> There have been attempts to bring bumble bees into Australia 
> for glasshouse pollination and tomatoes.  So far they have been 
> rejected.  One of our grounds for objection to the importation 
> is the possibility of getting Varroa destructor which we don't have.

You have the ultimate laboratory, as bumblebees have become established in
Tasmania, but not on the Australian Mainland.  What's been the impact on
Tasmania?

In the case of mainland Australia, the bumblebees themselves are currently
considered an invasive species.
For example, see:
http://www.aussiebee.com.au/bumblebeeharm.html
http://tinyurl.com/k97c2xk

The paper linked below might be the source of the apparently garbled claim
about varroa.
It is not the varroa itself that has been shown to  "jump species", but
instead, the DWV virus most often spread by varroa, and also nosema.
No surprise that bumblebees forcibly inoculated with DWV can carry DWV and
perhaps further spread DWV, and there is an impact on their lifespan.
Also no surprise that bumblebees can become infected with honeybee nosema,
as the nosema strains are very similar.
But these infections would not be a bumble bee colony-threatening events. 

http://phys.org/news/2014-02-honeybees-linked-diseases-wild-bees.html#inlRlv
http://tinyurl.com/nt22ll4

Now bumblebees have their own forms of Nosema, and bumblebees imported from
Europe for greenhouse pollination ended up being responsible for the sudden
extinction of at least two species of US-native bumblebees, but this was a
unique situation, as the species of bumblebees imported was, at the
insistence of the self-appointed "Pollinator Protector" pressure groups, a
US species.  So, US native bumblebees where exported to Europe, bred, and
then imported, bringing with them a nasty strain of bumblebee Nosema common
in Europe, but hitherto unknown in the USA.  The US experience tends to
support a continued ban to protect your native bee populations, as we simply
do not know enough about bumblebee diseases to construct more than a
stick-figure "WTO risk assessment".  But under WTO rules, what you don't
know, tends to end up pushing an import down your throat.  In the case of
mainland Australia, the bumblebees themselves are currently considered an
invasive species.

In the study above, it is important to note that no one has shown that DWV
or can actually be spread from managed honeybees to bumblebees in "the
field".  This seems like another shoe dropping from the sneaker-wearing
centipede of the "Pollinator Protection Racket", where honeybees are first
disparaged as "non-native", and now can be labeled as a tangible threat to
so-called "native" pollinators with the unproven speculation: 

"Infected honeybees can leave traces of disease, like a fungal spore or
virus particle, on the flowers that they visit and these may then infect
wild bees."

Yes, the above is perhaps possible, but bees have shown themselves to be
difficult subjects for epidemiological study, and the transfer of diseases,
via flowers, between species is something we are going to have to see before
we give it any more credence than the long-intoned misinformation about hive
tools (rather than infected comb transfers) spreading AFB.

But ignore my words at your own peril.  This study will be waved about as
cause to create "honeybee-free" areas where "native pollinators can thrive",
and managed honeybees will be further disparaged by the "Pollinator
Protection Racket" as "disease carriers" without adequate science.

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