Why should beekeepers avoid feeding unknown honey to their colonies?

Beekeepers should avoid feeding unknown honey to their colonies primarily because it poses a significant risk of transmitting serious diseases, most notably American foulbrood.12

American foulbrood is a highly contagious and destructive brood disease caused by the spore-forming bacterium Bacillus larvae (also referred to as Paenibacillus larvae). These spores are exceptionally resistant to heat and chemicals, allowing them to persist in honey harvested from an infected colony. If a healthy colony is fed honey containing these spores, the disease can spread rapidly, potentially leading to the loss of the entire colony.132

Because of the severity of this threat, many jurisdictions require the destruction of infected colonies by fire to prevent further outbreaks. Consequently, beekeepers are advised to use only honey from known, disease-free sources when supplementing their bees' food supply.12