Nosema, chalkbrood, sacbrood, viruses and tracheal mites

On the first warm day of April, Anne sees brown streaks down the front of one of her hives. Dysentery, she thinks, and she has seen online that it means nosema. She's ready to buy a treatment that afternoon. Her mentor tells her to slow down. In Ontario, brown streaks after winter are more often a sign of poor winter feed.

This lecture is about the diseases that don't announce themselves like foulbrood. Most are common, most are manageable, and the key to all of them is not guessing.

Start with nosema. It's a tiny parasite that infects the gut of adult bees. It is very common: a study of Ontario colonies found the newer species in eighty four percent of them. It does the most harm in spring and early summer, when heavy infections mean fewer bees, less brood and less honey. Most colonies recover by fall.

The catch is that you can't diagnose nosema by looking. It takes a microscope and a count of spores. There is a registered treatment, sold without a prescription, but it is only indicated when the count is high, and never with honey supers on. Replacing two or three of the oldest brood frames each year also helps.

So what made Anne's brown streaks? Most often it's the winter feed. Thin syrup stored for winter can give bees dysentery, which is one more reason to feed thick, two to one syrup in the fall.

Chalkbrood is a fungus. Infected larvae dry into hard little mummies, chalk white at first, then grey or black. You'll see them in cells and at the entrance. It's usually minor. There is no registered treatment, and if it keeps coming back, beekeepers requeen the colony.

Sacbrood is a virus. The dead larva lies in the cell with its head end curled up, and when you lift it out, it is a watery sac inside a tough skin. There is no treatment. Keep the colony strong and your mites low.

And the viruses in general. Deformed wing virus and several others are spread mainly by Varroa. There are no registered treatments for any bee virus. The way you control the viruses is by controlling the mites.

Finally, tracheal mites. These are found inside the breathing tubes of adult bees, and you can only find them by dissecting bees under a microscope. Ontario's guidance sets a treatment threshold of ten percent of bees infested, averaged over the yard, and the registered options are formic acid products.

Now let's change one fact. Suppose, instead of brown streaks, Anne finds chalky white mummies in the brood and on the landing board. That's chalkbrood. It looks alarming, but it is usually minor. Keep an eye on it, and if it persists season after season, requeen.

The mistake beginners make is diagnosing by guesswork and treating by reflex. Nosema and tracheal mites need a microscope, and several of these diseases have no chemical treatment at all. For a sample, ask your inspector or one of the diagnostic labs listed by the Ontario Beekeepers' Association.

Here is the rule, in one breath. Nosema and tracheal mites need a microscope to diagnose, chalkbrood and sacbrood have no registered treatment, the viruses are controlled by controlling Varroa, and nothing gets treated until you know what it is.

Next, beetles, moths, bears and pesticides.