Hi all,
Thank you for all the comments and information that you folks sent in response to my inquiry, both via the list and direct to me. It has been great to read everything that was sent. I thought I would briefly summarize what I have found out in case other people are interested. I meant to write this at the end of last week, but forgot. Robert Brenchley's posting today jogged my memory.
The general opinion is that bee dying is associated with Tilia in Europe, where it has been a subject of debate for many years. There are reports of it happening as far back as 1908. There doesn't seem to be any reports of bee death around Tilia in the U.S., though I was sent a photocopy of a page from "Manual of Landscape Plants" that mentions that bees find the leaves of Silver linden (Tilia petiolaris) "narcotic or poisonous and can be found in large numbers on the ground under such trees." In all, three species were named in the postings as being potentially bad: T. petiolaris, T. orbicularis, and T. tormentosa.
As for why this happens, no one is quite sure. There seem to be three threads to this:
1. Tilia is a late-flowering tree, when there are not many other sources of nectar, so it is old bees that forage and literally work themselves to death.
2. Starvation, as in urban areas there is little else for the bees to forage on and the trees cannot produce enough nectar to feed all the bees. (Research showed dead bees had empty stomachs.)
3. Poisoning due to the sugar mannose, which bees cannot metabolize.
As a foot note, bumble bee intoxication is fairly common on several flowers, possibly due to a parasite disrupting the nervous system.
So, thank you very much for all the suggestions and information I have received. As I said, it has been interesting to read it all and I certainly feel that I learnt something from this.
Best wishes,
Matthew
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Matthew Shepherd
Director, Pollinator Program and Publications
The Xerces Society
4828 SE Hawthorne Blvd, Portland, OR 97215
Tel: 503-232 6639 Fax: 503-233 6794
Email: [log in to unmask]
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The Xerces Society is an international nonprofit organization
dedicated to protecting biological diversity through the
conservation of invertebrates.
For information and membership details, see our website:
http://www.xerces.org/
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