18% fall in clothes moths ‘excellent news’ for textile collections says National Trust

Image: Cleaning in progress in the Wisteria Bedroom at Dunster Castle, Somerset (National Trust Images/ Sarah Allen)

A 2021 increase in moth numbers at historic houses, caused by closures, is now “a distant memory” the charity said.

An increase in clothes moths driven by lockdown closures is being reversed, the National Trust reports.

The number of clothes moths in the National Trust’s historic houses has fallen by 18% in the last year, according to the charity’s annual insect pests report.

The larvae of Tineola bisselliella, known colloquially as clothes moths, damage carpets, upholstery, taxidermy and woollen or silk objects.

The 18% fall this year follows a 39% slump the previous year.

The Trust’s Assistant National Conservator Alexandra Radford, who compiled the report, said an increase in the numbers of moths in 2021, driven by lockdown closures, is “now a distant memory”, which was “excellent news for all our collections”

“The drop is likely because pest numbers are still falling from their lockdown highs, but it also reflects the decisive action and relentless efforts of house teams to manage moth numbers.

“We’ve put in place more training and resources to help property teams with integrated pest management, which is crucial to good collections care.”

Overall insect counts were also down by 11%, compared to the Trust’s 2022 Integrated Pest Management data. The trust said this was likely aided by another year of turbulent weather, with record temperatures and rainfall, multiple named storms and rapid fluctuations.

Radford said: “Nature is reflecting back the impact of these extremes. Without a doubt, the ongoing unpredictability and extremes in temperatures and moisture are feeding through into insect breeding cycles and patterns.”

Larvae of a webbing clothes moth on Axminster carpet in the State Bedroom at Blickling, Norfolk (National TrustKenny Gray)

While overall numbers are down, the number of Silverfish insects, which feed on books, paper and cotton has risen by 6%.

Radford said the slight rise coincides with the UK becoming wetter over the past few decades.

“These more intense periods of rainfall can lead to water run-off and flooding, and we know silverfish will seek out and thrive in damp environments.”

Also on the rise are woolly bear – carpet beetle larvae which feed on silk, wool, fur and feathers – and booklice. Booklice and silverfish can graze on mould, with higher numbers to be expected when there is intensely wet weather and high humidity.

Alexandra continued: “Our booklice visitors appear to be more familiar within our collection spaces over the past few years. Because mould is very appetising to booklice and silverfish, our collections and house teams continue to monitor areas that could be more vulnerable to mould outbreaks, allowing them to take a more targeted approach.”