Urban Area Mosquito Control: Results
of Two Experiments
Dr. Grayson C. Brown
Public Health Entomology Laboratory
Department of Entomology
University of Kentucky
Lexington, KY 40546
Residual Adulticides for Residential
Mosquito Suppression
Most homeowners are skeptical that
PMPs can provide real mosquito
control at the spatial scale of an
individual back yard
Performance data with modern pyrethroids
has been lacking in actual suburban
environments.
We studied this technique
Study involved two
principal experiments
Will summarize results
here
More detail in the May,
2005 and August, 2006
issues of PCT magazine.
Study conducted at 24 residences
in Lexington, KY
Median assessed value: $185,750
2004 Lexington, KY median value: $143,100
Average age: 43.4 years
Average lot size: 0.31 A
Treatments applied with a
backpack mist blower
Applications made by a
certified PMP (Charlie
Asbury or Scott Quinton
both from All-Rite Pest
Control, Lexington)
Objective is to treat mosquito
adults’ daytime resting sites
Treat vegetation near home
perimeter
Treat vegetation in the yard
Treat vegetation on the perimeter
First Experiment Treatment
Specifications
Water
Placebo
Demand®CS
Syngenta
TalstarOne™
FMC
A. I.
Water
Lambdacyhalothrin
Bifenthrin
App. Rate
---
0.8 fl. Oz/ gallon
1.0 fl. Oz/gallon
Treatment
Flow Rate: 14 oz/min (“3”)
Droplet size: 50µ VMD
Avg of 21 minutes a Home
Avg of 6.5 Gallons/Home, or
ca. 3.3 gal/1,000 sq. ft treated
Mosquito Monitoring
• Sampled mosquitoes in
backyards weekly for 10
weeks (-2…8)
• All sampling after 6 pm
• Mosquito Surveillance
–
–
–
–
–
CDC Traps
Human Landing Rate
Gravid Traps
Ovitrap
Sweepnet
Two Mosquito Genera Dominate in
Most Kentucky Suburbs
Aedes
Culex
Cause majority of bites to humans
Mainly bites birds
Hide in bushes during day
Hide in tree canopies during day
Many species are primarily nuisance
Primary vectors of WNV, et al.
Human Landing Rate
98% Aedes species
Mosquito Bites/10 min
Demand CS
TalstarOne
Water Placebo
8
73% reduction over 6 weeks
6
4
85% reduction
after 1 week
2
0
-2
98% Aedes
-1
0
1
2
3
4
5
Weeks Post Treatment
6
7
8
Homeowner experience
Homeowners kept a “diary”
• 1 = We did not notice any
mosquitoes.
• 2 = We noticed or were bitten by
mosquitoes, but not enough to use
repellents or avoid being outdoors.
• 3 = At least some of us were
bothered enough by mosquitoes to
use repellents or avoid being
outdoors.
• 4 = Mosquitoes were very
noticeable and were a definite
annoyance for most of the week.
• 5 = Mosquitoes were very bad the
entire week.
• NA = I was out of town.”
Homeowner Experience
Average Homeowner diary rating
Average Diary Rating
Demand CS
Water Placebo
Avoided outdoors
3
2
TalstarOne
Did NOT avoid
outdoors
1
-2
-1
0
1
2
3
4
5
Weeks Post Treatment
6
7
8
Gravid Traps
96% Culex (A Principal WNV vector)
Mosquitoes/Trap/Night
Demand CS
TalstarOne
Water Placebo
60
No Effect
45
30
15
0
-1
96% Culex
0
1
2
3
4
5
Weeks Post Treatment
6
7
8
Conclusions from this Expt
• Mosquito bites were
reduced by 75 – 85% for
6 weeks.
• Degree of control was
noticeable by
homeowners.
• Nuisance species were
controlled but some
primary disease vectors
were not.
Why the difference between Aedes
& Culex?
Culex
resting sites
8 – 10 feet
Insecticide
layer & Aedes
resting sites
Next Questions
• If product could get into the tree canopy,
could the Culex disease vectors be
controlled in the spatial scale of the
residential backyard?
• How sensitive is the method with respect
to thoroughness of the coverage?
Launching insecticide into the trees will
create chemical trespass problems
Would the treatment be effective against
Culex if we could get it up there?
Treated tree lines with Demand
Eight Blocks, each had
100’ lengths with 100’
untreated borders
Used Demand at max
label rate and compared
to a water control
Height maxed at 25 – 30’
Sampled mosquitoes
near ground and at 25’
above ground
Lifted the trap into the tree canopy
In addition, another CDC
trap was mounted at the
standard height near the
ground
Finally, a Gravid Trap (not
shown) was also placed
on the ground – These
trap females that have
already had a blood meal
and are looking for a place
to lay eggs.
20 – 25 feet
Putting it in the canopy
locates it close to the
Culex mosquitoes
Canopy: 89% Reduction,
98% Culex
Results?
Ground: 58% Reduction,
94% Aedes
Then tried this technique at 24
residential properties in Lexington
Tested 2 techniques against
water: Quick/Fast vs. Thorough
(including tree canopies).
Treatment Specs
Compared Application Technique With Demand CS
Treatment
Rate
Product Cost
Time
Water
0
0
10 min
Quick/Cheap
3.2 g/home
$5 - 10
10 min
Slow/Thorough
6.5 g/home
$10 – 20
20 min
Results – Mosquito reduction compared with
control (2wk post treatment)
Method
Quick
Thorough,
includes tree
spraying
Aedes
(Responsible
for most bites)
33%
82%
Culex (Primary
WNV vector)
0%
85%
Mosquito
CDC Ground Trap Catch
Thorough
Quick
% Supression
100
80
60
40
20
0
1
2
3
Weeks Post Treatment
4
Culex were suppressed in both tree
traps and gravid traps
Culex/trap/niight
400
300
200
Control
Quick
Thorough
100
0
Tree
Gravid
Trap Type
Homeowner Opinion After One Month
Do you believe that the treatment reduced
mosquito populations to your satisfaction?
% Satisfaction
100
80
60
40
20
0
Throrough
Quick
Water
Homeowners spent more time in
their backyards
% more time spent in
backyard
100
Survey taken 4 weeks post treatment
80
75%
75%
60
40
27%
20
0
Thorough
Quick
Water
Placebo
Conclusions
• Culex can be suppressed if the product can get
into the tree canopy.
• Thorough coverage with significant volume is
critical to suppression of all mosquito species.
• In this study, homeowner satisfaction was NOT a
good indicator of mosquito suppression.
Lessons
• Understanding vector behavior is crucial to
the success of barrier applications.
• In many situations, “mosquitoes” are a
mixture of many species, each with its own
behavioral characteristics.
• A treatment that reduces mosquito bites
will not necessarily reduce disease risk.