Diagnostic evaluation of insect attack on existing timber structures: a review of some case studies

The problem of wood-boring insect attacks is gaining greater interest in Italy today. Wood-boring insects (Coleoptera, termites) often cause both structural and aesthetic damage on wooden structures which can sometimes give rise to human health concerns. Possible causes of current insect infestations include the use of timber originating from plantations, as well as bad post-felling practices such as late harvesting and stocking in unsuitable places before final processing. In the past, these insects were not thought to pose an economic threat to timber in service in Italy, but, in recent years, they have become a problem. The aim of this paper is to report on case studies concerning the occurrence of these unusual wood-boring insects on timber in service and, on the basis of the Authors' experience, to formulate an in situ inspection protocol. The species we are dealing with in the case studies are: Bostrichus capucinus, family Bostrichidae, associated with Lyctus spp. (Fam. Lyctidae) and Lymexylon navale, family Lymexylonidae, belonging to the group of the so-called "ambrosia beetles" or "pinhole borers". All these species were found on hardwoods, where they had bored into the sapwood except for L. navale which was also able to bore into heartwood, causing major concerns about its potential danger to timber in service. A technical integrated approach in evaluating insect attacks on on-site timber elements is also described here. The assessment is based on different methods, i.e. visual inspection and acoustic detection. This procedure is proposed as a basis for the development of an intervention protocol in the early stages of infestation.