Chennai, April 2, 2012 (Thanks to Arun Subramanian, Southern Illinois University, Carbondale, USA and Sridhar Rao, Beekeeping Industry, KVIC, Mumbai for the news alerts): "A widely used insecticide can threaten the health of bumblebee colonies and interfere with the homing abilities of honeybees, according to a pair of new studies," reports the American Association for the Advancement of Science, USA (AAAS), publishers of the journal Science in its news release dated March 29, 2012. Both the studies - one on bumble bees* and the other on honey bees** - are published online on March 29, 2012 at the Science Express Web site of the journal Science.
Though it is well-known that pesticides are toxic to several pollinators, the exact way in which they worked on the insect's metabolism has not been understood. Results from laboratory tests also vary from the actual effects under the field conditions. The present studies tried to understand the effects of the commonly used neonicotinoid insecticides on bees in field conditions.
In the study led by Mickaël Henry of the French National Institute for Agricultural Research (INRA), Henry and colleagues tagged foraging honey bees with tiny radio-frequency identification (RFID) microchips, that allowed the researchers to track the bees as they came and went from their hives. The researchers then treated some of the bees with a sublethal dose of thiamethoxam, a neonicotinoid. The research team found that the treated bees were about twice as likely as untreated bees to die away from the hives. The researchers therefore felt the chemical interfered with the insects' ability to find their way home.
The work on bumble bees was supervised by Professor Dave Goulson at the University of Stirling, UK. He notes (see news dated March 30, 2012 on Bumblebee Research, reported by the University of Stirling; a video of an interview with Professor Goulson may be seen here): "Our work suggests that trace exposure of our wild bees to insecticides is having a major impact on their populations. Only queen bumblebees survive the winter to build new nests in the spring, so reducing the number produced by 85% means far fewer nests the following year. Repeated year on year, the long term cumulative effects are likely to be profound."
The AAAS news release says that neonicotinoid insecticides were introduced in the early 1990s and have now become one of the most widely used crop pesticides in the world. The chemicals act on the insect's central nervous system, and spread to the nectar and pollen of the treated flowering crops.
The Indian Context
Though the situation in India at present appears not so alarming, the recent widespread use of neonicotinoid insecticides, particularly imidacloprid, is sure to have serious consequences in our agricultural production. A news dated January 17, 2011 in this site reported the research carried out by Dr. Parthiba Basu, University of Calcutta, and his team that indicated a decline in vegetable production due to use of pesticides. Colin Todhunter explains in an article published in the Deccan Herald dated January 13, 2011: "If the findings by Dr. Basu's team were extrapolated, this would offer a clear indication that India was facing a decline in natural pollinators, as ecological farming was only practiced on about 10-20 per cent of the country's arable land. There are serious implications. Unlike those with access to a varied diet, Basu says there are certain vegetable crops that many people living near the poverty threshold rely on. If there is a pollination crisis, Basu suggests nutritional security could be affected."
"There's still a lot we don't know about the massive bee die-offs. But one thing we do know is that bees are in trouble - by implication, we are too. Another thing we know is that Bayer continues to export or manufacture its pesticides across the world, including India. In fact, imidacloprid, another neonicotinoid, is one of India's highest selling pesticide."
*Whitehorn, P.R., O'Connor, S., Wackers, F.L. and Goulson, D. 2012. Neonicotinoid pesticide reduces bumble bee colony growth and queen production. Science. DOI: 10.1126/science,1215025 (Abstract), published online March 29, 2012
**Henry, M., Beguin, M., Requier, F., Rollin, O., Odoux, J.-F., Aupinel, P., Aptel, J., Tchamitchian, S. and Decourtye, A. 2012. A common pesticide decreases foraging success and survival in honey bees. Science. DOI: 10.1126/science.125039 (Abstract), published online March 29, 2012.