<<but when were the diseases first clearly distinguished?>> R.B.
Quoting from Morse's book, Honey Bee Pests, Predators and Diseases, he states
"Phillips, in his introduction to White's publication of 1906 on bacteria in
the apiary, used the terms EFB and AFB to differentiate the two conditions
but made it clear that the designation did not refer to the geographical
distribution of the disease."
Quoting from Morse and Hooper's Encyclopedia (American book)
"E F Franklin joined the USDA in 1907 i/c the bee department. Dr G F White,
under his direction, discovered the causes of EFB and AFB."
Incidentally, Snodgrass, of Anatomy and Physiology fame, was also in that
department.
I can find no earlier reference.                      Sid P.