Use of Acoustic Emission (AE) to detect activity of common European dry-woodboring insects: some practical considerations
J G M Creemers
Old house borer (Hylotrupes bajulus), Furniture beetle (Anobium punctatum), and Deathwatch beetle (Xestobium rufovillosum) are common dry-woodboring insects occurring throughout Europe. With the aim to prevent unnecessary use of biocidal products, to protect valuable wooden elements and objects from unwanted influences, and to have a more objective method, SHR has started to study the use of acoustic emission (AE) to assess activity of attack by these insects. This manuscript deals with the results of some experiments done in order to collect knowledge about the influence of (low) temperature or possible daily rhythms on the activity of the insects. Such knowledge is crucial for a trustworthy application of AE detection for European dry-woodboring insects in practice. Based on an 8-day-test with Hylotrupes with normal daily variation in temperature it is concluded that under these circumstances, temperature is the main influencing factor regarding insect activity. For individual larvae, phases of inactivity exist with a duration of up to 30 minutes. In practice, where probably more than one larva is present at one specific time, in the absence of AE events, measuring periods may need to be extended to at least these 30 minutes. With regard to minimum temperatures for detection, the insect species studied show small differences in behaviour at low temperature. Because the number of registered hits for all species shows a marked decrease at temperatures becoming lower than 10 °C, it is recommended that decisive assessments using AE for detection of activity of these dry-woodboring insects should be done at (wood) temperatures of 10 °C or higher.