"Crisco patties with Terramycin are no longer recommended for use against American Foul Brood (AFB), European Foul Brood, and Tracheal mites. Please don't use this treatment to avoid development of resistance of AFB to terramycin. To date, we have not found AFB resistance to Terramycin in Ontario."

from 2000 Ontario Recommendations for Honey Bee Disease Control

http://www.ontariobee.com/disease.htm