Some subs contain potassium sorbate and also sodium propionate, which are fungus and bacterial growth inhibitors respectively. These are very inexpensive (human) food preservatives available from Univar in bulk, and elsewhere in smaller amounts.

Since nosema is fungal, could the sorbate be a factor? I know Gilles Fert mentioned using sorbate in his thin syrup in his book about queen rearing to prevent fermentation, so the use of sorbate for bees has a history.

Nonetheless, I have asked many researchers if they have any knowledge about this and received blank stares. Mike Randall mentioned to me at the IPM Workshop in Edmonton that nosema has been reclassified -- as a fungus, if I got it right. This got me thinking again and I decided this is worth chasing. Being lazy, I am calling out the hounds (you folks) to join in the chase. Someone should make a test to see if these preservatives have any effect on the nosemas.

Of course, there are those who will find this revelation a further reason to condemn all subs, citing the tremendous importance of each and every microorganism in each and every hive on God's Green Earth, even though only some subs use these inhibitors. Those battling nosema, though, might want to consider making an exception.

Food for thought?

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The current levels of potassium sorbate and also sodium propionate in one well-known proprietary diet is listed as 0.1% (1 part per 1,000)

There is a lot of good info in Allen Carson Cohen's "Insect Diets" as well. See http://www.amazon.com/Insect-Diets-Science-Technology-ebook/dp/B000PWQMWS

I've scanned just two pages and think I can share them here as "fair use", since anyone who looks at them is going to want to rush out and get the rest of the book.

Enjoy.  Just remember this stuff can be toxic to your bees if you miscalculate by a factor of ten.

The following is worth reading
by Peter Borst.

I think are a lot of newbees here who have no idea of the history of beekeeping.

First a little about our great inventor Amos I. Root. According to his autobiography, he was interested in science from a very early age, first reading about electricity at the age of “nine or ten”. He claims to have published several articles in Scientific American before he was seventeen and at that young age, he took to the road as Prof. A. I. Root, giving scientific demonstrations in country schoolhouses. His handbill reads: “Flashes of Lightning! will be sent to different parts of the room. The Aurora Borealis will be exhibited on a small scale and the phenomena full explained.” Mr. Root soon got interested in bees, however, and perhaps if he had not, he would be remembered by the general public alongside Bell, Ford, and Edison as one of the great inventors of that era.

In 1875, he obtained some comb foundation and by 1876 he published instructions on how to press beeswax with copper plates. He found the process so tedious that he commissioned a mechanic to build him a set of rollers. With this device he could “roll out one continuous sheet a foot wide and a mile long if we wished.” He continued to experiment, attempting to reinforce the foundation with paper and cloth to prevent the inevitable sagging of the honey combs. He tried muslin and linen, and later metal and even very thin wood. It was another hundred years before Pierce perfected plastic foundation.

It appears that Mr. Root was also the first to experiment with much larger cells. He writes: “It evidently puzzled the bees.” But it was Monsieur Ursmar Baudoux of Belgium that took the experiment to great lengths in 1896. Roy Grout writes: “By means of stretching foundation, he experimented with various sizes of foundation having 750 cells to the square decimeter, 740, 730, 710, 700 and even 675 cells per square decimeter. This is in contrast to the U. S. standard size which is 857 cells per square decimeter.” Early experiments with very small cells were made in order to increase the number of bees raised on a comb, but these were given up in favor making larger bees. Grout states that in actuality, bees can’t really be enlarged more than about 2 per cent by this method.

Knowing that varroa do not reproduce in the smaller worker cells of its host Apis cerana, preferring the larger drone cells, speculation arose that varroa buildup could be reduced by forcing our bees onto foundation of a smaller size. Dr. Erickson experimented with this idea in the early 1990s but gave it up in favor of breeding bees for varroa resistance, as I mentioned in my previous article. Others continued the work and came up with some very interesting theories. Chief among these is the conjecture that European honey bees were smaller in the 1800s, prior to the widespread adoption of comb foundation.

They claim that the adopted sizes of foundation are unnaturally large and this accounts for the great success that varroa has had in devastating our bees.I suggest that this an entirely false premise. Early beekeeping books refer to the average size of worker brood cells as about 5 to the inch. Cell size varies considerably but a correct average is remarkably close to 5 per inch. Only later, were far more accurate measurements made. Denwood states that typical foundation of 850 cells per square decimeter would be the equivalent of cells measuring roughly 5.2 mm across. Badoux’s large cell foundation was 700 cells per dm2 or about 5.7 mm. Small cell advocates claim the correct size to be 4.9 mm, or about 950 per dm2. Comb foundation from South Africa runs about 1050 cells or about 4.7 mm, since the African honey bee is smaller than the European varieties.

There is little doubt in my mind that European bees were not smaller in the 1800s than they are now, and it seems unlikely that they were permanently enlarged by the use of foundation. It is more likely that the cells of our honey bees are naturally about 5.3 mm. Steve Taber studied natural comb building extensively and concluded that “foundation manufactured for the construction of new combs in hives does not have the correct dimensions. For example, Grout (1963) suggested 857 as a standard for worker comb. Our measurements, converted to square decimeters, were 813.8” which is about 5.3 mm. In other words, the natural size is actually a bit bigger than most foundation.

But some argue that he was using bees that had been raised on foundation and were already artificially enlarged. To see what the natural size of bee cells is, we would have to go somewhere where bees have never been raised on foundation. That place is Central America. As late as 1979, bees were still kept in hives without frames. The percentage of frame hives ranged from 44% in El Salvador, 15% in Costa Rica, to little or none used in Belize and Panama.

Marla Spivak spent much time in Costa Rica observing the onset of Africanization. She measured the cell size of the European bees before, during and after the arrival. She refers data collected by researchers as early as 1973 indicating European bees in the tropics built cells ranging from 5.0 to 5.4 mm. These bees, being kept in box hives for countless years, can hardly said to be affected by manufactured comb foundation. According to Marla Spivak, European bees in Costa Rica in 1984 built comb with cells averaging 5.3 mm.

Marla Spivak refers to one apiary that she studied in the mountains. There were 9 hives, which the owners filled with swarms. These hives were plain boxes filled with natural comb. The average cell size in each and every hive was 5.3 mm. The first arriving hybrid African swarms built comb around 5.0 mm and subsequent swarms (less hybridized) ranged from 4.7 to 5.0. This phenomenon was observed throughout South and Central America.

Finally, I offer this email from Ahlert Schmidt: “I would like to comment on bee cell size again. In Germany there has been beekeeping on natural combs for over five hundred years using skeps and there are still some apiaries using that technique. So there are bees that never have seen foundations for hundreds of generations. The cell size of combs constructed by these bees is still between 5.3 and 5.4 mm (805 cells per square decimeter) coming close to 5.37 mm which is the average of cell size for normal combs in Germany.”

Of course, the theory doesn’t matter that much, if the technique would work. But would it? A perfect test came when varroa arrived in South Africa. They already had small cells in all their hives! What happened next is highly instructive. According to Mike Allsopp, varroa mites were found in South Africa in 1997. Many people feared that honey bees, both in managed hives and in the wild, would be drastically reduced or wiped out altogether. At the onset, incredible numbers of mites were found in commercial hives. There were averages of 10,000 and maximum counts of 50,000 per colony. The much smaller cells of African bees were simply not a deterrent at all. Typical mite symptoms also appeared including spotty brood patterns, deformed wings, and eventual collapse. Thousands of colonies perished.

Yet by 2005, mite counts had plummeted to negligible numbers in regions that previously had the highest levels of infestation. Evidently, the Savanna honey bee (Apis mellifera scutellata) developed “varroa tolerance” in six to seven years. No effort had been made to breed resistant stock. Mike Allsopp states that the most likely explanation for the change is the ability of honey bee workers to remove reproducing mites. This trait became predominant due to natural selection in the wild and managed populations. He states emphatically: “Captive breeding programmes and especially gene selection programmes can never adequately keep up with the changing environment, certainly not to the extent that a ‘live-and-let-die’ approach can.”

Small cell advocates frequently state that the only thing they have changed is the cell size, so that would account for lowered mite levels in the colonies. However, they miss this key point: they have also stopped treating for mites, which means susceptible strains quickly die off and they are left with only bees that can deal with mites. This is corroborated by Mike Allsopp’s thesis.

It is certainly worthwhile to search for new methods of ridding ourselves of pests, but it isn't enough just to have a good idea.