Nosema is caused by the microsporidian Nosema apis, a small, unicellular organism that is unique to honey bees; it is the most widespread of the adult honey bee diseases. Nosema infects the epithelial cells of the honey bee ventriculus thereby causing dysentery. Queens, drones and workers are all susceptible to Nosema. The spore from the parasite must be ingested by the bee in order for infection to occur. The spore germinates in the midgut, penetrating the cell lining as it multiplies, reducing the life span of the honey bee. Nosema spores are spread to other colony members through fecal matter. Colonies in northern climates are more seriously affected than colonies in the south because of the increased amount of time bees are confined in the hive. Nosema, if left untreated, can cause queen supersedure, winter kills, reduced honey yields and dwindling populations. It is more common during times of confinement like winter and spring.

Symptoms of Nosema are vague and difficult to field diagnose. If you believe your colonies are infected with Nosema, send a sample of your bees in alcohol to your local county agent for verification.

The symptoms include: slow spring build-up (best indicator) disjointed wings, distended bloated abdomen, a lot of yellow streaks on the outside of colony and crawling bees outside of the hive. These symptoms may also be associated with tracheal mites.

Do not overlook this disease just because it is not common in the south. Prevention is the best way to keep your bees free of disease. Some good beekeeping practices are to avoid placing hives in low spots and to provide ample ventilation. Treat with Fumidil-B® according to the manufacturer's instructions.

Honey Bee Disorders / UGA Honey Bee Program / UGA Entomology Department