Lethal Harbourages – Cost Effective Bed Bug Control?

Researchers have devised a simple, cost-effective approach to modern bed bug control. 

There is a significant need for cost-effective bed bug control, as the level of bed bug infestations in lower socioeconomic areas of the world can be significant. Indeed, the level of infestation in government housing in some areas of the US has to be seen to be believed! Whether it’s governments spending the money or the residents themselves, budget is tight.

But with the high levels of insecticide resistance in these same bed bug infestations, any bed bug control not only needs to be low cost but also needs to be highly effective. Researchers led by Stephen Doggett in Australia have been exploring the concept of ‘lethal harbourages’ as a solution to the problem.

The idea of lethal harbourages taps into bed bug thigmotactic behaviour – they like to be in contact with surfaces, so cracks and crevices make ideal harbourages. The researchers investigated the potential for an artificial harbourage pre-treated with insecticide to control bed bugs. The use of cardboard, cheap and readily available, proved ideal, with bed bugs easily squeezing into the flutes between the sheets of cardboard (pictured above).

Working with both susceptible and resistant strains of bed bugs, the researchers evaluated the cardboard harbourages with six different insecticidal dust formulations – two pyrethroids, two silicone dioxides, one diatomaceous earth and one fipronil. Bed bugs were placed in small areas with either a treated harbourage or control harbourage (with no insecticide). The bed bugs were free to choose to enter the harbourage. The silica dust formulation proved to be the most efficacious, with the highest dose delivering 100% mortality between 14-17 days after treatment, even on the insecticide-resistant strain.

Although it may appear unexpected, the pyrethroid dusts at the highest dose, particularly the deltamethrin dust, delivered a similar level of performance to the silica dusts over the same timeframe. However, pyrethroids should be relatively fast acting – they gained control of the susceptible bed bug strain in less than two days – so for the pyrethroid treatments to take 15 or so days to achieve 100% control of the resistant strain indicates that their performance was indeed sub-optimal. The authors also note that the resistant strain used in the trials was the Parramatta strain, which is only mildly resistant. Performance of pyrethroids would be expected to be significantly worse on more strongly resistant strains.

The researchers also took the leading dust product – a silica dust – and applied the product to half the harbourages in a larger arena. Within 21 days all the bed bugs were dead. Over the same time period less than 10% of the bed bugs in the control arena had died.

The authors report this as an encouraging proof of concept, but state that field trials are required to understand their potential in practice. A number of studies would be required to understand the impact of lethal harbourage size, material, design, location of traps and number used, both as a preventative measure and in a curative treatment. Nevertheless, this study shows encouraging laboratory performance from what should be a low-cost bed bug control tool.

 

Further reading: Kerdsawang J., Dang K., Chareonviriyaphap T., Doggett S.L. (2023). Laboratory Insecticide efficacy trials of lethal harborages for control of the common bed bug, Cimex lectularius (Hemiptera: Cimicidae). Insects, 14: 814.