Pests cause damage

Manage collection responsibly
Published : 02/17/12
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Pests — insects and vermin — can cause considerable harm, and loss of value, for numismatic collections.

This month is the first in a series of columns discussing pest management.

The pests

What sort of pests can affect numismatic collections? We divide pests into two categories: vermin and insects.

The term vermin generally refers to mice and rats but, depending on the part of the country in which you live, can include squirrels, raccoons, skunks and bats.

Mice and rats consider paper an excellent nesting material. They will chew up paper to convert it into a nest.

This, as you can imagine, could have a devastating effect on a paper note collection.

In addition to eating your collection, their excrement can cause staining and degradation of notes and coins.

In terms of insects, we divide them along the lines of what they eat.

Dermestids (carpet beetles) and clothes moths (webbing and casemaking) eat proteins such as wool, silk, feathers and leather. These insects could be particularly problematic for collectors of exotic numismatic materials. Leather bookbindings would also be at risk.

Silverfish, firebrats and booklice feed on paper-based materials.

Silverfish and firebrats prefer to eat the sizing on paper, which results in holes in the paper; whereas booklice eat microscopic mold that is growing on paper. Although they eat pastes and glues, booklice do not chew holes in the paper.

Cockroaches are omnivorous and will eat paper, leather, adhesives and bookbindings.

Pest management

Pests are omnipresent and a fact of life. It is for this reason that conservators talk about pest management and not eradication.

Integrated Pest Management, whereby pest management is integrated into the day-to-day activities of a facility, is the approach now taken by pest management specialists, conservators and collections managers.

Integrated Pest Management has five steps — avoid, block, detect, respond (i.e., kill) and recover — that can help preserve collections from pest damage. Time and attention dedicated to the first steps will help eliminate, or lessen, time spent on the later ones.


One of the best ways to avoid pests is to eliminate food and habitat, the two things that they are in search of.

Food sources vary from pest to pest. Mice and rats are attracted to our food. Keep garbage cans and compost bins away from your house and dispose of kitchen waste on a regular basis.

Dermestids like to feed on pollen. It is for this reason that nonflowering plant species are recommended as foundation plantings (i.e., plants next to your house’s foundation). Clothes moths and dermestids are attracted to bird and insect nests, feeding on debris in the nests. These should be removed from around your home.

Water attracts insects. Insects, like us, need it to survive. Silverfish and firebrats thrive in areas with a high relative humidity. The presence of silverfish and firebrats in your collection indicates that you have a humidity problem (i.e., your RH is too high).

Standing water attracts insects and encourages mold growth.

Ensure that water drains away from your house through proper landscaping. This not only keeps your basement dry but also prevents mold growth and makes your home less attractive to insects. Avoid creating damp microclimates by ensuring that your collection is up off the floor and away from exterior walls.

Good housekeeping is also key to pest management. Insects thrive in dark undisturbed places such as storage boxes. Dust and dirt provide a hospitable habitat and also make it hard to detect them.

Dermestids eat dead insects and insect debris, which are often found in household dust. Ensuring that your storage area is vacuumed and dusted on a regular basis will create an environment that pests consider less inviting. Shelving should be 4 to 6 inches off the ground so that it is easy to clean under it.

I will continue this discussion next month. Readers wishing to know more about Integrated Pest Management should check out The website is a product of the Integrated Pest Management Working Group and is an excellent resource.

Susan L. Maltby, Toronto, is a private conservation consultant, with an interest in numismatic preservation.

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