Approaches to Insect Problems in Paper and Books
- Insect infestation
- Books about insects and books about books
- Detection of insect infestation
- How freezing kills insects
- Materials that should not be frozen
- Freezing books to kill insects
- Monitoring to detect insects
The Ransom Center receives many inquiries regarding the treatment of materials infested by insects. The contents of this handout have been gleaned from experiences with pest control at the Center over the past ten years and research into the field of integrated pest management, as well as attendance at national and international conservation conferences.
The information focuses mainly on the eradication of insect infestation in books. The process of freezing books is outlined, and some sources for learning more about insects and books are provided.
If a large number of books are infested it is suggested that the American Institute for Conservation of Historic & Artistic Works be consulted. This is a professional organization of conservators that provides a referral system for people with conservation questions.
The American Institute for Conservation
of Historic & Artistic Works
1156 15th Street NW, Ste. 320
Washington, DC 20005
(202) 452-9328 fax
There are several types of insects that damage collection materials including books. The most common pests are roaches, silverfish, and various types of beetles. These insects eat the protein and starch components in books and other materials, and the feces of these and other types of insects can disfigure collection materials. Protective enclosures can lessen the chance of insect damage. The most important safeguard against insect damage is good housekeeping. For specific information about pests of collection materials, please consult the books listed below.
Books about insects and books about books
The following books provide information on the identification of insects, their habits, and damage potential. Books that discuss setting up a collection-monitoring program and that provide general tips for the care of library collection materials are also listed.
Approaches to Pest Management in Museums by Keith Story is a U.S. government publication from the Smithsonian Institution Center for Materials Research and Education (SCMRE), available online at: www.si.edu/mci/english/learn_more/publications/articles.html
Heritage Eaters... by Mary-Lou E. Florian presents essential information about the materials that make up heritage objects, environments needed for such objects, and aspects of the biology of the insect pests and fungi that damage these materials. Control strategies are suggested. (ISBN 1873936494)
Common-Sense Pest Control by Olkowski and Daar covers pesticides, insect behavior, and solutions for problems. (ISBN 0-942391-63-2) www.birc.org
The Care of Fine Books by Jane Greenfield is a good text on care and handling. (ISBN 1-55821-003-2)
Urban Entomology by Walter Ebeling is a classic text for the identification of insects. It is no longer in print. (ISBN 0-931876-19-2) Most of this book is available online at: www.entomology.ucr.edu/ebeling
Museum pest list is an excellent resource for insect identification and discussion of insect pests of libraries, archives, and museums: www.museumpests.net/becomeamember.asp
Detection of insect infestation
In general, if materials are stored in a clean, cool, and dry environment and are looked at and dusted occasionally, the risk of damage by insects is greatly reduced, and problems will be detected before a lot of damage is done. Whenever an insect is found in a book it is advisable to inspect the area where the book was stored to see if more insects are present in the materials nearby. Look for little piles of "frass" (a term for insect excrement) on the shelf. The color of the frass varies depending on the type of insect and what it has eaten. Beetle frass is a fine granular powder (more like very fine sand than flour in texture). If a tiny dust pile is found near a book, examine the book for any damage an insect might have caused. Beetles make tiny holes (about the size of a pencil dot) usually along the spine of a book. Silverfish leave tiny black specks of frass. Silverfish eat along the surface of book cloth and the edges of pages that protrude from a stack of paper. Roaches produce 1-mm size fecal pellets and leave brown stains. They eat book cloth as well, but the damage they cause is less delicate than that of silverfish. It is important to determine the type of insects causing the infestation and the extent of the problem before planning a strategy to solve it.
How freezing kills insects
The article "The Freezing Process—Effects on Insects and Artifact Materials" in Leather Conservation News, 3(1) Fall 1986, pp. 1–13, written by Mary-Lou E. Florian, is an excellent reference on the treatment of insect-infested materials. Several insect collection pests are profiled in this article. The precise cause of death by freezing is not known. Possible factors include dehydration, osmotic swelling, loss of bound water, changed enzyme reaction rates, ice crystal formation, and the rupture of cell walls. Insects can survive freezing if they are not frozen quickly enough, not frozen at cold enough temperatures, or not thawed slowly enough. Repeated cycles of freezing and thawing can kill even those insects that are resistant to freezing.
The article "A Review of Published Temperatures for the Control of Pest Insects in Museums" in Collection Forum, 8(2), 1992, pp. 41–67, by Tom Strang, gives extremes of hot and cold temperatures that prove lethal for specific types of insects. Even the hardiest insects can be killed by a single exposure to temperatures between 45 to 65 degrees centigrade (113–149 degrees Fahrenheit) over a six-day period or -10 to -40 degrees centigrade (14 to -40 degrees Fahrenheit) over a 25-day period.
A good rule of thumb for most insects is to freeze to the center of the object within four hours at a temperature of -20 degrees centigrade (about -4 degrees Fahrenheit) for at least 72 hours, then to thaw the materials over a 24-hour period.
Materials that should not be frozen
Some materials should not be frozen. The fats contained in certain types of leather may rise to the surface of the leather if the leather is frozen, causing a phenomenon called "bloom." If an object is made up of more than one kind of material (for example, leather and wood used together to make the covers of a book), the differing materials can freeze at different rates. Damage can be caused by the expansion or contraction of these varying materials. A professional conservator will give the best advice on what materials not to freeze.
What follows is a partial list of materials that should not be frozen. It was adapted from a protocol used at the Conservation Unit at the Museum of New Mexico:
- paintings on canvas
- paintings on wood panel
- ivory, bone, teeth
- old or deteriorating—"weeping/crizzeling"—glass or glass components
- high-fire ceramics
- joined wooden panels
- wax or objects with wax fills
- objects with desiccated or failing glues or adhesives
- objects with finish craquelure or other evidence of finish deterioration
- objects in which layers, such as inlays or veneers, are splitting or cleaving away from the substrate
- objects with inlays or veneers that are warped, tented, or lifting
- drum heads
- stringed instruments under tension
- wooden objects with cracks which appear to be recent (unsoiled, dust free)
- objects with warping or other distortions may indicate that the structure of the object is already under stress.
- water-logged materials *
* If materials are already wet, freezing may be the least-damaging alternative for water-logged materials that cannot be treated immediately. When carefully packed, water-logged books can be safely frozen and then freeze-dried with good results. Consult a conservator or disaster response professional for packing instructions.
Freezing books to kill insects
If only one or two books are affected, treatment in a home freezer may solve the problem. If many books or archives are affected, a collection manager should select a commercial freezing facility and begin to consider the logistics of keeping the collection accounted for and in order before, during, and after the freezing treatment.
The basic procedure for freezing a book is as follows:
1. Put the book into a plastic bag. Bags with a "zipper" closure are worth the expense because of the time they save and their reusability. If the book does not fit into a commercially available bag, wrap it in a sheet of plastic. "Saran Wrap" is too thin; a heavy-duty polyethylene garbage bag that has been cut along the edges to produce a flat sheet is a more effective moisture barrier. Seal the plastic with an adhesive tape that is not affected by water. Test the tape if you are not sure; get it wet and see if it still sticks to the plastic. It is very important to wrap the book in plastic to prevent condensation from forming on it. Air trapped inside the plastic will hold water vapor, so it is important to squeeze out the air. As a book thaws, the water condensed on the book can dampen it, causing stains and other problems.
Whole boxes of books can be frozen without wrapping each book (or stack of archives) but only in a freezer that reaches temperatures well below -20 degrees centigrade (about -4 degrees Fahrenheit). Paper is an effective insulator, and it takes longer to freeze a thick book than a thin one. To freeze a lot of material quickly, arrange the books in the freezer with plenty of space between books so that the temperature inside each book will drop as quickly as possible. Stacks of books should be less than about 4 inches or 10 millimeters thick. Line the box with a plastic bag, load the books into it, squeeze out the air, and seal the bag. Wrap the outside of the box with plastic and seal this wrapping. If the boxes are to be transported, reinforcing the corners with additional tape is very important.
2. It is best to use a freezer that has no ice build-up because the moisture will end up on the books during defrosting. However, do not use a freezer that has just been defrosted and has not yet reached the coldest temperature possible. In general, "Frost-free" freezers do not work well for insect extermination because they cycle on and off; the temperature does not remain constant.
Placing the book or box into a freezer that is already cold increases the chance of killing the insects before they are able to acclimate to the colder temperature.
Most household-type freezers do not have a gauge that indicates the exact temperature inside of the freezer. A thermometer can be used to test the freezer temperature at different settings, but this measurement will vary, depending on how much material is being frozen and how tightly it is packed in the freezer. A device called a "thermocouple" can be used to keep track of the temperature inside a box of books. Radio Shack sells an indoor-outdoor thermometer for less than $30 that can also be used to monitor the temperature inside of the freezer.
3. Freeze for at least 72 hours, depending on the thickness of the book and the temperature of the freezer. It might be advisable to freeze the material for a three-week period, or two or three times in succession, if one is unsure whether the insects are dead.
4. Thaw the book as slowly as possible. If you have a whole freezer full of books, turn off the freezer and leave the door closed overnight. For a single book, put it into a refrigerator to slow down the thawing process. Slow thawing helps to kill the insects.
5. For several weeks after the freezing treatment, leave the book wrapped in the plastic in which it was frozen and watch for the appearance of holes in the plastic. This could indicate that new insects have hatched out after the freezing treatment, and they are eating their way out of the book and the bag. Insect eggs are especially difficult to kill, and the eggs of many insects (such as beetles) are microscopic in size.
6. Repeat the freezing procedure until the insects are dead.
The use of any substance (especially insecticide) directly on collection materials is not recommended. The danger of permanent and disfiguring damage is too great. There is also the possibility that pesticide-treated materials will pose a health risk for people using the materials. Finally, many insecticides are not effective on the eggs of insects. Insects such as beetles make their eggs inaccessible by laying them within collection materials.
Insecticide treatments can be used effectively in collection storage areas as part of an integrated pest management program. It is important to monitor storage areas for the presence of insects on a continuous basis to detect problems in the early stages. At the Ransom Center an insect monitoring program has been in use since 1994.
Monitoring to detect insects
The following information was presented in May 1996 by David Pinniger at the International Institute for Conservation–Canadian Group Twenty-second Annual Conference. It is used here with his permission.
TRAPS AND MONITORING—THE KEY TO SUCCESSFUL PEST MANAGEMENT
WHY USE TRAPS?
- Traps will catch insect pests before they can be found visually
- Traps will catch a wide range of pest species
- Traps will catch adults and larvae
- Traps can be placed in areas that are difficult to inspect
- Trapped insects are evidence that can be identified
- Trapped insects can be counted
- Sticky blunder traps for crawling and flying insects
- Large roach traps
- Smaller tent traps
- Hanging moth traps
- Window strips
- Traps with attractant pheromone lures. Lures are available for:
- Clothes moth
- Furniture beetle
- Cigarette beetle
- Biscuit beetle
- Carpet beetle
WHERE TO PLACE THEM:
- On the floor
- In wall/floor angles
- In corners
- In dark areas
- On windowsills
- Near sources of water
Use a general spread of blunder traps in all display areas and storage areas. Use a few pheromone traps in specific areas.
- Record regularly.
- Record species.
- Record whether they are adults or large or small larvae.
N.B. It is better to record catch once every two months regularly than to try to record every week for a month and then give up!
WHAT DO THE RESULTS MEAN?
- Trap catch may be used to identify the presence of a pest.
- One trap catch may not mean much; it is only by recording results over a period of time that a picture will emerge.
- Using a pheromone trap for the first time may cause panic as it may catch a great deal more insects than blunder traps.
Use pheromone traps in the same way as blunder traps, but remember that they are much more sensitive.
Catch may show:
- An increase in insect numbers in one area
- Spread of a pest from one area to another
- Invasion of adults in summer
- Localized infestation from a problem area
- Failure of a control treatment
- Better design of sticky traps
- Cheaper lures
- Pheromone lures for new species
- Broad spectrum lures for multiple species
A trapping program is an integral part of pest prevention—not an end in itself. Trapping programs should not be so intensive or extensive that they outstrip resources. Trap records enable you to make decisions based on facts—not guesswork.
The procedures described have been used by the staff of the conservation department of the Ransom Center and are considered suitable by the conservation department as described; however, the Center will not assume responsibility for damage to your collection should damage result from the use of these procedures.
Revised, 13 April, 2012 by Mary C. Baughman