You may have spotted small plastic boxes tucked into corners or against walls in old historic buildings. These are pest traps, and four times a year they're collected up and we take a look at what we’ve caught. This is a process called Integrated Pest Management. The arrival of Christmas and New Year signalled the last IPM of 2016 for us here at Nymans.
The traps we use at Nymans are called Blunder Traps and are the most commonly used traps in the National Trust. They're small plastic boxes with openings on three sides. Insects move along the edges of flooring, very close to the wall and would prefer to go over or through an item that’s blocking their path. Therefore, if we push the longest open edge of the trap against the wall, the insect will crawl up the side opening and straight across a sticky piece of cardboard hidden inside. Once they’re on the board, they're trapped.
Every three months we study our catches to get an idea of what insects are around at that time of year. Some insects are considered to be pests, meaning that they’re harmful and could eat or damage items in the collection. These traps are a way of monitoring the different species in the house and help us to decide if we need to take action against an infestation.
Once we've collected all the traps, we need to be able to identify all the pests and record their numbers in a database. Most insects are easily identifiable. We found 362 woodlice in the traps throughout 2016, but we don’t consider them to be pests as they're not harmful to the collection. Ladybirds however are also easily identifiable but are considered to be pests. They don’t eat the materials in the collection but they leave behind a trail of yellow excrement which can cause permanent stains.
There are also some very helpful guides we can use to identify pests. We use a identification guide published by English Heritage and information from the University of Birmingham. If we're still unable to identify an insect, like the species of this beetle shown above, we send photographs of our mystery pests to specialists, who can usually work out what they are and let us know if we should be concerned.
We won’t treat the collection for every pest that we find. Most pests can be kept away by regulating the environment around the collection. Pests thrive in overly warm, moist conditions, so we aim to keep the environment at a steady humidity and temperature.
If we find many of one type of pest in a single trap, that’s an indicator that there’s an infestation somewhere nearby and we need to take action.
We have to be very careful about how we handle pest infestations as some treatments, such as chemicals or insecticides, can do more damage to materials than the pests themselves. We found large numbers of beetle larvae in our autumn checks, and so we used a gas aerosol designed for fleas to kill them all off quickly. Because the gas was intended for domestic use it wasn't harmful to the collection or us and the results of the latest IPM show that the treatment worked.
While cleaning the Library, evidence of clothes moth damage was found on this yellow armchair cover. We can’t treat textiles chemically, so we wrapped it up airtight in plastic and put it in the freezer for a few weeks. The moths couldn’t survive in the freezing temperature, and so the population was dealt with quickly before they spread to anything else. The cover is now slowly coming back up to room temperature before being returned to its chair.