In Ontario, AFB prevention is typically done with an oxytetracycline mixture in the spring and late summer/early fall. The first application is in the early spring as the queen starts laying eggs after winter. Treatment must be timed so that the LAST application is at least 30 days before honey supers are placed on the hives. This is so that no antibiotic ends up in the honey. The second treatment is in the fall after the honey supers are removed. Supers need to be removed and treatment started while the queen is still actively laying so that she can produce strong and healthy winter bees. Avoid the temptation to get all the honey possible for that season, or it may end up being too late to treat. Once the queen stops laying for the season, it is too late to treat. The reason is that treatment is geared toward the brood. There is no benefit to the bee once it has emerged from its cell.
Treatment involves sprinkling a mixture of oxytetracycline and icing sugar into the hive. The calculator below will determine the ratio depending on how many hives are being treated. Keep in mind that this mixture will be enough to do all three treatments necessary. You will need a kitchen scale and large tub or pale. Once mixed thoroughly, it is ready to be applied to the colonies.
Sprinkle one level tablespoon on one end of the tops of the frames and another tablespoon on the other end. If you are running doubles, only treat the top brood box. Do this to each hive every 5-7 days for a total of 3 treatments. The bees will incorporate the icing sugar/oxytetracycline mixture with honey and pollen to make bee bread and will feed it to the growing larvae.