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]<mailto:[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]<mailto:[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<tel:757-220-7080> Cell 757-634-1175<tel:757-634-1175> E-Mail [email protected]<mailto:[email protected]> [X] On May 3, 2019, at 8:52 AM, Adrian Doyle <[email protected]<mailto:[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]<mailto:[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]> [mailto:[email protected]] On Behalf Of Sharon Penton Sent: 03 May 2019 13:51 To: [email protected]<mailto:[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]<mailto:[email protected]>. To post to this group, send email to [email protected]<mailto:[email protected]>. 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