Some more notes on the nosema study, in response to the following off-list
questions.
What did you think of that study? It appeared to me that they used spore
load as a proxy for fitness. They didn’t measure survival at all. It
appeared to me that the wheat syrup bees had more spores in May but they
leveled out by August.  It reminds me of another study which showed pollen
feeding increases spore levels but pollen feeding is beneficial overall.
So, that spore load is not a valid proxy for colony health.

Spore load can be very misleading with N. ceranae.  I'm covering the
subject in my recent articles in ABJ, which are subsequently posted to my
website.
Yes the authors measured spore loads, but to their credit, they also
measured prevalence -- the percentage of bees in a sample that were
infected.  Unfortunately, they made the mistake of taking their
warm-weather samples of bees from the entrance, which gives a very
misleading result.  Nosema samples should always be taken from inside the
hive, of bees at the outside edge of the cluster (for best comparison to
other studies).

Indeed, in August, their sampling of foragers and bees flying out to
defecate (entrance samples) indicated that 70% or more of those bees were
infected.  A colony would soon die if that were the case in the house bees,
which they unfortunately only sampled in November.

As far as fitness, they measured honey yield and amount of comb drawn.
Those were essentially the same for the colonies fed either honey or invert
sugar, and less for those fed sucrose or wheat syrup.  As far as colony
survival, I didn't notice that they kept track.

And yes, when bees are consuming pollen, especially in poor flight weather,
spore counts go up.  But that doesn't mean that the colony suffers to any
great extent.


-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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