Along with the Common Furniture Beetle (woodworm) and Death Watch Beetle, moths flourish at Knole and they very much enjoy eating our textile collection. The carpets seem to suffer the most, however some of the upholstery show signs of being munched.
Only three rooms at Knole have the luxury of having environmental control, the Great Hall, Museum Room and the King’s Room. These are the only rooms with any form of heating, controlled by humidistats, which enable us to control the levels of Relative Humidity (RH). High levels of RH create a damp environment which is very attractive to pest insects. Damp, dark spaces that are dirty are their favourite places to hang out. The carpets are in the prime place to get the dirtiest.
Good housekeeping combined with controlling RH levels to stay below 65% will discourage pest insects. However, not only can we not control the RH, we cannot keep the carpets dirt and dust free. The carpets are only vacuumed once a year in November, and then covered and ‘put to bed’ for the winter. The carpets are very fragile due to their age and damage caused by light over the centuries. We have to strike a balance between cleaning them regularly enough to prevent pest infestations and the dust bonding with the fibres, but also prevent causing more damage by over cleaning them.
We have three types of moth at Knole, the Webbing clothes moth, Case-bearing clothes moth, and new this year, the White-shouldered house moth. Both clothes moths are unfortunately a common find on our pest traps. Moths are not the only culprits however; carpet beetles have also joined the party, the Varied carpet beetle and the Brown carpet beetle also live at Knole. On our last pest trap check in June we found a Brown carpet beetle larvae, which we think is another new species to Knole.
It is the larvae stage of both the moths and beetles that cause the damage. They can rapidly eat their way through textiles, particularly wool and silk, as they moult their old skins and eat to expand their body to fill the new skin, before entering into the pupae stage of development.
We have three types of monitoring traps that we use at Knole, two blunder traps (that contain sticky inserts that insects crawl or fly into and get stuck) and a pheromone trap for Webbing clothes moth. The sticky inserts have been impregnated with the female moth pheromone and attracts male moths who then get caught. We check the traps four times a year, in March, June, September and December. This allows us to identify what species of pest or non-pest insects are present in the show rooms and gives us a rough idea of how many there might be and how serious an infestation we have.