Long-term exposure to Terramycin or
improper dosage levels apparently created the bacterial resistance. ... patties did
provide the means by which the antibiotic could be kept in the hive for many weeks or longer.
It has been reported that some beekeepers kept patties inside their colonies for several
months to a year. Leaving treatment materials in a hive longer than the label recommends is
not a good idea since it represents a violation of the label and can contribute to the
development of bacterial resistance to Terramycin Applying Terramycin in a powdered sugar
mix has always been a convenient method of administering the antibiotic. However, when the
treatment schedule is erratic and the bees consume all of the antibiotic before the brood nest
has been properly cleaned, the amount of AFB cycles up and down, but the disease is never
well-controlled. This type of imprecise treatment along with low doses or outdated Terramycin
probably contributed to the development of resistance in P. larvae.
        excerpt from article by Dr. Bill Wilson, in Bee Culture, Oct 2000