On Thu, 7/18/13, Christina Wahl <[log in to unmask]> wrote:

> Pete noted that some lindens are toxic to bumblebees.
> What evidence is there, Pete....do bumblebees just go ahead
> and Kamikaze pollinate the poison tree?  

> I'd like to know how serious the problem with lindens is,
> compared to a typical pesticide application.
 
http://www.jas.org.pl/jas_54_2_2010_7.pdf

"In 2003 during the warmer season with thermally similar flowering 
periods, flowers of Tilia tomentosa were visited twice as often as 
compared to flowers of Tilia cordite.  It was found that toxic properties 
of Tilia tomentosa nectar are stronger for bumblebees than for Apis 
mellifera."

Tilia tomentosa is the species of Linden involved in the two bumblebee
kills in Oregon.  One of the kills, involving 50,000 bumblebees, was
obviously caused by applicator error - an applicator sprayed 55 ornamental
Linden trees in a Wilsonville, Oregon parkling lot while they were 
in bloom just a few days before lots of dead bumblebees appeared
beneath the trees. 

The other kill, in Hillsboro, Oregon, involved only 100 bumblebees 
beneath this single Linden tree that was neonic treated via trunk
injection back in March
http://imageshack.com/a/img195/5088/46lq.jpg
The Oregon Dept. of Agriculture has not yet announced whether
this Hillsboro kill was likely caused by the neonic or high toxicity
of the nectar of that particular Linden tree.

Paul Cherubiini
El Dorado, Calif.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html