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Barrier applications for mosquito suppression in the suburban landscape

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With recent national attention on mosquito-borne viruses such as the Zika virus, an Integrated Pest Management approach to mosquito control is more important than ever. Dr. Grayson Brown, professor at the University of Kentucky’s Department of Entomology, offers his expertise and insight on how to best manage mosquito populations on your customers’ properties.

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Barrier applications for mosquito suppression in the suburban landscape

  1. 1. KY Entomology Public Health
  2. 2. Barrier Applications for Mosquito Suppression in the Suburban Landscape Dr. Grayson Brown Public Health Entomology Laboratory Department of Entomology University of Kentucky Lexington KY
  3. 3. Mosquitoes are top health concern among Americans 62 38 30 26 11 14 Mosquitoes Stinging Insects Ticks Spiders Bed Bugs Other Source: NPMA 2013 Summer Survey reported in PCT Online, Sept. 2013
  4. 4. Of those concerned, disease topped the list Source: NPMA 2013 Summer Survey reported in PCT Online, Sept. 2013 54 43 35 11 5 Disease Pain, sting/bite Infestation in home Allergy Disease history
  5. 5. Recent mosquito-borne disease outbreaks in N. America — West Nile Virus: 1999 – 2006 — Dengue: 2005 – 20011 — Chikungunya: 2011 – 2015 — Zika: 2016 – Present — More to come
  6. 6. Zika Symptoms Eye Redness Mild Viral Conjunctivas Flu-like symptoms Joint aches, particularly in wrists and ankles Mild rash •  Self-limiting, 3 days – week •  Not typically neuroinvasive, few complications, deaths extremely rare and only in immune-compromised individuals
  7. 7. Most people don’t need to worry about Zika It’s only a serious threat to one group
  8. 8. Result of decreased brain size
  9. 9. Microcephalic Births in Brazil 0 500 1000 1500 2000 2500 3000 3500 4000 4500 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 AnnualCases Year Before Zika April 2015 Post Zika
  10. 10. Extensive public concern at all levels
  11. 11. How do mosquitoes transmit disease? —  Mosquitoes are not “flying syringes” —  In order for a pathogen to be transmitted by a mosquito: —  It has to infect the mosquito in a specific way —  The mosquito must have the biological, behavioral and ecological traits to enable transmission —  The pathogen must have a pathogenic cycle inside its human host that enables a return to the mosquito (optional) —  We can’t do anything about the first & last of these. Our mosquito control efforts are targeted at the 2nd one.
  12. 12. Feeding • Once the mosquito lands, the labium slides back, exposing mandibles & maxillae (stylets) • Stylets pierce the skin and probe until sensors on the tip detect a capillary • Saliva continues to be injected during feeding as an anticoagulant. • Full blood meal is half to a couple of microliters (0.001 ml). Sensory Setae Human Hair Blood Capillary Sensors Lower “Lip” (labium) Palp Mandibles & Maxillae Compound Eye
  13. 13. Choumet V, Attout T, Chartier L, Khun H, Sautereau J, et al. (2012) Visualizing Non Infectious and Infectious Anopheles gambiae Blood Feedings in Naive and Saliva-Immunized Mice. PLoS ONE 7(12): e50464. doi:10.1371/journal.pone.0050464
  14. 14. Mosquito Life Cycle —  Larvae are wigglers —  Pupae are tumblers (quite active) —  Both breath air —  Eggs are laid on the surface of water in rafts (Culex) or singly (Anopheles) or near water (Aedes)
  15. 15. Eggs Anopheles (note floats) Culex egg raft Aedes eggs are laid near water
  16. 16. Mosquito Diet —  Most Larvae feed on algae & bacteria but a few are predaceous and feed on other mosquito larvae —  Only females are blood sucking —  Males and females feed on nectar and other plant juices
  17. 17. Mosquito Lifestyle —  Most mosquitoes do not travel far from the water from which they emerged —  Adults are active at night or twilight —  Many spend the day in hollow trees, culverts, and dense shaded areas
  18. 18. Mosquitoes in the N. American Suburban Landscape —  About 150 spp. of mosquitoes in N. America in 8 genera. Of these: —  < 10 are serious disease transmission threats —  About 10 more are less serious threats —  Another 20 or so are seasonal nuisance pests —  Most problems are confined to a few species in only 2 genera: Aedes and Culex. —  These two genera differ in very important ways.
  19. 19. Two  Generic  Biologies   Aedes/Ochlerotatus Culex Dengue, EEE, LaCrosse West Nile, SLE, other encephalitis Attacks mammals Attacks birds, few human bites Daytime – early evening Late night – early morning Prefers cleaner water Prefers stagnant water Few gens/year, OW as eggs Many gens/year, OW as adult Daytime resting sites < 10 ft (bushes) Daytime resting sites > 10 ft (trees)
  20. 20. Municipal Control Vs. Backyard Control Municipal ULV Backyard Perimeter AI Sumithrin Lambda cyhalothrin, bifenthrin, deltamethrin Application Time Late PM/Early AM Daytime Residual activity Hours Weeks/months Spatial Scale Area Code Single Backyard Most effective against Culex spp, some Anopheles Aedes, Ochlerotatus Diseases Controlled West Nile, other encephalitis Zika, Dengue, Chikungunya The two are compatible and complementary
  21. 21. Suburban backyard as a mosquito habitat Need Aedes Culex Water Clean Stagnant Hosts Mammals Birds Resting sites Low, dark, humid sites Trees Air movement Minimal Minimal Overwintering Areas that will be covered with water Crevices in tree bark, siding, etc.
  22. 22. How to they move about, What are their stimuli 1.  They have a simple stimulus response 2.  First day or so post-eclosion, they just sit 3.  Then they search for nectar (carbohydrate source) so they orient toward flowers 4.  Next they search for a blood meal. —  If no olfactory stimuli, they move toward light —  CO2 is a long distance stimulus —  Body heat for short range —  Other volatile chemicals for individual selection 5.  After a blood meal, they search for oviposition site —  Volatiles emitted by microfauna and other larvae are stimuli. This completes a gonotropic cycle. Next cycle begins with a return to step 3.
  23. 23. How do they move toward people? Direction of air movement CO2 Plume
  24. 24. CO2 Plume How do they move toward people? Direction of air movement
  25. 25. This is the basis for how perimeter applications for mosquito control work.
  26. 26. Objective is to treat mosquito adults’ daytime resting sites and work FROM the house
  27. 27. Start with vegetation near home
  28. 28. Then vegetation in the yard
  29. 29. Finally treat the perimeter
  30. 30. Objective is to flush the mosquitoes from the yard
  31. 31. Technique and properties are important —  Bad Things: —  Properties with little to no perimeter vegetation —  Properties whose predominate vegetation is grass and flower/vegetable/herb gardens —  Treating grass/flowers/vegetables —  Treating in a haphazard pattern —  Failing to use proper PPE
  32. 32. Bad Property, Bad Technique
  33. 33. Good Property, Good Technique
  34. 34. Dense non-flowering ground vegetation
  35. 35. Dense Canopies
  36. 36. Underneath decks, crawlspaces or other raised structures
  37. 37. Objective is to treat any location that is dark, cool and moist. Home’s Perimeter
  38. 38. Objective is to treat any location that is dark, cool and moist. Yard’s Perimeter
  39. 39. Use a vertical or circular motion to coat the undersides of the leaves
  40. 40. What results should you expect?
  41. 41. 0 3 6 9 12 -2 -1 0 1 2 3 4 5 6 7 8 Mosquitoes/Trap/Night Weeks Post Treatment Demand CS Water Placebo Excellent control of Aedes Avg. 75% reduction after 1 week Avg. 60% reduction over 6 weeks 96% Aedes Before Treatment After Treatment 96% Aedes species
  42. 42. Greatly reduced mosquito bites 0 2 4 6 8 -2 -1 0 1 2 3 4 5 6 7 8 MosquitoBites/10min Weeks Post Treatment Demand CS Water Placebo 85% reduction after 1 week 73% reduction over 6 weeks 98% Aedes 98% Aedes species
  43. 43. No effect on Culex mosquitoes 0 15 30 45 60 -1 0 1 2 3 4 5 6 7 8 Mosquitoes/Trap/Night Weeks Post Treatment Demand CS Water Placebo No Effect 96% Culex (Principal WNV vector)
  44. 44. Season-­‐long  Summary   (Totals  7/7/14  –  9/10/14)   Post-­‐ Treatment   Totals   Demand  CS   Demand  +   Archer   Control   CDC   Mosquitoes   102 68 763 Gravid  Trap   Mosquitoes   133 96 489 HLR  Counts   59 84 224 Larvae  in  Egg   Traps   89 35 1,788
  45. 45. 2014  Season-­‐Long  Summary    %  ReducNon    of  Selected  Species  RelaNve  to  Control   Species   Demand  CS   Demand  +  Archer   Aedes  albopictus   87 % 78 Culex  pipiens   34 61 Aedes  vexans   72 79 Anopheles  spp.   16 44
  46. 46. 2014 Aedes Trap Results 0   10   20   30   40   50   60   70   1   2   3   4   5   6   7   8   9   10   11   12   Total  mosquitoes/trap/night   Week   Demand  +  Archer   Demand  Alone   Control  
  47. 47. Most recent work is showing significant suppression for 2 months (2015 data) 0   10   20   30   40   50   60   70   1   2   3   4   5   6   7   8   9   Mosquitoes   Weeks  Post-­‐Treatment   Mean  (±SE)  -­‐  CDC  Trap   Demand   Demand  +  Archer   Control  
  48. 48. Mosquito bites on humans (2015 data) 0   2   4   6   8   10   12   14   16   18   2   3   4   5   6   7   8   9   Average  #  Mosquitoes/5  minutes   Weeks  Post-­‐Treatment   Mean  (±SE)  -­‐  Human  Landing  Rate  Count     Demand   Demand  +  Archer   Control  
  49. 49. Barrier treatments are only one part of a comprehensive management program
  50. 50. Homeowners —  They have responsibility too —  Source Reduction —  Avoiding pruning/removal of treated foliage —  Ideally removing harborage sites prior to treatment —  Gutter repair —  Expectations —  Suppression is not elimination —  May reduce some disease risk but not all
  51. 51. Problems —  Problems that can arise with these management programs and how to avoid/resolve them. —  Non-target effects —  Chemical trespass —  Resistance management and its importance —  Mosquito species not well controlled by these programs and their significance (Culex)
  52. 52. Non-Target Effects —  Some can be avoided —  Pollinators —  Aquatic organisms —  Plants —  Other beneficials —  Some cannot —  Lady beetles —  Fireflies —  Some spiders Chemical Trespass
  53. 53. Main method of avoiding chemical trespass is to keep the spray low on low wind days Insecticide layer & Aedes resting sites Culex resting sites 8 – 10 feet
  54. 54. Resistance Management —  Growing problem with resistance to synthetic pyrethroids in mosquitoes —  Greatest problem is with sumithrin —  Great variability between species —  Residuals have relatively little problem right now —  Typical neighborhoods have ~ 10% of homes treated so 90% of mosquitoes are not exposed —  We need to keep an eye on this and use resistance management strategies as much as possible.
  55. 55. —  Backyard perimeter applications will provide effective suppression of Zika vectors —  They should be used as part of a comprehensive program —  Consider printing a homeowner pamphlet on what they can do (cf. CDC, your Pub. Health Dept. sites) —  Consider products that minimize treatment frequency. —  Don’t forget that you are part of an overall mosquito management effort Tips for this coming year
  56. 56. KY Entomology Public Health Thank You

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