Integrated Pest Management Manual
Museum Pests
A pest in a museum can cause far more damage than the same pest in a home or an office building. Carpet beetles in a stuffed bear, clothes moths in a native American headdress, or cigarette beetles in a herbarium can destroy irreplaceable artifacts. But while museum specimens must be protected, their sensitivity to chemical and environmental stresses means that standard pest control procedures are often unacceptable. Liquid pesticides may stain certain materials, heat treatment can damage paintings, dusts can abrade sensitive specimens. Caution is the byword in museums.
Each new pest problem must be analyzed on its own. Before taking any actions to control a pest, be sure that those actions will not themselves damage the museum's collections. Although the use of pesticides may at times be necessary, indiscriminate use or dependence on pesticides is unacceptable.
Any pest with chewing mouthparts is a risk to museum specimens. Carpet beetles, clothes moths, powderpost beetles, cockroaches, and others pose direct threats to specimens through feeding damage, feces, and excretions. Some pests pose indirect risks such as fires (rodents gnawing on wires) and secondary infestations (dead cluster flies in attics can attract carpet beetles).
IDENTIFICATION AND BIOLOGY
Any pest that infests houses, restaurants, or other buildings may at some time become a pest in a museum. Certain pests, however, repeatedly threaten museum collections. They can loosely be grouped into five categories:
(1) Fabric pests
(2) Wood pests
(3) Stored product pests
(4) Moisture pests
(5) General pests
The first step in solving any pest problem is to identify the pest and learn about its biology and habits. While it is impossible to discuss each pest in detail in this manual, the brief discussions below may help you understand a little about the habits of the pests most likely to infest museums or damage museum specimens.
Fabric Pests
Most insect damage to fabrics is caused by carpet beetles (in the family Dermestidae) or clothes moths (in the family Tineidae). The adults stage is seen most often seen since adults fly and some are attracted to lights and windows, but it is not the adult insects that do the damage. They feed outside on pollen or not at all. It is the larva or immature stage that feeds on fabric, fur, feathers, or virtually anything made of animal fibers.
Carpet Beetles
Immature carpet beetles feed on dried animal products such as wool, silk, felt, hair, fur, feathers, dead animals, and stuffed trophy heads. They do not feed on synthetic fabrics, but sometimes damage wool-synthetic blends or synthetics stained with urine, sweat, or food.
Carpet beetle larvae are repelled by light and are usually found burrowed deeply into infested material or in little-used drawers, cases, and storage bins. To grow, they molt and shed their skins. In heavy infestations, you may find large numbers of these light-colored shed skins. The adults are often seen crawling up walls and congregating on window ledges.
There are many species of carpet beetles. In addition, many common beetles resemble carpet beetles. Be sure to get the pest beetle properly identified so that you can zero in on the infested goods and likely harborage sites. Four species of carpet beetle are most likely to be found in museums.
Black carpet beetle (Attagenus unicolor) is the most abundant and destructive of the carpet beetles. The adult is 1/8"- 3/16" long, a solid dark brown or dull black color, and more elongate than carpet beetles described below. The larva is less than 1/4" long and carrot-shaped. It is covered with golden brown hairs and has a characteristic "tail" of long hairs at the rear end.
Varied carpet beetle (Anthrenus verbasci) is primarily a scavenger. It is common in the nests of birds, on dead animals, and in insect collections, but can damage woolens, carpets, wall hangings, hides, horns, and bone artifacts. Small populations often go unnoticed behind furniture or along baseboards feeding on accumulated lint, hair, food crumbs, dead insects, and other organic debris. The adult is about 1/8" long, oval to round, with splotches of white, yellow, and black on its back. The larva is tear-drop shaped and covered with rows of light brown hairs.
Common carpet beetle (Anthrenus scrophulariae) attacks carpets, woolens, and animal products such as feathers, furs, leather, silks, mounted museum specimens, and pressed plants. The adult is about 1/8" long with a band of orange scales down the middle of its back. The larva is reddish-brown and covered with brown or black hairs. A mature larva is active and moves rapidly.
Furniture carpet beetle (Anthrenus flavipes) attacks furniture (particularly old horsehair-stuffed furniture) and items made from wool, fur, feathers, silk, horns and tortoise shell. The adult is about 1/8" long, and is rounded and blackish with variable mottling of yellow and white scales on the back and yellow scales on the legs. The larva is difficult to tell from the common carpet beetle.
Clothes Moths
These are small, silvery-beige moths with a wing span of less than 1/2". They have narrow wings fringed with long hairs. Small grain and flour-infesting moths are often confused with clothes moths. However, clothes moths have different flying habits. They avoid light and are rarely seen flying. They prefer dark corners, closets, and storage areas, and usually remain out-of-sight.
The primary food of clothes moth larvae is soiled woolens, but they also feed on silk, felt, fur, feathers, and hairs. In museums they often damage woolen clothes (particularly old military uniforms), feather hats, dolls and toys, bristle brushes, weavings, and wall hangings.
The webbing clothes moth (Tineola bisselliella) and the casemaking clothes moth (Tinea pellionella) are the two most common clothes moths found in museums. The larvae are small white caterpillars with brown heads. They feed on the surface of the material infested. The webbing clothes moth produces feeding tunnels of silk and patches of silken webbing on the fabric's surface. The casemaking clothes moth is rarely seen since it constructs a cylindrical case of fabric which it carries around to hide and feed in. The color of the larva's case can help you locate infested materials.
Wood Pests
Materials made of wood are susceptible to attack by a number of wood- infesting pests. The culprits in museums are usually powderpost beetles or drywood termites. Both can severely damage valuable artifacts while remaining invisible to the untrained eye.
Powderpost Beetles
These are a group of beetles in the insect families Anobiidae (anobiid, furniture, and deathwatch beetles), Lyctidae (true powderpost beetles), and Bostrichidae (false powderpost beetles). The term "powderpost" comes from the fact that the larvae of these beetles feed on wood and, given enough time, can reduce it to a mass of fine powder.
Powderpost beetles spend months or years inside the wood in the larval stage. Their presence is only apparent when they emerge from the wood as adults, leaving pin hole openings, often called "shot holes," behind and piles of powdery frass below. Shot holes normally range in diameter from 1/32" to 1/8", depending on the species of beetle. If wood conditions are right, female beetles may lay their eggs and reinfest the wood, continuing the cycle for generations. Heavily-infested wood becomes riddled with holes and galleries packed with a dusty frass (wood that has passed through the digestive tract of the beetles). Both hardwood and softwood can be attacked by powderpost beetles, although lyctids only infest hardwoods.
Items in museums that can be infested by powderpost beetles include wooden artifacts, frames, furniture, tool handles, gun stocks, books, toys, bamboo, flooring, and structural timbers.
Drywood Termites
Unlike their cousins the subterranean termites, drywood termites establish colonies in dry, sound wood with low levels of moisture, and they do not require contact with the soil. They are primarily found in the coastal southern states, California, and Hawaii, but they are easily transported to northern states in lumber, furniture, and wooden artifacts.
Drywood termites attack wooden items of all kinds. The termites feed across the grain of the wood, excavating chambers which are connected by small tunnels. The galleries feel sandpaper-smooth. Dry, six-sided fecal pellets are found in piles where they have been kicked out of the chambers. The pellets may also be found in spider webs or in the galleries themselves.
A swarming flight of winged reproductive termites can occur anytime from spring to fall. Most drywood termites swarm at night, often flying to lights.
Stored Product Pests
Many museums include items made in part of seeds, nuts, grains, spices, dried fruits and vegetables, and other foods. A long list of pests, traditionally called "stored product pests" or "pantry pests," can infest items containing these foods. Probably the most common of such pests in museums are the cigarette beetle and the drugstore beetle.
Cigarette beetle (Lasioderma serricorne) is named for the fact that it is a pest of stored tobacco, but is also a serious pest of flax, spices, crude drugs, seeds, and, most importantly for museums, books and dried plants. This beetle has been called the "herbarium beetle" because of the damage it can cause to dried herbarium specimens. It has also been found infesting rodent bait.
The adult beetle is light brown, 1/8" long, and the head is bent downward so that the beetle has a distinctive "hump-backed" look. It is a good flier. The small larva is grub-shaped and whitish, with long hairs that make it appear "fuzzy." It has yellow- brown markings on the head.
Drugstore beetle (Stegobium paniceum) feeds on a wide variety of foods and spices (particularly paprika or red pepper). It is also a serious pest of books and manuscripts, has been reported "feeding on a mummy," and has been known to chew through tin foil and lead sheeting.
The adult beetle is very similar to the cigarette beetle. With careful examination through a magnifying lens, the drugstore beetle may be distinguished by its three- segmented antennal club. The larva, too, is similar, but does not appear as "fuzzy."
Moisture Pests
Moisture is not only a threat to museum specimens on its own, it may attract a number of moisture-loving pests that can do additional damage. The most important of such pests are the molds and insects in the order Psocoptera that feed on those molds.
Molds. Molds are fungi that can cause damage or disintegration of organic matter. Basically plants without roots, stems, leaves, or chlorophyll, molds occur nearly everywhere. When moisture and other environmental conditions are right, molds can appear and cause significant damage to wood, textiles, books, fabrics, insect specimens, and many other items in a collection. Their growth can be rapid under the right conditions.
It is important to realize that fungal spores, basically the "seeds" of the fungus, are practically everywhere. Whether molds attack suitable hosts in a museum depends almost exclusively on one factor: moisture. When moisture becomes a problem, molds will likely become a problem too.
Psocids. Although psocids are commonly called booklice, they are not related to parasites such as head lice or body lice. Booklice got that name because they often infest damp, moldy books. They feed on the mold growing on paper and in the starchy glue in the binding. Psocids also infest such items as dried plants in herbaria, insect collections, manuscripts, cardboard boxes, and furniture stuffed with flax, hemp, jute, or Spanish moss.
Psocids do not themselves cause damage. They become pests simply by their presence. However, their presence also indicates a moisture problem and the likely presence of damaging molds. They are tiny insects, less than 1/8" long, and range in color from clear to light grey or light brown. Most indoor psocids are wingless, looking a bit like a tiny termite.
General Pests
Any household pest may become a pest in a museum. Cockroaches, rodents, silverfish, ants, and other common pests can invade and infest a museum as well as a house or other structure. The biology and ecology of these pests are covered in detail in other modules of this Integrated Pest Management Information Manual, and will not be repeated here.
MONITORING AND THRESHOLDS FOR MUSEUM PESTS
Visual
Regular and scheduled inspections of all specimens on display and all collections in storage can prevent pest infestations from building up undetected. Specimens on display should be checked monthly. All collections in storage should be opened and examined at least twice a year.
Monitors should use a bright flashlight during inspections and look for live adults and larvae and the presence of shed larval skins or feces. The presence of feeding debris or frass around or below specimens is an indication of infestation. So are exit holes, feeding holes, hair falling from fur or pelts, mats of fibers, silken feeding tubes or cases, or moth or beetle pupae. A hand lens can be used to examine for eggs if an infestation is suspected.
Window sills and the inside of ceiling light fixtures should be checked on a regular basis as many pests fly or crawl to light. The immediate display area should also be examined. Pests may be found behind baseboards, under furniture, behind moldings, in cracks in floors, behind radiators, or in air ducts.
Traps
Small sticky traps should be placed in hidden areas throughout the facility and inside specimen cases, particularly in high-risk areas. These traps should be checked at each visit, any pests identified and recorded, and the traps replaced as necessary.
Pheromone traps are one of the most valuable new tools for pest management in museums. Pheromones are the natural scents insects use to communicate with each other. Certain pests can be strongly attracted to the traps from the surrounding area, providing an extremely effective early warning system of pest presence.
Pheromone traps are only available for certain insects. Traps useful in museum settings include those for cigarette beetles, drug store beetles, Indianmeal moths, and warehouse beetles (Trogoderma). Others are being developed and may be available soon.
Insect electrocutors are useful for detecting and controlling flying insects. They emit ultraviolet light (black light) that attracts flying insects, particularly flies and moths. The insects are drawn into the trap and electrocuted or fall onto a glue board. These traps must be checked and emptied periodically or the dead insects will themselves attract dermestid beetles and other scavengers.
Recordkeeping
Careful records of inspection results, trap catches, etc. will help identify seasonal risk factors and areas with a high frequency of problems.
Threshold Levels
Because of the sensitivity of museum collections, for most pests in the immediate museum area the action level will be one live specimen. Presence of live adults or larvae indicate ongoing infestations which should be investigated immediately and treated as necessary. Shed larval skins and feeding damage may have resulted from old infestations, but in regularly monitored collections, these should be regarded as an indication of an active infestation. Thus, it is vitally important to maintain careful monitoring records.
NON-CHEMICAL MANAGEMENT OF MUSEUM PESTS
Introduction
Pest management in a museum is especially tricky because without careful management the cure could cause as much damage as the pest. Museum specimens by their nature are rare and valuable. They are often delicate and liable to stain, warp, or simply fall apart if control procedures are too aggressive.
Ideally, the focus of integrated pest management in a museum will be on habitat modification and exclusion to prevent pests rather than on control methods to eliminate them.
Safe and successful museum pest management requires an integrated pest management approach, combining careful and frequent monitoring of pest levels and conditions with a combination of tools, procedures, and strategies. The tactics chosen for a particular pest problem should be adapted to the conditions in a museum. Anticipate the consequences of each tactic. When deciding from among them, choose the combination of tactics least likely to put specimens and visitors at risk.
Nonchemical management tactics include cultural controls (temperature and humidity control, sanitation, lighting), pest-proofing (pest-proof containers or display cases, screening and caulking, etc.), trapping (mechanical, sticky, pheromone, and light traps), vacuuming, freezing or heating infested specimens, and, in rare cases, "radiation" such as microwave ovens and gamma irradiators.
Cultural Control
Sanitation plays an important role in the attractiveness to pests of a museum area. Poor sanitation--food debris, grease, loose hairs, and the like--in and around specimens, storage areas, and in cracks and crevices in floors and furniture attracts and holds pests. Good sanitation, particularly regular mopping, washing, and vacuuming, removes potential foods and even newly-arrived foraging pests.
Controlling lighting can also reduce the attractiveness of an area to pests. Minimize exterior lighting. Bright lights shining through doorways and windows can attract insects to the museum area. Light shields, curtains, and closed doors can reduce the numbers of flying insects attracted to the museum.
Temperature and humidity control also can affect pest populations. Lowered humidity and, to a lesser extent, lowered temperatures reduce the chance of infestation and slow down the growth of existing pest populations. For some pests, such as psocids, reducing humidity can be all that is required to eliminate a pest problem.
Pest-Proofing
The most effective way to prevent damage from dermestid beetles, clothes moths, and many other museum pests is to prevent establishment of infestations in the first place. Preparation of specimens should take place in areas other than collection rooms. All incoming specimens should be examined carefully for damage and live insects, and records kept. Incoming specimens showing signs of infestation should be isolated and disinfested. Contact your regional curator before undertaking any control measures on unfamiliar specimens.
Windows in areas where specimens are kept should be tightly screened or kept closed at all times to prevent pest entry. Caulk or otherwise seal cracks and holes in walls and floors, holes around pipes and other utility lines, and other points of pest entry. Install door sweeps where necessary. Air vents and hot air registers can be equipped with filters to trap potential incoming pests. Filters should be changed on a regular basis.
Adult dermestids and other museum pests feed on pollen and nectar, so decorative cut flowers should be kept out of specimen areas to reduce the chance of accidental infestation. Those specimens at high risk of insect damage should be kept in insect-proof cases and examined on a regular basis.
Trapping
Besides their monitoring function (as mentioned earlier), traps may also be used to control pests. Snap traps and glue boards are often used against rats and mice. Pheromone traps are also a good supplemental control tactic for certain pests, particularly in removing the last few individuals left in the area. Likewise, insect electrocutors and sticky traps can supplement other control measures.
Cold Treatment
Some infested museum specimens can be disinfested by freezing them in a large commercial freezer that can reach temperatures of 0
Heat Treatment
Small items can be heated in an oven to kill infesting pests. Larger items may require a commercial kiln. Powderpost beetle larvae and eggs will be destroyed if the internal temperature of the wood is held at 120
Microwaving
Microwaving as a pest control method is mostly an experimental technique at this time. However, it can be an option as long as the treatment will not damage the item being disinfested. For example, microwave ovens have been used to kill cockroaches, silverfish, and psocids inside books. The average infested book is microwaved on high for 20-30 seconds. Longer times risk damage to the glues and bindings of many books.
This method is safe for most hardback books printed after 1950 and high- quality soft-cover books with sewn bindings. Do not use this method on valuable old editions, older books with metallic dyes, inexpensive soft-covers (it will melt the glue), or books bound in leather.
Miscellaneous
Cedar wood chests are often recommended to protect fabrics from clothes moths and carpet beetles. However, only freshly cut cedar wood is toxic or repellent to fabric pests, and then only in an air-tight container. By the time the wood is two years old, there is no toxic effect left. (Of course, a tightly sealed box of any material will usually keep pests out.)
CHEMICAL CONTROL OF MUSEUM PESTS
Pesticides used in museum pest control are generally some of the same products used for household or other structural pest control. Most pesticide products are not specifically labeled for use in museums. If the product is not so labeled, be sure it is labeled for use in similar sites such as public buildings, institutional settings, etc.
Museums are a good site in which to use nonconventional pesticides such as repellents and insect growth regulators (IGRs) for controlling cockroaches, cigarette beetles, and certain other stored product pests. Cockroach and ant bait stations are an excellent choice for these pests since they pose no risk to museum collections.
When using any pesticide for general pest control (cockroaches, silverfish, ants, etc.), avoid direct treatment of museum specimens whenever possible. Instead, treat cracks and crevices, wall voids, and perhaps the legs of display cases rather than inside the cases themselves.
Paradichlorobenzene and naphthalene are commonly used as repellents in museum cases. These materials do not eliminate infestations, but may be useful in preventing them. Paradichlorobenzene and naphthalene may cause damage to certain plastics (bakelite, for example), and may soften and shrink resins, adhesives, and paints. Organic gas filters should be installed on the sides of cabinets to absorb fumes and replaced when the odor is detected in the room.
Specimen cases are sometimes treated with insecticidal dusts. This treatment poses some risk of abrasion to specimens stored in the case, and some risk to curators later working with the specimens. Such treatments should be done with care.
Treating Infested Materials
If nonchemical treatment of infested materials is not practical, some materials can be treated with standard insecticides. However, in most situations, infested museum specimens should be fumigated. Fumigation is hazardous and it requires professional training to do it safely and effectively. Fumigation of museum specimens is normally conducted in special fumigation chambers, vaults, or "bubbles." Some fumigation is done under tarpaulins. In severe and extensive infestations, an entire building may have to be "tented" and fumigated.
There are a number of different fumigants to choose from. The choice will depend mostly on the objects and materials to be fumigated, since different fumigants are best suited for certain jobs. Some fumigants cannot be used on certain materials because they may react with them (for example, methyl bromide may react with rubber goods). The most commonly used fumigants for museum specimens are methyl bromide, sulfuryl fluoride, ethylene oxide, and carbon dioxide.
REFERENCES
1. Bennett, G. W., Owens, J. M., and R. M. Corrigan. 1988. Truman's Scientific Guide to Pest Control Operations. (4th Edition). Edgell Communications, Duluth MN.
2. Ebeling. W. 1975. Urban Entomology. Univ. Calif., Div. Ag. Sci.
3. Mallis, A. 1990. Handbook of Pest Control (7th ed.) Franzak & Foster Co. Cleveland, OH.
4. Olkowski, W., Daar, S., and H. Olkowski. 1991. Common-Sense Pest Control. The Taunton Press, Newtown, CT.
5. Story, K.O. 1984. Approaches to Pest Management in Museums. Conservation Analytical Laboratory, Smithsonian Institution.
6. Zycherman, L. A. (ed.) 1988. A Guide to Museum Pest Control. Amer. Inst. for Conservation Hist. and Artistic Works and Assoc. Systematics Collections. Wash., D.C.