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Title: Impact of electrostatic and conventional sprayers characteristics on dispersion of barrier spray

item WALKER, TODD - Us Navy
item Hoffmann, Wesley
item Fritz, Bradley - Brad
item SMITH, VINCENT - Us Navy
item ROBINSON, CATHY - Us Navy
item ENGLISH, TREY - Adapco, Inc

Submitted to: Journal of the American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2010
Publication Date: 12/28/2010
Citation: Farooq, M., Walker, T.W., Heintschel, B.P., Hoffmann, W.C., Fritz, B.K., Smith, V.L., Robinson, C.A., English, T. 2010. Impact of electrostatic and conventional sprayers characteristics on dispersion of barrier spray. Journal of the American Mosquito Control Association. 26:422-429.

Interpretive Summary: Mosquito control personnel commonly spray insecticides on foliage surrounding the area of interest to create a protective barrier, which limits insect movement through the sprayed area, in order to limit the movement of mosquitoes and other biting insects into areas of human activity such as parks and ball fields. Studies were conducted to investigate the deposition characteristics of barrier sprays from electrostatic and conventional sprayers through measurement of penetration into and deposition onto natural vegetation. Sprayers producing larger droplets yielded significantly higher deposition on vegetation in barrier applications than the sprayers producing smaller droplets. The analysis shows that two sprayers were not suitable for barrier sprays on vegetation, two were suitable for 1-3 m wide barriers, and one was suitable for barriers wider than 3 m. Results of this study will help applicators select appropriate vector control equipment for making more effective spray applications.

Technical Abstract: A study was conducted to analyze the performance of three electrostatic (Electrolon BP-2.5TM, Spectrum Electrostatic 4010, and Spectrum Electrostatic head on a Stihl 420) and two conventional (Buffalo Turbine CSM2 and Stihl 420) sprayers for barrier sprays to suppress an adult mosquito population in an enclosed area. Sprayer characteristics such as charge-mass ratio, air velocity, flow rate, and droplet spectra were measured while spraying water. Dispersion of the spray cloud from these sprayers was determined using coverage on water-sensitive cards at various heights (0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m, and 3.0 m) and depths (1 m, 3 m, and 5 m) into the under-forest vegetation while spraying bifenthrin at the rate of 21.8 ml/300 m of treated row. The charge-mass ratio data show that Electrostatic head on a Stihl 420 did not impart enough charge to the droplets to be considered as an electrostatic sprayer. In general, the charged spray cloud moved down toward the ground. The Electrolon BP 2.5 had significantly lower spray coverage on cards, indicating lack of spray dispersion. This sprayer had the lowest air velocity and did not have the air capacity needed to deliver droplets close to the target for electrostatic force to affect deposition. The analysis shows that these two sprayers are not a suitable choice for barrier sprays on vegetation. The results indicate that the Buffalo Turbine is suitable for barriers wider than 3 m, and the Spectrum 4010 and Stihl 420 are suitable for 1-3 m wide barriers.