This is the final installment in a four-part series discussing integrated pest management. This month we will discuss the respond (i.e., kill) and recover steps. IPM stresses respond techniques that are toxic to the insects and vermin but not to humans.
Responding to vermin is comparable to the detect step. As noted last month, I recommend mechanical snap traps for trapping mice and rats. Snap traps are inexpensive and can be either reused or disposed of. I do not advocate the use of poisons.
Despite what many manufacturers say, rodents do not always die outside your home. They will often die in your walls or crawlspaces. In addition to the smell, dead mice and rats can become an attractant for insects such as dermestids.
Place traps where the rodents run, namely next to the wall. Narrowing the pathway to the trap will make the trap more effective.
Many schools of thought suggest the most effective baits. Options include peanut butter and dry pasta. Whatever bait you choose, it should draw the animal to it but be well enough secured to the trap that the pest cannot steal the bait without releasing the trap.
In the past, many toxic fumigants were used to respond to an insect infestation. Concerns over toxicity and the deleterious nature of many insecticides have resulted in less toxic methods being used.
These include freezing, a variety of inert (i.e., anoxic) environments and heat. Of the three, freezing is the most accessible and commonly used by museums across North America.
Freezing kills all stages of the insect — eggs, larvae and adults. Here are a few guidelines.
Insects are adaptable to their environments and quite adept at surviving. Insects have glycols in their systems that act as antifreeze allowing them to survive cold temperatures.
In order to counteract the glycols, it is important that they be exposed quickly to a low temperature. If the temperature drops slowly, their antifreeze will kick in and they will survive the treatment.
It is recommended that you freeze infested items to a temperature of at least -4 F (-20 C) for one week. You will need to use a chest freezer for this job. Unfortunately, the freezer attached to your refrigerator does not reach temperatures that are low enough to be effective.
If you discover that part of your collection is infested, promptly place it in a polyethylene bag and put it in the freezer for one week.
Once the week is up, remove the bag from the freezer and allow it to reach room temperature before opening the bag. This will prevent condensation from forming on your collection. Once the bag and its contents have reached room temperature, remove the items and carefully remove any insect evidence (e.g., bodies, larvae) that you can find. This will help prevent false alarms in the future.
Rebag in a clean bag and set aside for a few weeks to be certain your freezing technique was effective. Remember to look for live insects (either adult or larval stage) and frass (insect droppings). Frass will look like tiny grains of sand. If you find any of these, repeat the freezing treatment.
The last step in IPM is “recover.” At this stage, one should assess why an infestation took place and take steps to insure that it does not happen again.
Hopefully, time spent on the first few steps of IPM will keep all of you from having to deal with the latter ones.
Susan L. Maltby, Toronto, is a private conservation consultant, with an interest in numismatic preservation.