Nicotine-based pesticides kill bees

By Archita Bhatta
Published: Monday 30 June 2008

the Baden-Wrttemburg province in Germany has lost 60 per cent of its honey bee population to a newer generation of nicotine based pesticides in a span of a few months. The German Research Centre for Cultivated Plants has found that most of the dead bees it examined were killed because of clothianidin, a pesticide that belongs to the nicotine group called neonicotinoid. After the findings came to light, the country banned eight pesticides of which five belong to the neonicotinoid group. Clothianidin was introduced in Germany last year to tackle an outbreak of rootworm in corn.

Neonicotinoids, as it has been established in other countries, aren't bee friendly. In 2003, the French government declared that the treatment of seeds with imidacloprid, another neonicotinoid, spells out significant risk for scientists have also blamed this pesticide for the mysterious disappearance of honey bees in the us for a few years now. Termed colony collapse disorder, bees have been observed to abandon their hives leaving their keepers with little evidence, honey and no income. This left little scope to examine why the bees were disappearing.

Beekeepers in the us have lost about 30 per cent of bees this year to the disorder. Scientists studying the disorder say though neonicotinoids do not kill adult bees directly, it impairs their memory and the brain metabolism. They have found similar effects in termites. When termites feed on imidacloprid, they forget how to return to their homes. It also causes their immune system to collapse, said Jerry Hayes, chief of the apiary section, Florida Department of Agriculture and Consumer Services.

Toxic to bees
According to the us Environmental Protection Agency, clothianidin is not a selective insecticide and is highly toxic to honey bees on exposure through nectar and pollen. The effects of this toxic chronic exposure may include lethal effects in the larvae and reproductive effects in the queen bee, it says.

While bees are found dead in Germany, their cousins in the US do a complete disappearing act

Another study by the Institute of Science in Society, London, carried out in June 2007 said that a synergistic interaction of new pesticides and parasitic fungi used as biocontrol agent in agriculture was also a cause of decline of the bee population.

Imidacloprid and related neonicotinoids were brought in to replace organophosphorus and methylcarbamate compounds for effective pest control. Neonicotinoids, which act on the central nervous system, is effective against insects. Its use in the past six years has increased significantly. But then came the honey bee effect and the bans in France and Germany thereafter. Although on a much smaller scale, there are reports of disappearance of bees from India, Poland, Switzerland, Spain, Portugal, Italy, France, Greece and England.

Highest selling in India
India, like many other countries has not been able to zero in on the reason behind the loss of bees. Of immediate concern is the fact that imidacloprid is one of the highest selling pesticides in the country according to a study published in the June 2007 issue of Clinical Toxicology.

Scientists in India say other viral and bacterial diseases of honeybees are of more serious concern than pesticides as of now. "Diseases of honey bees caused due to mites, virus and bacteria are the primary concern here. Pesticides are of course toxic to honey bees but here they are much less of a problem," says P K Chuneja, a scientist at Punjab Agricultural University in Ludhiana. However, there are instances of pesticides affecting bees in the country (see box From mango to mustard).

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