Bumble bees and pathogens

New paper out in PLOS: Does Pathogen Spillover from Commercially Reared Bumble Bees Threaten Wild Pollinators?

You might not realize that not only are honeybees managed by humans, but so are bumble bees:

“Worldwide, five species of bumble bees are reared commercially for the pollination of at least 20 different crops. The sale of commercial Bombus has an estimated value of €55 million annually; crops pollinated by bumble bees have a value of at least €12 billion per year.

Peppers and tomatoes are the crops commonly grown in greenhouses that use captive bumble bees as pollinators.

The concern addressed in this paper is that commercially reared bumblebees in greenhouses could spread a potential pathogen to native bees.  They  created a model to describe how a pathogen might spread, and watched actual bumble bees foraging in and out of greenhouses to set the parameters on their model.

Half of bumble bees they captured outside a commercial greenhouse were the commercial bees! Clearly a potential for mixing with native populations exists.  This is the scary part:

“we investigated the prevalence of the pathogen C. bombi among bumble bees at varying distances to three industrial-scale greenhouse operations. At our two field sites where greenhouses were actively using commercial bumble bees, C. bombi infected, on average, 15% …and 23% …. of foraging workers. Near an industrial greenhouse that had stopped using commercial bumble bees, and away from greenhouses of any kind, wild Bombus were entirely free of C. bombi (site effect, G = 26.9, d.f. = 3, P<0.001).

….Bees foraging immediately adjacent to greenhouses also harboured significantly more intense infections, i.e., they carried more pathogen cells in their gut tracts, than bees collected further away (Z = −2.0, P = 0.04, n = 67).

I could go on quoting their stats, but I think you get the picture.  Not only is the infection of wild bees possible, it’s already happening.  From their conclusion:

“Here, we use a combination of mathematical modeling and field data to show that spillover from commercially reared bumble bees has introduced the contagious pathogen Crithidia bombi into wild bumble bee populations. During two years, and across nine sites in southern Ontario including our previous work: [35], we have found C. bombi infecting up to 75% of wild bumble bees, depending on the time of year and the host species, near industrial greenhouses that use commercial Bombus for pollination.”

Sigh. A nice piece of work, but quite depressing.

Full Reference

Otterstatter, M.C., Thomson, J.D., Adler, F.R. (2008). Does Pathogen Spillover from Commercially Reared Bumble Bees Threaten Wild Pollinators?. PLoS ONE, 3(7), e2771. DOI: 10.1371/journal.pone.0002771

5 thoughts on “Bumble bees and pathogens

  1. Another way to put it:

    We’re in for a heap of trouble if this situation doesn’t get under control. Thank you for posting this, Bug Girl.

  2. I’m more than a little worried over here in Scotland as bee numbers are down by 80-90% on previous years. As well as honey bees, we normally get five varieties of bumble bee but I’ve only spotted carder bees this year—and few of them. I was out topping hemp nettles today, which are normally thick with bees, and was lucky to see one bee per cut (the scythe cuts a 12ft wide swathe, in a 3ft deep arc.

  3. Yes–it is really disturbing. :(
    The British insect conservation group has a bumble bee watch going on–I’ll see if I can find that for you.

  4. Pingback: Bumblebee go home! « Bug Girl’s Blog

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