Battle of the booklice
Kew’s Herbarium and Library are fighting an ongoing battle with pest insects that can feast on dried plant specimens and precious books. Jonathan Farley and Paul Green reveal how they are tackling these infestations.
Know your enemies
Jonathan and his colleagues in Kew’s Preservation Unit are constantly on the lookout for insects in the collections. Should a large enough invasion of pests arrive in the Herbarium or Library then they can be sufficient in number to establish a sustainable colony, and it is these which can cause the most damage. Here are just a few of the insect pests encountered
- carpet beetle (Anthrenus verbasci) - attacking the woollen draft excluders of herbarium cabinets
- cigarette beetle (Lasioderma serricorne) - attacking the biological material on herbarium specimens
- common woodworm (Anobium punctatum) - attacking herbarium cabinets, books and paper
- Stockholm beetle (Trogoderma angustum) - attacking herbarium specimens and paper
- silverfish (Lepisma saccharina) - attacking the surfaces of documents and maps
- booklice (Psocoptera) - mainly feeding on the starch paste from old bindings
Decontamination
Kew operates an integrated pest management programme, the mainstay of which is constant monitoring and trapping. As part of this programme, no material may enter the building without first being decontaminated. This includes loans, donations and private material being brought in for research purposes, all of which could contain insect pests with the potential to contaminate Kew’s collections.
Kew uses two decontamination procedures:
Freezing: Items are frozen to 243K (-30⁰C) for seven days, to eliminate even temperate zone pests.
Anoxic method: Employed if the base material cannot withstand freezing. Items are placed in a container in which oxygen has been displaced, to suffocate the pests. This method is only employed when absolutely necessary as the anoxic environment must be maintained for a considerably longer time than the freezing process and the costs of maintaining an anoxic environment are high.
The secret life of booklice
One of the most common pests encountered are psocids (members of the insect order Psocoptera), in particular the booklouse Liposcelis bostrychophila. Females of this species can produce eggs that grow into new individuals without fertilisation by males (parthenogenesis) meaning a single individual can start a whole new population. Over half of the antiquarian accessions which are received by Kew’s Library, are contaminated by psocids. Hence the decontamination of incoming material is an essential part of the battle against infestation.
Where do booklice congregate?
Paul Green, a chemical ecologist in Kew’s Natural Capital and Plant Health Department, has had an interest in booklice for over 20 years and has experience of dealing with infestations. Recent research has revealed a great deal about the biology of booklice. They are able to select where they congregate based upon the chemicals in their environment. These chemicals can be from fungi, foodstuffs or the insects themselves and they are actually quite sensitive to small changes in the chemicals around them. This information could be used to develop more effective traps or repellents.
Continuing the fight to protect irreplaceable artefacts
Recent research has indicated that populations build up in libraries and museums as a result of sufficient food being available. Historic books bound with animal or plant glues can provide food for booklice, but in general books that are kept dry and free from dust and other nutritious debris are unlikely to allow populations of booklice to build up.
Unfortunately, dried plants in the Herbarium are often packed with nutrients, so can support large populations of insects that have the potential to reduce them to dust. So, preventing infestation by decontamination really is the best policy, although staff are always vigilant and there is always more to learn about the insect invaders that threaten Kew’s vital Herbarium and Library collections.
References
Green, P.W.C. & Farman, D.I. (2015). Can paper and glue alone sustain damaging populations of booklice, Liposcelis bostrychophila? Journal of Conservation and Museum Studies 13(1):3. Available online
Green, P.W.C. (2014). Volatile compounds from Liposcelis bostrychophila (Psocoptera: Liposcelididae) and their environment and their effects on settling behaviour. Biochemical Systematics and Ecology 57: 81-89.
Green, P.W.C. (2011). Insect-derived compounds affect the behaviour of Liposcelis bostrychophila: effects of combination and structure. Journal of Stored Products Research 47(3): 262-266.
Green, P.W.C. (2009). The effects of insect extracts and some insect-derived compounds on the settling behaviour of Liposcelis bostrychophila. Journal of Chemical Ecology 35(8): 1096-1107.
Green, P.W.C. (2008). Fungal isolates involved in biodeterioration of book-paper and their effects on substrate-selection by Liposcelis bostrychophila (Badonnel) (Psocoptera: Liposcelididae). Journal of Stored Products Research 44: 258-263.
Green, P.W.C. (2005). Substrate selection by Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae): effects of insect-extracts and microorganisms. Journal of Stored Products Research41(4): 445-454.
Green, P.W.C. & Turner, B.D. (2005). Food selection by the booklouse, Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelidae). Journal of Stored Products Research 41(1): 103-113.