PHOTO: iStock/Thinkstock
Kristina Mercedes Urquhart
November 15, 2016

The first year of beekeeping for most hobbyists is usually fun and mostly free of complications or concerns—but all beekeepers are tested sooner or later. One concern that may crop up for beekeepers is nosema, or bee dysentery. Targeting the adult population of the colony, nosema is a protozoan disease (a tiny microorganism) that attacks the lining of the intestinal tract, weakening the hive by shortening the lifespan of the affected adult bees. Nosema can be on the mild end of the spectrum, reducing a colony’s production by almost half, or it can be rather severe, killing an entire colony.

What Does Nosema Look Like?

It’s impossible to diagnose a colony of honeybees with nosema accurately without first performing an autopsy and looking at the digestive tract of the bee. Most beekeepers do not have access to facilities that can conduct this kind of research or know what to look for themselves, so in lieu of clinical accuracy, we have to make our best guesses. Fortunately, the signs of nosema are usually pretty clear.

Primarily, you’ll notice streaks of light brown feces in and around the hive. Remember that bees tend to be immaculately clean, defecating outside of the hive exclusively. If you see waste inside the hive or around the entrance, this is a telltale sign of nosema. Some beekeepers refer to this as “spotting.” Additionally, individual bees may look sick, moving about without direction, wandering around the entrance to the hive, or shivering (not to be confused with fanning honey or conducting waggle dances).

In the bigger picture, a hive that fails to build up in spring to significant numbers and potentially shows these other signs is likely afflicted with nosema.

So What Can Be Done About Nosema?

First and foremost, keep your colonies strong. The best course of action is to raise healthy, “survivor stock” bees whose genetics are diverse and adapted to your area. Strong bees are able to fight nosema and a number of other honeybee ailments, including the dreaded varroa mite.

You can further discourage nosema by situating your apiary in a location that receives a lot of sunlight and good airflow. Again, this is a good management practice for preventing a number of ailments. Offer the best winter ventilation you can while keeping the bees warm enough for the area where you live. If your climate is warm enough during the winter, consider opening a top entrance to the hive.

Nosema is most common in the very early spring, just after bees have been cooped up for the winter, holding their waste for weather that is warm enough to fly. For this reason, be mindful of the quality of feed you provide to your bees in both the fall and spring. Sugar syrup is great in a pinch—certainly a better alternative to the bees starving!—but even better is raw, local honey, preferably their own. Avoid overly feeding bees in the fall, as this has been known to lead to more instances of nosema come spring.

Finally, an antibiotic medication called Fumigilin-B is available for prophylactic treatment. Conventional instructions guide the beekeeper to feed the medication in both fall and early spring, mixed into sugar syrup. Personally, I choose not to use medications, certainly not antibiotics, because I believe they negatively impact the overall immune function of the bees, ultimately leading to weaker colonies that may be able to win the battle against nosema for one year but not the larger fight against varroa mites, pesticides, colony collapse disorder and the other hazards that confront honeybees in our current world.

Strengthen your bees through mindful hive management, reduced moisture and increased ventilation, healthy feeding practices, and source strong queens with good genetics from reputable breeders, and nosema is likely to be something you rarely encounter.


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