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MC Bed Bug Management Report, 2006
Doggett, Russell & Jones 0
THE EFFICACY OF DIATOMACEOUS
EARTH AGAINST THE COMMON
BED BUG, CIMEX LECTULARIUS
A report for Mount Sylvia Diatomite
Stephen L. Doggett, Merilyn J. Geary,
David Lilly* & Richard C. Russell
Department of Medical Entomology, ICPMR, Westmead Hospital, WESTMEAD, NSW
2145. *Ecolab Pest Elimination, SILVERWATER, NSW, 2128.
May 2008
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology i
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A report for Mount Sylvia Diatomite
Stephen L. Doggett, Merilyn J. Geary,
David Lilly* & Richard C. Russell
Department of Medical Entomology,
ICPMR and University of Sydney, Westmead Hospital,
WESTMEAD, NSW 2145.
Ph: 02 9845 7265 Fax: 02 9893 8659
Email: Stephen.Doggett@swahs.health.nsw.gov.au
* Ecolab Pest Elimination, 2 Wetherill St,
SILVERWATER, NSW, 2128.
©2007, 2008. This report was produced by The Department of Medical
Entomology on behalf of and for Mount Sylvia Diatomite. All images are
copyright to the Department of Medical Entomology. The Department of
Medical Entomology, ICPMR, accepts no responsibility for the use of this
report by other parties. The use of brand names and any mention or
listing of commercial products or services in this report does not imply
endorsement by the Department of Medical Entomology, ICPMR, or
discrimination against similar products or services not mentioned.
Warning and Disclaimer
Every effort has been made to make this document to be as complete
and accurate as possible, but no warranty or fitness is implied. The
information provided is on an ‘as is’ basis. The authors shall have neither
liability nor responsibility to any person, organisation or entity with
respect to any loss or damages arising from the information contained in
this document.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology ii
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Currently the world is experiencing a major resurgence in bed bugs
infestations, largely due to insecticide resistance. Bed bugs are now
resistant to most of the current commercially available insecticides, and
there is an urgent need for new products to be registered to combat this
emerging public health pest.
Diatomaceous Earth dust (DED) has many advantages over presently
registered insecticides, including indefinite shelf life, long residual action, low
risk of insecticide resistance developing, and very low mammalian toxicity.
Apropos of this, DED was supplied by Mount Sylvia Diatomite to test the
efficacy of the product against the Common bed bug,
Cimex lectularius
.
In the laboratory investigations, DED 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.
For the first instar stage, DED again produced a complete kill with all dose
rates and at a faster rate than adults. At the dose rate equivalent to 1g of
product/m2 this took 9 days; 2g/m2 – 9d; 4g/m2 – 3d; 8g/m2 – 4d.
Testing under different humidity levels demonstrated that the product was
slower acting, however a complete kill was again achieved. At the dose rate
equivalent to 1g of product/m2 this took 18 days; 2g/m2 – 20d; 4g/m2 –
11d; 8g/m2 – 11d.
Testing of the coarser grained Diatomaceous Earth Fines, produced a
complete kill of adult bed bugs with all dose rates, albeit of a longer
duration. At the dose rate equivalent to 1g of product/m2 this took 17
days; 2g/m2 – 12d; 4g/m2 – 11d; 8g/m2 – 11d.
Testing of DED in a simulated environment (a mesocosm) found the
product to be efficacious with a complete kill achieved within 9 days.
It was found that DED could be readily applied via typical pest control
equipment used for insecticidal dust application.
The experiments demonstrated that DED is highly efficacious against bed
bugs under a range of conditions, and the dose rate is not critical.
Stephen L. Doggett
Senior Hospital Scientist &
Principal Investigator
27/May/2008
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology iii
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W............................................................................... ii
The efficacy testing of Diatomaceous Earth Dust to the Common Bed
Bug,
Cimex
lectularius
, i. Laboratory Investigations................................. 1
Background............................................................................................ 1
Methods.................................................................................................. 2
Test Animal
........................................................................................... 2
Insecticide
............................................................................................. 2
Experimental Procedure
.......................................................................... 2
Results ................................................................................................... 3
Discussion .............................................................................................. 4
Conclusion.............................................................................................. 5
References ............................................................................................. 5
The efficacy testing of Diatomaceous Earth Dust to the Common Bed
Bug,
Cimex lectularius
, ii. Mesocosm Investigations............................... 36
Background.......................................................................................... 36
Methods................................................................................................ 37
Test Animal
......................................................................................... 37
Insecticide
........................................................................................... 37
Mesocosm Construction
........................................................................ 37
Bulb Hand Duster Calibration
................................................................. 37
Experimental Procedure
........................................................................ 37
Results & Discussion............................................................................ 38
Bulb Hand Duster Calibration
................................................................. 38
Application Dose Rate
........................................................................... 38
Efficacy Results
.................................................................................... 39
Conclusion............................................................................................ 39
References ........................................................................................... 39
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 1
The efficacy testing of Diatomaceous Earth Dust to
the Common Bed Bug,
Cimex lectularius
.
i. Laboratory Investigations
Background
Worldwide since the beginning of this century, there has been a dramatic increase
in the number of bed bug infestations, both of the Common (
Cimex lectularius
) and
Tropical (
Cimex hemipterus
) species (Doggett
et al
. 2003, 2004, 2005). During this
period, the number of infestations has increased by some 4,500% across Australia
(Doggett & Russell 2007). Numerous suggestions have been offered to account for
the return of this public health menace, however it is thought that insecticide
resistance has been the main contributing cause. Resistance has now been
reported overseas with the synthetic pyrethroids and the carbamates (Boase
et al
.
2006, Romero
et al
. 2007). Many Australian pest managers have reported product
failure (Doggett & Russell 2007) and the Department of Medical Entomology has a
strain of bed bugs that were collected off permethrin dust, suggesting that
resistance is a major issue in this country as well.
Unfortunately, most of the insecticides registered in Australia belong to those
groups that have demonstrated resistance. This has meant that control is a major
challenge and treatment failures have been all too common. Thus there is an
urgent need for new insecticides to become available for the control of bed bugs.
One candidate insecticide that could be of benefit in bed bug control is
Diatomaceous Earth dust (DED). This insecticidal dust has a number of advantages.
Being silica based it has an extremely long shelf; one study found that a silica
based product was still efficacious after 406 days of storage (Tarshis 1962). DED
has an extremely long residual action and tends to be nullified only by the built up
of dirt, household dust and other debris. DED’s mode of action limits the possibility
of resistance developing as it has a physical rather than a chemical/metabolic
action (Quarles & Winn 1996), in fact DED is not even listed by the International
Resistance Action Committee (http://www.irac-online.org/). DED leaves no
chemical residue (Quarles & Winn 1996) and has extremely low mammalian toxicity
and is often recommended by environmental groups. As DED has a long residual
action, there is a strong potential for this dust to be employed as a prophylactic
insecticide.
Currently, DED is registered for bed bug control in the US and has long been
employed in the management of this insect. However, despite being registered
overseas, efficacy data has not been published to date. The aim of this
investigation is to test the susceptibility of the Common bed bug,
Cimex lectularius
,
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 2
to DED in order to provide efficacy data towards having DED registered for the
control of bed bugs (
Cimex
spp.) in Australia.
Methods
The methods are loosely based on Fletcher & Axtell (1993).
Test Animal
The bed bugs used are the Common bed bug,
Cimex lectularius
, from a colony
established by the Department of Medical Entomology during 2004. The colonies
held by the Department are the only bed bug colonies in Australia. The founder
specimens were sourced from various infestations within the Sydney metropolitan
area and have not been profiled for insecticide susceptibility, however are known
from in-house efficacy testing to have a degree of insecticide resistance to both the
synthetic pyrethroids and the carbamates. The colony is maintained within 1L
containers, provided with a blood meal once per week via anesthetised rats, and
held at 25oC, with 80%RH. Active unengorged bed bug adults were removed and
used for the tests. Sex and age of the bed bugs were not determined.
Insecticide
The DED was supplied by Dr Ian Neering of Mount Sylvia Diatomite. No batch
number or date of manufacture was provided.
Experimental Procedure
The bed bugs were exposed to residues of the DED on filter paper within Petri
dishes (Figures 1 & 2). In each experiment, a variety of doses were used to
establish optimal dose rates. The DED was applied at the dose rates equivalent to
1, 2, 4 and 8g/m2, which covers the dose for which the product is currently
registered against other insect pests. The surface area of the filter paper was
calculated and the amount of DED required to treat the area at these rates
determined. The dust was applied to the filter paper and spread evenly over the
surface via a small paint brush. For each dose rate of DED, ten bed bugs where
exposed per Petri dish, with a total of four replicates (i.e. 40 bugs in total exposed
per treatment). The controls consisted of four replicates of ten bugs on filter paper
in Petri dishes not exposed to the DED (i.e. a further 40 bed bugs). Mortality was
determined daily from 24 hours onwards by counting bed bugs that do not move
after the dish is tapped. The experiments were conducted at 22±1oC, in a
darkened environment, relative humidity of 55±5%.
For each dose, the daily results were statistically compared with the control via one
way ANOVA.
Experiment 1 tested the efficacy of DED against adult bed bugs.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 3
Experiment 2 tested the efficacy of DED against first instar bed bugs, using a
modified test chamber (Figure 2).
Experiment 3 tested the efficacy of DED against adult bed bugs in high humidity
(approx 70%RH).
Experiment 4 tested the efficacy of Diatomaceous Earth ‘fines’ (DEF) against adult
bed bugs. Only two replicates were used for this experiment.
Results
A summary of Experiment 1 results are provided in Table 1 and graphed in Figure
3. Raw results are provided in Table 5 and complete statistical analysis in Table 9.
In summary, complete adult mortality was achieved with the high dose (8g/m2) by
Day 9 and by Day 15 with the lowest (1gm2). Mortality was significantly different
from the controls within 1 day with the high dose and by Day 3, with all the doses
of DED.
A summary of Experiment 2 results are provided in Table 2 and graphed in Figure
4. Raw results are provided in Table 6 and complete statistical analysis in Table 10.
Mortality was more rapid with the first instar nymphs compared with the adults;
100% death was achieved with the high dose by Day 4 and complete mortality
with all the doses by Day 9. Even within one day, mortality with all the treatments
was significantly different from the controls.
A summary of Experiment 3 results are provided in Table 3 and graphed in Figure
5. Raw results are provided in Table 7 and complete statistical analysis in Table 11.
The high humidity slowed down the death rate and it was not until Day 11 when
100% mortality was achieved with the high dose, and Day 20 that all bed bugs had
died for each treatment. Despite this, mortality was significantly different from the
controls with all treatments by Day 3 and for the two highest doses by Day 1.
Experiment 4 summary results are provided in Table 4 and graphed in Figure 6.
Raw results are provided in Table 8 and complete statistical analysis in Table 12.
Complete adult mortality was achieved by Day 11 in the high dose and by Day 17
with all the doses. Mortality was significantly different from the controls with all
treatments by Day 9 and for the highest dose by Day 4.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 4
Discussion
The experiments demonstrate that DED is efficacious against bed bugs, including
both adult and nymphal stages. A complete kill is achieved with DED no matter the
insecticidal dose rate, although is quicker at higher concentrations, and this
demonstrates that application dose rate is not critical. The time to death is
relatively slow for an insecticide, although this is due to its mode of action. DED is
very different to other insecticides; the waxy surface of the epicuticle is absorbed,
meaning that the insect can not maintain moisture levels and the insect dies from
dehydration (St. Aubin 1991). The DED readily adheres to the insect as it moves
about (Figures 7 & 8). Thus the mode of action is more physical rather than
affecting biochemical and metabolic pathways of the insect like most other
insecticides.
In studies investigating water conservation within the bed bug, it has been found
that first instar nymphs lose water at a faster rate relative to other stages (Benoit
et al
. 2007). This would account for the quicker mortality observed in Experiment
2. The modified test chamber for this experiment was required in order to contain
the insects to the treated area.
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).
DEF is a more coarsely ground formulation of DED, with a variable particle size
diameter between 10-1200um, whereas DED has a diameter around 10um.
Presumably the more coarse powder of DEF meant that the same surface area of
active insecticide was not available to the bed bugs and hence the longer time
required in achieving a complete kill.
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
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 5
Sylvia Diatomite Mines was highly efficacious. This implies that any Diatomaceous
Earth that is submitted for registration should be accessed for its efficacy.
The DED dust used for testing was observed to clump and so there were concerns
that the dust may not flow properly via an insecticide delivery system. Preliminary
testing with a termite duster found that this was not the case and that the product
flowed without causing any blockage to the nozzle. It was probable that the
clumping resulted from moving the test containers from the darkened to a light
environment to read the trials
As noted above DED has a number of advantages:
•
•
Indefinite shelf life,
•
•
Long residual action,
•
•
No chemical residues,
•
•
Low probability of resistance, &
•
•
Very low mammalian toxicity.
Additionally, as the experiments testify, the dose rate is not critical as all
treatments yielded a complete kill. However, an application rate around 2-4g/m2
would be a good compromise to achieve a moderate kill rate.
As DED is a grey dust, it would only be applied to non-obvious locations, which are
areas where bed bugs normally harbour. The dust’s unique properties mean that it
could be applied as a barrier treatment, or as a prophylactic insecticide to minimise
the spread of an infestation or to help contain potential new infestations.
With the lack of registered products in Australia and the high degree of insecticidal
resistance reported to those that are registered, new insecticidal compounds are
urgently required for bed bug control. The experiments show that DED is an
efficacious product and would be an additional useful tool in the arsenal of
products available to the pest manager for bed bug eradication.
Conclusion
DED was found to be highly efficacious against both nymphs and adults of the
Common bed bug,
Cimex lectularius
, at a variety of doses and under different
humidity levels.
References
Benoit J.A., Del Grosso N.A., Yoder J.A. and Denlinger D.L. (2007). Resistance
to dehydration between bouts of blood feeding in the bed bug,
Cimex
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 6
lectularius
, is enhanced by water conservation, aggregation, and
quiescence.
American Journal of Tropical Medicine and Hygiene
, 76(5): 987-
993.
Boase C., Small G., and Naylor R. (2006). Interim report of insecticides
susceptibility status of UK bedbugs.
Professional Pest Controller
, Summer:
12-13.
Doggett S.L. and Russell R.C. (2007). Bed Bugs – Latest Trends &
Developments.
Synopsis of The Australian Environmental Pest Managers
Association National Conference, Pacific Bay Resort, Coffs Harbour, 4-6
th
July 2007
,
pg 22-37.
Doggett S.L. (2005). Bed bug ecology and control. Chapter 7, Pests of
Disease & Unease.
Synopsis of Papers of the Symposium ‘Pests of Disease &
Unease’, held 22 April 2005, Westmead Hospital
.
Doggett S.L, Geary M.J., Crowe W.J., Wilson P. and Russell R.C. (2003). Has the
Tropical Bed Bug,
Cimex hemipterus
(Hemiptera: Cimicidae), invaded
Australia?
Environmental Health,
3: 80-82.
Doggett S.L, Geary M.J. and Russell R.C. (2004). The resurgence of bed bugs in
Australia, with notes on their ecology and control.
Environmental Health,
4:
30-38.
Fields P. and Korunic Z. (2000). The effect of grain moisture content and
temperature on the efficacy of diatomaceous earths from different
geographical locations against stored-product beetles.
Journal of Stored
Products Research
, 36: 1-13.
Fletcher M.G. and Axtell R.C. (1993). Susceptibility of the bed bug,
Cimex
lectularius
, to selected insecticides and various treated surfaces.
Medical
and Veterinary Entomology
, 7: 69-72.
Martindale C.B. and Newlands G. (1981). ‘Nature’s bug-killer’ doesn’t.
South
African Journal of Science
, 77: 352.
Quarles W. and Winn P.S. (1996). Diatomaceous earth and stored product
Pests.
The IPM Practitioner
, 13(5/6): 1-10.
Romero A., Potter M.F., Potter D.A., and Haynes K.F. (2007). Insecticide
resistance in the bed bug: a factor in the pest’s sudden resurgence?
Journal of Medical Entomology
, 44(2): 175-178.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 7
St. Aubin F. (1991). Everything old is new again.
Pest Control Technology
,
June: 50-102.
Tarshis I.B. (1962). The use of silica aerogel compounds for the control of
ectoparasites.
Proceedings of the animal care panel
, 217-258.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 8
Figure 1. Photograph of the experimental set up for measuring the efficacy of Diatomaceous Earth dust against the adult
bed bug,
Cimex lectularius
.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 9
Figure 2. Photograph of the experimental set up for measuring the efficacy of Diatomaceous Earth dust against first
instar bed bugs.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 10
Table 1. Cumulative percentage mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth
dust, summary data (Experiment 1).
Dose Day
1 Day
2 Day
3 Day
4 Day
5 Day
6 Day
7 Day
8 Day
9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15
8g/m2 37.5 62.5 80.0 85.0 92.5 95.0 97.5 97.5 100 100 100 100 100 100 100
4g/m2 15.0* 32.5 62.5 82.5 95.0 95.0 95.0 97.5 97.5 97.5 97.5 97.5 100 100 100
2g/m2 10.0* 35.0 47.5 90.0 95.0 95.0 95.0 95.0 95.0 100 100 100 100 100 100
1g/m2 0.0* 5.0* 22.5 32.5 60.0 60.0 65.0 77.5 80.0 90.0 95.0 95.0 95.0 97.5 100
0g/m2 2.5 2.5 2.5 2.5 5.0 5.0 7.5 7.5 10.0 15.0 17.5 22.5 22.5 22.5 27.5
*Not statistically different to the controls.
Table 2. Cumulative percentage mortality of first instar
Cimex lectularius
exposed to various doses of Diatomaceous
Earth dust, summary data (Experiment 2).
Dose Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9
8g/m2 92.5 95.3 99.1 100.0 100.0 100.0 100.0 100.0 100.0
4g/m2 96.5 99.1 100.0 100.0 100.0 100.0 100.0 100.0 100.0
2g/m2 41.1 66.1 87.5 91.1 96.4 98.2 98.2 98.2 100.0
1g/m2 17.1 64.3 81.4 92.9 97.1 97.1 98.6 98.6 100.0
0g/m2 0.0 0.0 3.6 5.5 5.5 5.5 5.5 9.1 14.5
Note: all treatments on all days were statistically different to the controls.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 11
Table 3. Cumulative percentage mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth at
high humidity, summary data (Experiment 3).
*Not statistically different to the controls.
Table 4. Cumulative percentage mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth
‘fines’, summary data (Experiment 4).
Dose Day
1 Day
2 Day
3 Day
4 Day
5 Day
6 Day
7 Day
8 Day
9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15 Day
16 Day
17
8g/m210.0* 25.0* 35.0* 65.0 65.0 75.0 75.0 80.0 85.0 90.0 100 100 100 100 100 100 100
4g/m20.0* 5.0* 20.0* 35.0* 45.0 60.0 70.0 80.0 85.0 85.0 100 100 100 100 100 100 100
2g/m20.0* 0.0* 10.0* 20.0* 30.0* 30.0* 30.0* 60.0 75.0 85.0 95.0 100 100 100 100 100 100
1g/m20.0* 0.0* 0.0 0.0 5.0* 10.0* 15.0* 35.0* 45.0 70.0 75.0 85.0 90.0 95.0 95.0 95.0 100
0g/m20.0 0.0 0.0 0.0 5.0 5.0 15.0 15.0 20.0 20.0 25.0 35.0 35.0 40.0 50.0 55.0 65.0
*Not statistically different to the controls.
Dose Day
1 Day
2 Day
3 Day
4 Day
5 Day
6 Day
7 Day
8 Day
9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15 Day
16 Day
17 Day
18 Day
19 Day
20
8g/m220.0 45.0 52.5 62.5 65.0 72.5 82.5 90.0 95.0 97.5 100 100 100 100 100 100 100 100 100 100
4g/m210.0 30.0 50.0 60.0 67.5 72.5 77.5 85.0 87.5 95.0 100 100 100 100 100 100 100 100 100 100
2g/m22.5* 7.5* 15.0 22.5 32.5 42.5 47.5 52.5 60.0 75.0 85.0 85.0 87.5 87.5 87.5 90.0 95.0 97.5 97.5 100
1g/m22.5* 10.0* 27.5 30.0 35.0 42.5 47.5 55.0 57.5 65.0 72.5 75.0 80.0 85.0 87.5 90.0 95.0 100 100 100
0g/m20.0 2.5 2.5 5.0 10.0 15.0 17.5 17.5 17.5 22.5 25.0 25.0 25.0 30.0 35.0 45.0 47.5 47.5 50.0 52.5
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 12
Fig 3. Cumulative Mortality of Adult Cimex lectularius
Exposed to Various Doses of Diatomaceous Earth
0
10
20
30
40
50
60
70
80
90
100
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Day 10 Day 11 Day 12 Day 13 Day 14 Day 15
Days Post Exposure
Cumulative Percent Mortality
8g/m2
4g/m2
2g/m2
1g/m2
0g/m2
Fi
g
ure 3.Cumulative mortality of adult
Cimex lectulariu
s
exposed
to various doses of Diatomaceous Earth dust.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 13
Figure 4. Cumulative Mortality of 1st Instar Bed bugs, Cimex lectularius,
exposed to varying doses of Diatomaceous Earth.
0
20
40
60
80
100
Day 0 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9
Days Post Exposure
Cumulative Percent Mortality
8g/m2
4g/m2
2g/m2
1g/m2
0g/m2
Fi
g
ure 4.Cumulative mortality of first instar
Cimex lectulariu
s
ex
p
osed to various doses of Diatomaceous Earth dust.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 14
Fig 5. Cumulative Mortality of Adult Cimex lectularius Exposed to
Various Doses of Diatomaceous Earth at high humidity
0
10
20
30
40
50
60
70
80
90
100
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15 Day
16 Day
17 Day
18 Day
19 Day
20
Days Post Exposure
Cumulative Percent Mortality
8g/m2
4g/m2
2g/m2
1g/m2
0g/m2
Fi
g
ure 5.Cumulative mortality of adult
Cimex lectulariu
s
exposed
to various doses of Diatomaceous Earth dust at hi
g
h humidit
y
.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 15
Fig 6. Cumulative Mortality of Adult Cimex lectularius Exposed to
Various Doses of Diatomaceous Earth 'fines'
0
10
20
30
40
50
60
70
80
90
100
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Day 10 Day 11 Day 12 Day 13 Day 14 Day 15 Day 16 Day 17
Days Post Exposure
Cumulative Percent Mortality
8g/m2
4g/m2
2g/m2
1g/m2
0g/m2
Fi
g
ure 6.Cumulative mortality of adult
Cimex lectulariu
s
exposed
to various doses of Diatomaceous Earth
‘
fines’.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 16
Figure 7. Dead adult common bed bugs,
Cimex lectularius
, after exposure to Diatomaceous Earth dust.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 17
Figure 8. Dead first instar common bed bugs,
Cimex lectularius
, after exposure to Diatomaceous Earth dust.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 18
Table 5. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust, raw data, results
Days 1 – 4 (Experiment 1).
Day 1 Day 2 Day 3 Day 4
Dose Replicate No.
Tested
Dust
Amount
(g)
No.
Dead %
Mortality No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 0.052 7 70 1 10 8 80 1 10 9 90 0 0 9 90
b 10 0.051 3 30 4 40 7 70 2 20 9 90 1 10 10 100
c 10 0.051 1 10 5 50 6 60 3 30 9 90 0 0 9 90
d 10 0.052 4 40 0 0 4 40 1 10 5 50 1 10 6 60
8g/m2
Total 40 15 37.5 10 25.0 25 62.5 7 17.5 32 80.0 2 5.0 34 85.0
a 10 0.025 0 0 1 10 1 10 1 10 2 20 4 40 6 60
b 10 0.025 3 30 2 20 5 50 4 40 9 90 1 10 10 100
c 10 0.025 1 10 3 30 4 40 3 30 7 70 3 30 10 100
d 10 0.025 2 20 1 10 3 30 4 40 7 70 0 0 7 70
4g/m2
Total 40 6 15.0 7 17.5 13 32.5 12 30.0 25 62.5 8 20.0 33 82.5
a 10 0.013 2 20 3 30 5 50 0 0 5 50 4 40 9 90
b 10 0.013 2 20 2 20 4 40 1 10 5 50 4 40 9 90
c 10 0.013 0 0 4 40 4 40 1 10 5 50 4 40 9 90
d 10 0.013 0 0 1 10 1 10 3 30 4 40 5 50 9 90
2g/m2
Total 40 4 10.0 10 25.0 14 35.0 5 12.5 19 47.5 17 42.5 36 90.0
a 10 0.006 0 0 1 10 1 10 2 20 3 30 2 20 5 50
b 10 0.006 0 0 1 10 1 10 1 10 2 20 0 0 2 20
c 10 0.006 0 0 0 0 0 0 2 20 2 20 1 10 3 30
d 10 0.006 0 0 0 0 0 0 2 20 2 20 1 10 3 30
1g/m2
Total 40 0 0.0 2 5.0 2 5.0 7 70.0 9 22.5 4 10.0 13 32.5
a 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
b 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
c 10 0 1 10 0 0 1 10 0 0 1 10 0 0 1 10
d 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0g/m2
(Control)
Total 40 1 2.5 0 0.0 1 2.5 0 0.0 1 2.5 0 0.0 1 2.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 19
Table 5, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust, raw data,
results Days 5 – 8.
Day 5 Day 6 Day 7 Day 8
Dose Replicate No.
Dead %
Mortality Cum.
Dead* % Cum.
Dead** No.
Dead %
Mortality Cum.
Dead* % Cum.
Dead** No.
Dead %
Mortality Cum.
Dead* % Cum.
Dead** No.
Dead %
Mortality Cum.
Dead* % Cum.
Dead**
a 0 0 9 90 1 10 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 1 10 10 90 10 100 10 100 10 100
d 2 20 8 80 0 0 8 80 1 10 9 90 0 0 9 90
8g/m2
Total 3 30.0 37 92.5 1 2.5 38 95.0 1 2.5 39 97.5 0 0.0 39 97.5
a 2 20 8 80 0 0 8 80 1 10 9 90 0 0 9 90
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 3 30 10 100 10 100 10 100 10 100
4g/m2
Total 5 12.5 38 95.0 0 0.0 38 95.0 1 2.5 39 97.5 0 0.0 39 97.5
a 0 0 9 90 0 0 9 90 0 0 9 90 0 0 9 90
b 1 10 10 100 10 100 10 100 10 100
c 1 10 10 100 10 100 10 100 10 100
d 0 0 9 90 0 0 9 90 0 0 9 90 0 0 9 90
2g/m2
Total 2 5.0 38 95.0 0 0.0 38 95.0 0 0.0 38 95.0 0 0.0 38 95.0
a 2 20 7 70 0 0 7 70 0 0 7 70 1 10 8 80
b 3 30 5 50 0 0 5 50 1 10 6 60 0 0 6 60
c 3 30 6 60 0 0 6 60 1 10 7 70 2 20 9 90
d 3 30 6 60 0 0 6 60 0 0 6 60 2 20 8 80
1g/m2
Total 11 27.5 24 60.0 0 0.0 24 60.0 2 5.0 26 65.0 5 12.5 31 77.5
a 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
b 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
c 1 10 2 20 0 0 2 20 1 0 3 30 0 0 3 30
d 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0g/m2
(Control)
Total 1 2.5 2 5.0 0 0.0 2 5.0 1 2.5 3 7.5 0 0.0 3 7.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 20
Table 5, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust, raw data,
results Days 9 – 12.
Day 9 Day 10 Day 11 Day 12
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 1 0 10 100 10 100 10 100 10 100
8g/m2
Total 1 2.5 40 100.0 40 100.0 40 100.0 40 100.0
a 0 0 9 90 0 0 9 90 0 0 9 90 0 0 9 90
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 10 100 10 100 10 100 10 100
4g/m2
Total 0 0.0 39 97.5 0 0.0 39 97.5 0 0.0 39 97.5 0 0.0 39 97.5
a 1 10 10 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 0 0 9 90 1 10 10 100 10 100 10 100
2g/m2
Total 1 2.5 39 95.0 0 2.5 40 100.0 40 100.0 40 100.0
a 0 0 8 80 1 10 9 90 1 10 10 100 10 100
b 1 10 7 70 1 10 8 80 1 10 9 90 0 0 9 90
c 0 0 9 90 0 0 9 90 0 0 9 90 0 0 9 90
d 0 0 8 80 2 20 10 100 10 100 10 100
1g/m2
Total 1 2.5 32 80.0 4 10.0 36 90.0 2 5.0 38 95.0 0 0.0 38 95.0
a 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
b 0 0 0 0 1 10 1 10 0 0 1 0 1 10 2 20
c 1 10 4 40 1 10 5 50 0 0 5 0 0 0 5 50
d 0 0 0 0 0 0 0 0 1 10 1 10 1 10 2 20
0g/m2
(Control)
Total 1 2.5 4 10.0 2 5.0 6 15.0 1 2.5 7 17.5 2 5.0 9 22.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 21
Table 5, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust, raw data,
results Days 13 – 15.
Day 13 Day 14 Day 15
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 100 10 100 10 100
b 10 100 10 100 10 100
c 10 100 10 100 10 100
d 10 100 10 100 10 100
8g/m2
Total 40 100.0 40 100.0 40 100.0
a 1 10 10 100 10 100 10 100
b 10 100 10 100 10 100
c 10 100 10 100 10 100
d 10 100 10 100 10 100
4g/m2
Total 1 2.5 40 100.0 40 100.0 40 100.0
a 10 100 10 100 10 100
b 10 100 10 100 10 100
c 10 100 10 100 10 100
d 10 100 10 100 10 100
2g/m2
Total 40 100.0 40 100.0 40 100.0
a 10 100 10 100 10 100
b 0 0 9 90 1 10 10 100 10 100
c 0 0 9 90 9 90 1 10 10 100
d 10 100 10 100 10 100
1g/m2
Total 0 0.0 38 95.0 1 2.5 39 97.5 1 2.5 40 100.0
a 0 0 0 0 0 0 0 0 2 20 2 20
b 0 0 2 20 0 0 2 20 2 20
c 0 0 5 50 0 0 5 50 5 50
d 0 0 2 20 0 0 2 20 2 20
0g/m2
(Control)
Total 0 0.0 9 22.5 0 0.0 9 22.5 2 5.0 11 27.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 22
Table 6. Mortality of first instar
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust, raw data, results
Days 1-6 (Experiment 2).
Day 1 Day 2 Day 3 Day 4 Day 5
Dose Replicate No.
Tested
Dust
Amount
(g)
No.
Dead %
Mortality No.
Dead Cum.
Dead*
%
Cum.
Dead**
No.
Dead Cum.
Dead*
%
Cum.
Dead**
No.
Dead Cum.
Dead*
%
Cum.
Dead
No.
Dead Cum
Dead**
%
Cum.
Dead**
a 41 0.052 37 90.2 2 39 95.1 2 41 100.0 41 100.0 41 100.0
b 20 0.051 17 85.0 1 18 90.0 2 20 100.0 20 100.0 20 100.0
c 17 0.051 17 100.0 17 100.0 17 100.0 17 100.0 17 100.0
d 28 0.052 27 96.4 0 27 96.4 0 27 96.4 1 28 100.0 28 100.0
8g/m2
Total 106 98 92.5 3 101 95.3 4 105 99.1 1 106 100.0 106 100.0
a 21 0.025 20 95.2 0 20 95.2 1 21 100.0 21 100.0 21 100.0
b 25 0.025 23 92.0 2 25 100.0 25 100.0 25 100.0 25 100.0
c 37 0.025 37 100.0 0 37 100.0 37 100.0 37 100.0 37 100.0
d 31 0.025 30 96.8 1 31 100.0 31 100.0 31 100.0 31 100.0
4g/m2
Total 114 110 96.5 3 113 99.1 1 114 100.0 114 100.0 114 100.0
a 23 0.013 15 65.2 3 18 78.3 1 19 82.6 1 20 87.0 1 21 91.3
b 7 0.013 0 0.0 3 3 42.9 3 6 85.7 0 6 85.7 1 7 100.0
c 11 0.013 5 45.5 3 8 72.7 3 11 100.0 11 100.0 11 100.0
d 15 0.013 3 20.0 5 8 53.3 5 13 86.7 1 14 93.3 1 15 100.0
2g/m2
Total 56 23 41.1 14 37 66.1 12 49 87.5 51 91.1 3 54 96.4
a 14 0.006 4 28.6 3 7 50.0 4 11 78.6 1 12 85.7 1 13 92.9
b 27 0.006 5 18.5 16 21 77.8 2 23 85.2 3 26 96.3 0 26 96.3
c 19 0.006 3 15.8 7 10 52.6 5 15 78.9 2 17 89.5 2 19 100.0
d 10 0.006 0 0.0 7 7 70.0 1 8 80.0 2 10 100.0 10 100.0
1g/m2
Total 70 12 17.1 33 45 64.3 12 57 81.4 8 65 92.9 3 68 97.1
a 17 0 0 0.0 0 0 0.0 0 0 0.0 0 0 0.0 0 0 0.0
b 10 0 0 0.0 0 0 0.0 0 0 0.0 1 1 10.0 0 1 10.0
c 14 0 0 0.0 0 0 0.0 0 0 0.0 0 0 0.0 0 0 0.0
d 14 0 0 0.0 0 0 0.0 2 2 14.3 0 2 14.3 0 2 14.3
0g/m2
Total 55 0 0.0 0 0 0.0 2 2 3.6 1 3 5.5 0 3 5.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 23
Table 6, cont. Mortality of first instar
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust, raw data,
results Days 6-9.
Day 6 Day 7 Day 8 Day 9
Dose Replicate No.
Tested No.
Dead Cum.
Dead* % Cum.
Dead** No.
Dead Cum.
Dead* % Cum.
Dead** No.
Dead Cum.
Dead* % Cum.
Dead** No.
Dead Cum.
Dead* %Cum.
Dead**
a 41 41 100.0 41 100.0 41 100.0 41 100.0
b 20 20 100.0 20 100.0 20 100.0 20 100.0
c 17 17 100.0 17 100.0 17 100.0 17 100.0
d 28 28 100.0 28 100.0 28 100.0 28 100.0
8g/m2
Total 106 106 100.0 106 100.0 106 100.0 106 100.0
a 21 21 100.0 21 100.0 21 100.0 21 100.0
b 25 25 100.0 25 100.0 25 100.0 25 100.0
c 37 37 100.0 37 100.0 37 100.0 37 100.0
d 31 31 100.0 31 100.0 31 100.0 31 100.0
4g/m2
Total 114 114 100.0 114 100.0 114 100.0 114 100.0
a 23 1 22 95.7 22 95.7 0 22 95.7 1 23 100.0
b 7 7 100.0 7 100.0 7 100.0 7 100.0
c 11 11 100.0 11 100.0 11 100.0 11 100.0
d 15 15 100.0 15 100.0 15 100.0 15 100.0
2g/m2
Total 56 1 55 98.2 55 98.2 55 98.2 1 56 100.0
a 14 0 13 92.9 1 14 100.0 14 100.0 14 100.0
b 27 0 26 96.3 0 26 96.3 0 26 96.3 1 27 100.0
c 19 19 100.0 19 100.0 19 100.0 19 100.0
d 10 10 100.0 10 100.0 10 100.0 10 100.0
1g/m2
Total 70 0 68 97.1 1 69 98.6 69 98.6 1 70 100.0
a 17 0 0 0.0 0 0 0.0 0 0 0.0 0 0 0.0
b 10 0 1 10.0 0 1 10.0 0 1 10.0 2 3 30.0
c 14 0 0 0.0 0 0 0.0 1 1 7.1 1 2 14.3
d 14 0 2 14.3 0 2 14.3 1 3 21.4 0 3 21.4
0g/m2
Total 55 0 3 5.5 0 3 5.5 2 5 9.1 3 8 14.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 24
Table 7. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust at high humidity, raw
data, Days 1-4 (Experiment 3).
Day 1 Day 2 Day 3 Day 4
Dose Replicate No.
Tested
Dust
Amount
(g)
No.
Dead %
Mortality No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 0.052 0 0 1 10 1 10 0 0 1 10 2 20 3 30
b 10 0.051 3 30 3 30 6 60 0 0 6 60 1 10 7 70
c 10 0.051 2 20 2 20 4 40 3 30 7 70 0 0 7 70
d 10 0.052 3 30 4 40 7 70 0 0 7 70 1 10 8 80
8g/m2
Total 40 8 20.0 10 25.0 18 45.0 3 7.5 21 52.5 4 10.0 25 62.5
a 10 0.025 1 10 2 30 3 30 2 20 5 50 2 20 7 70
b 10 0.025 0 0 3 30 3 30 0 0 3 30 2 20 5 50
c 10 0.025 2 20 0 0 2 20 4 40 6 60 0 0 6 60
d 10 0.025 1 10 3 30 4 40 2 20 6 60 0 0 6 60
4g/m2
Total 40 4 10.0 8 20.0 12 30.0 8 20.0 20 50.0 4 10.0 24 60.0
a 10 0.013 0 0 0 0 0 0 1 10 1 10 1 10 2 20
b 10 0.013 1 10 0 0 1 10 0 0 1 10 1 10 2 20
c 10 0.013 0 0 1 1 1 10 1 10 2 20 1 10 3 30
d 10 0.013 0 0 1 1 1 10 1 10 2 20 0 0 2 20
2g/m2
Total 40 1 2.5 2 5.0 3 7.5 3 7.5 6 15.0 3 7.5 9 22.5
a 10 0.006 0 0 0 0 0 0 3 30 3 30 0 0 3 30
b 10 0.006 0 0 2 2 2 20 3 30 5 50 0 0 5 50
c 10 0.006 0 0 0 0 0 0 0 0 0 0 1 10 1 10
d 10 0.006 1 10 1 1 2 20 1 10 3 30 0 0 3 30
1g/m2
Total 40 1 2.5 3 7.5 4 10.0 7 17.5 11 27.5 1 2.5 12 30.0
a 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
b 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
c 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
d 10 0 0 0 1 1 1 10 0 0 1 10 1 10 2 2
0g/m2
Total 40 0 0.0 1 2.5 1 2.5 0 0.0 1 2.5 1 2.5 2 5.0
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 25
Table 7, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust at high
humidity, raw data, Days 4-8.
Day 5 Day 6 Day 7 Day 8
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 0 0 3 30 1 10 4 40 2 20 6 60 2 20 8 80
b 1 10 8 80 0 0 8 80 0 0 8 80 1 10 9 90
c 1 10 8 70 2 20 10 100 10 100 10 100
d 0 0 8 80 0 0 8 80 1 10 9 90 0 3 9 90
8g/m2
Total 2 5.0 27 65.0 3 7.5 30 72.5 3 7.5 33 82.5 3 7.5 36 90.0
a 1 10 8 80 0 0 8 80 0 0 8 80 1 10 9 90
b 0 0 5 50 1 10 6 60 2 20 8 80 1 10 9 90
c 1 10 7 70 1 10 8 80 0 0 8 80 1 10 9 90
d 1 10 7 70 0 0 7 70 0 0 7 70 0 0 7 70
4g/m2
Total 3 7.5 27 67.5 2 5.0 29 72.5 2 5.0 31 77.5 3 7.5 34 85.0
a 0 2 2 20 0 0 2 20 0 0 2 20 1 10 3 30
b 2 20 4 40 2 20 6 60 1 10 7 70 1 10 8 80
c 0 0 3 30 0 0 3 30 0 0 3 30 0 0 3 30
d 2 20 4 40 2 20 6 60 1 10 7 70 0 0 7 70
2g/m2
Total 4 10.0 13 32.5 4 10.0 17 42.5 2 5.0 19 47.5 2 5.0 21 52.5
a 0 0 3 30 1 10 4 40 1 10 5 50 1 10 6 60
b 0 0 5 50 1 10 6 60 0 0 6 60 0 0 6 60
c 2 20 3 30 0 0 3 30 1 10 4 40 0 0 4 40
d 0 0 3 30 1 10 4 40 0 0 4 40 2 20 6 60
1g/m2
Total 2 5.0 14 35.0 3 7.5 17 42.5 2 5.0 19 47.5 3 7.5 22 55.0
a 0 0 0 0 1 10 1 10 0 0 1 10 0 0 1 10
b 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
c 1 10 1 10 0 0 1 10 0 0 1 10 0 0 1 10
d 1 10 3 30 1 10 4 40 1 10 5 50 0 0 5 50
0g/m2
Total 2 5.0 4 10.0 2 5.0 6 15.0 1 2.5 7 17.5 0 0.0 7 17.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 26
Table 7, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust at high
humidity, raw data, Days 8-12.
Day 9 Day 10 Day 11 Day 12
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 0 0 8 80 1 10 9 90 1 10 10 100 10 100
b 1 10 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 1 10 10 100 10 100 10 100 10 100
8g/m2
Total 2 5.0 38 95.0 1 2.5 39 97.5 1 10.0 40 100.0 40 100.0
a 0 0 9 90 1 10 10 100 10 100 10 100
b 0 0 9 90 1 10 10 100 10 100 10 100
c 0 0 9 90 0 0 9 90 1 10 10 100 10 100
d 1 10 8 80 1 10 9 90 1 10 10 100 10 100
4g/m2
Total 1 2.5 35 87.5 3 7.5 38 95.0 2 5.0 40 100.0 40 100.0
a 2 20 5 50 2 20 7 70 2 20 9 90 0 0 9 90
b 0 0 8 80 0 0 8 80 0 0 8 80 0 0 8 80
c 1 10 4 40 3 30 7 70 0 0 7 70 0 0 7 70
d 0 0 7 70 1 10 8 80 2 20 10 100 10 100
2g/m2
Total 3 7.5 24 60.0 6 15.0 30 75.0 4 10.0 34 85.0 0 0.0 34 85.0
a 0 0 6 60 1 10 7 70 1 10 8 80 0 0 8 80
b 0 0 6 60 1 10 7 70 0 0 7 70 0 0 7 70
c 1 10 5 50 1 10 6 60 2 20 8 80 0 0 8 80
d 0 0 6 60 0 0 6 60 0 0 6 60 1 10 7 70
1g/m2
Total 1 2.5 23 57.5 3 7.5 26 65.0 3 7.5 29 72.5 1 2.5 30 75.0
a 0 0 1 10 0 0 1 10 0 0 1 10 0 0 1 10
b 0 0 0 0 1 10 1 10 1 10 2 20 0 0 2 20
c 0 0 1 10 1 10 2 20 0 0 2 20 0 0 2 20
d 0 0 5 50 0 0 5 50 0 0 5 50 0 0 5 50
0g/m2
Total 0 0.0 7 17.5 2 5.0 9 22.5 1 2.5 10 25.0 0 0.0 10 25.0
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 27
Table 7, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dustat high humidity,
raw data, Days 13-16.
Day 13 Day 14 Day 15 Day 16
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 10 100 10 100 10 100 10 100
8g/m2
Total 40 100.0 40 100.0 40 100.0 40 100.0
a 10 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 10 100 10 100 10 100 10 100
4g/m2
Total 40 100.0 40 100.0 40 100.0 40 100.0
a 1 10 10 100 10 100 10 100 10 100
b 0 0 8 80 8 80 0 0 8 80 8 80
c 0 0 7 70 7 70 0 0 7 70 1 1 8 80
d 10 100 10 100 10 100 10 100
2g/m2
Total 1 2.5 35 87.5 35 87.5 0 0.0 35 87.5 1 2.5 36 90.0
a 0 0 8 80 0 0 8 80 0 0 8 80 0 0 8 80
b 1 10 8 80 1 10 9 90 1 10 10 100 10 100
c 1 10 9 90 1 10 10 100 10 100 10 100
d 0 0 7 70 0 0 7 70 0 0 7 70 1 1 8 80
1g/m2
Total 2 5.0 32 80.0 2 5.0 34 85.0 1 2.5 35 87.5 1 2.5 36 90.0
a 0 0 1 10 1 10 2 20 0 0 2 20 1 10 3 30
b 0 0 2 20 1 10 3 30 0 0 3 30 1 10 4 40
c 0 0 2 20 0 0 2 20 2 20 4 40 1 10 5 50
d 0 0 5 50 0 0 5 50 0 0 5 50 1 10 6 60
0g/m2
Total 0 0.0 10 25.0 2 5.0 12 30.0 2 5.0 14 35.0 4 10.0 18 45.0
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 28
Table 7, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth dust at high
humidity, raw data, Days 17-20.
Day 17 Day 18 Day 19 Day 20
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 10 100 10 100 10 100 10 100
8g/m2
Total 40 100.0 40 100.0 40 100.0 40 100.0
a 10 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 10 100 10 100 10 100 10 100
4g/m2
Total 40 100.0 40 100.0 40 100.0 40 100.0
a 10 100 10 100 10 100 10 100
b 2 20 10 100 10 100 10 100 10 100
c 0 0 8 80 1 10 9 90 0 0 9 90 1 10 10 100
d 10 100 10 100 10 100 10 100
2g/m2
Total 2 5.0 38 95.0 1 2.5 39 97.5 0 0.0 39 97.5 40 100.0
a 1 10 9 90 1 10 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
c 10 100 10 100 10 100 10 100
d 1 10 9 80 1 10 10 100 10 100 10 100
1g/m2
Total 2 5.0 38 95.0 2 5.0 40 100.0 40 100.0 40 100.0
a 1 10 4 40 4 40 4 40 4 40
b 4 40 4 40 4 40 4 40
c 5 50 5 50 1 10 6 60 1 10 7 70
d 6 60 6 60 6 60 6 60
0g/m2
Total 1 2.5 19 47.5 0 0.0 19 47.5 1 2.5 20 50.0 1 2.5 21 52.5
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 29
Table 8. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth ‘fines’, raw data, Days 1-4
(Experiment 4).
Day 1 Day 2 Day 3 Day 4
Dose Replicate No.
Tested
Dust
Amount
(g)*
No.
Dead %
Mortality No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 0.052 0 0 0 0 0 0 1 10 1 10 4 40 5 50
b 10 0.052 2 20 3 30 5 50 1 10 6 60 2 20 8 80
8g/m2
Total 20 2 10 3 15 5 25 2 10 7 35 6 30 13 65
a 10 0.025 0 0 1 10 1 10 0 0 1 10 2 20 3 30
b 10 0.025 0 0 0 0 0 0 3 30 3 30 1 10 4 40
4g/m2
Total 20 0 0 1 5 1 5 3 15 4 20 3 15 7 35
a 10 0.013 0 0 0 0 0 0 1 10 1 10 1 10 2 20
b 10 0.013 0 0 0 0 0 0 1 10 1 10 1 10 2 20
2g/m2
Total 20 0 0 0 0 0 0 2 10 2 10 2 10 4 20
a 10 0.06 0 0 0 0 0 0 0 0 0 0 0 0 0 0
b 10 0.06 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1g/m2
Total 20 0 0 0 0 0 0 0 0 0 0 0 0 0 0
a 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
b 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0g/m2
Total 20 0 0 0 0 0 0 0 0 0 0 0 0 0 0
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 30
Table 8, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth ‘fines’, raw data,
Days 5-8.
Day 5 Day 6 Day 7 Day 8
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 0 0 5 50 1 1 6 60 0 0 6 60 1 10 7 70
b 0 0 8 80 1 10 9 90 0 0 9 90 0 0 9 90
8g/m2
Total 0 0 13 65 2 11 15 75 0 0 15 75 1 5 16 80
a 1 10 4 40 2 20 6 60 2 20 8 80 1 10 9 90
b 1 10 5 50 1 10 6 60 0 0 6 60 1 10 7 70
4g/m2
Total 2 10 9 45 3 15 12 60 2 10 14 70 2 10 16 80
a 0 0 2 20 0 0 2 20 0 0 2 20 4 40 6 60
b 2 20 4 40 0 0 4 40 0 0 4 40 2 20 6 60
2g/m2
Total 2 10 6 30 0 0 6 30 0 0 6 30 6 30 12 60
a 1 10 1 10 0 0 1 10 2 20 3 20 0 0 3 30
b 0 0 0 0 1 10 1 10 0 0 1 10 3 30 4 40
1g/m2
Total 1 5 1 5 1 5 2 10 2 10 3 15 30 15 7 35
a 0 0 0 0 0 0 0 0 2 20 2 20 0 0 2 20
b 1 10 1 10 0 0 1 10 0 0 1 10 0 0 1 10
0g/m2
Total 1 5 1 5 0 0 1 5 2 10 3 15 0 0 3 15
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 31
Table 8, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth ‘fines’, raw data,
Days 9-12.
Day 9 Day 10 Day 11 Day 12
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 1 10 8 80 0 0 8 80 2 20 10 100 10 100
b 0 0 9 90 1 1 10 100 10 100 10 100
8g/m2
Total 1 5 17 85 1 5 18 90 2 10 20 100 20 100
a 1 10 10 100 10 100 10 100 10 100
b 0 0 7 70 0 0 7 70 3 30 10 100 10 100
4g/m2
Total 1 5 17 85 0 0 17 85 20 100 20 100
a 3 30 9 90 1 10 10 100 10 100 10 100
b 0 0 6 60 1 10 7 70 2 20 9 90 1 10 10 100
2g/m2
Total 3 15 15 75 2 10 17 85 2 10 19 95 20 100
a 1 10 4 40 3 30 7 70 0 0 7 70 1 10 8 80
b 1 10 5 50 2 20 7 70 1 10 8 80 1 10 9 90
1g/m2
Total 2 10 9 45 5 25 14 70 10 5 15 75 2 10 17 85
a 0 0 2 20 0 0 2 20 0 0 2 20 1 10 3 30
b 1 10 2 20 0 0 2 20 1 10 3 30 1 10 4 40
0g/m2
Total 1 5 4 20 0 0 2 20 1 5 5 25 2 10 7 35
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 32
Table 8, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth ‘fines’, raw data,
Days 13-16.
Day 13 Day 14 Day 15 Day 16
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 1 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
8g/m2
Total 20 100 20 100 20 100 20 100
a 1 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
4g/m2
Total 20 100 20 100 20 100 20 100
a 1 100 10 100 10 100 10 100
b 10 100 10 100 10 100 10 100
2g/m2
Total 20 100 20 100 20 100 20 100
a 0 0 8 80 1 10 9 90 0 0 9 90 9 90
b 1 10 10 100 10 100 10 100 10 100
1g/m2
Total 1 5 18 90 1 5 19 95 19 95 19 95
a 0 10 3 30 1 10 4 40 1 10 5 50 0 0 5 50
b 0 0 4 40 0 0 4 40 1 10 5 50 1 10 6 60
0g/m2
Total 0 0 7 35 1 5 8 40 2 10 1 50 1 5 11 55
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 33
Table 8, cont. Mortality of adult
Cimex lectularius
exposed to various doses of Diatomaceous Earth ‘fines’, raw data, Day
17.
Day 17
Dose Replicate No.
Dead %
Mortality Cum.
Dead*
%
Cum.
Dead**
a 10 100
b 10 100
8g/m2
Total 20 100
a 10 100
b 10 100
4g/m2
Total 20 100
a 10 100
b 10 100
2g/m2
Total 20 100
a 1 10 10 100
b 10 100
1g/m2
Total 1 5 20 100
a 1 10 6 60
b 1 10 7 70
0g/m2
Total 2 10 13 65
*Cumulative mortality, **Percent cumulative mortality
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 34
Table 9. P values of the statistical analysis for comparing the treatments with the controls for Experiment 1.
Dose Day
1 Day
2 Day
3 Day
4 Day
5 Day
6 Day
7 Day
8 Day
9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15
8g/m2 * * * * * * * * * * * * * * *
4g/m2 0.12 * * * * * * * * * * * * * *
2g/m2 0.28 * * * * * * * * * * * * * *
1g/m2 0.36 0.54 * * * * * * * * * * * * *
*less than 0.05, i.e. statistically different to the controls
Table 10. P values of the statistical analysis for comparing the treatments with the controls for Experiment 2.
Dose Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9
8g/m2 * * * * * * * * *
4g/m2 * * * * * * * * *
2g/m2 * * * * * * * * *
1g/m2 * * * * * * * * *
*less than 0.05, i.e. statistically different to the controls
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 35
Table 11. P values of the statistical analysis for comparing the treatments with the controls for Experiment 3.
*less than 0.05, i.e. statistically different to the controls
Table 12. P values of the statistical analysis for comparing the treatments with the controls for Experiment 4.
Dose Day
1 Day
2 Day
3 Day
4 Day
5 Day
6 Day
7 Day
8 Day
9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15 Day
16 Day
17
8g/m20.42 0.42 0.30 * * * * * * * * * * * * * *
4g/m21 1 0.43 0.18 * * * * * * * * * * * * *
2g/m21 1 1 1 0.10 0.15 0.31 * * * * * * * * * *
1g/m21 1 1 1 1 0.42 0.70 0.11 * * * * * * * * *
*less than 0.05, i.e. statistically different to the controls
Dose Day
1 Day
2 Day
3 Day
4 Day
5 Day
6 Day
7 Day
8 Day
9 Day
10 Day
11 Day
12 Day
13 Day
14 Day
15 Day
16 Day
17 Day
18 Day
19 Day
20
8g/m2* * * * * * * * * * * * * * * * * * * *
4g/m2* * * * * * * * * * * * * * * * * * * *
2g/m20.36 0.21 * * * * * * * * * * * * * * * * * *
1g/m20.36 0.28 * * * * * * * * * * * * * * * * * *
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 36
The efficacy testing of Diatomaceous Earth Dust to the
Common Bed Bug,
Cimex lectularius
.
ii. Mesocosm Investigations
Background
In the initial laboratory trials, Diatomaceous Earth dust (DED) was found highly
efficacious against the Common bed bug,
Cimex lectularius
. Ideally the next step in
testing the efficacy of a product is to undertake field trials. However, as DED is a
dust, it would not be applied to all locations where bed bugs may harbour, such as
on mattresses. Dusts being obvious are unsightly and it is inappropriate to apply
such insecticide formulations to areas when they can be readily seen and/or quickly
removed via vacuuming, which would render them ineffective. For bed bug control,
dusts should be applied to non-obvious locations such as underneath carpets and
straight edges, behind skirtings, in wall voids, ensemble bases and power points
(for more information on appropriate bed bug control consult the ‘Code of Practice
for the Control of Bed Bug Infestations in Australia”, www.bedbug.org.au, which
was compiled by the author of this report). Thus other insecticide formulations,
notably liquids, must always be employed in conjunction with dusts. This means
that in the field situation it is not possible to assess the efficacy solely of dusts in a
scientific manner when bed bugs are the target pest, as the other insecticide/s will
have a confounding effect.
To circumvent this issue, mesocosms were constructed for the purpose of further
testing the efficacy of DED. A mesocosm is essentially an artificial or a simulated
environment, and allows for the testing of a product on a larger scale to produce
results that should be indicative of what would occur with a field infestation. With
the mesocosm, a single product can be tested without the confounding effects of
other insecticides. It was also important to access if DED can be applied with
normal pest control equipment for insecticidal dust applications such as bulb hand
puffers.
Thus the aims of the experiment were to;
• To test the efficacy of Diatomaceous Earth dust in a simulated environment (a
‘mesocosm’), and,
• To demonstrate that the product can be applied via normal insecticide dusting
equipment, namely a bulb hand puffer.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 37
Methods
Test Animal
The bed bugs used are the Common bed bug,
Cimex lectularius
, from a colony
established by the Department of Medical Entomology during 2004. The colonies
held by the Department are the only bed bug colonies in Australia. The founder
specimens were sourced from various infestations within the Sydney metropolitan
area and have not been profiled for insecticide susceptibility, however are known
from in-house efficacy testing to have a degree of insecticide resistance to both the
synthetic pyrethroids and the carbamates. The colony is maintained within 1L
containers, provided with a blood meal once per week via anesthetised rats, and
held at 25oC, with 80%RH. Active unengorged bed bug adults were removed and
used for the tests. Sex and age of the bed bugs were not determined.
Insecticide
The DED was supplied by Dr Ian Neering of Mount Sylvia Diatomite. No batch
number or date of manufacture was provided. This was the same DED batch as
used in the initial laboratory investigations.
Mesocosm Construction
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. Four
such mesocosms were constructed; two tests (which had DED introduced) and
two controls.
Bulb Hand Duster Calibration
A Rega bulb hand insecticide dust puffer was employed to deliver the DED, which
was purchased from Garrards (www.garrards.com.au). To calculate the delivery
rate of the insecticide with the bulb hand puffer, a calibration trial was
undertaken. This involved charging the bulb hand puffer with DED, weighing the
unit, delivering ten puffs of DED, reweighing the unit and calculating the average
amount of dust per puff. This was then repeated a further nine times to achieve
ten replicates with 100 puffs in total, and the total average per puff was then
calculated. This amount was then used to determine the number of puffs
required to treat the mesocosms at the target rate.
Experimental Procedure
Fifty adult unsexed Common bed bugs (
Cimex lectularius
) were placed into each
mesocosm (Fig. 10). The Perspex lid was then fixed into position and the bed
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 38
bugs left for one hour before the introduction of the dust so that the bugs would
settle in a harbourage as they do in a typical infestation. In all the mesocosms
the bugs aggregated in the corners and along the edges of the mesocosm (Fig.
11).
In each end of the test mesocosms, two holes were drilled to allow for the
introduction of the DED via a bulb hand puffer insecticidal dust applicator (Fig.
12). From the results of the initial laboratory investigations, it was decided that a
target dose rate of the lower mid level, namely 2g/m2 would be used. The
internal dimensions of the mesocosms were: 50cm (l) x 41cm (w) x 2cm (h),
giving a surface area for treatment of approximately 0.23m2 (this included the
side walls but not the Perspex lid). At a dose rate of 2g/m2, a total of 0.47g per
test mesocosm was required.
Prior and post application, the bulb hand puffer was weighed in order to record
the insecticidal delivery amount. To each end of the mesocosm, an equivalent
number of puffs of DED were applied and the holes plugged so that bed bugs
could not escape. Mortality was determined daily from 24 hours onwards by
counting and removing bed bugs that did not respond to gentile stimuli (slight prod
with a fresh wooden applicator stick). The experiments were conducted at 22±1oC,
in a darkened environment, relative humidity of 55±5%. For each insecticidal dose,
the daily results were statistically compared with the control via one way ANOVA.
Results & Discussion
Bulb Hand Duster Calibration
Table 13 provides the calibration results of the bulb hand duster. The average
delivery amount per puff was 0.0325g. It is known that bulb hand dusters are
highly variable in their delivery for various reasons, and this was demonstrated
with the large range in delivery amounts per replicate, with average puffs
ranging from 0.01g to 0.05g.
Application Dose Rate
As mentioned in the methods above, for the target dose rate of 2g/m2, a total of
0.47g of DED per test mesocosm was required. This meant that 14.55 puffs in
total were needed and this was rounded up to 16 with 8 puffs of DED per each
end of mesocosm. This gave a theoretical application amount of 0.52g per
mesocosm, which equated to 2.2g/m2. The 16 puffs were applied to the first
mesocosm (Test 1) and the weight before application was 162.04g and 160.15g
after, with a difference of 1.89g. This amount was well above the target dose,
however as bulb hand dusters are notoriously inaccurate in their dose rate, it
was felt justified to continue with the experiment as such variability would be
normally experienced with pest controllers in the field. For the second mesocosm
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 39
however, the number of puffs was halved to a total of eight, or four each end.
Pre application to Test 2, the weight of the bulb hand duster was 160.15g and
159.51g after dosing, which give a difference of 0.64g and this was much closer
to the target dose.
Efficacy Results
Despite the different application amounts, the results of the test mesocosms
were remarkably similar and hence the test results were combined. Table 14
provides the summary data of the percent cumulative mortality over time of the
adult
Cimex lectularius
when exposed to DED within the mesocosm. Table 15 has
the raw data and Fig. 13 is a graphical representation of the summary data.
By 24 hours, test mortality was 21% and this was significantly different to the
control mortality of 0%. By Day 9, all bed bugs in the test mesocosms were
dead, with only 4% control mortality.
In the initial laboratory trials, some clumping of the DED was observed and so
there were concerns that the dust may not flow properly via an insecticide dust
applicator. This was not an issue as the dust flowed smoothly with the bulb hand
duster and spread throughout the mesocosm, with the result that all bed bugs
were dusted. Over the duration of the experiment, the DED was observed to
clump, however as the mesocosm was regularly moved from a dark to light area
for observation purposes, it was probable that the clumping was the result of
movement and this is unlikely to be an issue once the product has been applied in
the field situation. Despite the clumping, a complete kill was achieved.
Conclusion
DED was found to be highly efficacious against adults of the Common bed bug,
Cimex lectularius
, in a simulated environment and could be readily applied via
typical pest control equipment employed in insecticidal dust application.
References
Doggett S.L. (2007). A Code of Practice for the Control of Bed Bug
Infestations in Australia. 2nd Edition.
Department of Medical Entomology &
The Australian Environmental Pest Managers Association, Westmead Hospital,
Sydney
. 67pp. ISBN 1740800974.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 40
Figure 9. The ‘Mesocosm’ for testing the efficacy of Diatomaceous Earth dust when applied by a bulb hand duster.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 41
Figure 10. Bed bugs being placed within the ‘Mesocosm’.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 42
Figure 11. Bed bugs one hour after being placed in the ‘Mesocosm’.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 43
Figure 12. Applying the Diatomaceous Earth dust to the ‘Mesocosm’.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 44
Table 13. Calibration of hand bulb duster through measuring the weight of the
duster after puffing ten times with Diatomaceous Earth dust.
Weight (g)
Replicate* Before After Difference Ave/Puff
1 151.15 150.91 0.24 0.02
2 150.91 150.54 0.37 0.04
3 150.54 150.09 0.45 0.04
4 150.09 149.69 0.40 0.04
5 149.69 149.51 0.18 0.02
6 149.51 149.37 0.14 0.01
7 149.37 149.13 0.24 0.02
8 149.13 148.70 0.43 0.04
9 148.70 148.24 0.46 0.05
10 148.24 147.90 0.34 0.03
Total average: 0.0325
*Each replicate represents ten puffs of the duster.
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 45
Table 14. Percent cumulative mortality of adult
Cimex lectularius
exposed to Diatomaceous Earth dust within the
mesocosm, summary data*.
Day 0 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9
Test 0 21.0 54.0 74.0 85.0 91.0 97.0 98.0 99.0 100.0
Control 0 0.0 1.0 1.0 1.0 1.0 1.0 4.0 4.0 4.0
*From and including Day 1, all test results were significantly different to the controls.
Table 15. Mortality of adult
Cimex lectularius
exposed to Diatomaceous Earth dust within the mesocosm, raw data.
Day 1 Day 2 Day 3 Day 4 Day 5
No. No.
Dead Cum
Mort*
%
Cum
Mort** No.
Dead Cum
Mort
%
Cum
Mort No.
Dead Cum
Mort
%
Cum
Mort No.
Dead Cum
Mort
%
Cum
Mort No.
Dead Cum
Mort
%
Cum
Mort
Test 1 49 11 11 22.4 12 23 46.9 7 30 61.2 8 38 77.6 4 42 85.7
Test 2 51 10 10 19.6 21 31 60.8 13 44 86.3 3 47 92.2 2 49 96.1
Control 1 50 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Control 2 50 0 0 0 1 1 2.0 0 1 2.0 0 1 2.0 0 1 2.0
*cumulative mortality, **percentage cumulative mortality.
Day 6 Day 7 Day 8 Day 9
No. Mort. Cum
Mort
%
Cum
Mort Mort. Cum
Mort
%
Cum
Mort Mort. Cum
Mort
%
Cum
Mort Mort. Cum
Mort
%
Cum
Mort
Test 1 49 4 46 93.9 1 47 95.9 1 48 98.0 1 49 100
Test 2 51 2 51 100 51 100 51 100 51 100
Control 1 50 0 0 0 2 2 4.0 0 2 4.0 0 2 4.0
Control 2 50 0 1 2.0 1 2 4.0 0 2 4.0 0 2 4.0
Efficacy Testing of Diatomaceous Earth for Bed Bugs
Department of Medical Entomology 46
Fig 13. Cumulative Mortality of Adult Common Bed Bugs, Cimex lectularius,
exposed to Diatomaceous Earth in the Mesocosm.
0
10
20
30
40
50
60
70
80
90
100
Day 0 Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9
Percentage Cumulative Mortality
Test
Control
Fi
g
ure 13.Cumulative mortality of adult
Cimex lectulariu
s
ex
p
osed to Diatomaceous Earth in the mesocosm.
