[Syrphidae] freeze desinfection of insect drawers

Frank Dziock frank.dziock at tu-berlin.de
Mon Oct 23 09:36:30 BST 2006

Dear Andrew,

thanks for the detailed and very helpful information.

We also have a freeze for down to -80 degrees here, but I do not know
whether that would be too cold? It is possible to adjust the temperature
though, but then my colleagues that have genetic material stored in the
freezer would not be amused.

I will see, whether it is possible to relocate the genetic samples and
have the temperature adjusted to -35 degrees for my material and use
that more powerful freezer for freeze-fumigation.

Thanks very much again and best wishes from Berlin,


Andrew Whittington schrieb:
> Dear Frank
> Sorry, I was away at the time your email arrived, so I've come into the
> answering string quite late. I'm copying my response directly to the
> discussion list as well, because these details may be of use to other
> people.
> I was directly responsible for freeze-fumigation at the National Museums
> of Scotland, prior to my resignation. We used the
> following technique for museum-grade freeze-fumigation:
> For all mites and coleopterous museum pests the temperature needs to
> fall below -32 degrees Celsius for a minimum of 72 hours. For moths, and
> perhaps fungi, a slightly higher temperature is fine, but to ensure
> the mites and coleopterous museum pests are destroyed, you do need the
> above grade freeze-fumigation to rid a collection completely. My
> experience suggests that if you have moths, then you are as well
> treating for mites and coleopterous museum pests as well.
> We used these levels of freezing even for collections not suspected of
> being infested - this way the entire collection had the same base level
> fumigation. As is common at many institutions (thanks Chris!) all in
> coming material and all suspect material within the collections were
> thus treated. All materials were bagged and sealed prior
> to freeze-fumigation, but the period to leave them there after removal
> from the freezer, before removing the plastic bags, is not as long as
> mentioned in the responses.  We left collections only as long as it
> takes to reach room temperature again, and this was usually under twelve
> hours. No damage was ever experienced from this short duration over
> thousands of trials. In fact, no damage was experienced to any of the
> collections, drawers, pins or materials freeze-fumigated in this way.
> Now, you have a freezer reaching about -18 degrees Celsius. This can be
> a problem in three ways:
> 1. it is not cold enough to kill the eggs of known museum-pests (and
> sometimes the other stages of insects or spores of fungi). 
> 2. if you have a pest problem it may only suppress the infestation until
> temperatures rise again (perhaps as late as summer next year if
> you freeze-fumigate it now).
> 3. you will be lulled into a state of false self-security.
> Increasing the duration beyond the 72 hours mentioned above, to
> counter-act the effect of the higher temperature of your freezer (i.e.
> domestic freezers) may work, but to my knowledge it is scientifically
> untested and may result in 2 and 3 in the list above. If you do use your
> domestic freezer, you will need to remain vigilant over your collection
> to ensure it remains free of infestation after  you have processed it in
> this way -- it's a good idea to do this anyway!! Given that you do not
> have a known infestation, it will at least give you peace of mind, but
> it will not guarantee infestation free conditions; I have used the
> method myself (with a two week freezing period), but when in doubt, I
> try to get my material to the National Museums of Scotland. You likewise
> should be able to find some organisation with a freezer reaching -32 or
> lower. If the Museum doesn't have one, try some of the University
> Departments or commercial bulk freezing companies in the city.
> At present I know of no literature off-hand that I can direct you
> toward, but I'll keep an eye out.  The above is, however, good, well
> tried and tested practical experience.
> All the best
> Andrew
> -- 
> Andrew E. Whittington PhD FRES
> Consultant Entomologist
> FlyEvidence
> 2 Newhouse Terrace
> Queen's Road
> Dunbar EH42 1LG
> Mobile: 077 3400 6866
> *SKYPE: Flyevidence*
> Phone: +44 (0)1368 869 722
> Email: andrew at flyevidence.co.uk <mailto:%20andrew at flyevidence.co.uk>
> http://www.flyevidence.co.uk <http://www.flyevidence.co.uk/>
> Honorary Fellow of the School of Molecular and Clinical Medicine,
> College of Medicine and Veterinary Science, 
> University of Edinburgh


Prof. Dr. Frank Dziock
Fachgebiet Biodiversitätsdynamik
der TU Berlin
Sekr. AB 1
Rothenburgstr. 12
D - 12165 Berlin

Tel: 030 – 314 71368
Fax: 030 – 314 71355


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