Nosema disease in honey bees is caused by the protozoa spore nosema apis that infects the epithelial cells of the bees’ ventricles. Nosema ceranae is another type of nosema discovered in bees in our region recently, and it is believed that this may play a role in the heavy losses that many beekeepers have experienced.

Fumagilin-B, an antibiotic registered for the treatment of nosema infection in honey bees, is the recommended method of control. Fumagilin-B works by attacking the actively multiplying disease-producing parasites in the bee’s digestive tract.

Fumagilin-B should be fed only in sugar syrup, as dusting and extender patties are not very effective.

Medicated syrup should be fed in the fall after the honey supers have been removed. This fall feeding is very important to protect bees during the winter season, when they’re cooped up in the hive. About 8 to 12 litres (2-3 gallons) of 2:1 sugar syrup will usually be needed for each colony. If you’re making your own sugar syrup for fall feeding, mix 2 parts sugar to 1 part water. Commercial bee syrup may also be used.

Mix 1 rounded teaspoon of Fumagilin-B into 4 ounces of warm water (38-49°C or 100-120°F), and stir this into 4 litres (1 US gallon) of sugar syrup until it has dissolved. One 454g bottle of Fumagilin-B will usually be enough to treat 50 colonies.

Country Fields Beekeeping Supplies website has a fact sheet with more information about the safe and effective use of Fumagilin-B to treat both Nosema apis and Nosema ceranae according to the manufacturer’s instructions.