Whilst the good old donger still has a place in the inspector’s toolkit, researchers are now investigating more advanced methods of termite detection within timber.
Latest termite detection research
Finding timber pests in museums
In museums, the main focus of termite detection is on structural timber. However, a niche market exists for the detection of termites and other timber pest activity in high value items such as furniture and picture frames. This is particularly the case in museums where invasive inspection techniques are simply not possible.
Researchers in the US have recently developed a technique that combines a visual inspection with the use of CT scanning.1 The resulting images not only allow individual insects to be identified (in this case drywood termites in a picture frame) but also enable a full assessment of the item.
The inspection maps any damage and the quantity of wood loss — facts that determine the structural integrity of the frame. Appropriate decisions about treatment, restoration and ongoing management can then be made.
An important side note to this study was that although the museum storage room was held at a certain temperature and humidity level to minimise pest and mould issues, drywood termites were capable of thriving in the storage room for an estimated 15 years.
Powering up timber pest detection
Timber utility poles are a significant component of power and communication networks. Even with preservative treatments they are still susceptible to timber pests over time. However, using timber pest inspectors to assess the health of timber poles can be both inaccurate and time-consuming. As such, research into methods that can help in assessing the strength of power poles and determine the presence of timber pests is of significant value. Recent research has demonstrated that using stress wave propagation coupled with a neural network pattern-recognition algorithm can provide encouraging results, with the three models assessed producing between 81-92% success rates in identifying both healthy and defective poles.2
The ultimate donger
The ‘donger’, really any hard tool for tapping wood, is an essential part of the timber pest inspector’s toolkit. Experienced inspectors use the changes in sound to alert them to potential issues. Now, research has begun on ways to use deep neural networks to analyse the sound that results from hitting a piece of timber, to assess the condition of the timber.3 Using timber blocks with a single, drilled core through the middle, accuracy of the system was up to 92%, regardless of the shape of the timber piece and location of the ‘hit’ on the timber.
Although encouraging, the researchers noted that greater investigation is required. In particular to assess the technology in real-life situations — where damage is enclosed within a piece of timber (rather than a hole drilled all the way through), looking at different types of damage, and in different types of timber. However, unlike the stress wave methodology described previously, which requires a sensor to be installed prior to testing, the researchers believe this technology will allow for the development of a low-cost inspection device that can be used on site.
Improving detection devices
Other researchers have used computer software to investigate ways of improving termite detection devices. Whilst many devices allow for the detection of termites, it is difficult to predict the population size. Researchers identified a list of 40 acoustic and ten temperature features that could be useful in determining the presence of termites and predicting population size.4
Using a Boruta package (an algorithm that can identify the key factors influencing outcomes), this list was refined to 25 acoustic and four temperature features that were relevant. In using the reduced data to detect and assess populations of Coptotermes curvignathus infestations in pine board, the detection accuracy increased to over 97% and improved the accuracy in the prediction of termite population size. The researchers believe this has potential in improving the accuracy of commercial termite detection devices.
For more information on how termites are detected during a termite inspection go to our termite inspection page.
References
1 Arbat, Shivani & Forschler, Brian & Mondi, Annelies & Sharma, Ajay. (2021). The Case History of an Insect Infestation Revealed Using X-ray Computed Tomography and Implications for Museum Collections Management Decisions. Heritage. 4. 1016-1025. 10.3390/heritage4030056.
2. Bandara, Sahan & Rajeev, Pat & Gad, E. & Sriskantharajah, Baraneedaran & Flatley, I.. (2021). Structural Health Assessment of Timber Utility Poles Using Stress Wave Propagation and Artificial Neural Network Techniques. Journal of Nondestructive Evaluation. 40. 10.1007/s10921-021-00821-6.
3 Chen, Lin & Xiong, Haibei & Sang, Xiaohan & Cheng, Yuan & Li, Xiuquan & Kong, Qingzhao. (2021). An innovative deep neural network– based approach for internal cavity detection of timber columns using percussion sound. Structural Health Monitoring. 147592172110285. 10.1177/14759217211028524.
4 Achirul Nanda, Muhammad & Seminar, Kudang & Maddu, Akhiruddin & Nandika, Dodi. (2021). Identifying relevant features of termite signals applied in termite detection system. Ecological Informatics. 64. 101391. 10.1016/j.ecoinf.2021.101391.
Termite Professional Australian edition, 2021
Low power microwaves for termite detection
Wooden power poles are susceptible to wood decay and termite attack. Structural failure of power poles can have serious, expensive and potentially life-threatening consequences. The 2014 Perth bushfire that destroyed 57 homes (fortunately with no lives lost) was caused by a power pole failure due to termite damage on private property. Both the property owner and maintenance contractor were held liable. In a bid to minimise the fire risk, Australian researchers have developed a new device that uses very low power microwave energy to detect damaged power poles.
Testing of power pole integrity is somewhat subjective and involves ‘sounding the timber’ using a donger or tapping device, making visual observations and drilling holes to inspect the shavings. Successful assessment is not guaranteed even for experienced termite professionals, but with variable skill levels in pole inspectors, poles with damage are often missed. In addition, drilling into poles not only causes damage, but can itself introduce decay, fungi and sometimes termites into the timber.
Australian researchers evaluated two low power microwaves systems, one a ‘look through’ system that required sensors to be positioned either side of the pole and a second, radar-based system that only has to be positioned on one side of the power pole.1 A key requirement is that the systems need to penetrate the complete depth of the wood (some commercial products can assess wood integrity but only to a depth of a few centimetres).
Both systems work on the principle that the breakdown of wood by termites and wood decay affect the wood structure, in turn affecting the dielectric properties of the wood. This impacts the microwaves passing through the wood and creates a distinct profile compared to sound wood. Both systems were 100% accurate in picking up termite activity and decay. In fact, the radar-based system proved very sensitive, even picking up active termite movement as per other commercial termite detection devices. With assessment of a single pole taking a little over one and half minutes, this technology offers significant benefits to the power utility industry and potentially to the pest management industry as a termite inspection tool.
References
1 Brodie, G., Thanigasalam, D.B., Farrell, P., Kealy, A., French, J.R.J., Ahmed (Shiday), B., 2020. An In-Situ Assessment of Wood-in-Service Using Microwave Technologies, with a Focus on Assessing Hardwood Power Poles. INSECTS 11. https://doi.org/10.3390/insects11090568
