Hi Gretchen, No, it is not self-defrosting. In fact, the frost builds up on the walls a bit so that I have put some foam there to protect the bagged items from it, and I make sure to manually defrost and clean it whenever it is empty so that the ice does not build up over time.
I do an immediate freeze from room temperature to -30ºC and then allow objects to defrost at room temperature for at least a day before opening the bag. There have been times when I was busy and left the bag sealed on the lab bench for a good week or so, only to find fresh frass and even live larvae when I finally got round to inspecting. I saw no holes in the bag to suggest a new, external infestation. So as Rich said, I say this based on personal experience, not controlled experiments. I'm aware it doesn't seem to make sense and that the articles and theory don't necessarily support it, but what can I say. This is what we see with T. herbarius here, which is not a beetle that shows up on the literature as far as I have found. As others have mentioned regarding odd beetles being seemingly resistant as opposed to other beetles, I can only imagine this is a similar case where T. herbarius happens to be particularly resilient. I hope none of you ever get it where you work because it is a nightmare of a beetle! Thank you all for the input and information. It's really helpful! Angelica On Fri, 3 May 2019 at 14:18, Anderson, Gretchen <[email protected]> wrote: > Angelica, > > Is your freezer self-defrosting? A self-defrosting freezer defrosts by > raising the temperature, thus creating a cycle of warming and cooling – > this can affect the kill rates. > > > > Research over the past 30 (+) years has demonstrated that a double freeze > is not necessary to achieve the kill rate. The more often you freeze the > more likely the pests are to develop anti-freeze tendencies – actually you > are mimicking natural freeze thaw cycles. In general, we feel that a fast > freeze (do not cool down the objects in a refrigerator) and a slow thaw is > best. The critical temperature is – 20 C, but you can go colder (See Tom > Strang articles). Once the object is in the freezer, leave it there for > longer than you think necessary (if you can). The other key factor is to > double bag items. This will significantly reduce moisture loss. > > > > There was research some years ago out of Sweden about freezing as pest > control. Preliminary findings were that even if eggs hatched after being > frozen – but the DNA seemed to be damaged, and Gretchen Anderson > > Conservator > > Carnegie Museum of Natural History. > > > > *From:* [email protected] <[email protected]> *On Behalf > Of *Angelica Isa-Adaniya > *Sent:* Friday, May 3, 2019 2:40 PM > *To:* [email protected] > *Subject:* Re: [pestlist] Freeze once or freeze twice? > > > > I have also had to re-freeze (not very dense) objects infested with > Tricorynus herbarius beetles even though I keep things in the freezer at > -30ºC for up to 3 weeks, and I always place objects in directly into the > -30ºC temperature. 😐 > > > > During the episode I told you about last year where the beetles were > making their way into the freezer, they always woke up within about 10mins > when I pulled them out for examination. Obviously, I don't know how long > they had been in there before I pulled them out, so it could have been just > a short time, but I don't take chances with these anymore. > > > > I guess some of these insects are just crazy resistant? > > > > - Angelica > > > > On Fri, 3 May 2019 at 11:33, Pollack, Richard J < > [email protected]> wrote: > > Todd, > > > > Generally, the faster the temperature drops, the more likely the pests > will succumb. Many cold-hearty arthropods will, indeed, modify the > osmolality if their hemolymph, and there may be intracellular protective > strategies that offer protection from ice crystal formation and > resultant tissue damage. Slowly chilling some of these arthropods can > induce the physiological changes. Hence, a rapid freeze is often most > successful in causing the demise of the target pests. > > > > In the case I mentioned earlier, we believe that odd beetle eggs may be > more freeze tolerant then the eggs of other pests. This belief is based on > observations and experience (failure from a single freeze/thaw events), > rather than carefully-crafted laboratory studies. Whereas the lab studies > would be preferable, independent observations here suffice (for now) to > convince us that a the second freeze/thaw cycle seems justified. > > > > I'd encourage others to provide data or their own observations, as those > might serve to modify our recommendations. > > > > -Rich > > > > *Richard J. Pollack, PhD* > > *HARVARD UNIVERSITY* > Environmental Health and Safety (EH&S) > Senior Environmental Public Health Officer > 46 Blackstone St. > Cambridge, MA 02139 > *Office*: 617-495-2995 *Cell*: 617-447-0763 > www.ehs.harvard.edu > > [email protected] > > > ------------------------------ > > *From:* [email protected] <[email protected]> on behalf > of Todd Holmberg <[email protected]> > *Sent:* Friday, May 3, 2019 12:01 PM > *To:* [email protected] > *Subject:* Re: [pestlist] Freeze once or freeze twice? > > > > For the group that believes a second freezing is necessary, is it because > of how some insects can apparently create some sort of internal antifreeze > like material that can allow them to come back to life after being frozen? > The second freeze then kind of "catches them by surprise" in a way as > they are unthawing thinking "winter is over". (Is that the general theory?) > > > > I have been told that as long as the freezer temp is already at -30 when > the object is placed inside, the rate that the object cools down is rapid > enough to prevent insects from protecting themselves with the antifreeze. > > > > Hypothetically, if you are freezing wood that is pretty thick/dense, and > wood boring beetles had burrowed deep into the object near the > center, could the thickness of the wood give those insects near the > center a little extra time to protect themselves? Would this type of > scenario benefit from a "double freeze"? > > > > -Todd > > > > On Fri, May 3, 2019 at 9:29 AM Voron, Joel <[email protected]> wrote: > > At -30 for 72 hours once is sufficient to kill all life stages of pests. > JTV > > > > > > *Joel Voron Colonial Williamsburg Foundation* > > Conservation Dept. > > Integrated Pest Management > > Office 757-220-7080 > > Cell 757-634-1175 > > E-Mail [email protected] > > > > > > > On May 3, 2019, at 8:52 AM, Adrian Doyle <[email protected]> wrote: > > Dear all > > Double freezing shouldn’t be necessary so long as the core temperature of > the object is at the correct temperature for the correct time > > Adie > > > > Mr Adrian (Adie) Doyle > > Integrated Pest Management Manager > > British Museum > > Property & Facilities Management > > Great Russell Street, > > London WC1B 3DG > > > > Tel: 020 7323 8207 > > Mobile 07813 363292 > > Also available by Radio > > > > Email: [email protected] > > > > *The British Museum* > > Great Russell Street, London WC1B 3DG > > britishmuseum.org > <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.britishmuseum.org_&d=DwMFaQ&c=WO-RGvefibhHBZq3fL85hQ&r=GO7C3XN3WgFy2IP-bFBbnUs_CYntqj57Dprtl40-_KE&m=HYc5B0R7euCxciXPUyhUN5Yp7PDC_pFjrS93rADVcRk&s=cOs2Cw5IGmVLWGTh6JqzlMKPhJAPJgeKrViPED0kNGM&e=> > > > > *The security classification for this message is OFFICIAL* > > > > > > > > > > *From:* [email protected] [mailto:[email protected] > <[email protected]>] *On Behalf Of *Sharon Penton > *Sent:* 03 May 2019 13:51 > *To:* [email protected] > *Subject:* [pestlist] Freeze once or freeze twice? > > > > Good morning all, > > > > Some of my colleagues are adamant about freezing collection twice when > dealing with pest. They freeze a first time then let everything get back to > room temperature for a day or so then freeze again. Is this common > practice? I've always thought if we can achieve a reliable -30 that should > take care of all adults larvae and eggs? > > Would someone mind weighing in? > > Thanks! > > Sharon > > -- > You received this message because you are subscribed to the Google Groups > "Museumpests" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/pestlist > <https://urldefense.proofpoint.com/v2/url?u=https-3A__groups.google.com_group_pestlist&d=DwMFaQ&c=WO-RGvefibhHBZq3fL85hQ&r=GO7C3XN3WgFy2IP-bFBbnUs_CYntqj57Dprtl40-_KE&m=HYc5B0R7euCxciXPUyhUN5Yp7PDC_pFjrS93rADVcRk&s=pgLORCbA5vlzLkPV9KAO_R8b5FphuyxKDUTEU80TUTA&e=> > . > To view this discussion on the web visit > https://groups.google.com/d/msgid/pestlist/CALWceqtcq04tuBmBQP0uvpFfmNezUsXoCdFkWH4YMc%3DDYTP3KQ%40mail.gmail.com > 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<https://urldefense.proofpoint.com/v2/url?u=https-3A__groups.google.com_d_optout&d=DwMFaQ&c=WO-RGvefibhHBZq3fL85hQ&r=GO7C3XN3WgFy2IP-bFBbnUs_CYntqj57Dprtl40-_KE&m=HYc5B0R7euCxciXPUyhUN5Yp7PDC_pFjrS93rADVcRk&s=FGpNtbcuiAjTD0XZ4dlHOptV18DFnjfgnVmm0MUW2ck&e=> > . > > -- > You received this message because you are subscribed to the Google Groups > "Museumpests" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/pestlist > <https://urldefense.proofpoint.com/v2/url?u=https-3A__groups.google.com_group_pestlist&d=DwMFaQ&c=WO-RGvefibhHBZq3fL85hQ&r=GO7C3XN3WgFy2IP-bFBbnUs_CYntqj57Dprtl40-_KE&m=HYc5B0R7euCxciXPUyhUN5Yp7PDC_pFjrS93rADVcRk&s=pgLORCbA5vlzLkPV9KAO_R8b5FphuyxKDUTEU80TUTA&e=> > . > To view this discussion on the web visit > https://groups.google.com/d/msgid/pestlist/9C51E7E8-C337-46D1-BE8C-A7CF7F7220DE%40cwf.org > 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