Freezing bird specimens to kill pests

From: Brian Schmidt
Subject: Re: [AVECOL-L] pest management and freezing
To: AVECOL-L at LISTSERV.LSU.EDU

Alison,

The NMNH Bird's collection has been successfully using freezing as part of
our Integrated Pest Management program for at least 14 years. The key is to
get the pests frozen as quickly as possible. It's the formation of ice
crystals in the cells of the pests that kill them. If the pests are not
completely frozen (i.e. killed) they can develop "anti-freeze" in their system
and become resistant to further freezing. We use a -20C chest freezer to
accomplish this task, and keep our specimens in there for a minimum of 3
days (10 days typical). The specimens either placed in a sealed plastic box
and/or in a plastic bag before they are placed in the freezer. This
prevents condensation on the specimens when they are later removed from the
freezer and allowed to come to room temperature.

We have not seen any effects on the specimens from freezing. There are
some papers (sorry I don't have the references handy) that show that
repeated freezing and thawing may cause the bill covering to come off from
either a direct result of freezing or from the expansion and contraction of
the wooden stick that has been 'seated' into the bill during the preparation
process. However,(at least in our collections) most specimens will probably
not be frozen more than a couple of times in their lifetime. Thus, it's a
minimal risk from the freezing compared to the damage that pests can do to
the skins.

In the event of an outbreak that cannot be accommodated by our freezer(s),
we seal the case with an overdose of PDB for at least a month.

Hope this helps,

Brian K. Schmidt
Museum Specialist
Division of Birds
Smithsonian Institution

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From: Brian Schmidt <SCHMIDTB at SI.EDU>
Subject: Re: [AVECOL-L] pest management and freezing
To: AVECOL-L at LISTSERV.LSU.EDU

A couple additional comments:

First to correct a typo on my previous post...we use a -10C freezer not a
-20C freezer.

Second, I have been reminded by my co-worker (Claudia Angle) that another
effective freezing method for dealing with infestations is to quickly freeze
the object(s), quickly raise the temperature, then freeze the object(s)
again. This creates a temperature shock effect that will help kill insects
that might survive the initial freezing. This has been said to be more
effective than a single freeze to kill the "hard to kill" eggs of dermestids
and other museum pests.

Third, in addition to insects developing a chemical antifreeze, insect
larvae can eliminate their systems of water when faced with slowly falling
temperatures. This leaves only fatty tissue, which is not vulnerable to
freezing.

Main point: The most important thing to remember about using a freezer for
killing pests for preventative measure and dealing with infestations is the
faster the freeze rate, the more certain the kill will be.

-Brian

PS A useful reference is "Approaches to Pest Management in Museums" by
Keith Story 1985

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From: "Hinshaw, Janet" <jhinshaw at UMICH.EDU>
Subject: Re: [AVECOL-L] pest management and freezing
To: AVECOL-L at LISTSERV.LSU.EDU

We also have been using freezing for a number of years, and it seems to work just fine for incoming material. We usually do it for at least 72 h- 1 week. Freezing quickly (so don't just pop a box of specimens wrapped in cotton in the freezer) and then thawing for a few hours, then refreezing will really do the job. If you have good seals on your cases, air conditioning (under 84 degrees), and low humidity all year (under about 55%), that really is the best prevention. However, if you discover an infestation in a case, you can't freeze the whole case. You could freeze all the drawers, but I think you would still have to fumigate the case. We have university pest control people who can do that, and they use an encapsulated pyrethrum. They also treat the skin room every spring by spraying a 6" wide strip along the floor/bottom edges of the cases, under the windows, doors, pipe openings, etc. If a bug walks through that, it is dead. It is safe for you (I guess unless you want to lick the floor), and you can apparently wash (but not wax) the floor and it will stay there. It lasts about 6 months. We have it done in the spring, which lasts all through the warm months any bugs are likely to get in through the windows if they don't seal tightly (as our old ones).

The bugs that damage skins are not the same species as the ones used to clean skeletons. The wild ones here that are a problem for skins are much smaller integument specialists (adults about 1/8").  As we are sort of on this topic, here is a great link (if I do say so) to information on setting up and keeping a bug colony for skeletons:

http://www.ummz.lsa.umich.edu/mammals/dermestid.html

Janet Hinshaw, Collection Manager
Bird Division
Museum of Zoology
Univ. of Michigan