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The five most common insect pests at National Trust places in 2021

Written by
Image of Hilary Jarvis
Hilary JarvisAssistant National Conservator, National Trust
Silverfish damage to the wallpaper in the Chinese bedroom at Saltram, Devon.
Silverfish damage to the wallpaper in the Chinese bedroom at Saltram | © National Trust/Hilary Jarvis

Hilary Jarvis, one of the National Trust’s Assistant National Conservators has identified the most common pests found in 2021 at National Trust places during a year that saw us emerge from lockdown and welcome visitors once again.

A destructive minority

Only a tiny proportion of the UK’s insect species cause damage to the collections and interiors at the places we care for. However, the few species that do cause harm can become serious pests and cause irreversible damage to objects including books, textiles and taxidermy in a short period of time.

Pest numbers in 2021

Last year, National Trust staff identified and logged 56,742 insects at the places we care for.

The five most common insect pests found in 2021 remain the same as those recorded in 2020. Interestingly, though, there has been movement at the top, with the webbing clothes moth knocking silverfish off the number one spot.

Here are the troublesome pests that topped the damage-causing leaderboard in 2021:

Webbing clothes moth (Tineola bisselliella)
This pest rose 18 per cent in 2021, leaping to the number one spot and outnumbering silverfish.
Silverfish (Lepisma saccharina)
SIlverfish slumped 31 per cent to take the number two slot in 2021, continuing their decline from a 2019 peak. The fall in numbers is possibly due to drier conditions across the year overall.
Australian spider beetle (Ptinus tectus)
Numbers of this pest are showing signs of retreat but remain high at Tredegar in Wales and are growing at three sites in Northern Ireland. The Australian spider beetle remains a 'north of the Midlands' phenomenon, with regional weather trends likely to be the determining factor as we see warmer, wetter winters. Unfortunately, once embedded, they’re very difficult to evict.
Common booklouse (Liposcelis bostrychophila)
The common booklouse was fourth on the list in 2021, after a sharp increase in 2019 and a steady climb in 2020.
Woolly bear
The woolly bear (a generic term for various carpet beetle larvae) occupies fifth place in the chart of least welcome visitors for 2021.

How your visits help to protect precious collections

Insect pests such as moths and silverfish thrived during Covid-19 lockdowns. Less disturbance and relative darkness provided the perfect conditions for pest larvae and adults and their numbers increased by 11 per cent during this time. However, their efforts were slowed in 2021.

With the reopening of houses in May 2021, visitors unknowingly played an important role in keeping pests at bay, helping drive a 6 per cent downturn in moths, silverfish and other insects that can cause damage to historic collections.

The white walled entrance and red and white striped tower of Souter Lighthouse lit by winter sun, with a glimpse of dark blue sea behind

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