Beekeepers:

>and there were several other cells with dead larvae that had suffered
chalk or some other problem, but the bees seemed to have the AFB under
control.

In the book Honey Bee Pests, Predators, & Diseases (Morse, Flottum):

p. 45: “Shimanuki, et al. (1992) found that antibacterial material from
chalkbrood mummies inhibited the growth of Melissococcus pluton and B.
larvae. This material was subsequently identified as the fatty acid,
linoleic acid (Feldlaufer et al. 1993)”

p. 95: “A recent interesting discovery about the interaction of bee
diseases concerns the effect of chalkbrood on European and American
foulbrood. Shimanuki, et al. (1992) noted a decline in the incidence of
European foulbrood in the United States was accompanied by an increase in
chalkbrood. Ethanol extracts of mixtures of mycelia and spores of A. apis
were shown to contain an antimicrobial substance active against the
bacterial pathogens of both European foulbrood and American foulbrood
diseases.”

Regards,
Dick