Nosema. This gut fungus is still a mystery to me. The more I sample, the less it seems to make sense. I take samples for Nosema, analyze them, and provide the results to the beekeeper. The idea is to provide hopefully useful information to help with treatment decisions or decisions on choosing breeder. However, when I provide the beekeeper with the results, I do not know what to tell them. Nosema levels just don’t seem to correlate with colony health: huge and healthy colonies can have 30 million spores per bee. I don’t even know what levels are considered to be high or potentially damaging. Or even if it is above a treatment threshold, if the one registered treatment, Fumagilin, will work. I have sampled the same colonies before and after treatment, and could not detect a difference in Nosema levels. Also, beekeepers that treated and those that did not often had similarNosema levels.  One further frustration is I cannot tell the beekeeper if what species ofNosema is in their bees: N. apis or N. ceranae. I have been assuming that the spores I am seeing are the more virulent and prevalent N. ceranae, but I do not know for sure.

Part of my issue may be that the effects of Nosema are subtle. Spores may only injure the colony when there are other stressors like poor nutrition or viruses, so healthy colonies may be able to carry a larger load. Another issue could be that after a Fumagilin treatment the spores may still remain in the bee, but not do any more damage. Since I cannot tell the vegetative and reproductive spores apart in the microscope, I may get a misleading picture.

The more I sample, the more I wonder and worry if the information I provide to the beekeepers is actually useful. Am I giving them the curse of too much information? Do they actually need to treat if the spore level is high? Or is it just a waste of money? I do think sampling for Nosema is important since it seems to be one of the best ways to try and make sense of it. If I sample a beekeeper’s colony, then I will give them the information I find and just explain that we don’t really know what the levels mean. I don’t understand what is going on, but I will keep trying to figure it out.  (Photo by Michael Andree showing Nosema spores as seen with a microscope. The spores are the really regular-shaped ovals with a dark halo around them.)

Written By: Katie Lee

Katie Lee has written 53 post in this blog.

I'm a part of the Midwest Bee Team based out of the University of Minnesota. I work with commercial migratory beekeepers in North Dakota and Minnesota to help them monitor pest and disease levels. Before I was on the Midwest Team, I was on the CA Bee Team working for the Northern California bee breeders. I was introduced to honey bees during my last semester as an undergrad when I took a class on social insects with Dr. Marla Spivak. Marla asked me to work in the U of MN Bee Lab over the summer, and have been enthralled with bees ever since. My main interests are bee breeding, Varroa, disease ecology, and extension work. I received both a BS in Ecology, Evolution, and Behavior and a MS in Entomology from the University of Minnesota.


9 Responses to “Nosema”

  1. David Bradshaw

    Have your thoughts on nosema changed or become more clear. I went into winter with high levels and didn’t know if I should treat or how to treat. Now I think I should have treated had a big dwindle in december 2012. Talking to a few queen breeders they had nil to very low levels going into winter.