On Thu, 4 Oct 2007 13:02:57 -0700, William Farler <[log in to unmask]>
wrote:

>Does irradiation (food grade gamma irradiation) of honey kill all spores
that may be present in honey?  (EFB, AFB, various virus', etc.)

I am assuming that you are contemplating irradiating frames with honey
rather than honey for human consumption, otherwise James' comments supersede
the ones I am about to write.  

We did a study with electron beam (e-beam) radiation of comb a few years ago
with AFB to determine guidelines for W Canadian beekeepers.  I understand
that e-beam has less penetration for a given kGy dose than electron beam. 
The study was published in ABJ.  We had the operators shoot beams through a
stack of 9 empty combs or 9 combs containing either liquid or crystalised
honey.  While the effective dose (10 kGy) was maintained across all 9 empty
combs, the beam decayed to an ineffective dose as soon as it passed through
one frame of honey, regardless of whether it was crystalised or liquid.  We
also embedded vials containing either chalkbrood mummies or AFB scale within
frames containing varying amounts of honey and discovered both remained
viable if situated on a full frame of honey.  This is how we put in the paper:

"Beam penetration through limited amounts of honey in comb is important to
beekeepers, for frequently a 2 – 10 cm arc of honey crests frames of
disease-infected brood. Apiculturists currently recommend frames with honey
be extracted prior to irradiation to ensure adequate exposure across the
entire frame (Hornitzky 1994). Our preliminary findings suggest that
two-sided irradiation of frames containing small amounts of residual honey
along the frame tops (< 9 cm) results in the decontamination of A. apis or
P. l. larvae located in the nest area below. Whether spores of either
organism trapped within honey remain viable following radiation, however,
hasn’t been tested. Before guidelines can be established for the irradiation
of brood comb containing small amounts of honey, research must determine the
extent of decontamination within the honey itself". 

In absence of the aforementioned "more study" we recommended that any
beekeeper irradiating comb with e-beam should cull out all the honey-full
frames for rendering and only send forward combs that are fairly free of
honey.  Other jurisdictions recommend the same thing.  It is certainly a lot
easier and convenient to turn around deadouts for irradiation without
sorting them, particularly in W. Canada where the time between collecting
the deadouts and the arrival of packages is tight.  These deadouts, however,
often have a few outer slabs of honey.  I suspect that if the infection were
high enough in the deadout, that package would end up being reinfected and
the $5/box spent on irradiation, the cost of preparing and shipping the
deadouts and the price of the package may be partially or completely all be
wasted.

We ran dose responses on chalkbrood mummies and AFB scale and found both
organisms dead well below the 10kGy dose (no P. larvae growth when
irradiated above 6.25 kGy and no A. apis growth at doses above 8 kGy).  When
I did a literature search on Nosema and irradiation  I found no studies
specifically with N. apis (which is all we knew about back then), however
studies with other Nosema species suggests a 10 kGy dose would be lethal.
The inconsistency with Trevor's post may have to due to differences with
equipment in Australia and Canada.  

Adony

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