DRYWOOD TERMITES

Although a species rarely encountered by Australian pest managers, the West Indian drywood termite is an invasive species that pest managers should be well informed about.

Latest drywood termite research

The West Indian drywood termite, Cryptotermes brevis, is one of the most difficult termites to control and an important invasive termite, with its distinctive pellet-like frass (pictured) helping in its identification. Due to its nesting behaviour, where it develops small nests completely within its wood food source that can survive at low moisture levels, the nests are difficult to detect and easy to inadvertently transport. When buildings become infested, control is difficult as the standard treatment is to fumigate the entire building, which tends to be expensive and concerning from a safety and environmental point of view. This issue is of particular focus in Australia at the moment, as although the West Indian drywood termite is classified as an invasive pest, the Queensland Government has recently decided that when an infestation is identified, the cost of the treatment is now the responsibility of the property owner.

Drywood termite control — the heat is on!

With heat treatments being utilised commercially for other pests, the question is whether this is a suitable technique for the control of drywood termites. The challenge in using heat treatment for drywood termites is that whereas treatment of wooden furniture may be possible, treatment of whole buildings becomes more problematic.

Australian researchers have established that although exposure to 40°C for up to an hour did not kill the termites, exposure at 45°C for one hour was lethal.¹ Higher temperatures were even more effective — as little as three minutes’ exposure at 50°C or two minutes at 55°C was lethal. The researchers suggested that localised heat spot treatment could be an effective option. However, getting the internal temperature of the wood (where the termites are hiding) up to the required heat level can be a challenge.

However, in the US, heat treatment is increasing in popularity to treat West Indian drywood termite infestations, although they suffer from the same issue, that such treatments may not be able to kill all the termites due to the difficulty in heating some areas. Focusing on blocks of units, where West Indian drywood termites primarily infested wooden furniture and kitchen cabinets, researchers identified ways to improve the heat circulation in treatments.² The key action they took was to drill holes in the base of kitchen cabinets and pump heated air into these voids. The result was a 100% success rate, rather than a 33% callback rate with standard heat treatments. The researchers emphasised the importance of achieving even heat distribution, not only to ensure control, but to avoid the need to try and heat to excessive temperatures to overcome the failings of poor heat distribution.

References

¹ McDonald, Janet & Fitzgerald, Chris & Hassan, Babar & Morrell, Jeffrey. (2022). Thermal tolerance of an invasive drywood termite, Cryptotermes brevis (Blattodea: Kalotermitidae). Journal of Thermal Biology. 104. 103199. 10.1016/j.jtherbio.2022.103199.

² Tay, Jia-Wei & James, Devon. (2021). Field Demonstration of Heat Technology to Mitigate Heat Sinks for Drywood Termite (Blattodea: Kalotermitidae) Management. Insects. 12. 1090. 10.3390/insects12121090.