Urban Area Mosquito Control: Results of Two Experiments

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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
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Residual Adulticides for Residential Mosquito
Suppression
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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.
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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.
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Study conducted at 24 residences in Lexington, KY
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Median assessed value 185,750
2004 Lexington, KY median value 143,100
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Average age 43.4 years
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Average lot size 0.31 A
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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)
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Objective is to treat mosquito adults daytime
resting sites
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Treat vegetation near home perimeter
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Treat vegetation in the yard
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Treat vegetation on the perimeter
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First Experiment Treatment Specifications
Treatment Water Placebo DemandCS Syngenta TalstarOne FMC
A. I. Water Lambda-cyhalothrin Bifenthrin
App. Rate --- 0.8 fl. Oz/ gallon 1.0 fl. Oz/gallon
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
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Mosquito Monitoring

• Sampled mosquitoes in backyards weekly for 10
  weeks (-28)
• All sampling after 6 pm
• Mosquito Surveillance
• CDC Traps
• Human Landing Rate
• Gravid Traps
• Ovitrap
• Sweepnet

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Two Mosquito Genera Dominate in Most Kentucky
Suburbs
Aedes
Culex
Cause majority of bites to humans Hide in bushes
during day Many species are primarily nuisance
Mainly bites birds Hide in tree canopies during
day Primary vectors of WNV, et al.
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Human Landing Rate
98 Aedes species
73 reduction over 6 weeks
85 reduction after 1 week
98 Aedes
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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.

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Homeowner Experience
Average Homeowner diary rating
Avoided outdoors
Did NOT avoid outdoors
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Gravid Traps
96 Culex (A Principal WNV vector)
No Effect
96 Culex
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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.

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Why the difference between Aedes Culex?
Culex resting sites
8 10 feet
Insecticide layer Aedes resting sites
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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?

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Launching insecticide into the trees will create
chemical trespass problems
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Would the treatment be effective against Culex if
we could get it up there?
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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
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Lifted the trap into the tree canopy
Putting it in the canopy locates it close to the
Culex mosquitoes 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.
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Results?
Canopy 89 Reduction, 98 Culex
Ground 58 Reduction, 94 Aedes
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Then tried this technique at 24 residential
properties in Lexington
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Tested 2 techniques against water Quick/Fast
vs. Thorough (including tree canopies).
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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
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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
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CDC Ground Trap Catch
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Culex were suppressed in both tree traps and
gravid traps
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Homeowner Opinion After One Month
Do you believe that the treatment reduced
mosquito populations to your satisfaction?
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Homeowners spent more time in their backyards
Survey taken 4 weeks post treatment
75
75
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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.

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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.