If one links the bumble Xerces society page and go under threats this
parragraph jumps on front

"Commercial bumble bee rearing may be the greatest threat to *B. affinis*, *B.
occidentalis*, *B. terricola*, and *B. franklini*. In North America, two
bumble bee species have been commercially reared for pollination of
greenhouse tomatoes and other crops: *B. occidentalis* and *B. impatiens*.
Between 1992 and 1994, queens of *B. occidentalis* and *B. impatiens* were
shipped to European rearing facilities, where colonies were produced then
shipped back to the U.S. for commercial pollination. Bumble bee expert
Robbin Thorp has *hypothesized* that these bumble bee colonies acquired a
disease (probably a virulent strain of the microsporidian *Nosema bombi*)
from a European bee that was in the same rearing facility, the buff-tailed
bumble bee (*Bombus terrestris*). The North American bumble bees would have
had no prior resistance to this pathogen. Dr. Thorp *hypothesizes* that the
disease then spread to wild populations of *B. occidentalis* and *B.
franklini* in the West (from exposure to infected populations of
commercially reared *B. occidentalis*), and *B. affinis* and *B.
terricola*in the East (from exposure to commercially reared B.
impatiens). In the late
1990’s, biologists began to notice that *B. affinis*, *B. occidentalis*, *B.
terricola*, and *B. franklini* were severely declining."


I wonder if it is proved or only hypothesized the link with Nosema bombi?

-- 
Juanse Barros J.
APIZUR S.A.
Carrera 695
Gorbea - CHILE
+56-45-271693
08-3613310
http://apiaraucania.blogspot.com/
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