Critters in Collections: An Overview of Integrated Pest Management

Things are well underway at the Horniman and I have begun to do all sorts of work. Some of the work includes actual object treatments, environmental conditions assessment and monitoring, tissue dyeing methods, and research into object materials and context. While I will be talking about many of these ongoing experiences in due time, something that we've focused on a bit has been a critical skill to develop and implement as a conservator: Integrated Pest Management (IPM). IPM is a management system for the prevention, identification, and response to various pests and vermin (including bugs, birds, and rodents) which pose different threats to a museum and its collections. Like environmental controls, it is an ongoing practice, and when well-executed can prevent unwanted and unnecessary damage to collections and buildings.

There are four major stages for effective implementation of IPM. These stages include: Access Prevention, Detection and Tracking, Identification, and Response.

Access Prevention

(Image adapted from https://butterfly-conservation.org/moths/common-clothes-moth )

Pests, like any creature, require food, water, and shelter. Keeping them out is a must. While any building or structure is likely to provide water and shelter, museum institutions also provide an abundance of food - in the form of artifacts and collections - for pests to munch. Depending on the species and life-cycle stage, certain insects may prefer general dust, dirt, and debris, other pests, adhesives, starches, and/or proteins present in the collections and museum spaces. This also means that different types of objects will appeal to different types of pests. The water element is a tad trickier to address as high humidity and darkness are considered prime real estate for pests. Anyone who has ever been in a storage space, cleaning closet, basement, or the like, knows that humidity and darkness are a daily reality for these spaces. The shelter element is also difficult to manage, simply because by virtue of having a museum building or storage area, you inadvertently provide shelter for pests who would otherwise be outside.

Good housekeeping and cleaning practices for the museum and building site reduce the amount of dirt present in the building, you already make conditions less desirable for pests. Keeping up with building maintenance is critical, as this can literally close off physical access points for pests to take from the outside. For example, where are the main access points, how often are they used, and by whom? How effectively have we sealed cracks and damage to walls, sealed off 'dead spaces' beneath floor boards, within walls, or above or below display cases? Are we monitoring and controlling our museum environment effectively? Addressing these questions will help to reduce pests. When bringing new objects into a museum or storage space, it is best for them to be placed in quarantine - often in polyethylene bags in a designated location - to assess whether or not a new object or incoming loan is already infested. Continued monitoring of these factors will help to reduce risk of unwanted access.

Detection and Tracking

(See Image Source)

No matter how hard you try, pests will always find their way into your museum. It’s an unfortunate fact, but it’s why we use detection and tracking methods! Understanding what pests you have around and in proximity to which collections will help you to formulate an action plan to resolve any problems. Detection methods for insect pests are conducted with the use of traps. There are two basic kinds of traps for insect pests: sticky blunder traps - which can inform you of what is crawling around in what spaces, sticky pheromone traps - which attract the males of pest species – reducing the potential for breeding and allowing you to locate an infestation if placed strategically. These traps should be placed in all museum spaces at carefully selected locations where there may be pest access. Collecting and replacing traps regularly and recording what is present in the traps will allow you to accurately track what pests (threatening or non-threatening) are in your collections spaces. For example, while the presence of book lice may not be threatening to a collection, it is indicative of an exceedingly humid environment and therefore you may need to be on the lookout for moisture-related issues in the space, rather than solely pest ones.

At the Horniman Museum, I've spent time with Charlotte going around the galleries to check and replace all of the pest traps for routine detection and tracking. Blunder traps were placed in areas where pests might have more access, such as corners of the room, along exterior walls, beneath floor board in 'dead spaces', and beneath or above display cases. Each trap is labelled accordingly and has a specific location on the IPM map for the museum spaces. I will be honest, bugs are not my favorite (namely spiders), but it’s part of the job and we have to be able to go through and collect all the data for the good of the collections. Bringing us to our next step!

Identification

(Sample identification information for the Cigarette Beetle (Lasioderma serricorne) Image Source: MuseumPests.net)

In order to effectively log the data from your traps, it is necessary to sit down at the microscope and visually identify the pests present in your traps. While an experienced conservator will be able to recognize a number of common museum pests, early career professionals like me need resources to help accurately identify the pests, and very importantly the stage of their life-cycle that is appearing. Identification posters can be found readily available on the internet (see this example from English Heritage), MuseumPests.net provides incredible resources for pest identification and IPM practice in general, as does the Conservation Center for Art and Historic Artifacts (CCAHA) through their Know Your Bugs! resource. Using these resources, identifying the life-cycle stage of the pests present in a space will help to 1) identify the pest of issue, 2) determine the severity of the issue - based on the number of pests observed and the type of collections in the vicinity, 3) track movements of the pests within the museum space. With a better understanding of the pest problem at hand, you can begin to prepare an action plan for response to the issue. Bringing us to the final step!

Response

(Image adapted from the following sources: Action Plan and English Heritage)

Responses to infestation range in scale and severity and are dependent on the type of pest, where they are in the collection, and the resources available to the institution. For example, if the adult moth stage of the webbing clothes moth (Tineola bisselliella) is observed in a collection, this can have dire consequences for organic materials. Observing adult moths indicates that breeding has and is taking place, which means the moths have found reliable sources of food, water, and shelter - which usually means there is already damage to your collection. This type of moth can be devastating and action must be taken immediately to stem the tide. Overall, there are several types of response to evidence of infestation: vacuuming affected areas of the collection, isolating or quarantining individual objects, temperature treatments (which include low-temperature and heat treatments), atmospheric treatments (which include oxygen-deprivation, carbon dioxide and nitrogen gas displacement), and pesticide application to non-object materials – such as floor and skirting boards.

Vacuuming technically falls under the auspices of good housekeeping and cleaning and, while helpful, does not in itself resolve pest infestations. Vacuuming pests only removes the remnants and remains of pests and does not halt or inhibit their breeding or the balance of their food, water, and shelter. Isolation and quarantine, as discussed above, should already be part of receiving loaned objects or new acquisitions. Where evidence of infestation is found for individual objects within a case, the affected objects should be isolated from the others and those remaining in the case should be monitored closely. Temperature treatments are fairly common, especially low-temperature treatments, as they are commonly a routine part of receiving incoming loan objects or new acquisitions.

For example, during our IPM rounds, Charlotte and I found evidence of mild infestation on two taxidermy specimens in the Natural History Collection: an Albino Grey Squirrel and a "double prepped" European Rabbit. A "double prep" refers to a taxidermy specimen that contains visible elements of both the specimen’s skeleton and traditional taxidermy of the skins and furs simultaneously. These objects were packed into boxes, sealed with plastic, and placed in a chest freezer dedicated to the low-temperature treatment of objects (at around -30 °C). The goal of the low-temperature treatment is to create conditions under which the pests are unable to survive. Many insects have biological and metabolic adaptations to exceedingly low-temperature environments, though these processes generally require time for the insects themselves to prepare. Low-temperature treatments are most effective when the change in the object’s environment is done quickly, preventing the pests from mobilizing their natural defenses which avoid or tolerate being in frozen conditions. Effective low-temperature treatments at the Horniman are conducted at or below -30 °C and generally last about one week or more to ensure the complete death of the infestation.

Concentrated loss of fur (left) is often reliable evidence for a pest issue with taxidermy specimens. This happy little boy will feel much better after a freeze treatment. (Image Credit: Charlotte Ridley)

Proper packing and sealing of the objects in suitable containers - such as acid-free or low-acid card boxes - and sealing them with plastic will help to ensure a successful freeze treatment and prevent further unwanted damage to the objects. (Image Credit: Charlotte Ridley)

Atmospheric treatments, such as anoxia, are used to the same effect as the temperature treatments and can be done locally on individual objects – sealed within bags – or on larger scales in sealed sections of rooms. All atmospheric treatments displace or remove oxygen, depriving pests of this necessary gas. Gas displacement treatments, using carbon dioxide or nitrogen, are alternative methods of lowering the oxygen content in a space. More than suffocation from the absence of oxygen, anoxia treatments kill the insect pests via internal dehydration. This is accelerated in dry and warm conditions. The biological response of the insects, attempting to breathe in the warm, dry, oxygen-deprived environment, actually results in their dehydration, desiccation, and death. While often effective, these treatments tend to be both expensive and time-consuming, taking up to two weeks to ensure the complete desiccation of some pest species and their eggs. For gas-displacement treatments, dry nitrogen gas also needs to be humidified before delivery to prevent the object itself drying out. This helps to achieve and maintain a suitable moisture level for the preservation of the object. To make such treatments cost-effective, larger systems often need to be put in place to treat multiple objects at a time; however, these systems are difficult to set up if an institution lacks this infrastructure, and can take weeks to be effective. This is often difficult and costly to implement for institutions with both limited space and funds.

In the past, pesticide treatments have been applied directly to objects, especially taxidermy specimens; famously the cumulative toxin arsenic. Today, direct application of pesticides to objects is ill-advised as 1) it is detrimental for the humans who handle and care for the objects (always wear gloves with taxidermy for this reason; better safe than sorry!) and 2) the application of chemicals to objects may cause unwanted changes to the object, such as discoloration, embrittlement of object components, and other forms of accelerated deterioration. If pesticides need to be used it is often more effective to apply them to the collections space in a way that remains safe for people. Desiccant dusts are an effective way to manage the water element of pest survival. Desiccant dusts are often used in 'dead spaces' beneath floor boards or beneath display cases; these dusts will remove ambient moisture from the local area and create inhospitable conditions for the pests. As another example, Constrain is a water-based insecticide with a neutral pH that has been safety-tested and is known to be effective in the reduction of wood-borers, clothes moths, carpet beetles, biscuit beetles, silverfish, book lice, and more (Constrain). As with any materials used in conservation or for pest control, please always consult field professionals (see guidance from English Heritage) and individual product safety data sheets before endeavouring to use such materials in your own collections spaces.

Overall, IPM is an integral part of the conservator's job in managing and caring for objects within a collection. When conducted routinely, alongside effective environmental controls, any problems that develop can be identified and addressed quickly. While the popular picture of a conservator in the eyes of the public is one who does nothing but actively conduct object treatments, the reality is that a conservator's job is much more broad in its scope, encompassing not just the materials which comprise an object, but all aspects of the environment within a collection. We are managers of environmental conditions and problems as much as we are scientifically- and artistically-minded heritage specialists. Thanks for tuning in, and I'm looking forward to creating more content about my experience at the Horniman to share with everyone! For more information about IPM please see the below resources, many of which I used to put this post together.

Resources and More Info:

Burke, John, 1999. Anoxic Microenvironments: A Treatment for Pest Control, Conserve O Gram, vol. 3, no. 9 [online]. Available at: https://www.nps.gov/museum/publications/conserveogram/03-09.pdf

Conservation Center for Art and Historic Artifacts (CCAHA), 2020. Integrated Pest Management. [online]. Available at: https://www.youtube.com/watch?v=dWLBX9V7oSM&t=2560s

Conservation Center for Art and Historic Artifacts (CCAHA), 2020. Know Your Bugs!. [online]. Available at: https://ccaha.org/resources/know-your-bugs

English Heritage, undated. English Heritage Guidelines for Insect Pest Management in English Heritage Historic Properties. [online]. Available at: https://www.english-heritage.org.uk/siteassets/home/learn/conservation/collections-advice--guidance/eh-guidelines-insect-pest-management.pdf

MuseumPests.net, 2020. Museum Pests. [online]. Available at: https://museumpests.net/

Strang, Thomas, 1997. Controlling Insect Pests with Low Temperature – Canadian Conservation Institute (CCI) Notes 3/3. [online]. Available at: https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/controlling-insects-low-temperature.html