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According to the web site of the film Vanishing of the Bees:

Bees are dying in their billions. In the UK, around one fifth of honeybee hives were lost in the winter of 2008/2009.

Is there evidence of bees disappearing and what are scientific theories on this subject?

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up vote 15 down vote accepted

I would hesitate to say that "bees are disappearing". But yes, there is a problem.
It's called Colony Collapse Disorder and there is nothing certain about why it happens. It's probably a combination of factors. The Wikipedia article is good. I've recently read some articles claiming that they have found a definitive link to some disease, but I can't find it right now, so I don't know if there is any good basis for the claim.

Update: The claims blaming the pesticide Imidacloprid seems promising and seem to be the strongest claims of a cause at the moment.

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Here is a link: sciencedaily.com/releases/2010/10/101007183018.htm. The real root cause of the issue is, of course, the fact that bees are constantly being trucked around to different fields, so localized infections are given ample opportunity to spread. –  Satanicpuppy Mar 1 '11 at 14:41
    
@Lennart The article as well uses term " Disappearing". Does it means that bees abandon their beehive and die in disperse? –  Egle Mar 1 '11 at 14:45
    
@Egle: Probably, yeah. They are hardly in hiding, and hence "disappear" needs qualification, and the Wikipedia article have it. They are saying the "worker bees disappear from a colony", in contrast to "bees are disappearing" which is to general for me. It gives me mystical connotations. :) –  Lennart Regebro Mar 1 '11 at 14:53
    
@Satanicpuppy: Yeah, that is one of the factors that has been said to be involved. I agree it sounds likely. –  Lennart Regebro Mar 1 '11 at 14:54
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Last week, a bee was sitting next to me in the bus on the window border. Although I learned that day in A.I. that they can fly far and go home in a straight line by comparing their heading angle against the sun and using place marks, I don't think that a bee that takes a bus ride can do the same and thus I agree with @Satanicpuppy. –  Tom Wijsman Mar 22 '11 at 23:24
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Current research by Jeff Pettis [1] shows that the most widely used pesticide, imidacloprid, compromises bees’ immune system even when present in sub-lethal doses. Bees thus weakened are very susceptible to infection with other pathogens.

Both of the groups that had been exposed to imidacloprid harboured an average of 700,000 parasite spores in each bee. Bees from the control colonies, by contrast, harboured fewer than 200,000 spores in their bodies. The insecticide, in other words, was exposing bees to infestation, and thus to a much greater chance of dying prematurely.

Other research [2,3,4] had similar findings. In fact, the pesticide may be enough in producing colony collapse disorder even without the presence of a pathogen, merely by affecting their nervous system, as suggested by Lu & al. [2]:

[T]o test the effect of even small amounts of these pesticides on western honeybees …, Harvard researchers treated 16 hives with different levels of imidacloprid, leaving four hives untreated. After 12 weeks, the bees in all twenty hives—treated and untreated—were alive, though those treated with the highest does of imidacloprid appeared weaker. But by 23 weeks everything had changed: 15 out of the 16 hives (94 percent) treated with imidacloprid underwent classic Colony Collapse Disorder: hives were largely empty with only a few young bees surviving. The adults had simply vanished. The hives that received the highest doses of imidacloprid collapsed first. Meanwhile the four untreated hives were healthy

They manage to replicate the exact conditions of colony collapse disorder. This suggests that their explanation is likely the correct one.

  • [1] Jeffery S. Pettis, Dennis vanEngelsdorp & al., Pesticide exposure in honey bees results in increased levels of the gut pathogen Nosema, Naturwissenschaften, Jan 2012. DOI 10.1007/s00114-011-0881-1

  • [2] Chensheng Lu, Kenneth M. Warchol, Richard A. Callahan. In situ replication of honey bee colony collapse disorder. Bulletin of Insectology. 2012.

  • [3] Penelope R. Whitehorn, Stephanie O’Connor, & al., Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production, Science, Mar 2012. DOI: 10.1126/science.1215025

  • [4] Mickaël Henry, Maxime Béguin, & al., A Common Pesticide Decreases Foraging Success and Survival in Honey Bees, Science, Mar 2012. DOI: 10.1126/science.1215039

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From what I can recall without proper access to reference materials at this time, is that one postulated explanation for Colony Collapse Disorder was attributed to a co-infection of the bees by both the Insect Iridescent Virus (IIV6) and a unicellular fungal parasite called Nosema ceranae. From what I recall, the conjecture was that the synergistic effect of co-infection greatly increases lethality over that of infection with either pathogen alone. I believe this information is not definitive and of course will need further study, experimentation, and observation. Certainly for the curious, this may represent an interesting point at which to begin investigation. For the interested, one study done on the topic can be found here.

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We strongly encourage posting links to relevant material, especially if it's to back up one of your claims. Of course, if its own products, you must disclose your affiliation in your answers. –  Borror0 Mar 16 '11 at 3:43
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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

2 Studies have linked a pesticide (named only as a neonicotinoid) to CCD (NY Times: 2 Studies Point to Common Pesticide as a Culprit in Declining Bee Colonies)

Clothianidin is a Neonicotinoid so may be the chemical referred to in the article. (Wikipedia article has a NPOV warning but presumably that Clothianidin is a Neonictinoid is not disputed)

The Wikipedia article and a leaked EPA memo show that the EPA permitted only conditional registration because of fears about the toxicity to bees.

Clothianidin has not been used in Germany since 2009, but I have not seen any studies that show whether or not this has had an effect on the rate of CCD in Germany.

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The effect is called Colony Collapse Disorder.

Theres research that suggests that a pesticide named clothianidin is responsible for it.

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CCD is not limited to the US: guardian.co.uk/environment/2007/apr/12/… –  rjstelling Mar 16 '11 at 11:43
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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

It might be the Varroa Mite.

The influx of tracheal and Varroa mites (particularly the latter), however, poses problems far greater than any faced before. From all indications, we can breed strains of tracheal mite-resistant bees and can do so ever better as we gain greater understanding of the interaction of those parasites with their bee hosts. Varroa mites, by contrast, feed on the blood of larvae, pupae and adults and can reproduce astonishingly fast; faster, that is, than the rate at which bee colonies can replace their losses.

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