According to a Reuters report, scientists have discovered even less dosage of widely used pesticides can harm bumblebees and honeybees, eventually destroying their homing and path-finding instincts.
The revelations were made by two studies, published in the journal Science on Thursday, in French and British researchers examined bees and neonicotinoid insecticides – which was introduced in the 1990s and now stands as the most widely used crop pesticide across the world.
Bee populations have been dropping in the recent years drastically partly because of the Colony Collapse Disorder phenomenon. Scientists also fear that usage of pesticides is damaging bee populations, however, they are not sure about the reasons behind the destruction and are engaging in further studies.
Dave Goulson of Stirling University in Scotland insisted that bumblebee species have declined hugely. “In North America, several bumblebee species which used to be common have more or less disappeared from the entire continent, while in Britain, three species have become extinct,” said the researcher who led the British study.
Experts say that bee population is under threat now in Asia, South America and the Middle East.
Flowering plants, including many fruit and vegetable crops, rely heavily on bees as they are important pollinators of flowering plants. According to a 2011 UN report, bees and other pollinators such as butterflies, beetles or birds do work worth $203 billion a year to the human economy.
University of Stirling exposed the developing colonies of bumblebees to lower level of neonicotinoid named as imidacloprid as part of an experiment, and arranged the colonies in enclosed field where the bees could fly around collecting pollen under natural conditions for six weeks.
The bumblebee nests – including bees, wax, honey, bee grubs and pollen – were weighed by the researchers at the beginning and end of the experiment to find out how much the colony had expanded.
The researchers noted that treated colonies gained less weight due to less food intake than the control colonies which were not exposed to imidacloprid.
At the end of the experiment, the treated colonies were on average 8-12% smaller than the controlled colonies and also produced 85% less queens – producers of the next generation of bees.
A study led by Mickael Henry team of the Avignon-based French National Institute for Agricultural Research (INRA) tagged free– ranging honeybees with tiny radio-frequency identification microchip stuck to their backs. This helped them keep a track of bees commuting from their hives. Few bees were given minor dosage of non harmful neonicotinoid pesticide named as thiamethoxam for comparison purposes. French researchers found that the treated bees were about two to three times more likely to die while away from their nests. They believe pesticides probably interfered with the bees’ homing systems and as a result died while finding their way back home.
Henry said the findings raised important issues about pesticide authorisation procedures.
“So far, they (the procedures) mostly require manufacturers to ensure that doses encountered on the field do not kill bees, but they basically ignore the consequences of doses that do not kill them but may cause behavioural difficulties,” he said in a statement.