Continuing from the citation of KRAUS AND PAGE: Varroa on feral A. mellifera:

The extent to which Varroa reduces the feral honey bee population suggests that there is no widespread, general preadaptation to Varroa mites in honey bees. Varroa swept rapidly through the feral and commercial populations of California and devastated them. 

Other honey bee diseases have had similarly devastating effects upon populations. A large portion of the honey bee population in the United Kingdom perished at the beginning of this century because of the Isle of Wight disease, probably caused by Acarapis woodi. In Hawaii, American foulbrood killed 90% of the honey bee population in the 1930s. 

Apparently, selection for avoidance of potential sources of diseases and parasites did not occur, suggesting that parasites and diseases have not been important selective agents in the natural history of honey bees.

PLB

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