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Management of library and archival pests

The role of insecticides in library insect control programs
Exterior and interior rodent control programs
The use of fumigants for pest control
Alternative pest management methods
Mechanical and physical control

The role of insecticides in library insect control programs

A review of the literature pertaining to pests of library and archival materials reveals that librarians responsible for protecting collections have used a myriad of chemical approaches to control and prevent pests. Many of these materials were used in combination with binding pastes and glues as well as on the bindings themselves. Often potions and formulations were wiped or sprayed on the shelving and books.

Some of the chemicals used in the past seem almost silly today. Some are acutely toxic. A partial listing of chemicals used as dips, sprays, in combination with glues, or as wipes on books follows:

Care should be taken in handling some of the older volumes, particularly if they seem to have discoloration or staining which may indicate previous treatment. Fortunately some of the older remedies will have dissipated, such as various oils, camphor, kerosene, formalin, creosote, pyrethrum powder, thymol and turpentine. However, some of the more toxic chemicals, such as arsenic, mercuric chloride, sodium fluoride, sodium fluosilicate, and strychnine may remain as deposits on the materials.

When working with older volumes, management should be aware of the possibility of toxic substances on the materials and instruct personnel to wear rubber or cloth gloves. Individuals should be instructed not to touch themselves and to wash their hands thoroughly after handling the materials and prior to smoking or eating.

As previously discussed in this paper, certain insecticide formulations, when sprayed on surfaces, can release molecules of insecticide and solvents into the air. If any spray program is to be instituted in a library, spray formulations must be chosen that contain no solvents, volatilize minimally, exhibit long residual properties, and are odorless.

Spraying programs, based on the likelihood of infestation in a library, are primarily aimed at the control of silverfish and firebrats, cockroaches, carpet beetles, booklice, and spiders. By using wettable powder or encapsulated formulations as the basis for a spray program, quarterly spray applications should suffice. In more tropical areas the frequency may have to be increased to monthly spraying, particularly on the exterior. Such products as encapsulated diazinon (Knox-Out 2FM), encapsulated chlorpyrifos (Dursban ME), propoxur wettable powder (Baygon), bendiocarb wettable powder (Ficam W or Ficam Plus), or cypermethrin wettable powder (Demon WP) are examples of materials which may be used in a residual spraying program.

For German cockroach control, insect growth regulators may be used along with the residual insecticide to enhance control. An insect growth regulator in the environment of a German roach infestation will result in last instar nymphs molting into twisted wing adults which are sterile. Methoprene (Dianex) and hydroprene (Gencor) are in common use today.

Chemical baiting programs are particularly helpful in controlling cockroaches. Two products that are readily accepted by the large species of cockroaches, and have been shown to give excellent control are propoxur bait (Baygon 2% Cockroach Bait) and boric acid paste (Blue Diamond MRF 2,000 Paste). Applications of very small amounts of Baygon 2% Cockroach Bait should be applied to quiet corners, along walls, elevator shafts, boiler rooms, false ceilings and other areas where large roaches hide during the daytime. In their nightly forays the cockroaches will find these bait particles, consume them and be killed immediately. Pastes should be used sparingly where roaches hide during the daytime.

A bait trap has been successful in eliminating populations of the German cockroach. Hydromethylon roach bait traps (Maxforce or Combat) are currently in use in commercial kitchen and vending areas for the control of German roaches. Immatures and adults seek out the bait trap for harborage. Once inside, they consume a small portion of the bait, crawl away from the trap, and die. These child-proof traps are extremely effective in German roach control, particularly if they are used on vertical surfaces in areas of infestation. The previously-mentioned Blue Diamond boric acid paste may also be used for German roach control.

Exterior and interior rodent control programs

For rat control, exterior baiting programs should suffice to eliminate populations. Child-proof bait stations, such as those available from Bell Laboratories or J. T. Eaton and Company, should be paced in outdoor areas where rats are likely to burrow or follow walls to gain access to the building. Various rodent baits are available for baiting these large rat cafeterias. Bromadiolone (Contrac and Maki), warfarin (Final), chlorophacinone (Rozol), or diphacinone (Eaton's Bait Bitz) are examples of rodenticides that may be used in an exterior baiting program.

Rodent baits should not be used in interior situations under any circumstances for a number of reasons:

1. Often carpet beetles are brought into a library in rodent bait. Their eggs will hatch, the larvae will consume the bait, and adults will fly to other parts of the library to infest materials.

2. Rodent baits often act as food sources for cockroaches, particularly the large species.

3. If toxicants are used to kill mice on the interior, their carcasses will act as a food source to generate large populations of carpet beetles.

Traps or glueboards, or both, should be used for the control of mice on the interior of a library. The carcasses of the trapped mice can then be discarded. Traps and glueboards, which can be baited with a cotton ball smeared with peanut butter, should be placed in quiet corners, closets, storage areas, basements, attics, and in the immediate vicinty of mouse droppings.

The use of fumigants for pest control

The use of toxic fumigants in the library community has been popular for many years. D. B. Mackie of the California Department of Agriculture is credited with devising a fumigation system in 1930 that utilized the principle of vacuum fumigation. It was in 1932 that Thomas M. Iiams used this approach with ethylene oxide and carbon dioxide to fumigate rare books and manuscripts in the Huntington Library. The use of ethylene oxide for the fumigation of library materials soon became the standard in the library community.

Various fumigants have been used in "chambers", even before the advent of vacuum fumigation techniques. Such gaseous fumigants as methyl bromide, ethylene oxide, hydrocyanic gas, carbon disulphide, methyl formate, ethylene dichloride/carbon tetrachloride, and sulfuryl fluoride have been used in chambers for the fumigation of books and library materials. In many cases the fumigation of all incoming goods is routine before they are brought into the library. Most of this type of fumigation is unwarranted and may create health hazards for personnel.

Only two groups of pests found in library materials may require fumigation with toxic gases: bookworms and drywood termites, because they tunnel so deeply inside the materials.

As previously stressed, fumigation will not control mold and mildew if the library materials are returned to the same conditions from which they came. In many instances library materials that have been fumigated for mold are later stored in areas which do not have an environment conducive to mold growth. The fumigation is given as a reason for the successful control of mold and mildew when in fact the new area in which the materials have been placed is the governing factor in the mold and mildew control.

As research takes a closer look at many of the fumigants, hazards to human health, both acute and chronic, are becoming more obvious. Ethylene oxide, either in combination with freon or carbon dioxide, has been found to be a carcinogenic material. In the United States a chamber must have no more than 1 ppm of ethylene oxide left after aeration before the materials can be removed safely. One of the major problems with ethylene oxide is that very few chambers in the world meet this requirement. Any fumigation chamber relying on an airwash system to aerate the goods after fumigation has been completed, usually will not reach levels of 1 ppm or below at the end of the airwash cycles.

An airwash cycle is a term coined by the manufacturers of chambers to mean one complete cycle of "air washing. of the goods inside the chamber after exposure to a toxic gas. At the end of the exposure phase, the chamber is under vacuum. The operator, either manually or electronically, allows fresh air to come into the chamber. Another vacuum is then drawn, removing some of the toxic air by expelling it to the atmosphere. After a vacuum has been drawn, fresh air once again is allowed to rush into the chamber. Then another vacuum is drawn, and this contaminated air is once again expelled to the atmosphere. This series of alternation between pulling a vacuum and allowing fresh air to rush into the chamber is termed an airwash cycle. Most chambers are set up to allow for up to five total air washes before the electronics must be reset.

After such a limited number of airwash cycles, a chamber rarely meets the current standard of 1 ppm residual ethylene oxide. Studies have shown that in some chambers after 75 airwash cycles 4 ppm still remained in the chamber. In designing, modifying and testing chambers, it is difficult, if not impossible, to reach such low levels without a flow-through ventilation system. Even with a flow-through ventilation system, depending on the materials being fumigated, 1 pmm is difficult to obtain with ethylene oxide.

A study performed by the Center of Occupational Hazards, which surveyed the use of ethylene oxide fumigation chambers in 11 New England institutions in 1984, found that most operators perform one to four airwashes before removing the goods from the chamber. Some relied on window fans, air-conditioning units, or separate exhaust systems to vent the gas to the atmosphere. Most did not regularly monitor ethylene oxide levels nor did they meet current OSHA (Occupational Safety and Health Act) standards.

The negative properties of fumigating library materials with ethylene oxide must also be considered. Ethylene oxide is used industrially to increase the wet strength of paper by reacting with the paper cellulose to create another, stronger molecule. Conservationists should be aware that using ethylene oxide on cellulosic materials such as paper and textiles changes the very nature of the material (Peltz and Rossol 1983). Other undesirable effects of ethylene oxide fumigation include the loss of adhesiveness of gum arabic and animal glues, increased solubility of some paints and pigments, and a cross-linking reaction with protein materials which prematurely ages them and makes them brittle. In addition, some researchers have found that materials fumigated with ethylene oxide for mold control are actually more prone to mold attack and growth after the fumigation than before.

Ethylene oxide is soluble in oils, fats, and lipids, making leather-bound books retain ethylene oxide for long periods of time after fumigation. After bringing books out of a chamber, they will volatilize ethylene oxide into the air for varying periods of time up to and exceeding 3 months. It is therefore critical that the management of major libraries test in-house chambers and study fumigation policies and procedures to determine if they are meeting current requirements. Most will find that fumigation chamber modifications and procedural changes are required to meet current standards.

Other fumigants such as methyl bromide, hydrogen sulfide, and some of the liquid fumigants are not generally acceptable for library materials foe several reasons. Methyl bromide sometimes chemically reacts with materials high in sulfur. If this chemical reaction takes place, mercaptans are formed creating an irreversible, foul-smelling odor. Hydrogen sulfide is explosive and dangerous to use. Some of the liquid fumigants have been found to be carcinogenic and are very poor ovicides (egg killers).

Recently in the United states Vikane (sulfuryl fluoride), manufactured by Dow Chemical Company, has been registered for use in chambers as a fumigant. As with all fumigants, this material does not impart any residual control, but can effectively penetrate dense materials, such as library materials, and will kill all stages of insects. Vikane is, however, a poor ovicide and therefore dosages must be increased in order to penetrate the eggs of certain species of insects, including those of bookworms.

To date this material has been found to be fairly non-reactive with materials and is commonly used as a structural fumigant in wood-destroying insect control. Recent research on Vikane (The Getty Conservation Institute 1987) has shown that Vikane may tarnish and discolor metals and that it will cause changes in the physical properties of cellulose. A team from the University of Florida, under the direction of Nan-Yao Su, is investigating the lowest amount of Vikane needed to eliminate beetle adults, larvae, and eggs in an effort to minimize the effects of Vikane on materials.

Alternative pest management methods

Insect Growth Regulators - As previously discussed in this paper, certain insect growth regulators are currently being used in pest prevention and control, specifically to control fleas, ants and German cockroaches. They may be of use in ant and cockroach control in libraries. These non-toxic materials affect either the ability of insects to properly molt and mature or their reproductive capability.

Habitat Modification - The management of pests infesting collections may be realized in some instances by maintaining a constant environment. Certain pests, such as bookworms, silverfish, booklice, and mold, are more likely to develop in moist environments. By maintaining relative humidities in the 50 percent range, the rapidity with which they develop and the suitability of the food source can be altered. Even if sophisticated air-conditioning systems cannot be installed, the use of fans to circulate air will eliminate pockets of high moisture which may occur in "dead spaces" in stacks and collections, particularly at floor level.

Mechanical and physical control

As will be detailed later in this study, specific measures may be used to physically keep insects and rodents from invading a structure or collection. Screening windows; screening air intakes and louvers; weatherstripping exterior doors; installing bottom rubber door flaps and thresholds on doors; sealing areas where pipes penetrate walls with copper wool; placing caps or screening, or both, on unused chimneys; and sealing exterior roll doors with brushes attached to their frames will help to keep insects and rodents from penetrating the interior.

Proper lighting of the structure is important so that insects are not attracted to a building. The use of high-pressure sodium vapor lighting is superior to mercury vapor, fluorescent, or halide lighting. The latter three give off high amounts of ultraviolet light, which is highly attractive to nocturnal insects. Whenever possible, focus lights at a building rather than attaching them to the building. The insects will then be drawn to the point source of light away from the building.

Ornamental plantings around the building should be carefully planned so that carpet beetles are not attracted to the building. Carpet beetle adults feed on flowers high in pollen content. They are particularly fond of multiple heads of blue or white flowers. For this reason plants such as Spirea (Bridle Veil), daisies, and asters should not be planted adjacent to a building.

Often it is possible to store library materials and other artifacts on open shelving for long periods of time by enclosing them in ziplock or polyethylene, heat-sealed bags. As long as the item going into the bag does not have a high moisture content, the threat of mold within is minimal. The polyethylene bag acts as a buffer to temperature and humidity extremes in the room. No insects of importance to collections will chew their way into a bag to lay eggs on the item. Not only will bagging prevent insect attack, but it will also keep the item in a dust-free environment. If infestation were to be inadvertently bagged with an artifact, the polyethylene bag would contain the spread of the insects to other parts of the building.

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