US Coins

Managing pests

In last month’s column I began a multipart series discussing pest management and numismatic collections.

You will remember Integrated Pest Management is the approach now taken by conservators and museum professionals for dealing with pests.

IPM has five steps — avoid, block, detect, respond (i.e., kill), and recover — that can help preserve collections from pest damage.

IPM is the classic “stitch in time saves nine” approach. IPM also stresses the use of response techniques and materials that have low human toxicity. As a result, much of our approach is borrowed from the food industry.


You will remember that we avoid pests by trying to eliminate their habitat and food source.

The next IPM step is to block pests by keeping them away from your collection. The first line of defense is your home. Ensure that it is well-sealed. Cracks and small holes allow insects and vermin access. Mice can get in through a hole the size of a dime and rats a hole the size of a quarter dollar. Insects require only millimeters.

Sealing your house will keep out pests and reduce energy costs.

Window screens are an inexpensive and easy way to keep many insects out.

Vents (e.g., kitchen and dryer) should be covered with screening (approximately one-quarter inch) to keep mice out.

Quarantine new acquisitions

Another key way to block insect pests is to quarantine new acquisitions to ensure that they are not infested. This is common procedure in museums. New items should be carefully examined to see if they show evidence of infestation.

Work over a clean surface covered with a white sheet of paper. Look for live insects, in either adult or larval stage, and frass (insect droppings). Frass will look like tiny grains of sand and will be the color of your object.

It is important to remember that most of the insects we are worried about cause damage in the larval stage. The adults lay their eggs in an object to provide a food source for their young when they hatch.

If you find live insects, or frass, immediately bag the items in a clear plastic bag and set them aside for treatment (this will be covered under the “respond” step). It is important to remember that these insects are quite small (millimeters in size) and not always easy to spot.

If you are having a hard time identifying the insects you are finding, check out the “Insect Fact Sheets” or the “Image Library” on Both are excellent resources.

If you see no evidence of insect presence, place the items in a clear plastic bag and seal tightly.

Set this aside for a few weeks and reexamine (through the clear plastic bag). If you see no insect activity, you can integrate your new acquisitions into your collection.


Detecting the presence of insects and vermin is often easier said than done. In many cases, an infestation is not noticed until the insects are well-ensconced and have caused considerable damage.

Insects thrive in nice dark undisturbed places such as storage boxes and closets, and mice and rats tend to keep a low profile around humans.


A variety of traps have been developed to help identify and monitor the presence of insects and vermin. These traps are either mechanical (e.g., a mouse trap) or adhesive. Most mechanical traps are designed to kill the animal quickly. However, this is not always the case.

A number of “humane” mouse and rat traps on the market capture the animal alive, allowing you to let it go somewhere outside. I personally cannot recommend these traps. Chances are if the mouse got inside your house once, he will do it again.

I will continue this discussion next month.

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

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