Kate Kelland Reuters Yahoo News 29 Mar 12;
LONDON (Reuters) - Scientists have discovered ways in which even low doses of widely used pesticides can harm bumblebees and honeybees, interfering with their homing abilities and making them lose their way.
In two studies published in the journal Science on Thursday, British and French researchers looked at bees and neonicotinoid insecticides - a class introduced in the 1990s now among the most commonly used crop pesticides in the world.
In recent years, bee populations have been dropping rapidly, partly due to a phenomenon known as Colony Collapse Disorder. Scientists also fear pesticides are destroying bee populations, but it is not clear how they are causing damage.
Dave Goulson of Stirling University in Scotland, who led the British study, said some 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, he said in a statement.
The threat to bee populations also extends to Asia, South America and the Middle East, experts say.
Bees are important pollinators of flowering plants, including many fruit and vegetable crops. A 2011 United Nations report estimated that bees and other pollinators such as butterflies, beetles or birds do work worth 153 billion euros ($203 billion) a year to the human economy.
In the first of the Science studies, a University of Stirling team exposed developing colonies of bumblebees to low levels of a neonicotinoid called imidacloprid, and then placed the colonies in an enclosed field site where the bees could fly around collecting pollen under natural conditions for six weeks.
At the beginning and end of the experiment, the researchers weighed each of the bumblebee nests - which included the bees, wax, honey, bee grubs and pollen - to see how much the colony had grown.
Compared to control colonies not exposed to imidacloprid, the researchers found the treated colonies gained less weight, suggesting less food was coming in.
The treated colonies were on average eight to 12 percent smaller than the control colonies at the end of the experiment, and also produced about 85 percent fewer queens - a finding that is key because queens produce the next generation of bees.
In the separate study, a team led by Mickael Henry of the French National Institute for Agricultural Research (INRA) in Avignon tagged free-ranging honeybees with tiny radio-frequency identification microchips glued to each bee's back. This allowed them to track the bees as they came and went from hives.
The researchers gave some of the bees a low dose of the neonicotinoid pesticide thiamethoxam which they knew would not kill them and compared them to a control group of bees that was not exposed to the pesticide.
The treated bees were about two to three times more likely to die while away from their nests, and the researchers said this was probably because the pesticide interfered with the bees' homing systems, so they couldn't find their way home.
Henry said the findings raised important issues about pesticide authorization 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 behavioral difficulties," he said in a statement.
($1 = 0.7525 euros)
(Reporting by Kate Kelland; Editing by Karolina Tagaris)
Pesticides hit queen bee numbers
Richard Black BBC News 29 Mar 12;
Some of the world's most commonly used pesticides are killing bees by damaging their ability to navigate and reducing numbers of queens, research suggests.
Scientific groups in the UK and France studied the effects of neonicotinoids, which are used in more than 100 nations on farm crops and in gardens.
The UK team found the pesticides caused an 85% drop in queen production.
Writing in the journal Science, the groups note that bee declines in many countries are reducing crop yields.
In the UK alone, pollination is calculated to be worth about £430m to the national economy.
And the US is among countries where a succession of local populations has crashed, a syndrome known as Colony Collapse Disorder.
Many causes have been suggested, including diseases, parasites, reduction in the range of flowers growing wild in the countryside, pesticides, or a combination of them all.
The neonicotinoids investigated in the two Science papers are used on crops such as cereals, oilseed rape and sunflowers.
Often the chemical is applied to seeds before planting. As the plant grows, the pesticide is contained in every part of it, deterring insect pests such as aphids.
But it also enters the pollen and nectar, which is how it can affect bees.
Dave Goulson from the UK's University of Stirling and colleagues studied the impact of the neonicotinoid imidacloprid on bumblebees.
They let bees from some colonies feed on pollen and sugar water containing levels of imidacloprid typically found in the wild, while others received a natural diet.
Then they placed the colonies out in the field.
'Severely compromised'
After six weeks, colonies exposed to the pesticide were lighter than the others, suggesting that workers had brought back less food to the hive.
But the most dramatic effect was on queen production. The naturally-fed hives produced around 14 queens each - those exposed to the pesticide, just two.
"I wouldn't say this proves neonicotinoids are the sole cause of the problems bees face," said Dr Goulson, "but it does suggest they're likely to be one of the causes, and possibly a significant one.
"The use of these pesticides is so widespread that most bee colonies in areas of arable farming are likely to be exposed to them, so there is potential for them to be playing a significant role in suppression of bee populations on a pretty staggering scale."
The French research group investigated the impact of a different neonicotinoid, thiamethoxam, on the number of bees able to make it back to the colony after release.
Using tiny tags attached to the bees' backs, they showed that significantly fewer insects came back if they had previously been exposed to levels of thiamethoxam that they might encounter on farms.
Calculations showed the impairment was bad enough that the capacity of colonies survive could be severely compromised.
"What we found is that actually if colonies are exposed to pesticides, the population might decline to a point that would put them at risk of collapse due to other stressors," said lead scientist Mickael Henry from the French National Insitute for Agricultural Research (Inra) in Avignon.
Dr Henry told BBC News that it was time for authorities to re-design the safety tests that pesticides have to pass.
"To date, the tests mostly require that the doses found in nature do not kill bees," he said.
"But those authorisation processes ignore possible consequences for the behaviour of bees, and we hope the people in charge will be more careful."
Worldwide business
Neonicotinoids are a multi-billion dollar business worldwide. Even though some countries have banned them partially, a complete global prohibition, as some environmental groups advocate, might be impossible.
May Berenbaum, head of entomology at the University of Illinois and one of the leading US experts on CCD, said the chemicals should be used more carefully.
"There is no question that neonicotinoids are being used recklessly, for want of a better word," she said.
"Fifty years of experience should have taught us that overuse of a single class of compounds is an inherently unsustainable practice, and that pre-treating seeds when pest problems might not even be present is collossally unwise.
"But neonicotinoids could be banned everywhere in the world, and honeybees would still have problems with pathogens, parasites, habitat degradation and overuse of just about every other class of chemical pesticide."
At EU level, the Agriculture and Rural Development Committee has asked the European Commission to increase research and produce an action plan to conserve bees.
"When the action plan is produced, we are ready to give member states a deadline to use or not use a specific pesticide - until then it is up to individual states," said Paolo de Castro MEP, the committee's chairman.
In the UK context, Dr Goulson added, it would certainly be worth re-considering neonicotinoid use in gardens.
"Personally I would ban insecticides completely in gardens," he said.
"There are very few serious insect pests in Britain as far as gardening's concerned, it's too cold; and if roses have a few aphids on, then tough, it's not a big deal."
His research team now plans to expand their study to other bee species, while Dr Henry's group will try to discover exactly how thiamethoxam does its damage.
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