I've been looking at the bee associated microbes for about two years now, ever since I heard that pollen has to ferment to become viable food for bees. Fermented pollen (beebread) boosts the protein content of pollen and supplies necessary substances. The beebread functions not only as food but medicine for the colony.
The fermentation process takes a couple of weeks, beginning with inoculation of the pollen by the bees with unique bacteria from the honey stomach. Fermenting yeasts provide food for more bacteria and eventually lactic acid ends up preserving the pollen creating a "pollen pickle". Because amino acids, vitamins, enzymes, antibiotics, proteins, sterols, etc., are being synthesized and/or released during this process, it's really important that it be allowed to occur uninterrupted. One sterol, 24-methylene chloresterol, is necessary for developing brood . If it is unavailable in the beebread, the bees will pull it from their bodies. After ~ two brood cycles, the bees will run out and be unable to feed the brood properly unless they have an influx of real pollen. Pollen supplement preserved with lactic acid is not the same as real fermented pollen. Any pollen supplement must have at least some (10-15%?) to be effective.
Formic acid, oxalic acid and HFCS all alter the fungal mycroflora of the colony. Balanced fungi are important in disease resistance as some fungi that can cause one bee disease can prevent another. Inhibiting some can open up niches for others to expand. The fungi also synthesize antibiotics and one particular fungus seems to be responsible for synthesizing 24-methlene chloresterol (this seems to happen within an hour or so of the bee collecting?inoculating the pollen).
When we first started looking into the microbes two years ago we immediately thought of the implications of formic acid which on the Miteaway 2 site is described as an anti-microbial. Fungicides also came to mind as a concern. Since then, we've learned that while fungicides are considered OK for bees as they don't outright kill them, they end up highly concentrated in beebread. Even if the grower is extra careful to not spray on open blooms, some fungicides that are labeled as "contact" actually function as "systemic", migrating through the foliage, and can show up in the nectar and pollen 3-5 days after spraying. Before the bees can even gather and inoculate the pollen, the microbes are already inhibited with the fungicides. The yeasts and their byproducts seem to play an extremely important role in the nutrition and "medicinal" value of the beebread to the bees...it makes sense that fungicides could inhibit the fermentation of the yeasts outright.
Because the window of opportunity for larval feeding is so short (6 days) any colonies exposed to fungicides or organic acids could experience glitches in larval development. Those bees suffering from sub-par nutrition and underdeveloped hypophrangeal glands (where brood food comes from) then have to go on to feed a next generation. Small deficiencies over time can have big impacts.
There was a recent discussion on Bee-L about the pollen being so contaminated on crops that beekeepers doing pollination are now feeding pollen patties while the bees are foraging to discourage them from collecting and/or consuming the pollen in the field.
The more we learn about the microbes the more fundamental they appear to be to the working of the bees and the colony. The microbes, bees, flowers and pollen have co-evolved over millions of years to function together in highly specialized ways.
I'm away from my house right now but have a whole file box full of studies that back up everything here. If anyone is interested, I'll be happy to post the titles of relevant studies when I get a chance. There are also pending releases of studies looking specifically at the effect of fungicides on beebread...not sure when they will be out.
Our best hives are far from any agriculture. Our most challenging locations are the ones closest to farms and orchards (not monoculture crops, small operations). This is our observation, not a statistically significant sample.
Ramona