Trendswatch | Tackling insect infestations

Not all museum visitors are welcome. Under lockdown, with buildings shut and collections at times inaccessible, many venues have unfortunately attracted more pests, as the little critters suddenly had a better chance of finding the undisturbed spaces they need to thrive.

The National Trust recorded an 11% rise in insect numbers at its properties last year. But help is at hand.

At Blickling Hall in Norfolk, the family home of the Tudor queen Anne Boleyn, webbing clothes moths have blighted silk and wool objects. A pheromone-based and sustainable pest- management method is being trialled, which involves microscopic parasite wasps laying their eggs inside the moths’ eggs, preventing its larvae from hatching. It is the first time this method has been used in a heritage setting alongside natural remedies.

Joint initiative

Meanwhile, South West Museum Development, with the support of Historic England, has launched Pest Partners, a project to help up to 200 heritage organisations in its region tackle pests.

Each Pest Partner receives a monitoring and ID kit featuring an illuminated loupe (magnifier) and guidance on setting and checking the traps provided.

“Lockdown meant we knew there was an increased risk of pest infestations because there was such a reduction in the human activity that normally inhibits the movement of adult pests looking for mates and new egg-laying sites,” says Helena Jaeschke, conservation development officer for South West Museum Development.

A lot of the region’s museums are small and rely on volunteers, many of whom had to shield during lockdown. With staff on furlough, there were also fewer trained or experienced people going into museums to check traps and look for pests flying or crawling around.

Jaeschke paints a vivid picture of the damage that insects can do. “Every category of organic object in museums across the south-west has been attacked,” she says. “Insect collections have had all the soft parts eaten, taxidermy literally eaten to the bone, textiles and costumes with countless holes, books and wallpaper grazed, and furniture and building timber weakened by woodworm larvae boring it.”

Damp-loving species such as silverfish and woodlice have also taken up residence, so it has been particularly difficult for small museums that rely on portable dehumidifiers, for example.

Changing life cycles

Climate change is likely to be affecting the life cycles of insects, with milder winters allowing them to complete more life cycles each year.

“We found live case-bearing clothes moth larvae, even in December, happily chewing through costume,” says Jaeschke.

The National Trust for Scotland (NTS) has reported a rise in infestations over lockdown. Flash flooding at one property allowed silverfish to flourish in the library because of the increase in humidity.

“The speed of the first lockdown left little time to be able to plan,” says Lesley Scott, a conservation advisor for the NTS. “Staffing was so skeletal that the security of premises and enabling public access to outdoor spaces were the priorities.

“We were aware of past issues, and had implemented preventative measures, such as regular dusting behind bookcases and understanding where the silverfish were entering through trappings. It’s a case of needing to keep on top of numbers.”

The Bowes Museum in County Durham, known for its fashion and textile collection, has also seen a rise in the number of clothes moths since March 2020.

“This was brought about by the seasonal increase in temperature and normal seasonal moth patterns, but also the lack of people, air flow and daily housekeeping routines while the museum was closed,” says the museum’s preventive conservator, Frederick Stubbs. “The numbers reduced dramatically from June, when our conservation team carried out a deep clean to combat the problem.”

The museum plans to use pheromone sex disruptors to prevent the seasonal peak experienced last year.

It’s a complex picture. Fewer people being around during lockdown meant less food and detritus for insects, birds and rodents to feed on. But some properties reported an increase in rodent activity as well as casual invaders such as wasps that had got caught within properties and were unable to get out again.

“There has certainly been an adjustment to working practice in response to lockdown,” says Suzanne Ryder, senior curator in charge, hymenoptera, at London’s Natural History Museum (NHM).

But she says the museum’s integrated pest management programme was considered one of the essential tasks that should continue through the period of closure, to protect the collections. As a result, the NHM experienced a decrease in pest activity.

Pest Odyssey 2021 – The Next Generation virtual conference in September will focus on developments in pest control. Deborah Mulhearn is a freelance writer