Most interesting about the HMF levels, heating and acidification.
Nettle tea has a good write up in the literature should anyone feel it
appropriate to feed. Make the syrup with an infusion of nettles (a good handful
steeped in boiling water) rather than with plain water. In view of Paul’s
comments best to let the water cool before adding sugar (plain white).
Gareth
On 21 Sep 2020, at 14:06, Juli Cohen <juliane.cohen@xxxxxxxxx> wrote:
Thank you, Paul. That’s really interesting.
I also have no intention of feeding our bees. We took the top box off both
our Warrés for us, and there is plenty of honey in the second box for the
bees. Plus they are still busily foraging in the lovely weather we’ve been
having. They’re particularly enjoying the caryopteris and dahlias at the
moment.
Juli
On 21 Sep 2020, at 13:58, Zuzana Meryova <zuzanameryova@xxxxxxxxx> wrote:
Thank you Paul, just to say, this is my third beekeeping season and I do not
feed (strictly) - Im very stubborn about it. I really believe feeding makes
bees ill.
On Mon, 21 Sep 2020 at 13:37, Oxnatbees <oxnatbees@xxxxxxxxx
<mailto:oxnatbees@xxxxxxxxx>> wrote:
Hi folks,
This time of year, people often talk about feeding bees sugar syrup. My
views here have changed.
In the past I have followed BBKA recommendations and poured syrup into
feeders until the bees had 20kg of stores; eventually I realised this is
"worst case requirement" and I do not live in Scotland, or a forage-poor
area, or have vast colonies with excessive numbers from stimulating their
laying and buying over-fecund queens. In fact my colonies get through winter
with something like a quarter of the stores the BBKA suggests, and they seem
to gather enough themselves. So for a couple of years I have not fed them at
all.
But if you do decide to feed, what should you feed them?
Well one golden rule is don't feed them honey from another apiary, because
of the risk of transmitting spores of nasty things.
In general the advice is strong sugar syrup, heated to ensure you dissolve
as much sugar as possible; plus various additives, lemon juice is often
mentioned. I have discovered this is bad advice.
I attach a couple of research papers. To summarise:
If you heat sugars you make small quantities of the chemical HMF, which is
present in honey at low levels but bad for bees in high levels. Dissolving
sugar in water at 50C is probably not a problem but the amount of HMF
increases exponentially with increasing temperature and many recipes
recommend boiling the syrup. Don't boil it!!!
If you add lemon juice the acidity is unpredictable - depending on many
factors such as the ripeness of the lemons. Honey's pH is around 3.4 to 6.1
but lemon juice can reduce the syrup to between 2 - 3. That's very acidic
indeed and does not do the bees' guts any good.
Both these factors severely impact bee lifetime.
Mirjanic et als' key findings after 3 years' tests:
Diet
Average life of bees (days)
Comments
Honey
27
Sugar syrup
22
Acid inverted syrup
12
They used tartaric acid rather than lemon juice. I've added vitamin C to
syrup in the past - also called ascorbic acid - it probably does the same
thing.
(They tested a wider range of diets and found adding brewers' yeast, and
enzymatically inverting the sugar, somewhat ameliorated the hits to
lifespan.)
The other paper is focused on HMF levels (boiling, lemon juice) and shows
similar dramatic life expectancy problems with syrups, albeit a bit trickier
to summarise in a simple chart.
The bottom line here is -
if you do decide to feed your bees, don't boil the syrup and don't add any
kind of acid;
most recipes, including those I myself have recommended in the past, are not
based on evidence-based research.
Paul
P.S. you also see adverts for supplements and pollen substitutes. These
should not be required in Britain, where the bees and plants have
co-evolved, though there are areas like New Zealand where the bees have
difficulty finding certain amino acids in native plants' pollen. They are
sometimes commercially useful to large bee farmers who force their colonies
to breed early, in late winter when there is little pollen around. In their
case they have hundreds of hives in one spot and use early, large colonies
to pollinate orchards, etc. None of us have vast numbers of hives and they
are all static, and we tend to leave most of the honey in the hives, so
ignore such advertisements and remember, the wild colonies do quite well
without them!
