>> Someone asked the question,
>> "What is the pH of nectar?"
>> [Bush] could not answer
> Having heard him here (Australia)
> recently I am not surprised. I am
> surprised that Missouri couldn't
> attract proper speakers.
In the defense of Missouri, they do call themselves the "show-me state", and
at least they did not have to underwrite the cost of airline tickets to
Australia to be shown whatever they saw. :)
I have been forced to make "deprogramming" an integral part of mentoring and
teaching, so as to help discouraged beekeepers avoid wasting another year
driving yet another hive or two directly into a ditch due to their innate
need believe in alluringly simplistic and/or mystical answers to complex
questions regarding bees.
The specific [Bush, et al] suggestion to use ascorbic acid to bring the pH
of sugar syrup from a claimed "6" to "3.5-4.0" is most often justified with
the following claims:
1) syrup with ascorbic acid in it keeps much longer
2) syrup with ascorbic acid in it is closer to the pH of honey
3) chalkbrood, afb and nosema reproduce badly at the "pH of honey" and well
at the "pH of sugar syrup"
4) Use 7 grams of Ascorbic acid to five gallons of 5:3 syrup (sugar:water)
to get a pH of 4.5, which may work for one place's water but not another's,
and certainly not everywhere.
On the far other end of the scale, there's another fellow, again out of the
Midwest USA, imply egg-laying rates in excess of 3000 eggs per day, all from
a flat refusal to feed sugar at any time, and stacking up drawn comb well in
excess of what the bees would ever be able to utilize. Queens are for sale,
clearly very special queens with traits hitherto unknown to science.
We've already talked about the advantages of enzyme-driven inversion of
sucrose over acid-driven or heat-driven inversion in bee feed. But pH?
Seriously?
The range of actual pH values of nectars found in nectar plants runs from pH
4.2 to pH 8.5, sez Baker in "Non-Sugar Chemical Constituents of Nectar"
Apidologie, 1977, 8 (4), pp.349-356.
But Yates, ( a UK author who wrote the study guides for their
national-standard certification tests) says that the ph of nectar ranges
from pH 2.7 - pH 6.4. So, the range is wide enough to make one wonder when
bees start to reject nectar as being "too acid" or "too basic". From what
I've read, they don't - it seems that odor is the repellent rather than pH.
So while justification (1) above is certainly true, making (2) true requires
far more acid than anyone would need to achieve (1), and (3) is just
nonsense in light of the wide range of pH in nectars gathered by bees, eaten
directly, and used directly to feed larvae.
Not sure as to final percentages that would result, but (4) seems a recipe
for acid hydrolyzed invert syrup. Keep that in mind in reading the quote
pasted below.
When dissected midguts were compared among bees fed each of several (very
simplistic) diets:
"The most significant bee mortality was found during autumn supplemental
feeding with acid hydrolyzed invert syrup."
and
"honey had no harmful effects on the midgut epithelial layer, and the
intestinal contents were completely attached to this layer, which leads to
the quality of digestion and maximum nutrient resorption. Similar results
were got when feeding bees with sugar syrup and enzyme inverted syrup
without the addition of yeast and malt. This means that each addition of
yeast and malt lead to damage to the midgut epithelial layer, and the
differences arise, depending on food source. The most serious damage on the
epithelial layer was found in midgut of bees fed with acidic invert syrup
(in all examined combinations)."
"Impact of Different Feed on Intestine Health of Honey Bees"
Mirjanic, Gajger, Mladenovic, Kozaric
Apimondia 2013
http://www.apimondia.com/congresses/2013/Biology/Plenary-Session/Impact%20Of
%20Different%20Feed%20On%20Intestine%20Health%20Of%20Honey%20Bees%20-%20Gora
n%20Mirjanic.pdf
http://tinyurl.com/jggzskg
(The paper includes color photos to compare the midguts, and even I can see
a big difference.)
Further, the pH argument is often linked to statements about the "microbial
health" of larvae, which is always good for a laugh:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3749107/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3318792/
"The presence of a gut microbiota is nearly universal among animals, but our
non-culture-based methods revealed that healthy A. mellifera larvae from
colonies at three geographic locations had few or no bacteria in their guts
(Table 3). The scarcity or absence of gut bacteria in A. mellifera larvae
seems especially odd in light of the well-characterized gut community of
nurse workers that orally feed larvae...."
"....However, other culture-based studies have suggested that larvae
naturally have large amounts of the characteristic phylotypes within their
guts. In these studies, larvae were not surface sterilized, and
contamination from the brood cell could have transferred small amounts of
these phylotypes to the surface of the larvae."
Yep, contaminated samples. Surprise.
"Alternatively, most larvae screened were concurrently infected with the
pathogen Paenibacillus larvae, potentially altering the natural dynamics of
the larval microbiota and allowing microbial colonization, as we observed
for colonies known to be infected with European foulbrood. Using
culture-independent methods, Mohr and Tebbe determined 16S rRNA gene
profiles but not total numbers of bacteria in adult and larval A. mellifera.
They found that gut community profiles of adults were consistent during 3
years of sampling (and consisted of the phylotypes we report here), but that
larval profiles differed from adult profiles, varied within and between
sampling years, and often lacked the characteristic microbiota phylotypes.
The irregularity of bacterial presence suggests that the larval microbiota
represents the bacterial community present in their food, bee bread."
To summarize, I think novice beekeepers might do better to turn on their
radio and listen to the girl who is "all about that base, 'bout that
base...", and realize that acids won't help them or their bees.
Some other references of interest on the subject, for those suffering
insomnia:
Detzel, A. and Wink, M. 1993. "Attraction, deterrence or intoxication of
bees (Apis mellifera) by plant allelochemicals" - Chemoecology 4: 8-18.
Hagler, J. R. and Buchmann, S. L. 1993. "Honey bee (Hymenoptera: Apidae)
foraging responses to phenolic-rich nectars" - J. Kansas Ent. Soc. 66:
223-230.
London-Shafir, I., Shafir, S. and Eisikowitch, D. 2003. Amygdalin in almond
nectar and pollen - facts and possible roles. - Plant Syst. Evol. 238:
87-95.
Singaravelan, N., Nee'man, G., Inbar, M. and Izhaki, I. 2005. "Feeding
responses of free-flying honeybees to secondary compounds mimicking floral
nectars" -31: 2791-2804.
Baker HG, Baker I. "The predictive value of nectar chemistry to the
recognition of pollinator types". Isr J Bot. 1990;39:157-166.
Freeman CE, Reid WH, Becvar JE, Scogin R. "Similarity and apparent
convergence in the nectar-sugar composition of some hummingbird-pollinated
flowers. Bot Gazz. 1984;145:132-135
Baker HG, Baker I, Hodges SA. Sugar composition of nectars and fruits
consumed by birds and bats in the tropics and subtropics. Biotropica.
1998;30:559-586.
Dupont YL, Hansen DM, Rasmussen JT, Olesen JM. Evolutionary changes in
nectar sugar composition associated with switches between bird and insect
pollination: the Canarian bird-flower element revisited. Funct Ecol.
2004;18:670-676.
Kromer T, Kessler M, Lohaus G, Schmidt-Lebuhn AN. Nectar sugar composition
and concentration in relation to pollination syndromes in Bromeliaceae.
Plant Biol. 2008;10:502-511. [PubMed]
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