“Silverfish” bugs which feed on books, paper and cotton, and webbing clothes moths are the most prolific insect pests affecting National Trust stately homes.
The charity has revealed the findings of its annual assessment of key insect pests that are causing damage to its collections at historic houses and castles in its care.
It is likely that warmer winters and hotter summers as the climate heats up are supporting pest cycles and making diligent housekeeping ever more crucial in protecting heritage, the National Trust said.
Throughout the year, staff at historic properties monitor insect activity indoors to safeguard more than a million objects such as books, carpets, furniture and fabrics, and the information is gathered to create a national picture of pests.
In 2019, 164 historic properties reported on 15 different insect pest species.
The top five problem bugs were:
– Silverfish (Lepisma saccharina), which feeds on books, paper and cotton;
– Webbing clothes moth (Tineola bisselliella), which feeds on silk, wool, fur and feathers;
– Woolly bear (a generic term for various carpet beetle larvae), which eat silk, wool, fur and feathers;
– Australian spider beetle (Ptinus tectus), which eats dust and detritus;
– Common booklouse (Liposcelis bostrychophila) which feeds on paper.
There is a north-south divide for some bugs, with webbing clothes moths skewed mostly towards the southern half of the country and Australian spider beetles more prevalent from the Midlands northwards.
Silverfish are a common problem across most of the UK, the National Trust said.
Other pests that are monitored in historic properties include the deathwatch beetle, furniture beetles, the biscuit beetle and the vodka beetle.
Data on the bugs has been collected centrally since 2012 and monitoring was expanded after a spike in insect numbers during 2015.
Insect numbers rose again in 2016, fell slightly in 2017 and have remained broadly static since then, the Trust said.
Hilary Jarvis, assistant preventive conservator, who collates the data for the annual review, said: “There is rarely one single driver of pest activity or relative species prevalence, but it is likely that warmer winters and hotter summers lead to more pest cycles.
“Although pest numbers at our places have actually remained relatively static in recent years, our housekeeping teams need to remain diligent in their efforts to keep insect pests at bay.”
Nigel Blades, the Trust’s preventive conservation adviser responsible for interior environmental conditions, said insect damage to objects is not new – with textiles and foods suffering infestations as far back as ancient Egypt.
“Fortunately, only a tiny proportion of insect species in the UK attack or eat historic material.
“However, a small percentage of these have the potential to become serious pests and can cause irreversible damage to collections in a short period of time,” he said.
Staff use housekeeping routines such as meticulous vacuuming, sweeping chimneys, and regular checking in dark corners and in folds of textiles to keep bugs down.
If an infestation is found, the Trust uses insecticides that are harmless to humans and collections, and may even freeze textiles like rugs to kill larvae and eggs.
The Trust also maintains the environment around collections to keep pests low, by preventing humid conditions that bugs such as silverfish and furniture beetles prefer.