It's been well more than 5 years of intensive study now, trying to figure out what affects the bees, and why.
I recently read an article in The Economist: Subtle Poison, which reported on several recent developments in the investigation:
Many researchers believe the label “colony collapse disorder” covers a multitude of problems; that would account for the long list of possible causes. But neonicotinoids have the explanatory virtue of being a fairly recent development and also one which, as these two pieces of work suggest, could be a common factor in weakening a colony without actually pushing it over the edge. The killer blow would then be administered by something else: a mite infestation, perhaps, or a fungal infection, or whatever else happened to turn up that a healthy hive would have shrugged off. A paper published earlier this year in Naturwissenschaften, for example, showed that even small doses of neonicotinoids weakened bees’ resistance to Nosema, a common fungal parasite.
The recent developments were published in Science Magazine, and include:
- Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production
We exposed colonies of the bumble bee Bombus terrestris in the laboratory to field-realistic levels of the neonicotinoid imidacloprid, then allowed them to develop naturally under field conditions. Treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared with control colonies.
- A Common Pesticide Decreases Foraging Success and Survival in Honey Bees
Simulated exposure events on free-ranging foragers labeled with a radio-frequency identification tag suggest that homing is impaired by thiamethoxam intoxication.
I love the part in the second paper about "labeled with a radio-frequency identification tag"; as The Economist article observes, this involved an interesting field experiment:
To that end, he and his colleagues glued tiny radio transmitters to the thoraxes of worker bees. These triggered a detector on the hive whenever a worker bearing one returned from a foraging trip. Some hives were given realistic doses of thiamtethoxam, a variety of neonicotinoid, while others were left alone. Dr Henry found that around twice as many treated bees as untreated ones failed to return to the hive.
I can tell you for sure that one task I wouldn't be very good at is gluing tiny radio transmitters to the thoraxes of worker bees!
What's the bottom line? Well, as the American Chemical Society points out: Pesticides Harm Hive Behavior. That's pretty simple, and now it seems that it's quite well-established.
And The Economist notes that countries are starting to take action:
A few countries, including France, Germany and Slovenia, have already restricted the use of neonicotinoids because of worries about their effects on bees.
Hopefully more countries will follow suit, and we can halt the poisoning of the bees soon.