Garth had written about using bees to spread beneficial agents.  Here is an example from Australia.
 
I quote from the Australian Bee Journal of December, 1997.
 
"Keith Turnbull Research Institute in Victoria (Australia) is conducting biological control experiments on the weed, St. John's wort by releasing a microscopic mite onto the weed.  An experimental release of these mites will take place at Mt. Alexander, near Harcourt (just out of Castlemaine) during the last week of November, and the release will be by way of using honey bees as the vectors.  Four hives will be placed in the particular area and the mites introduced.  The hives will be fitted with pollen traps and the contents of the traps will be studied under the microscope to determine the eventual success or otherwise of the exercise."
 
I will let the list know of any further developments.
 
Trevor Weatherhead
AUSTRALIA