The book:
https://books.google.com/books?id=xq7xCAAAQBAJ&pg=PA81&lpg=PA81&dq=pH+of+floral+nectar&source=bl&ots=8WH5RxxxHn&sig=Tl5LN5tqQG0wTUQaWfIQhfKbOBs&hl=en&sa=X&ved=0ahUKEwjb34aexrbJAhWG7D4KHRckBCgQ6AEIYTAI#v=onepage&q=pH%20of%20floral%20nectar&f=false
States that nectars vary in pH from 3.0 to 10 depending on plant species.
Beans have a nectar pH of 4.4 per:
http://www.pakbs.org/pjbot/PDFs/45%286%29/34.pdf
Sugar water solutions are going to have the pH of the water used to make the solution. So, generally 7.5 more or less.
Waller reports:
"An artificial-flower feeder was designed to compare the acceptibility of sugar solutions to foraging honey bees, Apis mellifera L. Discrimination against the least preferred solutions was apparently reduced and then eliminated as the number of bees imbibing was increased. Honey bees collected sucrose in preference to fructose and fructose in preference to glucose; 30-50% sucrose in preference to higher or lower concentrations; showed no preference between solutions ranging in pH from 3.2 to 8.8 but rejected those with a pH lower or higher; and showed an aversion to sucrose solutions containing potassium salts."
http://aesa.oxfordjournals.org/content/65/4/857.abstract
Artificial nectar has been seeded with several bacteria found in a honey bees gut and cultured, then tested for attractiveness to foragers. Bacteria which caused the nectar to become acidic were found to lose attractiveness to foragers. Bacteria that did not cause lower pH values resulted in no attractiveness changes.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086494
There are a great many publications on bacteria and yeasts found in nectar directly from the flower. Typical nectars have lots and lots of both yeasts and bacteria. If the nectar resides in the flower any length of time some of the bacteria are going to aerobically ferment the sugars present to make short chain acids, mainly acetic acid. Such acids will acidify the nectar unless there is enough foraging pressure to harvest most of the nectar secreted fast enough that it does not have time to ferment.
Dick
" Any discovery made by the human mind can be explained in its essentials to the curious learner." Professor Benjamin Schumacher talking about teaching quantum mechanics to non scientists. "For every complex problem there is a solution which is simple, neat and wrong." H. L. Mencken
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