Wednesday, 5 November 2014

Pest Management: A Bag Full Of Trouble!

Signs of moth © Pitt Rivers Museum
Although the three galleries in the Museum have many display cases filled with objects, there are another 57,500 objects not currently on display. These reserve collections are homed in storage in and around the galleries. It is the job of the Conservation Department to care for and monitor the collections both on display and in storage.

Over the past few years, museums across the UK have seen an alarming increase in the number of common clothes moth (Tineola bisselliella) amongst their collections. This increase could be attributed to a rise in temperature, the decline of pesticides used within museums and an increase in visitor numbers. Much of the collection at the Pitt Rivers is made from natural fibres such as textiles, skins, hair, fur, feathers and foodstuff. Unfortunately these are the materials that the larvae of the clothes moth consume. If a moth infestation goes unnoticed it can devastate an object leaving it unrecognisable. It is therefore vital that the Conservation Team have an ongoing integrated pest management (IPM) program in place.

The IPM program at the Pitt Rivers involves weekly checks of a number of moth pheromone traps located throughout the Museum. The pheromone traps are designed to attract the male moth, which get stuck on the traps sticky surface. Capturing the male moth reduces the potential for reproduction and the number of moth caught indicate if there is an increase in moth activity within a case. As a Department we also train the other museum staff, including the Collections Department and Front of House Staff, to be vigilant and report any moth seen within the Museum. Even with these safeguards moth infestations can unfortunately still occur.

Removing debris © PRM
During October 2014 one of the Collection Team retrieved a number of textile bags from storage under a case in the Lower Gallery ready for a Visiting Researcher. The member of staff noticed a moth in the polythene wrapping of one bag. Conservation was notified and went to investigate. 32 textile and fur bags were fond to have moth within their polythene wrapping. As a precaution all 32 bags were removed and placed in a freezer at minus 31 degrees for one week. Freezing at such a low temperature kills the eggs, larvae and adult moth.

The saddlebag after conservation,
PRM 1947.1.13 © PRM
Once removed from the freezer the bags were checked over in Conservation. 8 of the bags were found to have an active infestation, whereas the remaining bags showed no sign of moth. Unfortunately 3 of the 8 bags had been adversely affected.

One of these was a section from a woollen saddlebag thought to be from Turkey. The polythene wrapping was not quite big enough for the saddlebag and where the wool was exposed along one edge the moth had gathered. Thankfully once the moth and larvae was removed there was relatively little damage.

Below you can see a woollen shoulder bag from Greece. This bag had a large number of moth within its folds and again along an exposed edge. There are patches of yellowed staining thought to be ethnographic food deposits from use. The stained areas had attracted the moth and were the places most affected by the infestation. The staining is part of the object's history and can tell the story of its use therefore we would never try to remove it. Once the moth debris was removed there was some loss of fibres.

From left to right: Section of the bag showing staining with moth damage before and after treatment, the complete bag after being treated in conservation; PRM 1965.11.4B © Pitt Rivers Museum

The next one was a bag from the Miju Mishmi peoples of the Lohit Valley, Tibet. At first this decorative cotton bag appeared to only have a small number of moth on its handle. However the inside of the bag had plant debris remaining from when the bag was in use. This debris had attracted a large number of moth. Thankfully although the moth appeared plentiful there was no physical damage to the textile.

Left and centre: the damage found inside the bag, right: the bag after conservation treatment:
cotton bag from Tibet PRM 1948.7.49 © Pitt Rivers Museum

All the bags that had been removed for freezing have now been placed in sealed polythene bags for storage. The affected storage drawers, along with a number of other 'high risk' cases containing natural fibres, have been highlighted and marked with a sparkly moth sticker. These stickers are designed to indicate to all staff to be extra vigilant and take the time to check through the contents for any sign of moth.

Kate Jackson

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