Nosema disease can be treated successfully with Fumigillin (trade name Fumidil). Colonies are usually treated in the fall, spring, or both. Follow the directions on the label and feed the correct dosage in 50% sugar syrup (1:1 sugar:water, with antibiotic dissolved in 5-10 ml warm water then mixed into the syrup) in the spring, 66% in the fall. Nosema ceranae also responds to Fumidil treatment, but may require a higher dosage. The antibiotic does not kill the spores, but disrupts vegetative reproduction of the pathogen inside the host cells. Fumidil will not, therefore, completely remove the spore source if colonies are heavily infected because both honey and beeswax can be a reservoir for Nosema spores. – Zachary Huang, Michigan State University