It turns out that there is another diatomaceous earth trial.
It is a report produced by Stephen Doggett and colleagues on behalf of diatomaceous earth manufacturer Mount Sylvia Diatomite.
Stephen L. Doggett, Merilyn J. Geary, David Lilly, Richard C. Russell. 2008. The Efficacy of Diatomaceous Earth against the Common Bed Bug, Cimex lectularius: a report for Mount Sylvia Diatomite. (PDF) Department of Medical Entomology, ICPMR and University of Sydney, Westmead Hospital.
In the laboratory investigations, DED [diatomaceous earth] produced a complete kill of adult bed bugs with all dose rates. At the dose rate equivalent to 1g of product/m2 this took 15 days; 2g/m2 – 10d; 4g/m2 – 13d; 8g/m2 – 9d.
The researchers also tested DE in conditions of higher humidity (70% RH) and also in a simulated environment.
(Lab investigations were of bed bugs confined to DE-treated filter paper in covered petri dishes. The bed bugs are from the Department of Medical Entomology’s colony, established in 2004, and have “a degree of insecticide resistance to both the synthetic pyrethroids and the carbamates.”)
It is well known that DED is less effective at higher humidities (Quarles & Winn 1996, Fields & Korunic 2000). As bed bugs are particularly problematic in tropical regions, it was thus important that testing was undertaken at a high relative humidity to examine if the product was still insecticidal. The longer time taken to achieve a complete kill was not unexpected in Experiment 3, however 100% mortality was still obtained with all treatment rates. The higher humidity however, does not affect the insecticide dust itself, rather the insect takes longer to die from desiccation. In Australia, humidity levels tend to be greater in the north of the country and it thus may be expected that DED would be less efficacious in these regions, however it is well known that DED is more effective at higher temperatures and this may counteract the higher humidities (Quarles & Winn 1996).
At 70% RH, 100% mortality occurred on Day 11 of exposure for the highest dose of 8g/m2.
The trial with simulated environments (new to me: mesocosms) used bulb dusters:
Mesocosms (Fig. 9) were constructed out of materials that are often typically encountered in dwellings; notably gyprock and pine, and were designed to simulate a bed bug infestation in a cavity such as a wall void. The lid of the mesocosm consisted of clear Perspex sheeting, which was fixed into position with removable screws. Perspex was used so that the flow of the DED into the mesocosm cavity could be observed, to facilitate the introduction of living bed bugs, to aid in experimental observation, and the removal of dead insects.
You should check out the cool photographs in the article, starting on page 40.
One mesocosm received 16 puffs of DE (the target dose rate was 2g/m2). A second mesocosm received 8 puffs.
100% mortality in the simulated environments by Day 9.
It’s a shame that no identifying information for the diatomaceous earth used in this study is provided.
I’ll leave you with this quote, an essential caveat about DE:
It is worth noting that there are many different types of DED and not all have insecticidal properties. A study undertaken in South Africa against a wide range of pests including the Common bed bug, found that the DED tested had little to no efficacy (Martindale & Newlands 1981). In contrast, the DED supplied by Mount Sylvia Diatomite Mines was highly efficacious. This implies that any Diatomaceous Earth that is submitted for registration should be accessed for its efficacy.