Urban Area Mosquito Control: Results of Two Experiments

1. 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

2. Residual Adulticides for Residential Mosquito Suppression

3. 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.

4. 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.

5. Study conducted at 24 residences in Lexington, KY

6. Median assessed value: $185,750 2004 Lexington, KY median value: $143,100

7. Average age: 43.4 years

8. Average lot size: 0.31 A

9. 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)

10. Objective is to treat mosquito adults’ daytime resting sites

11. Treat vegetation near home perimeter

12. Treat vegetation in the yard

13. Treat vegetation on the perimeter

14. First Experiment Treatment Specifications 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

15. 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

16. 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.

17. Human Landing Rate 98% Aedes species 73% reduction over 6 weeks 85% reduction after 1 week 98% Aedes

18. 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.”

19. Homeowner Experience Average Homeowner diary rating Avoided outdoors Did NOT avoid outdoors

20. Gravid Traps 96% Culex (A Principal WNV vector) No Effect 96% Culex

21. 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.

22. Why the difference between Aedes & Culex? Culex resting sites 8 – 10 feet Insecticide layer & Aedes resting sites

23. 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?

24. Launching insecticide into the trees will create chemical trespass problems

25. Would the treatment be effective against Culex if we could get it up there?

26. 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

27. 20 – 25 feet 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.

28. Canopy: 89% Reduction, 98% Culex Results? Ground: 58% Reduction, 94% Aedes

29. Then tried this technique at 24 residential properties in Lexington

30. Tested 2 techniques against water: Quick/Fast vs. Thorough (including tree canopies).

31. Treatment Specs • Compared Application Technique With Demand CS

32. Results – Mosquito reduction compared with control (2wk post treatment) Method Mosquito

33. CDC Ground Trap Catch

34. Culex were suppressed in both tree traps and gravid traps

35. Homeowner Opinion After One Month Do you believe that the treatment reduced mosquito populations to your satisfaction?

36. Homeowners spent more time in their backyards Survey taken 4 weeks post treatment 75% 75% 27%

37. 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.

38. 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.