Biological Management for Pests, Mold and Other Microorganisms in Exhibits

• Examine objects or signs of infestation and active mold as part of the preliminary condition check. lf signs of infestation are found, consult a conservator about treatment options.
• Design exhibits to inhibit infestations. Make sure the exhibit area is insect-proof by screening open windows or doors, filling gaps in the building construction, and avoiding gaps and undercuts where dust can collect.
• Enclose objects. When the risk of infestation is high, place susceptible objects inside well-sealed cases or sealed acrylic boxes to prevent new infestation. Limit the gaps and holes to prevent insect entry.
• Avoid introducing insects through props and unchecked exhibit materials. Do not use wool carpets and other materials that attract and harbor insects. Avoid using organic exhibit props. Fumigate vegetative props or expose them to freezing temperatures before bringing them into the museum.
• Control human behaviors that encourage infestation. During exhibit production and installation and after the exhibit opens, never allow food in the object holding areas or the exhibit space, even if no objects are in the area.

Prevent biological infestation by implementing a plan, sealing areas of entry, and enclosing vulnerable objects in cases.

General Guidelines

Biological agents of deterioration can attack and damage many types of cultural heritage collection materials. Even a small-scale infestation can cause significant damage if it goes undetected. Biological infestation includes damage caused by:

• Insects such as wood-boring beetles, carpet beetles, silverfish, and moths
• Vertebrates (larger pests) such as mice and squirrels
• Microorganisms such as mold/mildew/fungus

It is important to understand and assess risk based on your specific location, building envelope and collection vulnerabilities. Some collection types are very susceptible to infestation such as objects such as textiles, natural history collections, and freeze-dried taxidermy specimens. MuseumPests.net is a comprehensive web-based resource that provides information about prevention, monitoring, assessment, identification and mitigation. Specific links from the site include:

• https://museumpests.net/prevention-introduction
• https://museumpests.net/monitoring-introduction/
• https://museumpests.net/identification/
• https://museumpests.net/solutions/

Many cultural heritage institutions are expanding outreach to new audiences by mounting exhibits in non-traditional gallery spaces and holding public events in spaces where collection objects are typically displayed. These efforts can increase the risk of pest infestation or biological growth and damage to collection objects if preventive strategies are not thoroughly considered. Institutional policies for Integrated Pest Management (IPM) will help in establishing guidelines and behaviors for controlling biological agents in the museum environment.
Considering pest ingress, water sources, and relative humidity considerations in exhibit design and construction will restrict pest entry and help in preventing the introduction of what pests need for survival: food, water and harborage.

Gallery Space Design, Inspection and Maintenance

Design exhibits to reduce the potential for pest infiltration and infestation:

• Limit pest ingress by screening open windows or doors, filling gaps in the building construction, and avoiding gaps and undercuts where dust can collect.
• Maintain a moderate relative humidity (preferably below 60% RH and never above 75% RH) to discourage growth of mold/mildew/fungal growth.
• Eliminate moisture from leaks, floor drains, or other water sources near the exhibit space.
• Keep light levels relatively low in exhibits, and place lights outside the display chamber of a case. Brightly lit areas attract some insects and adult stages of moths and dermestids, while other insect species and generally larval stages avoid light.
• Design and maintain an IPM plan, with consideration for such elements as the regular proximity of food and drink, location of trash receptacles and housekeeping schedules.

Exhibit Case Design and Inspection

• When the risk of infestation is high, place susceptible objects inside well-sealed cases or sealed acrylic boxes to prevent new infestation. Limit the gaps and holes to prevent insect entry. Poorly sealed cases provide insects and rodents with an easy path to food; insect entry routes follow airflow, but gaps measuring smaller than 0.3 mm prevent entry.
• Accumulated dust and food are breeding grounds for insects. Avoid (when designing new displays) or eliminate (where possible in existing cases) inaccessible voids, undercuts, and barriers in cases that collect dust and make inspection and cleaning difficult.
• Research safe options for treatment of vegetative props before bringing them into the museum. Avoid introducing insects through props, and exhibit materials that have not been adequately examined such as wool carpets and other materials that attract and harbor insects. Avoid using organic exhibit props.
• Make every effort to ensure that no infested objects or construction materials find their way into an exhibit. While examining each object and/or material, look for evidence of an infestation, taking note of potential evidence such as exit holes and frass. If signs of infestation are found, consult a conservator about treatment options.

Special Events, Floral Displays and Housekeeping Policies

• Use your IPM policy and strategy to control human behaviors that encourage infestation. Ensure that event staff are trained in housekeeping measures required to prevent risk of infestation. MuseumPest.net and the Society for the Preservation of Natural History Collections wiki provide information on food management for staff and visitors:
• Be aware, floral displays may increase risk without thorough preventive planning to avoid introducing insects or microorganisms into the exhibit space.

Guideline: Mitigating Pest Hazards
Effective measures must protect exhibit objects from damage by pests

Pests, which include insects, rodents and molds, pose a threat to exhibit objects, especially organic materials. Objects may be consumed as a source of food or shredded, by rodents, for nesting materials. Molds and the excrement from insects and rodents can weaken and stain objects.

Best Practice: Museum policies are instituted to discourage the presence of pests

What policies can discourage the presence of pests?

It is essential to maintain a clean environment free of food and dust, which is attractive to egg-laying adult insects. Pests should also be deterred from entering the exhibit environment. Organic materials on which pests could hitch a ride should be thoroughly inspected before being brought into the exhibit building, and all gaps that could allow pests access into the building should be closed or sealed.
Policies that deter pests include:

• Receptions that include food are not held in the galleries
• Food is prohibited near galleries
• Windows are kept closed
• The museum avoids using organic construction and furnishing materials that could harbor pests (wool carpets, old wood)
• All organic materials are inspected for infestation before they are brought into the museum
• Structural repairs are carried out promptly; cracks in walls and gaps around windows and doors are sealed to prevent pests getting access to the museum.
• Housekeeping maintains a clean environment and removes dust.
• Landscaping surrounding the museum does not attract or harbor pests
• Effective monitoring is conducted to identify a pest outbreak immediately
• A pest control program, such as an Integrated Pest Management Program (IPM), is instituted and staff training provided
• The museum budget includes funds for IPM program and maintenance.

Fumigants and pesticides should not be used for routine maintenance because of health concerns and the potential damage to objects, such as corrosion of metals, embrittlement of leathers, and alteration of dyes.

How is an IPM Program implemented?

There are several good web resources with information on implementing an IPM program in collection holding institutions

• The Museumpests.net website created by the Integrated Pest Management Working Group contains information on the four main elements of an IPM program: prevention, monitoring, identification and remediation.
• Collection Trust's What's Eating Your Collection? organizes its resources into two main sections: Identify & Solve and Pest Recording. The site also maintains an extensive bibliography.

Best Practice: Exhibit design discourages the presence of pests

What exhibit design strategies discourage pests?

Use tightly sealed cases to block access by pests

• Gaps measuring smaller than 0.3mm prevent the entry of almost all museum pests. Tightly sealed cases prevent or deter pest infestation.

Use furnishing designs that do not create harborage for pests

• Eliminate undercuts and gaps in furniture that collect dust and make cleaning difficult.
• Build a solid kick-plate along the bottom edge so that dust cannot accumulate below furnishings.

Avoid construction materials that harbor pests

• Organic building materials such as wood boards, thatch, unfinished timbers and composite boards are a potential source of infestation. Flooring materials, including dirt, sand, pebbles and earth can also introduce pests.

Avoid using organic materials for props, or use only with caution. Animal products, wool, feathers, fur, vegetal matter, wood, and preserved foods may introduce pests or molds into the museum.

• Use reproduction botanical models, such as silk or wax replicas, to avoid the problem. Original natural history specimens must be pre-treated before inclusion in exhibits.
• Use freeze-dried vegetal materials where possible.
• Inspect ALL materials for infestation before bringing them into the museum.
• Fumigate or freeze organic material before introduction, if in doubt. This kills eggs and larvae. (Mobile truck freezers can be utilized on site.)

Use structural modifications to block pest access

• Seal areas of entry such as cracks and gaps around doors and windows and cracks and crannies in walls to prevent infestation.
• Install insect screens on windows or doors, if it is not possible to keep them closed.

Ensure the exhibit layout allows for adequate cleaning

• Provide access behind and around exhibited objects, to ensure that exhibit areas can be adequately cleaned and inspected for pests (e.g., underneath and behind display areas).

[For more information on safe materials, props and visual effects see Standard *.]

Best Practice: Controls discourage the presence of pests

What controls will discourage growth of molds?

Molds can grow on virtually any substance, providing moisture is present. Controlling indoor moisture is therefore an effective way to prevent mold. Use the HVAC system, air conditioners and dehumidifiers to control temperature and humidity and reduce the relative humidity to levels below 60%.
[For more information on relative humidity see Standard *.]

How does exhibit lighting affect insects?

Some insect species are attracted to bright lights, while others avoid light. In general, keep light levels relatively low in exhibits, and place lights outside a case display chamber.