the efficiency of solar sail propulsion. Once deployed, its large sail will catch the so-called solar wind and slowly reach what scientists hope to be substantial speed. VOA’s George Putic reports.

Video FIFA Trains Somali Referees

As stability returns to the once lawless nation of Somalia, the world football governing body, FIFA, is helping to rebuild the country’s sport sector by training referees as well as its young footballers. Abdulaziz Billow has more from Mogadishu.

Video With US Child Obesity Rates on the Rise, Program Promotes Health Eating

In its fifth year, FoodCorps puts more than 180 young Americans into 500 schools across the United States, where they focus on teaching students about nutrition, engaging them with hands-on activities, and improving their access to healthy foods whether in the cafeteria or the greater community. Aru Pande has more.

Video Virginia Neighborhood Draws People to Nostalgic Main Street

In the U.S., people used to grow up in small towns with a main street lined by family-owned shops and restaurants. Today, however, many main streets are worn down and empty because shoppers have been lured away by shopping malls. But in the Del Ray neighborhood of Alexandria, Virginia, main street is thriving. VOA’s Deborah Block reports it has a nostalgic feel with its small restaurants and unique stores.

VOA Blogs