Canopy penetration and deposition of barrier sprays from electrostatic and conventional sprayers

Authors: Hoffmann, Wesley; FAROOQ, MUHAMMED - Us Navy; WALKER, TODD - Us Navy; Fritz, Bradley - Brad; SZUMLAS, D - US-NAVY; Bernier, Ulrich; Hogsette, Jerome - Jerry; Lan, Yubin; Huang, Yanbo; Quinn, Brian; SMITH, V - Us Navy; ROBINSON, C - Us Navy

Submitted to: Journal of the American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2009
Publication Date: 9/29/2009
Citation: Hoffmann, W.C., Farooq, M., Walker, T.W., Fritz, B.K., Szumlas, D., Bernier, U.R., Hogsette Jr., J.A., Lan, Y., Huang, Y., Quinn, B.P., Smith, V.L., Robinson, C.A. 2009. Canopy penetration and deposition of barrier sprays from electrostatic and conventional sprayers. Journal of the American Mosquito Control Association. 25:323-331.

Interpretive Summary: In order to limit the movement of mosquitoes and other biting insects into areas of human activity such as parks or ball fields, mosquito control personnel will commonly spray insecticides on the foliage surrounding the area of interest to create a protective barrier, which limits insect movement through the sprayed area. Studies were conducted to investigate the effectiveness of barrier sprays from electrostatic and conventional sprayers through measurement of penetration into and deposition on to natural vegetation. The results indicated that sprayers producing larger droplets produced significantly higher deposition on vegetation in barrier applications than the sprayers producing smaller droplets. Sprayers with higher air velocity at the nozzle discharge have proven significantly better for barrier sprays than the sprayers with lower air velocity. Through a better understanding of which sprayers producer higher spray depositions, users of vector control equipment will make more effective spray applications.

Technical Abstract: An experimental study was conducted to investigate the effectiveness of barrier sprays from electrostatic and conventional sprayers through measurement of penetration into and deposition on to natural vegetation. Two conventional and three electrostatic sprayers were used in the study. One sprayer in each category was truck/trailer mounted and the rest were back pack sprayers. Talstar adulticide was applied at labeled rates of 21.8 ml/300 m2 of treated row. Caracid Brilliant Flavine FFS fluorescent dye was added to the tank mix to serve as tracers for the deposition studies. As the sprayers used in the study had different flow rates and travel speeds, the concentration of dye in the tank mix was varied so that each sprayer applied the same amount of dye and insecticide in a spray plot. The droplet size spectrum for each sprayer was measured while spraying water. Top and bottom of the leaf were washed separately to determine deposition on two sides of the vegetation. The deposition was determined using fluorometry. The results indicated that sprayers producing larger droplets produced significantly higher deposition on vegetation in barrier applications than the sprayers producing smaller droplets. Sprayers with higher air velocity at the nozzle discharge have proven significantly better for barrier sprays than the sprayers with lower air velocity. Electrostatic sprayers did not show any improvement in deposition on vegetation or in penetration in to vegetation over the conventional sprayers. There was no difference in deposition between truck mounted and back pack sprayers.