As Rich pointed out, we also had trouble with Odd Beetle eggs on herbarium sheets. We froze a temperature of at least -20C if not -25C and our thaw did not effect internal box temperatures. Even after 4 weeks we would have larvae hatch out after being at room temperature for something around a week. Refreezing did the trick.
I know that lab evidence shows things to be different, especially with precisely controlled temperatures, but even with a freezer we closely monitor we had this problem. It killed the Cigarette Beetle larvae, eggs, and adults no problem though. Generally refreezing is not necessary, but know your pests and if you’re worried then observe after thawing before putting back into storage/exhibition. Good luck all! Genevieve ================================================= Genevieve E. Tocci Senior Curatorial Technician Harvard University Herbaria 22 Divinity Ave., Cambridge, MA 02138 U.S.A. Phone: 617-495-1057 Fax: 617-495-9484 [email protected]<mailto:[email protected]> From: [email protected] <[email protected]> On Behalf Of Anderson, Gretchen Sent: Friday, May 03, 2019 3:18 PM To: [email protected] Subject: RE: [pestlist] Freeze once or freeze twice? 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]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> On Behalf Of Angelica Isa-Adaniya Sent: Friday, May 3, 2019 2:40 PM To: [email protected]<mailto:[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]<mailto:[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<http://www.ehs.harvard.edu> [email protected]<mailto:[email protected]> ________________________________ From: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> on behalf of Todd Holmberg <[email protected]<mailto:[email protected]>> Sent: Friday, May 3, 2019 12:01 PM To: [email protected]<mailto:[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]> 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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