One of the greatest threats to a herbarium is insects, which can infest the cabinets and eat specimens. Beetles, such as the cigarette beetle (Lasioderma sp), target asters and roses, demolishing flowers which are so important to identification. Other pests include silverfish (Lepisma saccharina) and book lice (Order Psocoptera). To prevent damage, herbaria adopt a myriad of pest control practices, including fumigation, poisoning, insect trapping, temperature and humidity control, and periodic specimen freezing. The process of pressing and drying new specimens is both for preservation and protection – all new specimens must go through some sterilization process in order to kill insects before being shelved with the regular collection.
Here at the Sewanee Herbarium, we do not use toxic treatments. Instead, we control the temperature and humidity, and we frequently freeze specimens. After finding a live insect crawling on a specimen this fall, we began the process of freezing all our specimens. Specimens are frozen at below -23 °C for a period of four days, then returned to sanitized shelves. We hope that this process will protect our specimens for many years to come.