Dear Alan
BT is harmless to anything except in the mid gut of certain moth larva (caterpillars). A few years back, we beekeepers had a product called Certan that was a Bacillus Thuringiensis strain to be sprayed on honey comb to kill wax moth larva. I don't believe even when sprayed directly on the bees it ever caused any harm.

Best wishes
Stan
______________________________________________________
       -            Stan Umlauft dba
      "  `          A & Bee Honey Farms       /)
      "   `         P.O. Box 5155          -8|||}-
  _- -_`-_|'\  /`   Bay Point, CA USA         \)
_/ / / -' `~()()    94565-0655  North 37  West 121
 \_\ _ /\-._/\/     (925)458-3900, fax (925)458-5560
      /   | |       email:    [log in to unmask]
     '`   ^ ^       web site: www.honeybee.com
~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*